/* vi: set ts=2 shiftwidth=2 expandtab:
 *
 * Copyright (C) 2003-2008  Simon Baldwin and Mark J. Tilford
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 * USA
 */

/*
 * Module notes:
 *
 * o ...
 */

#include <assert.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <setjmp.h>

#include "scare.h"
#include "scprotos.h"
#include "scgamest.h"


/* Assorted definitions and constants. */
enum { LINE_BUFFER_SIZE = 256 };
static const sc_char NUL = '\0';
static const sc_char SPECIAL_PATTERN = '#';
static const sc_char WILDCARD_PATTERN = '*';
static const sc_char *const WHITESPACE = "\t\n\v\f\r ";
static const sc_char *const SEPARATORS = ".,";


/*
 * run_is_task_function()
 *
 * Check for the presence of a command function in the first task command,
 * and action it if found.  This is a 4.0.42 compatibility hack -- at
 * present, only getdynfromroom() exists.  Returns TRUE if function found
 * and handled.
 */
static sc_bool
run_is_task_function (const sc_char *pattern, sc_gameref_t game)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  sc_vartype_t vt_key[3];
  sc_int room, object;
  sc_char *argument;

  /* Simple comparison against the one known task expression. */
  argument = sc_malloc (strlen (pattern) + 1);
  if (sscanf (pattern, " # %%object%% = getdynfromroom (%[^)])", argument) == 0)
    {
      sc_free (argument);
      return FALSE;
    }

  /*
   * Compare the argument read in against known room names.
   *
   * TODO Is this simple room name comparison good enough?
   */
  vt_key[0].string = "Rooms";
  for (room = 0; room < gs_room_count (game); room++)
    {
      const sc_char *name;

      vt_key[1].integer = room;
      vt_key[2].string = "Short";
      name = prop_get_string (bundle, "S<-sis", vt_key);
      if (sc_strcasecmp (name, argument) == 0)
        break;
    }
  sc_free (argument);
  if (room == gs_room_count (game))
    return FALSE;

  /*
   * Select a dynamic object from the room.
   *
   * TODO What are the selection criteria supposed to be?  Here we use "on
   * the floor".
   */
  vt_key[0].string = "Objects";
  for (object = 0; object < gs_object_count (game); object++)
    {
      sc_bool bstatic;

      vt_key[1].integer = object;
      vt_key[2].string = "Static";
      bstatic = prop_get_boolean (bundle, "B<-sis", vt_key);
      if (!bstatic && obj_directly_in_room (game, object, room))
        break;
    }
  if (object == gs_object_count (game))
    return FALSE;

  /* Set this object reference, unambiguously, as if %object% match. */
  gs_clear_object_references (game);
  game->object_references[object] = TRUE;
  var_set_ref_object (vars, object);

  return TRUE;
}


/* Structure used to associate a pattern with a handler function. */
typedef struct sc_commands_s
{
  const sc_char *const command;
  sc_bool (*const handler) (sc_gameref_t game);
} sc_commands_t;
typedef sc_commands_t *sc_commandsref_t;

/* Movement commands for the four point compass. */
static sc_commands_t MOVE_COMMANDS_4[] = {
  {"{go {to {the}}} [north/n]", lib_cmd_go_north},
  {"{go {to {the}}} [east/e]", lib_cmd_go_east},
  {"{go {to {the}}} [south/s]", lib_cmd_go_south},
  {"{go {to {the}}} [west/w]", lib_cmd_go_west},
  {"{go {to {the}}} [up/u]", lib_cmd_go_up},
  {"{go {to {the}}} [down/d]", lib_cmd_go_down},
  {"{go {to {the}}} [in]", lib_cmd_go_in},
  {"{go {to {the}}} [out/o]", lib_cmd_go_out},
  {NULL, NULL}
};

/* Movement commands for the eight point compass. */
static sc_commands_t MOVE_COMMANDS_8[] = {
  {"{go {to {the}}} [north/n]", lib_cmd_go_north},
  {"{go {to {the}}} [east/e]", lib_cmd_go_east},
  {"{go {to {the}}} [south/s]", lib_cmd_go_south},
  {"{go {to {the}}} [west/w]", lib_cmd_go_west},
  {"{go {to {the}}} [up/u]", lib_cmd_go_up},
  {"{go {to {the}}} [down/d]", lib_cmd_go_down},
  {"{go {to {the}}} [in]", lib_cmd_go_in},
  {"{go {to {the}}} [out/o]", lib_cmd_go_out},
  {"{go {to {the}}} [northeast/north-east/ne]", lib_cmd_go_northeast},
  {"{go {to {the}}} [southeast/south-east/se]", lib_cmd_go_southeast},
  {"{go {to {the}}} [northwest/north-west/nw]", lib_cmd_go_northwest},
  {"{go {to {the}}} [southwest/south-west/sw]", lib_cmd_go_southwest},
  {NULL, NULL}
};

/* "Priority" library commands, may take precedence over the game. */
static sc_commands_t PRIORITY_COMMANDS[] = {

  /* Acquisition of and disposal of inventory. */
  {"[[get/take/remove/extract] [all/everything] from/empty] %object%",
   lib_cmd_take_all_from},
  {"[[get/take/remove/extract] [all/everything] from/empty] %object%"
   " [[except/but] {for}/apart from] %text%",
   lib_cmd_take_from_except_multiple},
  {"[get/take/remove/extract] [all/everything]"
   " [[except/but] {for}/apart from] %text% from %object%",
   lib_cmd_take_from_except_multiple},
  {"[get/take/remove/extract] %text% from %object%",
   lib_cmd_take_from_multiple},
  {"[get/take] [all/everything] from %character%", lib_cmd_take_all_from_npc},
  {"[get/take] [all/everything] from %character%"
   " [[except/but] {for}/apart from] %text%",
   lib_cmd_take_from_npc_except_multiple},
  {"[get/take] [all/everything]"
   " [[except/but] {for}/apart from] %text% from %character%",
   lib_cmd_take_from_npc_except_multiple},
  {"[get/take] %text% from %character%", lib_cmd_take_from_npc_multiple},
  {"[[get/take/pick up] [all/everything]/pick [all/everything] up]",
   lib_cmd_take_all},
  {"[get/take/pick up] [all/everything] [[except/but] {for}/apart from] %text%",
   lib_cmd_take_except_multiple},
  {"[get/take/pick up] %text%", lib_cmd_take_multiple},
  {"pick %text% up", lib_cmd_take_multiple},
  {"[[drop/put down] [all/everything]/put [all/everything] down]",
   lib_cmd_drop_all},
  {"[drop/put down] [all/everything] [[except/but] {for}/apart from] %text%",
   lib_cmd_drop_except_multiple},
  {"[drop/put down] %text%", lib_cmd_drop_multiple},
  {"put %text% down", lib_cmd_drop_multiple},
  {NULL, NULL}
};

/* Standard library commands, other than movement and priority above. */
static sc_commands_t STANDARD_COMMANDS[] = {

  /* Inventory, and general investigation of surroundings. */
  {"[inventory/inv/i]", lib_cmd_inventory},
  {"[x/ex/exam/examine/l/look {at}] {{the} [room/location]}", lib_cmd_look},
  {"[x/ex/exam/examine/look {at/in}] %object%", lib_cmd_examine_object},
  {"[x/ex/exam/examine/look {at}] %character%", lib_cmd_examine_npc},
  {"[x/ex/exam/examine/look {at}] [me/self/myself]", lib_cmd_examine_self},
  {"[x/ex/exam/examine/look {at}] all", lib_cmd_examine_all},

  /* Attempted acquisition of and disposal of NPCs. */
  {"[get/take/pick up] %character%", lib_cmd_take_npc},
  {"pick %character% up", lib_cmd_take_npc},

  /* Manipulating selected objects. */
  {"put [all/everything] [in/into/inside {of}] %object%", lib_cmd_put_all_in},
  {"put [all/everything] [[except/but] {for}/apart from] %text%"
   " [in/into/inside {of}] %object%", lib_cmd_put_in_except_multiple},
  {"put %text% [in/into/inside {of}] %object%", lib_cmd_put_in_multiple},
  {"put [all/everything] [on/onto/on top of] %object%", lib_cmd_put_all_on},
  {"put [all/everything] [[except/but] {for}/apart from] %text%"
   " [on/onto/on top of] %object%", lib_cmd_put_on_except_multiple},
  {"put %text% [on/onto/on top of] %object%", lib_cmd_put_on_multiple},
  {"open %object%", lib_cmd_open_object},
  {"close %object%", lib_cmd_close_object},
  {"unlock %object% with %text%", lib_cmd_unlock_object_with},
  {"lock %object% with %text%", lib_cmd_lock_object_with},
  {"unlock %object%", lib_cmd_unlock_object},
  {"lock %object%", lib_cmd_lock_object},
  {"read %object%", lib_cmd_read_object},
  {"read *", lib_cmd_read_other},
  {"give %object% to %character%", lib_cmd_give_object_npc},
  {"sit {down/up} [on/in] %object%", lib_cmd_sit_on_object},
  {"stand {up/down} [on/in] %object%", lib_cmd_stand_on_object},
  {"[lie/lay] on %object%", lib_cmd_lie_on_object},
  {"get {down/up} off %object%", lib_cmd_get_off_object},
  {"get off", lib_cmd_get_off},
  {"sit {down/up} {[on/in] {the} [ground/floor]}", lib_cmd_sit_on_floor},
  {"stand {up/down} {[on/in] {the} [ground/floor]}", lib_cmd_stand_on_floor},
  {"[lie/lay] {down/up} {[on/in] {the} [ground/floor]}", lib_cmd_lie_on_floor},
  {"eat %object%", lib_cmd_eat_object},

  /* Dressing up, and dressing down. */
  {"[[wear/put on/don] [all/everything]/put [all/everything] on]",
   lib_cmd_wear_all},
  {"[wear/put on/don] [all/everything] [[except/but] {for}/apart from] %text%",
   lib_cmd_wear_except_multiple},
  {"[wear/put on/don] %text%", lib_cmd_wear_multiple},
  {"put %text% on", lib_cmd_wear_multiple},
  {"[[remove/take off/doff] [all/everything]/take [all/everything] off/strip]",
   lib_cmd_remove_all},
  {"[remove/take off/doff] [all/everything]"
   " [[except/but] {for}/apart from] %text%",
   lib_cmd_remove_except_multiple},
  {"[remove/take off/doff] %text%", lib_cmd_remove_multiple},
  {"take %text% off", lib_cmd_remove_multiple},

  /* Selected NPC interactions and conversation. */
  {"ask %character% about %text%", lib_cmd_ask_npc_about},
  {"[attack/hit/kick/slap/shoot/stab] %character% with %object%",
   lib_cmd_attack_npc_with},
  {"[attack/shoot] %character%", lib_cmd_attack_npc},

  /* More movement, waiting, and miscellaneous administrative commands. */
  {"[goto/go {to}] %text%", lib_cmd_go_room},
  {"[goto/go {to}] *", lib_cmd_print_room_exits},
  {"[exit/exits/directions/where]", lib_cmd_print_room_exits},
  {"[wait/z] %number%", lib_cmd_wait_number},
  {"[wait/z]", lib_cmd_wait},
  {"save", lib_cmd_save},
  {"[restore/load]", lib_cmd_restore},
  {"restart", lib_cmd_restart},
  {"[again/g]", lib_cmd_again},
  {"[redo /!]%number%", lib_cmd_redo_number},
  {"[redo /!]%text%", lib_cmd_redo_text},
  {"[redo/!]", lib_cmd_redo_last},
  {"[quit/q]", lib_cmd_quit},
  {"turns", lib_cmd_turns},
  {"score", lib_cmd_score},
  {"undo", lib_cmd_undo},
  {"[hist/history] %number%", lib_cmd_history_number},
  {"[hist/history]", lib_cmd_history},
  {"[hint/hints]", lib_cmd_hints},
  {"verbose", lib_cmd_verbose},
  {"brief", lib_cmd_brief},
  {"[notify/notification] %text%", lib_cmd_notify_on_off},
  {"[notify/notification]", lib_cmd_notify},
  {"time", lib_cmd_time},
  {"date", lib_cmd_date},
  {"[help/commands]", lib_cmd_help},
  {"[gpl/license]", lib_cmd_license},
  {"[about/info/information/author]", lib_cmd_information},
  {"[clear/cls/clr]", lib_cmd_clear},
  {"status{line}", lib_cmd_statusline},
  {"version", lib_cmd_version},

  {"[locate/where {is/are}/find] %object%", lib_cmd_locate_object},
  {"[locate/where {is}/find] %character%", lib_cmd_locate_npc},

  {"[count/num]", lib_cmd_count},

  /* Standard response commands; no real action, just output. */
  {"[get/take/pick up] *", lib_cmd_get_what},
  {"open *", lib_cmd_open_what},
  {"close *", lib_cmd_close_other},
  {"give %object% *", lib_cmd_give_object},
  {"give *", lib_cmd_give_what},
  {"lock %text%", lib_cmd_lock_other},
  {"lock", lib_cmd_lock_what},
  {"unlock %text%", lib_cmd_unlock_other},
  {"unlock", lib_cmd_unlock_what},
  {"sit {down/up} [on/in] *", lib_cmd_sit_other},
  {"stand {up/down} [on/in] *", lib_cmd_stand_other},
  {"[lie/lay] {down/up} [on/in] *", lib_cmd_lie_other},
  {"[remove/take off/doff] *", lib_cmd_remove_what},
  {"[drop/put down] *", lib_cmd_drop_what},
  {"[wear/put on/don] *", lib_cmd_wear_what},
  {"[shit/fuck/bastard/cunt/crap/hell/shag/bollocks/bollox/bugger] *",
   lib_cmd_profanity},
  {"[x/examine/look {at}] *", lib_cmd_examine_other},
  {"[locate/where {is/are}/find] *", lib_cmd_locate_other},
  {"[cp/mv/ln/ls] *", lib_cmd_unix_like},
  {"dir *", lib_cmd_dos_like},
  {"ask %character% *", lib_cmd_ask_npc},
  {"ask %object% *", lib_cmd_ask_object},
  {"ask *", lib_cmd_ask_other},
  {"block %object% *", lib_cmd_block_object},
  {"block %text%", lib_cmd_block_other},
  {"block", lib_cmd_block_what},
  {"[break/destroy/smash] %object% *", lib_cmd_break_object},
  {"[break/destroy/smash] %text%", lib_cmd_break_other},
  {"break", lib_cmd_break_what},
  {"destroy", lib_cmd_destroy_what},
  {"smash", lib_cmd_smash_what},
  {"buy %object% *", lib_cmd_buy_object},
  {"buy %text%", lib_cmd_buy_other},
  {"buy", lib_cmd_buy_what},
  {"clean %object% *", lib_cmd_clean_object},
  {"clean %text%", lib_cmd_clean_other},
  {"clean", lib_cmd_clean_what},
  {"climb %object% *", lib_cmd_climb_object},
  {"climb %text%", lib_cmd_climb_other},
  {"climb", lib_cmd_climb_what},
  {"cry *", lib_cmd_cry},
  {"cut %object% *", lib_cmd_cut_object},
  {"cut %text%", lib_cmd_cut_other},
  {"cut", lib_cmd_cut_what},
  {"dance *", lib_cmd_dance},
  {"drink %object% *", lib_cmd_drink_object},
  {"drink %text%", lib_cmd_drink_other},
  {"drink", lib_cmd_drink_what},
  {"eat *", lib_cmd_eat_other},
  {"feed *", lib_cmd_feed},
  {"feel *", lib_cmd_feel},
  {"fight *", lib_cmd_fight},
  {"fix %object% *", lib_cmd_fix_object},
  {"fix %text%", lib_cmd_fix_other},
  {"fix", lib_cmd_fix_what},
  {"fly *", lib_cmd_fly},
  {"hint *", lib_cmd_hint},
  {"hit %character%", lib_cmd_attack_npc},
  {"hit %object% *", lib_cmd_hit_object},
  {"hit %text%", lib_cmd_hit_other},
  {"hit", lib_cmd_hit_what},
  {"hum *", lib_cmd_hum},
  {"jump *", lib_cmd_jump},
  {"kick %character%", lib_cmd_attack_npc},
  {"kick %object% *", lib_cmd_kick_object},
  {"kick %text%", lib_cmd_kick_other},
  {"kick", lib_cmd_kick_what},
  {"kiss %character% *", lib_cmd_kiss_npc},
  {"kiss %object% *", lib_cmd_kiss_object},
  {"kiss *", lib_cmd_kiss_other},
  {"kill *", lib_cmd_kill_other},
  {"lift %object% *", lib_cmd_lift_object},
  {"lift %text%", lib_cmd_lift_other},
  {"lift", lib_cmd_lift_what},
  {"light %object% *", lib_cmd_light_object},
  {"light %text%", lib_cmd_light_other},
  {"light", lib_cmd_light_what},
  {"listen *", lib_cmd_listen},
  {"mend %object% *", lib_cmd_mend_object},
  {"mend %text%", lib_cmd_mend_other},
  {"mend", lib_cmd_mend_what},
  {"move %object% *", lib_cmd_move_object},
  {"move %text%", lib_cmd_move_other},
  {"move", lib_cmd_move_what},
  {"please *", lib_cmd_please},
  {"press %object% *", lib_cmd_press_object},
  {"press %text%", lib_cmd_press_other},
  {"press", lib_cmd_press_what},
  {"pull %object% *", lib_cmd_pull_object},
  {"pull %text%", lib_cmd_pull_other},
  {"pull", lib_cmd_pull_what},
  {"punch *", lib_cmd_punch},
  {"push %object% *", lib_cmd_push_object},
  {"push %text%", lib_cmd_push_other},
  {"push", lib_cmd_push_what},
  {"repair %object% *", lib_cmd_repair_object},
  {"repair %text%", lib_cmd_repair_other},
  {"repair", lib_cmd_repair_what},
  {"rub %object% *", lib_cmd_rub_object},
  {"rub %text%", lib_cmd_rub_other},
  {"rub", lib_cmd_rub_what},
  {"run *", lib_cmd_run},
  {"say *", lib_cmd_say},
  {"sell %object% *", lib_cmd_sell_object},
  {"sell %text%", lib_cmd_sell_other},
  {"sell", lib_cmd_sell_what},
  {"shake %object% *", lib_cmd_shake_object},
  {"shake %text%", lib_cmd_shake_other},
  {"shake", lib_cmd_shake_what},
  {"shout *", lib_cmd_shout},
  {"sing *", lib_cmd_sing},
  {"sleep *", lib_cmd_sleep},
  {"smell %object% *", lib_cmd_smell_object},
  {"smell *", lib_cmd_smell_other},
  {"stop %object% *", lib_cmd_stop_object},
  {"stop %text%", lib_cmd_stop_other},
  {"stop", lib_cmd_stop_what},
  {"suck %object% *", lib_cmd_suck_object},
  {"suck %text%", lib_cmd_suck_other},
  {"suck", lib_cmd_suck_what},
  {"talk *", lib_cmd_talk},
  {"thank *", lib_cmd_thank},
  {"turn %object% *", lib_cmd_turn_object},
  {"turn %text%", lib_cmd_turn_other},
  {"turn", lib_cmd_turn_what},
  {"touch %object% *", lib_cmd_touch_object},
  {"touch %text%", lib_cmd_touch_other},
  {"touch", lib_cmd_touch_what},
  {"unblock %object% *", lib_cmd_unblock_object},
  {"unblock %text%", lib_cmd_unblock_other},
  {"unblock", lib_cmd_unblock_what},
  {"wash %object% *", lib_cmd_wash_object},
  {"wash %text%", lib_cmd_wash_other},
  {"wash", lib_cmd_wash_what},
  {"whistle *", lib_cmd_whistle},
  {"[why/when/what/can/how] *", lib_cmd_interrogation},
  {"xyzzy *", lib_cmd_xyzzy},
  {"campbell", lib_cmd_egotistic},
  {"[yes/no] *", lib_cmd_yes_or_no},
  {"* %object% *", lib_cmd_verb_object},
  {"* %character% *", lib_cmd_verb_npc},

  /* SCARE debugger hook command, placed last just in case... */
  {"{#}debug{ger}", debug_cmd_debugger},

  {NULL, NULL}
};


/*
 * run_priority_commands()
 * run_standard_commands()
 *
 * Compare a user input string against commands recognized by the library,
 * and action any command.  Returns TRUE if the string matched a command
 * that then ran successfully, FALSE otherwise.
 *
 * "Priority" commands are ones that Adrift seems to action no matter what
 * the game tries to override.  For example, a simple game with one "ball"
 * object and a task "* ball *" should, if the task is restricted, override
 * "take ball" such that the ball can never be acquired.  Adrift lets the
 * "take" succeed, though (and more curiously, may respond "I don't
 * understand..." to "drop ball").  This could be an Adrift bug.  Shrug.
 *
 * For now, I can't find any better way to try to handle it than to make
 * object acquisition take precedence over game commands.
 */
static sc_bool
run_priority_commands (sc_gameref_t game, const sc_char *string)
{
  sc_commandsref_t command;

  for (command = PRIORITY_COMMANDS; command->command; command++)
    {
      if (uip_match (command->command, string, game))
        {
          if (command->handler (game))
            return TRUE;
        }
    }

  /* Nothing matched match the string.  Or if it did, its handler failed. */
  return FALSE;
}

static sc_bool
run_standard_commands (sc_gameref_t game, const sc_char *string)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  sc_vartype_t vt_key[2];
  sc_bool eightpointcompass;
  sc_commandsref_t command;

  /* Select the appropriate movement commands. */
  vt_key[0].string = "Globals";
  vt_key[1].string = "EightPointCompass";
  eightpointcompass = prop_get_boolean (bundle, "B<-ss", vt_key);
  command = eightpointcompass ? MOVE_COMMANDS_8 : MOVE_COMMANDS_4;

  /*
   * Search movement commands first, returning TRUE if any matching command
   * handler succeeded.  Then repeat for standard library commands.
   */
  for (; command->command; command++)
    {
      if (uip_match (command->command, string, game))
        {
          if (command->handler (game))
            return TRUE;
        }
    }

  for (command = STANDARD_COMMANDS; command->command; command++)
    {
      if (uip_match (command->command, string, game))
        {
          if (command->handler (game))
            return TRUE;
        }
    }

  /* Nothing matched match the string.  Or if it did, its handler failed. */
  return FALSE;
}


/*
 * run_update_status()
 *
 * Update the game's current room and status line strings.
 */
static void
run_update_status (sc_gameref_t game)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  sc_vartype_t vt_key[2];
  const sc_char *name, *status;
  sc_char *filtered;
  sc_bool statusbox;

  /* Get the current room name, and filter and untag it. */
  name = lib_get_room_name (game, gs_playerroom (game));
  filtered = pf_filter (name, vars, bundle);
  pf_strip_tags (filtered);

  /* Free any existing room name, then save this room name. */
  sc_free (game->current_room_name);
  game->current_room_name = filtered;

  /* See if the game does a status box. */
  vt_key[0].string = "Globals";
  vt_key[1].string = "StatusBox";
  statusbox = prop_get_boolean (bundle, "B<-ss", vt_key);
  if (statusbox)
    {
      /* Get the status line, and filter and untag it. */
      vt_key[1].string = "StatusBoxText";
      status = prop_get_string (bundle, "S<-ss", vt_key);
      filtered = pf_filter (status, vars, bundle);
      pf_strip_tags (filtered);
    }
  else
    /* No status line, so use NULL. */
    filtered = NULL;

  /* Free any existing status line, then save this status text. */
  sc_free (game->status_line);
  game->status_line = filtered;
}


/*
 * run_notify_score_change()
 *
 * Print an indication of any score change, if appropriate.  The change is
 * detected by comparing against the undo game.  Uses if_print_string()
 * directly for printing, rather than the filter, so that it can place its
 * output ahead of buffered printfilter text.
 */
static void
run_notify_score_change (sc_gameref_t game)
{
  const sc_gameref_t undo = game->undo;
  sc_char buffer[32];
  assert (gs_is_game_valid (undo));

  /*
   * Do nothing if no undo available, or if notification is off, or if we've
   * already done this once this turn.
   */
  if (!game->undo_available
      || !game->notify_score_change || game->has_notified)
    return;

  /* Note any change in the score. */
  if (game->score > undo->score)
    {
      if_print_string ("(Your score has increased by ");
      sprintf (buffer, "%ld", game->score - undo->score);
      if_print_string (buffer);
      if_print_string (")\n");
    }
  else if (game->score < undo->score)
    {
      if_print_string ("(Your score has decreased by ");
      sprintf (buffer, "%ld", undo->score - game->score);
      if_print_string (buffer);
      if_print_string (")\n");
    }
  game->has_notified = TRUE;
}


/*
 * run_match_task_common()
 * run_match_task_commands()
 * run_match_task_functions()
 *
 * Helpers for run_game_commands_common().
 *
 * Search task command for a match to the string passed in, returning TRUE
 * if a task command matches, FALSE otherwise.  Ordinary or reverse commands
 * are selected by 'forwards'.
 */
static sc_bool
run_match_task_common (sc_gameref_t game,
                       sc_int task, const sc_char *string, sc_bool forwards,
                       sc_bool is_library, sc_bool is_normal)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  sc_vartype_t vt_key[4];
  sc_int command_count, command;
  sc_bool is_matched;

  /* Get the count of task commands. */
  vt_key[0].string = "Tasks";
  vt_key[1].integer = task;
  vt_key[2].string = forwards ? "Command" : "ReverseCommand";
  command_count = prop_get_child_count (bundle, "I<-sis", vt_key);

  /* Iterate over commands, looking for patterns that match string. */
  is_matched = FALSE;
  for (command = 0; command < command_count; command++)
    {
      const sc_char *pattern;
      sc_int first;

      /* Retrieve the pattern for this command, find its first character. */
      vt_key[3].integer = command;
      pattern = prop_get_string (bundle, "S<-sisi", vt_key);
      first = strspn (pattern, WHITESPACE);

      /* Match using either the parser, or the special function matcher. */
      if (is_normal)
        {
          if (pattern[first] != SPECIAL_PATTERN)
            {
              /*
               * Make a special case of library calls and commands that begin
               * with a wildcard; these we ignore for this match attempt.
               */
              if (is_library && pattern[first] == WILDCARD_PATTERN)
                is_matched = FALSE;
              else
                is_matched = uip_match (pattern, string, game);
            }
        }
      else
        {
          if (pattern[first] == SPECIAL_PATTERN)
            is_matched = run_is_task_function (pattern, game);
        }

      /* Stop searching if we find a match. */
      if (is_matched)
        break;
    }

  /* Return TRUE if we found a pattern match. */
  return is_matched;
}

static sc_bool
run_match_task_commands (sc_gameref_t game,
                         sc_int task, const sc_char *string,
                         sc_bool forwards, sc_bool is_library)
{
  /*
   * Match tasks using the normal pattern matcher, with or without any note
   * about whether the call is from the library.
   */
  return run_match_task_common (game, task, string, forwards, is_library, TRUE);
}

static sc_bool
run_match_task_functions (sc_gameref_t game,
                          sc_int task, const sc_char *string, sc_bool forwards)
{
  /* Match tasks against "task command functions". */
  return run_match_task_common (game, task, string, forwards, FALSE, FALSE);
}


/*
 * run_task_is_unrestricted()
 * run_task_is_loudly_restricted()
 *
 * Helpers for run_game_commands_common().
 *
 * Adapters for uncovering task restriction state.  The first returns TRUE
 * if the task is unrestricted, and can therefore run unimpeded.  The second
 * returns TRUE iff the task is restricted and has a fail message that
 * indicates why it fails; such tasks, if run, produce their failure message
 * and don't change state.
 */
static sc_bool
run_task_is_unrestricted (sc_gameref_t game, sc_int task)
{
  sc_bool restrictions_passed;
  const sc_char *fail_message;

  /*
   * Evaluate task restrictions, and if they fail to parse for some reason,
   * return as if restrictions did not pass.
   */
  if (!restr_eval_task_restrictions (game, task,
                                     &restrictions_passed, &fail_message))
    {
      sc_error ("run_task_is_unrestricted: restrictions error, %ld\n", task);
      return FALSE;
    }

  /* Return TRUE if the task is unrestricted. */
  return restrictions_passed;
}

static sc_bool
run_task_is_loudly_restricted (sc_gameref_t game, sc_int task)
{
  sc_bool restrictions_passed;
  const sc_char *fail_message;

  /*
   * Evaluate task restrictions, and if they fail to parse for some reason,
   * return as if restrictions did not pass.
   */
  if (!restr_eval_task_restrictions (game, task,
                                     &restrictions_passed, &fail_message))
    {
      sc_error ("run_task_is_loudly_restricted:"
                " restrictions error, %ld\n", task);
      return TRUE;
    }

  /* Return TRUE if the task is restricted and indicates why. */
  return !restrictions_passed && (fail_message != NULL);
}


/*
 * run_game_commands_common()
 * run_game_commands_in_parser_context()
 * run_game_commands_in_library_context()
 *
 * The central handler for running, or at least trying to run, game-defined
 * tasks that have commands that match the input string.  Here's the algorithm
 * as currently understood (and it may not be right, so be warned):
 *
 *  for each task executable in the current room
 *    for direction in forwards, backwards
 *      for each command string defined by the task for this direction
 *        match against player input
 *      if any command string matched player input
 *        if task restrictions pass
 *          run the task actions in the current direction
 *          if the task actions produced output
 *            return
 *          is_matched := true
 *          break out of all loops
 *
 *  if not is_matched and we're allowing restrictions to fail tasks
 *    for each task executable in the current room
 *      for direction in forwards, backwards
 *        for each command string defined by the task for this direction
 *          match against player input
 *        if any command string matched player input
 *          if task restrictions fail with an error message
 *            run the task, to persuade it to print this error message
 *            return
 *
 * Part of the fun and games is that run_game_task_commands() is called by the
 * library to try to run "get " and "drop " game commands for standard get/drop
 * handlers and get_all/drop_all handlers.  No pressure, then.
 */
static sc_bool
run_game_commands_common (sc_gameref_t game, const sc_char *string,
                          sc_bool include_restrictions, sc_bool is_library)
{
  sc_bool is_matched = FALSE, is_handled = FALSE;
  sc_bool *is_matching;
  sc_int task_count, task, direction;

  /*
   * Matching is expensive, so it helps to use a cache of results from the
   * first loop in the second.  If we're using the second, that is.
   */
  task_count = gs_task_count (game);
  if (include_restrictions)
    {
      is_matching = sc_malloc (task_count * sizeof (*is_matching));
      memset (is_matching, FALSE, task_count * sizeof (*is_matching));
    }
  else
    is_matching = NULL;

  /*
   * Iterate over every task, ignoring those not runnable.  For each runnable
   * task, try matching task commands, and on matches, check restrictions and
   * if they pass, try running the task.
   */
  for (task = 0; task < task_count; task++)
    {
      if (!task_can_run_task (game, task))
        continue;

      /*
       * Try matching forwards and reverse commands.  If there's a match for
       * unrestricted tasks, run the task, and if it runs (defined as printing
       * some game output), we're done; otherwise, note the command match but
       * keep searching for other possible matches.
       */
      for (direction = 0; direction < 2; direction++)
        {
          const sc_bool is_forwards = !direction;

          if (task_can_run_task_directional (game, task, is_forwards)
              && run_match_task_commands (game, task, string,
                                          is_forwards, is_library))
            {
              if (run_task_is_unrestricted (game, task))
                {
                  if (task_run_task (game, task, is_forwards))
                    is_handled = TRUE;
                  is_matched = TRUE;
                  break;
                }

              if (is_matching)
                is_matching[task] = TRUE;
            }
        }
      if (is_matched)
        break;
    }

  /*
   * If no match, and we've been asked to consider failing restrictions, look
   * through all of the runnable tasks again, this time searching for
   * restricted ones with a fail message.  Use the cache built above to weed
   * out matches that are certain to fail.
   */
  if (!is_handled && !is_matched && include_restrictions)
    {
      for (task = 0; task < task_count; task++)
        {
          if (!is_matching[task] || !task_can_run_task (game, task))
            continue;

          /*
           * Check matches of forwards and reverse commands.  If there's a
           * match for restricted tasks (ones that have and will print a fail
           * message if we try to run them), run the task to get the print of
           * the fail message, and we're done.
           */
          for (direction = 0; direction < 2; direction++)
            {
              const sc_bool is_forwards = !direction;

              if (task_can_run_task_directional (game, task, is_forwards)
                  && run_match_task_commands (game, task, string,
                                              is_forwards, is_library))
                {
                  if (run_task_is_loudly_restricted (game, task))
                    {
                      if (task_run_task (game, task, is_forwards))
                        {
                          is_handled = TRUE;
                          break;
                        }
                    }
                }
            }
          if (is_handled)
            break;
        }
    }

  /* Return TRUE if any game task handled the command in some way. */
  sc_free (is_matching);
  return is_handled;
}

static sc_bool
run_game_commands_in_parser_context (sc_gameref_t game, const sc_char *string,
                                     sc_bool include_restrictions)
{
  /*
   * Try game commands, either with or without restrictions, and all full and
   * complete parse matching (no special case for game commands that begin
   * with a '*' wildcard).
   */
  return run_game_commands_common (game, string, include_restrictions, FALSE);
}

static sc_bool
run_game_commands_in_library_context (sc_gameref_t game, const sc_char *string)
{
  /*
   * Try game commands, including restrictions, and noting that this is a
   * library call so that the parse matcher can exclude game commands that
   * begin with a '*' wildcard.
   */
  return run_game_commands_common (game, string, TRUE, TRUE);
}


/*
 * run_game_functions()
 *
 * Iterate over every task, ignoring those not runnable, searching just for
 * "task command functions".  These seem to happen in addition to any regular
 * command matches, so we try them as a separate action.
 */
static void
run_game_functions (sc_gameref_t game, const sc_char *string)
{
  sc_int task_count, task, direction;

  /* Iterate over every task, ignoring those not runnable. */
  task_count = gs_task_count (game);
  for (task = 0; task < task_count; task++)
    {
      if (!task_can_run_task (game, task))
        continue;

      /*
       * Try matching forwards and reverse commands.  I don't know if it's
       * valid to put a function in a reverse command, but nevertheless...
       */
      for (direction = 0; direction < 2; direction++)
        {
          const sc_bool is_forwards = !direction;

          if (task_can_run_task_directional (game, task, is_forwards)
              && run_match_task_functions (game, task, string, is_forwards))
            {
              if (run_task_is_unrestricted (game, task))
                task_run_task (game, task, is_forwards);
            }
        }
    }
}


/*
 * run_all_commands()
 * run_game_task_commands()
 *
 * Alternative facets of run_commands_common().  The first is used by the
 * main user input handling loop; the latter by the library when looking for
 * game commands that override standard actions.
 */
static sc_bool
run_all_commands (sc_gameref_t game, const sc_char *string)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  sc_bool status;

  /*
   * Adrift command matching is just weird, perhaps broken.  In theory, a
   * game can override system commands with a properly constructed task and
   * set of command matchers.  However, the Runner isn't terribly consistent
   * in when this will work and when not, and some games rely on that in-
   * consistency.  In particular, a game with a "* object" task that has
   * failing restrictions will not be able to override the system's "take
   * object", whereas a game's "take object", under the same circumstances,
   * will.  Yet if the restrictions pass, a game's "* object" overrides the
   * system's "take object" with no apparent difficulty.
   *
   * For example, "The Woods Are Dark" has a "* ball *" task with the
   * restriction "must be holding ball".  Without special casing it, there's
   * no way to get the ball in the first place.
   *
   * Trying to find the right way to do things here, then, has been tricky.
   * Here's the current process:  First, run game commands, ignoring any
   * cases where restrictions fail to let the task run.  Next, try "priority"
   * system commands; ones that move objects to inventory.  These system
   * commands will call back into trying game commands for objects taken or
   * dropped, and in those tries, allow overrides only if the game task is
   * explicit about what it's doing (that is, doesn't start with "*"), and
   * handle restrictions in those tries.  After that, retry all game commands
   * again with restrictions enabled.  And finally, try all other standard
   * library commands.
   *
   * TODO This is the fourth or fifth attempt at getting this to match the
   * Runner, which is surprisingly inconsistent in this area.  What on earth
   * is the real behavior supposed to be?
   */
  status = run_game_commands_in_parser_context (game, string, FALSE);
  if (!status)
    status = run_priority_commands (game, string);
  if (!status)
    status = run_game_commands_in_parser_context (game, string, TRUE);
  if (!status)
    status = run_standard_commands (game, string);

  /*
   * For version 4.0 games, it seems that if any command succeeded, we need
   * need to scan for and run any matching "task command functions", in
   * addition to anything done above.
   */
  if (status && !game->is_admin)
    {
      sc_vartype_t vt_key;
      sc_int version;

      /* Check "task command functions" for version 4.0 only. */
      vt_key.string = "Version";
      version = prop_get_integer (bundle, "I<-s", &vt_key);
      if (version == TAF_VERSION_400)
        run_game_functions (game, string);
    }

  return status;
}

sc_bool
run_game_task_commands (sc_gameref_t game, const sc_char *string)
{
  return run_game_commands_in_library_context (game, string);
}


/*
 * run_player_input()
 *
 * Take a line of player input and buffer it.  Split the line into elements
 * separated by periods.  For the first element, try to match it to either a
 * task or a standard command, and return TRUE if it matched, FALSE otherwise.
 *
 * On subsequent calls, successively work with the next line element until
 * none remain.  In this case, prompt for more player input and continue as
 * above.
 *
 * For the case of "again" or "g", rerun the last successful command element.
 *
 * One extra special special case; if called with a game that is not running,
 * this is a signal to reset all noted line input to initial conditions, and
 * just return.  Sorry about the ugliness.
 */
static sc_bool
run_player_input (sc_gameref_t game)
{
  static sc_char line_buffer[LINE_BUFFER_SIZE];
  static sc_char prior_element[LINE_BUFFER_SIZE];
  static sc_char line_element[LINE_BUFFER_SIZE];

  const sc_filterref_t filter = gs_get_filter (game);
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  const sc_memo_setref_t memento = gs_get_memento (game);
  sc_bool is_rerunning, was_undo_available, status;
  sc_char *filtered, *replaced;
  const sc_char *command;

  /* Special case; reset statics if the game isn't running. */
  if (!game->is_running)
    {
      memset (line_buffer, NUL, sizeof (line_buffer));
      memset (prior_element, NUL, sizeof (prior_element));
      memset (line_element, NUL, sizeof (line_element));
      return TRUE;
    }

  /*
   * Save the settings of the game's do_again and undo_available flags for
   * later checks.
   */
  is_rerunning = game->do_again;
  was_undo_available = game->undo_available;

  /* See if the player asked to rerun a command element. */
  if (game->do_again)
    {
      game->do_again = FALSE;

      /* Check there is a last element to repeat. */
      if (prior_element[0] == NUL)
        {
          pf_buffer_string (filter, "You can hardly repeat that.\n");
          return FALSE;
        }

      /* Make the last element the current input element. */
      strcpy (line_element, prior_element);
    }
  else
    {
      sc_int length, extent;

      /*
       * If there's none buffered, read a new line of player input.  Other-
       * wise, separate output so far with a newline.
       */
      if (line_buffer[0] == NUL)
        if_read_line (line_buffer, sizeof (line_buffer));
      else
        if_print_character ('\n');

      /*
       * Find the length of the next input line element.  Unless the line
       * buffer is empty, we always take the first character, even if it's a
       * separator.  This catches odd input like "." and turns it into a
       * parser complaint, rather than treating it as two empty commands with
       * a separator between them; this makes it close to what Inform does
       * with similar inputs.
       */
      length = (line_buffer[0] == NUL) ? 0 : 1;
      while (line_buffer[length] != NUL
             && strchr (SEPARATORS, line_buffer[length]) == NULL)
        length++;

      /*
       * Make this the current input element, and remove it, the separator,
       * and any trailing whitespace, from the front of the line buffer.
       * Removing whitespace prevents "i. ." looking like "i" and ""; it
       * instead looks like "i" and ".", and results in a parser complaint.
       */
      memcpy (line_element, line_buffer, length);
      line_element[length] = NUL;

      extent = length;
      extent += (line_buffer[length] == NUL
                 || strchr (SEPARATORS, line_buffer[length]) == NULL) ? 0 : 1;
      extent += strspn (line_buffer + extent, WHITESPACE);
      memmove (line_buffer,
               line_buffer + extent, strlen (line_buffer) - extent + 1);
    }

  /* Copy the current game to the temporary undo buffer. */
  gs_copy (game->temporary, game);

  /* Filter the input element for synonyms, then for pronouns. */
  filtered = pf_filter_input (line_element, bundle);
  replaced = uip_replace_pronouns (game, filtered ? filtered : line_element);

  /*
   * If filtering didn't replace synonyms, or no pronouns were replaced, use
   * the original line element.
   */
  command = replaced ? sc_normalize_string (replaced)
            : (filtered ? sc_normalize_string (filtered) : line_element);
  if (command != line_element)
    {
      if_print_tag (SC_TAG_ITALICS, "");
      if_print_character ('[');
      if_print_string (command);
      if_print_character (']');
      if_print_tag (SC_TAG_ENDITALICS, "");
      if_print_character ('\n');
    }

  /* Try the command line element against command matchers. */
  status = run_all_commands (game, command);
  if (!status)
    {
      /* Only complain on non-empty command input line elements. */
      if (!sc_strempty (command))
        {
          sc_vartype_t vt_key[2];
          sc_char *escaped;
          const sc_char *message;

          /* Command line element not understood. */
          escaped = pf_escape (sc_normalize_string (line_element));
          var_set_ref_text (vars, escaped);
          sc_free (escaped);
          vt_key[0].string = "Globals";
          vt_key[1].string = "DontUnderstand";
          message = prop_get_string (bundle, "S<-ss", vt_key);
          pf_buffer_string (filter, message);
          pf_buffer_character (filter, '\n');

          /*
           * On a line element that's not understood, throw out any remaining
           * input line elements.
           */
          line_buffer[0] = NUL;
          sc_free (filtered);
          sc_free (replaced);
          return status;
        }
    }
  else
    {
      /*
       * Unless administrative, back up any valid undo, copy the temporary
       * game into the undo buffer, flag the undo buffer as available, and
       * assign any pronouns used in the command ready for the next iteration.
       */
      if (!game->is_admin)
        {
          if (game->undo_available)
            memo_save_game (memento, game->undo);

          gs_copy (game->undo, game->temporary);
          game->undo_available = TRUE;

          uip_assign_pronouns (game, command);
        }
    }
  sc_free (filtered);
  sc_free (replaced);

  /*
   * If do_again is set, we'll come round with the prior command in line
   * element in a moment, so save nothing for that case.  Otherwise save the
   * command in the history.
   */
  if (!sc_strempty (line_element) && !game->do_again)
    {
      /*
       * If this is a failed redo, redo_sequence will be set but do_again will
       * be clear.  Suppress the save for this special case; otherwise, failed
       * redo commands get into the history, where they can cause problems
       * later on.
       */
      if (game->redo_sequence == 0)
        {
          sc_int timestamp;

          timestamp = var_get_elapsed_seconds (vars);
          memo_save_command (memento, line_element, timestamp, game->turns);
        }
      else
        game->redo_sequence = 0;
    }

  /*
   * Special case restart and restore commands; throw out any remaining input
   * and return straight away.  Do the same if this was an undo, detected by
   * noting that undo is no longer available, where it was on entry.
   */
  if (game->do_restart || game->do_restore
      || (was_undo_available && !game->undo_available))
    {
      line_buffer[0] = NUL;
      return status;
    }

  /* If not empty, consider as saving for "again" calls and in the history. */
  if (!sc_strempty (line_element))
    {
      /*
       * Unless "again", note this line element as prior input.  "Again" shows
       * up as do_again set in the game, where it wasn't when we entered here.
       */
      if (!game->do_again && !is_rerunning)
        strcpy (prior_element, line_element);

      /*
       * If this was a request to run a command from the history, copy that
       * command into the prior_element for the next iteration.  The library
       * should have verified the value in redo_sequence, so fetching the
       * command string should not fail.
       */
      if (game->do_again && game->redo_sequence != 0)
        {
          const sc_char *redo_command;

          redo_command = memo_find_command (memento, game->redo_sequence);
          if (redo_command)
            strcpy (prior_element, redo_command);
          else
            {
              sc_error ("run_player_input: invalid redo sequence request\n");
              game->do_again = FALSE;
            }
          game->redo_sequence = 0;
        }
    }

  return status;
}


/*
 * run_main_loop()
 *
 * Main interpreter loop.
 */
static void
run_main_loop (sc_gameref_t game)
{
  const sc_filterref_t filter = gs_get_filter (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  const sc_prop_setref_t bundle = gs_get_bundle (game);

  /*
   * This may not be the very first time this game has been used, for example
   * saving a game right at the start, or undo-ing back to the start through
   * memos.  Caught by looking to see if the player room is marked as seen.
   */
  if (!gs_room_seen (game, gs_playerroom (game)))
    {
      sc_vartype_t vt_key[2];
      const sc_char *gamename, *startuptext;
      sc_bool disp_first_room, battle_system;

      /* If battle system and no debugger display a warning. */
      vt_key[0].string = "Globals";
      vt_key[1].string = "BattleSystem";
      battle_system = prop_get_boolean (bundle, "B<-ss", vt_key);
      if (battle_system && !debug_get_enabled (game))
        {
          if_print_tag (SC_TAG_CLS, "");
          lib_warn_battle_system ();
        }

      /* Initial clear screen. */
      pf_buffer_tag (filter, SC_TAG_CLS);

      /* Print the game name. */
      vt_key[0].string = "Globals";
      vt_key[1].string = "GameName";
      gamename = prop_get_string (bundle, "S<-ss", vt_key);
      pf_buffer_string (filter, gamename);
      pf_buffer_character (filter, '\n');

      /* Print the game header. */
      vt_key[0].string = "Header";
      vt_key[1].string = "StartupText";
      startuptext = prop_get_string (bundle, "S<-ss", vt_key);
      pf_buffer_string (filter, startuptext);
      pf_buffer_character (filter, '\n');

      /* If flagged, describe the initial room. */
      vt_key[0].string = "Globals";
      vt_key[1].string = "DispFirstRoom";
      disp_first_room = prop_get_boolean (bundle, "B<-ss", vt_key);
      if (disp_first_room)
        lib_cmd_look (game);

      /* Handle any introductory resources. */
      vt_key[0].string = "Globals";
      vt_key[1].string = "IntroRes";
      res_handle_resource (game, "ss", vt_key);

      /* Set initial values for NPC and object states. */
      npc_setup_initial (game);
      obj_setup_initial (game);

      /* Nudge events and NPCs. */
      evt_tick_events (game);
      npc_tick_npcs (game);

      /*
       * Notify the debugger that the game has started.  This is a chance to
       * set watchpoints to catch game startup actions.  Done before setting
       * the initial room visited as this is how the debugger differentiates
       * restarts from restore or undo back to game start.
       */
      debug_game_started (game);

      /* Note the initial room as visited. */
      gs_set_room_seen (game, gs_playerroom (game), TRUE);
    }
  else
    {
      /* Notify the debugger that the game has restarted. */
      debug_game_started (game);
    }

  /*
   * Game loop, exits either when a command parser handler sets the game
   * running flag to FALSE, or by call to run_quit().
   */
  while (game->is_running)
    {
      sc_bool status;

      /*
       * Synchronize any resources in use; do this before flushing so that any
       * appropriate graphics/sound appear before waits or waitkey tag delays
       * invoked by flushing the printfilter.  Also, print any score change
       * notifications.
       */
      res_sync_resources (game);
      run_notify_score_change (game);

      /*
       * Flush printfilter of any accumulated output, and clear any prior
       * notion of administrative commands from input.
       */
      pf_flush (filter, vars, bundle);
      game->is_admin = FALSE;

      /* If waitcounter is zero, accept and try a command. */
      if (game->waitcounter == 0)
        {
          /* Not waiting, so handle a player input line. */
          run_update_status (game);
          status = run_player_input (game);

          /*
           * If waitcounter is now set, decrement it, as this turn counts as
           * one of them.
           */
          if (game->waitcounter > 0)
            game->waitcounter--;
        }
      else
        {
          /*
           * Currently "waiting"; decrement wait turns, then run a turn having
           * taken no input.
           */
          game->waitcounter--;
          status = TRUE;
        }

      /*
       * Do usual turn stuff unless either something stopped the game, or the
       * last command didn't match, or the last command did match but was
       * administrative.
       */
      if (status && !game->is_admin)
        {
          /* Increment turn counter, and clear notifications done flag. */
          game->turns++;
          game->has_notified = FALSE;

          if (game->is_running)
            {
              /* Nudge events and NPCs. */
              evt_tick_events (game);
              npc_tick_npcs (game);

              /* Update NPC and object states. */
              npc_turn_update (game);
              obj_turn_update (game);

              /* Note the current room as visited. */
              gs_set_room_seen (game, gs_playerroom (game), TRUE);

              /* Give the debugger a chance to catch watchpoints. */
              debug_turn_update (game);
            }
        }
    }

  /*
   * Final status update, for games that vary it on completion, then notify
   * the debugger that the game has ended, to let it make a last watchpoint
   * scan and offer the dialog if appropriate.
   */
  run_update_status (game);
  debug_game_ended (game);

  /*
   * Final resource sync, score change notification and printfilter flush
   * on game-instigated loop exit.
   */
  res_sync_resources (game);
  run_notify_score_change (game);
  pf_flush (filter, vars, bundle);

  /*
   * Reset static variables inside run_player_input() with a call to it with
   * is_running false; this is a special case.
   */
  assert (!game->is_running);
  run_player_input (game);
}


/*
 * run_create()
 *
 * Create a game context from a callback.
 */
sc_gameref_t
run_create (sc_read_callbackref_t callback, void *opaque)
{
  sc_tafref_t taf;
  sc_prop_setref_t bundle;
  sc_var_setref_t vars, temporary_vars, undo_vars;
  sc_filterref_t filter;
  sc_gameref_t game, temporary_game, undo_game;
  assert (callback);

  /* Create a new TAF using the callback; return NULL if this fails. */
  taf = taf_create (callback, opaque, TRUE);
  if (!taf)
    return NULL;

  /* Dump out the TAF if requested. */
  if (if_get_trace_flag (SC_DUMP_TAF))
    taf_debug_dump (taf);

  /*
   * Create a properties bundle, and parse the TAF data into it.  If requested,
   * dump out the bundle.
   */
  bundle = prop_create (taf);
  if (!bundle)
    {
      sc_error ("run_create: error parsing game data\n");
      taf_destroy (taf);
      return NULL;
    }
  if (if_get_trace_flag (SC_DUMP_PROPERTIES))
    prop_debug_dump (bundle);

  /* Try to set an interpreter locale from the properties bundle. */
  loc_detect_game_locale (bundle);

  /*
   * Create a set of variables from the bundle, and dump them too if requested.
   */
  vars = var_create (bundle);
  if (if_get_trace_flag (SC_DUMP_VARIABLES))
    var_debug_dump (vars);

  /* Create a printfilter for the game. */
  filter = pf_create ();

  /*
   * Create an initial game state, and register it with variables.  Also,
   * create undo buffers, and initialize them in the same way.
   */
  game = gs_create (vars, bundle, filter);
  var_register_game (vars, game);

  temporary_vars = var_create (bundle);
  temporary_game = gs_create (temporary_vars, bundle, filter);
  var_register_game (temporary_vars, temporary_game);

  undo_vars = var_create (bundle);
  undo_game = gs_create (undo_vars, bundle, filter);
  var_register_game (undo_vars, undo_game);

  /* Add the undo buffers and memos to the game, and return it. */
  game->temporary = temporary_game;
  game->undo = undo_game;
  game->memento = memo_create ();
  return game;
}


/*
 * run_restart_handler()
 *
 * Return a game context to initial states to restart a game.
 */
static void
run_restart_handler (sc_gameref_t game)
{
  const sc_filterref_t filter = gs_get_filter (game);
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  sc_gameref_t new_game;
  sc_var_setref_t new_vars;

  /*
   * Create a fresh set of variables from the current game properties,
   * then a new game using these variables and existing properties and
   * printfilter.
   */
  new_vars = var_create (bundle);
  new_game = gs_create (new_vars, bundle, filter);
  var_register_game (new_vars, new_game);

  /*
   * Overwrite the dynamic parts of the current game with the new one.
   */
  new_game->temporary = game->temporary;
  new_game->undo = game->undo;
  gs_copy (game, new_game);

  /* Destroy invalid game status strings. */
  sc_free (game->current_room_name);
  game->current_room_name = NULL;
  sc_free (game->status_line);
  game->status_line = NULL;

  /*
   * Now it's safely copied, destroy the temporary new game, and its
   * associated variable set.
   */
  gs_destroy (new_game);
  var_destroy (new_vars);

  /* Reset resources handling. */
  res_cancel_resources (game);
}


/*
 * run_restore_handler()
 *
 * Adjust a game context for continuation after restoring a game.
 */
static void
run_restore_handler (sc_gameref_t game)
{
  /* Invalidate the undo buffer. */
  game->undo_available = FALSE;

  /*
   * Resources handling?  Arguably we should re-offer resources active when
   * the game was saved, but I can't see how this can be achieved with Adrift
   * the way it is.  Canceling is too broad, so I'll go here with just
   * stopping sounds (in case looping).
   *
   * TODO Rationalize what happens here.
   */
  game->stop_sound = TRUE;
}


/*
 * run_quit_handler()
 *
 * Tidy up printfilter and input statics on game quit.
 */
static void
run_quit_handler (sc_gameref_t game)
{
  const sc_filterref_t filter = gs_get_filter (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  const sc_prop_setref_t bundle = gs_get_bundle (game);

  /* Flush printfilter and notifications of any dangling output. */
  run_notify_score_change (game);
  pf_flush (filter, vars, bundle);

  /* Cancel any active resources. */
  res_cancel_resources (game);

  /*
   * Make the special call to reset all of the static variables inside
   * run_player_input().
   */
  assert (!game->is_running);
  run_player_input (game);
}


/*
 * run_interpret()
 *
 * Intepret the game in a game context.
 */
void
run_interpret (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  /* Verify the game is not already running, and is runnable. */
  if (game->is_running)
    {
      sc_error ("run_interpret: game is already running\n");
      return;
    }
  if (game->has_completed)
    {
      sc_error ("run_interpret: game has already completed\n");
      return;
    }

  /* Refuse to run a game with no rooms. */
  if (gs_room_count (game) == 0)
    {
      sc_error ("run_interpret: game contains no rooms\n");
      return;
    }

  /* Run the main interpreter loop until no more restarts. */
  game->is_running = TRUE;
  do
    {
      /* Run the game until some form of halt is requested. */
      if (setjmp (game->quitter) == 0)
        run_main_loop (game);

      /*
       * If the halt was a restart or restore, cancel the request, handle
       * restart or restore game adjustments, and set the game running
       * again.
       */
      if (game->do_restart)
        {
          game->do_restart = FALSE;
          run_restart_handler (game);
          game->is_running = TRUE;
        }

      if (game->do_restore)
        {
          game->do_restore = FALSE;
          run_restore_handler (game);
          game->is_running = TRUE;
        }
    }
  while (game->is_running);

  /* Tidy up the printfilter and input statics. */
  run_quit_handler (game);
}


/*
 * run_destroy()
 *
 * Destroy a game context, and free all resources.
 */
void
run_destroy (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  /* Can't destroy the context of a running game. */
  if (game->is_running)
    {
      sc_error ("run_destroy: game is running, stop it first\n");
      return;
    }

  /*
   * Cancel any game state debugger -- this frees its resources.  Only the
   * primary game may have acquired a debugger.
   */
  debug_set_enabled (game, FALSE);
  assert (!debug_get_enabled (game->temporary));
  assert (!debug_get_enabled (game->undo));

  /*
   * Destroy the game state, variables, properties bundle, memos, undo
   * buffers and their variables, and filter.  The bundle and printfilter
   * are shared by the main game, the undo game, and the temporary game, so
   * destroy these only once!  The main game has a memento, but it is not
   * visible to these other two games, neither of which have one.
   */
  assert (gs_get_bundle (game->temporary) == gs_get_bundle (game));
  assert (gs_get_filter (game->temporary) == gs_get_filter (game));
  assert (gs_get_vars (game->temporary) != gs_get_vars (game));
  assert (!gs_get_memento (game->temporary));
  var_destroy (gs_get_vars (game->temporary));
  gs_destroy (game->temporary);

  assert (gs_get_bundle (game->undo) == gs_get_bundle (game));
  assert (gs_get_filter (game->undo) == gs_get_filter (game));
  assert (gs_get_vars (game->undo) != gs_get_vars (game));
  assert (!gs_get_memento (game->undo));
  var_destroy (gs_get_vars (game->undo));
  gs_destroy (game->undo);

  prop_destroy (gs_get_bundle (game));
  pf_destroy (gs_get_filter (game));
  var_destroy (gs_get_vars (game));
  memo_destroy (gs_get_memento (game));

  gs_destroy (game);
}


/*
 * run_quit()
 *
 * Quits a running game.  This function calls a longjump to act as if
 * run_main_loop() returned, and so never returns to its caller.
 */
void
run_quit (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  /* Disallow quitting a non-running game. */
  if (!game->is_running)
    {
      sc_error ("run_quit: game is not running\n");
      return;
    }

  /* Exit the main loop with a longjump. */
  game->is_running = FALSE;
  longjmp (game->quitter, 1);
  sc_fatal ("run_quit: unable to quit cleanly\n");
}


/*
 * run_restart()
 *
 * Restarts either a running or a stopped game.  For running games, this
 * function calls a longjump to act as if run_main_loop() returned, and so
 * never returns to its caller.  For stopped games, it returns.
 */
void
run_restart (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  /*
   * If the game is running, stop it, request a restart, and exit the main
   * loop with a longjump.
   */
  if (game->is_running)
    {
      game->is_running = FALSE;
      game->do_restart = TRUE;
      longjmp (game->quitter, 1);
      sc_fatal ("run_restart: unable to restart cleanly\n");
    }

  /* Restart locally, and ensure that the game remains stopped. */
  run_restart_handler (game);
  game->is_running = FALSE;
}


/*
 * run_save()
 * run_save_prompted()
 *
 * Saves either a running or a stopped game.
 */
void
run_save (sc_gameref_t game, sc_write_callbackref_t callback, void *opaque)
{
  assert (gs_is_game_valid (game));
  assert (callback);

  ser_save_game (game, callback, opaque);
}

sc_bool
run_save_prompted (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  return ser_save_game_prompted (game);
}


/*
 * run_restore_common()
 * run_restore()
 * run_restore_prompted()
 *
 * Restores either a running or a stopped game.  For running games, on
 * successful restore, these functions call a longjump to act as if
 * run_main_loop() returned, and so never return to their caller.  On failed
 * restore, and for stopped games, they will return, with TRUE if successful,
 * FALSE if restore failed.
 */
static sc_bool
run_restore_common (sc_gameref_t game,
                    sc_read_callbackref_t callback, void *opaque)
{
  sc_bool is_running, status;

  /*
   * Save the game running flag, and call the restore appropriate for the
   * caller.  The indication of a call from run_restore_prompted() is a
   * callback of NULL; callback cannot be NULL for run_restore() calls.
   */
  is_running = game->is_running;
  status = callback ? ser_load_game (game, callback, opaque)
                    : ser_load_game_prompted (game);
  if (status)
    {
      /* Loading a game clears is_running -- restore it here. */
      game->is_running = is_running;

      /*
       * If the game is (was) running, set flags so that the interpreter
       * loop cycles, and exit the main loop with a longjump.
       */
      if (game->is_running)
        {
          game->is_running = FALSE;
          game->do_restore = TRUE;
          longjmp (game->quitter, 1);
          sc_fatal ("run_restore_common: unable to restart cleanly\n");
        }
    }

  /* Return TRUE on successful restore of a stopped game, FALSE on error. */
  return status;
}

sc_bool
run_restore (sc_gameref_t game, sc_read_callbackref_t callback, void *opaque)
{
  assert (gs_is_game_valid (game));
  assert (callback);

  return run_restore_common (game, callback, opaque);
}

sc_bool
run_restore_prompted (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  return run_restore_common (game, NULL, NULL);
}


/*
 * run_undo()
 *
 * Undo a turn in either a running or a stopped game.  Returns TRUE on
 * successful undo, FALSE if no undo buffer is available.
 */
sc_bool
run_undo (sc_gameref_t game)
{
  const sc_memo_setref_t memento = gs_get_memento (game);
  sc_bool is_running;
  assert (gs_is_game_valid (game));

  /* Save the game's running state, so we can restore it later. */
  is_running = game->is_running;

  /* If there's an undo buffer available, restore it. */
  if (game->undo_available)
    {
      /* Restore the undo buffer, and then restore running flag. */
      gs_copy (game, game->undo);
      game->undo_available = FALSE;
      game->is_running = is_running;

      /* Location may have changed; update status. */
      run_update_status (game);

      /* Bring resources into line with the revised game. */
      res_sync_resources (game);
      return TRUE;
    }

  /*
   * If there is no undo buffer, try to restore one saved previously in a
   * memo.  Handle as if restoring from a file.
   */
  if (memo_load_game (memento, game))
    {
      /* Loading a game clears is_running -- restore it here. */
      game->is_running = is_running;

      /*
       * If the game is (was) running, set flags so that the interpreter
       * loop cycles, and exit the main loop with a longjump.
       */
      if (game->is_running)
        {
          game->is_running = FALSE;
          game->do_restore = TRUE;
          longjmp (game->quitter, 1);
          sc_fatal ("run_undo: unable to restart cleanly\n");
        }

      /* Game undo on non-running game accomplished with memos. */
      return TRUE;
    }

  /* No undo buffer and no memos available. */
  return FALSE;
}


/*
 * run_is_running()
 *
 * Query the game running state.
 */
sc_bool
run_is_running (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  return game->is_running;
}


/*
 * run_has_completed()
 *
 * Query the game completion state.  Completed games cannot be resumed,
 * since they've run the exit task and thus have nowhere to go.
 */
sc_bool
run_has_completed (sc_gameref_t game)
{
  assert (gs_is_game_valid (game));

  return game->has_completed;
}


/*
 * run_is_undo_available()
 *
 * Query the game turn undo buffer and memo availability.
 */
sc_bool
run_is_undo_available (sc_gameref_t game)
{
  const sc_memo_setref_t memento = gs_get_memento (game);
  assert (gs_is_game_valid (game));

  return game->undo_available || memo_is_load_available (memento);
}


/*
 * run_get_attributes()
 * run_set_attributes()
 *
 * Get and set selected game attributes.
 */
void
run_get_attributes (sc_gameref_t game,
                    const sc_char **game_name, const sc_char **game_author,
                    const sc_char **game_compile_date,
                    sc_int *turns, sc_int *score, sc_int *max_score,
                    const sc_char **current_room_name,
                    const sc_char **status_line, const sc_char **preferred_font,
                    sc_bool *bold_room_names, sc_bool *verbose,
                    sc_bool *notify_score_change)
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  sc_vartype_t vt_key[2];
  assert (gs_is_game_valid (game));

  /* Return the game name, author, and compile date if requested. */
  if (game_name)
    {
      if (!game->title)
        {
          const sc_char *gamename;
          sc_char *filtered;

          vt_key[0].string = "Globals";
          vt_key[1].string = "GameName";
          gamename = prop_get_string (bundle, "S<-ss", vt_key);

          filtered = pf_filter_for_info (gamename, vars);
          pf_strip_tags (filtered);
          game->title = filtered;
        }
      *game_name = game->title;
    }
  if (game_author)
    {
      if (!game->author)
        {
          const sc_char *gameauthor;
          sc_char *filtered;

          vt_key[0].string = "Globals";
          vt_key[1].string = "GameAuthor";
          gameauthor = prop_get_string (bundle, "S<-ss", vt_key);

          filtered = pf_filter_for_info (gameauthor, vars);
          pf_strip_tags (filtered);
          game->author = filtered;
        }
      *game_author = game->author;
    }
  if (game_compile_date)
    {
      vt_key[0].string = "CompileDate";
      *game_compile_date = prop_get_string (bundle, "S<-s", vt_key);
    }

  /* Return the current room name and status line if requested. */
  if (current_room_name)
    *current_room_name = game->current_room_name;
  if (status_line)
    *status_line = game->status_line;

  /* Return any game preferred font, or NULL if none. */
  if (preferred_font)
    {
      vt_key[0].string = "CustomFont";
      if (prop_get_boolean (bundle, "B<-s", vt_key))
        {
          vt_key[0].string = "FontNameSize";
          *preferred_font = prop_get_string (bundle, "S<-s", vt_key);
        }
      else
        *preferred_font = NULL;
    }

  /* Return any other selected game attributes. */
  if (turns)
    *turns = game->turns;
  if (score)
    *score = game->score;
  if (max_score)
    {
      vt_key[0].string = "Globals";
      vt_key[1].string = "MaxScore";
      *max_score = prop_get_integer (bundle, "I<-ss", vt_key);
    }
  if (bold_room_names)
    *bold_room_names = game->bold_room_names;
  if (verbose)
    *verbose = game->verbose;
  if (notify_score_change)
    *notify_score_change = game->notify_score_change;
}

void
run_set_attributes (sc_gameref_t game,
                    sc_bool bold_room_names, sc_bool verbose,
                    sc_bool notify_score_change)
{
  assert (gs_is_game_valid (game));

  /* Set game options. */
  game->bold_room_names = bold_room_names;
  game->verbose = verbose;
  game->notify_score_change = notify_score_change;
}


/*
 * run_hint_iterate()
 *
 * Return the next hint appropriate to the game state, or the first if
 * hint is NULL.  Returns NULL if none, or no more hints.  This function
 * works with pointers to a task state rather than task indexes so that
 * the token passed in and out is a pointer, and readily made opaque to
 * the client as a void*.
 */
sc_hintref_t
run_hint_iterate (sc_gameref_t game, sc_hintref_t hint)
{
  sc_int task;
  assert (gs_is_game_valid (game));

  /*
   * Hint is a pointer to a task state; convert to a task index, adding one
   * to move on to the next task, or start at the first task if null.
   */
  if (!hint)
    task = 0;
  else
    {
      /* Convert into pointer, and range check. */
      task = hint - game->tasks;
      if (task < 0 || task >= gs_task_count (game))
        {
          sc_error ("run_hint_iterate: invalid iteration hint\n");
          return NULL;
        }

      /* Advance beyond current task. */
      task++;
    }

  /* Scan for the next runnable task that offers a hint. */
  for (; task < gs_task_count (game); task++)
    {
      if (task_can_run_task (game, task) && task_has_hints (game, task))
        break;
    }

  /* Return a pointer to the state of the task identified, or NULL. */
  if (task < gs_task_count (game))
    return game->tasks + task;
  else
    return NULL;
}


/*
 * run_get_hint_common()
 * run_get_hint_question()
 * run_get_subtle_hint()
 * run_get_unsubtle_hint()
 *
 * Return the strings for a hint.  Front-ends to task functions.  Each
 * converts the hint "address" to a task index through pointer arithmetic,
 * then filters it and returns a temporary, valid only until the next hint
 * call.
 *
 * Hint strings are NULL if empty (not defined by the game).
 */
static const sc_char *
run_get_hint_common (sc_gameref_t game, sc_hintref_t hint,
                     const sc_char *(*handler) (sc_gameref_t, sc_int))
{
  const sc_prop_setref_t bundle = gs_get_bundle (game);
  const sc_var_setref_t vars = gs_get_vars (game);
  sc_int task;
  const sc_char *string;
  sc_char *filtered;
  assert (gs_is_game_valid (game));

  /* Verify the caller passed in a valid hint. */
  task = hint - game->tasks;
  if (task < 0 || task >= gs_task_count (game))
    {
      sc_error ("run_get_hint_common: invalid iteration hint\n");
      return NULL;
    }
  else if (!task_has_hints (game, task))
    {
      sc_error ("run_get_hint_common: task has no hint\n");
      return NULL;
    }

  /* Get the required game text by calling the given handler function. */
  string = handler (game, task);
  if (sc_strempty (string))
    return NULL;

  /* Filter and strip tags, note in game. */
  filtered = pf_filter (string, vars, bundle);
  pf_strip_tags_for_hints (filtered);
  sc_free (game->hint_text);
  game->hint_text = filtered;

  return filtered;
}

const sc_char *
run_get_hint_question (sc_gameref_t game, sc_hintref_t hint)
{
  return run_get_hint_common (game, hint, task_get_hint_question);
}

const sc_char *
run_get_subtle_hint (sc_gameref_t game, sc_hintref_t hint)
{
  return run_get_hint_common (game, hint, task_get_hint_subtle);
}

const sc_char *
run_get_unsubtle_hint (sc_gameref_t game, sc_hintref_t hint)
{
  return run_get_hint_common (game, hint, task_get_hint_unsubtle);
}
