npctalk: add true/false text responses in JSON

Add a new response option for response text, "truefalsetext", which
takes a condition and displays a "true" text if the condition is true
and false otherwise.  The response trial, effects, etc. are the same
for both texts.

doc/NPCs.md

@@ -378,6 +378,20 @@ The player will always have the option to return to a previous topic or end the
 will otherwise have the option to give a $500, $50, or $5 bribe if they have the funds.  If they
 don't have at least $50, they will also have the option to provide some other bribe.
 
+### truefalsetext
+The player will have one response text if a condition is true, and another if it is false, but the same trial for either line.  `condition`, `true`, and `false` are all mandatory.
+
+```C++
+{
+    "truefalsetext": {
+        "condition": { "u_has_cash": 800 },
+        "true": "I may have the money, I'm not giving you any.",
+        "false": "I don't have that money."
+    },
+    "topic": "TALK_WONT_PAY"
+}
+```
+
 ### text
 Will be shown to the user, no further meaning.
 

src/dialogue.h

@@ -163,6 +163,13 @@ struct talk_response {
      * displayed.
      */
     std::string text;
+    /*
+     * Optional responses from a true/false test that defaults to true.
+     */
+    std::string truetext;
+    std::string falsetext;
+    std::function<bool( const dialogue & )> truefalse_condition;
+
     talk_trial trial;
     /**
      * The following values are forwarded to the chatbin of the NPC (see @ref npc_chatbin).
@@ -297,6 +304,9 @@ struct dynamic_line_t {
         }
 };
 
+// the truly awful declaration for the conditional_t loading helper_function
+void read_dialogue_condition( JsonObject &jo, std::function<bool( const dialogue & )> &condition,
+                              bool default_val );
 /**
  * A condition for a response spoken by the player.
  * This struct only adds the constructors which will load the data from json

src/npctalk.cpp

@@ -750,7 +750,10 @@ talk_response &dialogue::add_response( const std::string &text, const std::strin
                                        const bool first )
 {
     talk_response result = talk_response();
-    result.text = text;
+    result.truetext = text;
+    result.truefalse_condition = []( const dialogue & ) {
+       return true;
+    };
     result.success.next_topic = talk_topic( r );
     if( first ) {
         responses.insert( responses.begin(), result );
@@ -1664,6 +1667,7 @@ void dialogue::add_topic( const talk_topic &topic )
 talk_data talk_response::create_option_line( const dialogue &d, const char letter )
 {
     std::string ftext;
+    text = truefalse_condition( d ) ? truetext : falsetext;
     if( trial != TALK_TRIAL_NONE ) { // dialogue w/ a % chance to work
         ftext = string_format( pgettext( "talk option", "%1$c: [%2$s %3$d%%] %4$s" ),
                                letter,                         // option letter
@@ -1808,7 +1812,7 @@ talk_topic dialogue::opt( dialogue_window &d_win, const talk_topic &topic )
 
     talk_response chosen = responses[ch];
     std::string response_printed = string_format( pgettext( "you say something", "You: %s" ),
-                                   chosen.text );
+                                   response_lines[ch].second.substr( 3 ) );
     d_win.add_to_history( response_printed );
 
     if( chosen.mission_selected != nullptr ) {
@@ -2289,7 +2293,17 @@ talk_response::talk_response( JsonObject jo )
     if( jo.has_member( "failure" ) ) {
         failure = talk_effect_t( jo.get_object( "failure" ) );
     }
-    text = _( jo.get_string( "text" ) );
+    if( jo.has_member( "truefalsetext" ) ) {
+        JsonObject truefalse_jo = jo.get_object( "truefalsetext" );
+        read_dialogue_condition( truefalse_jo, truefalse_condition, true );
+        truetext = _( truefalse_jo.get_string( "true" ) );
+        falsetext = _( truefalse_jo.get_string( "false" ) );
+    } else {
+        truetext = _( jo.get_string( "text" ) );
+        truefalse_condition = []( const dialogue & ) {
+           return true;
+        };
+    }
     // TODO: mission_selected
     // TODO: skill
     // TODO: style
@@ -2301,6 +2315,33 @@ json_talk_response::json_talk_response( JsonObject jo )
     load_condition( jo );
 }
 
+void read_dialogue_condition( JsonObject &jo, std::function<bool( const dialogue & )> &condition,
+                              bool default_val )
+{
+    const auto null_function = [default_val]( const dialogue & ) {
+        return default_val;
+    };
+
+    static const std::string member_name( "condition" );
+    if( !jo.has_member( member_name ) ) {
+         condition = null_function;
+    } else if( jo.has_string( member_name ) ) {
+        const std::string type = jo.get_string( member_name );
+        conditional_t sub_condition( type );
+        condition = [sub_condition]( const dialogue & d ) {
+            return sub_condition( d );
+        };
+    } else if( jo.has_object( member_name ) ) {
+        const JsonObject con_obj = jo.get_object( member_name );
+        conditional_t sub_condition( con_obj );
+        condition = [sub_condition]( const dialogue & d ) {
+            return sub_condition( d );
+        };
+    } else {
+        jo.throw_error( "invalid condition syntax", member_name );
+    }
+}
+
 conditional_t::conditional_t( JsonObject jo )
 {
     const auto parse_array = []( JsonObject jo, const std::string &type ) {
@@ -2628,25 +2669,7 @@ void json_talk_response::load_condition( JsonObject &jo )
 {
     is_switch = jo.get_bool( "switch", false );
     is_default = jo.get_bool( "default", false );
-    static const std::string member_name( "condition" );
-    if( !jo.has_member( member_name ) ) {
-        // Leave condition unset, defaults to true.
-        return;
-    } else if( jo.has_string( member_name ) ) {
-        const std::string type = jo.get_string( member_name );
-        conditional_t sub_condition( type );
-        condition = [sub_condition]( const dialogue & d ) {
-            return sub_condition( d );
-        };
-    } else if( jo.has_object( member_name ) ) {
-        const JsonObject con_obj = jo.get_object( member_name );
-        conditional_t sub_condition( con_obj );
-        condition = [sub_condition]( const dialogue & d ) {
-            return sub_condition( d );
-        };
-    } else {
-        jo.throw_error( "invalid condition syntax", member_name );
-    }
+    read_dialogue_condition( jo, condition, true );
 }
 
 bool json_talk_response::test_condition( const dialogue &d ) const