Add replacement method to requirements

src/requirements.cpp

@@ -823,6 +823,42 @@ void requirement_data::blacklist_item( const std::string &id )
     blacklisted |= apply_blacklist( components, id );
 }
 
+template <typename T>
+static void apply_replacement( std::vector<std::vector<T>> &vec, const std::string &id,
+                               const std::string &replacement )
+{
+    // If the target and replacement are both present, remove the target.
+    // If only the target is present, replace it.
+    for( auto &opts : vec ) {
+        typename std::vector<T>::iterator target = opts.end();
+        typename std::vector<T>::iterator replacement_target = opts.end();
+        for( typename std::vector<T>::iterator iter = opts.begin(); iter != opts.end(); ++iter ) {
+            if( iter->type == id ) {
+                target = iter;
+            } else if( iter->type == replacement ) {
+                replacement_target = iter;
+            }
+        }
+        // No target to replace, do nothing.
+        if( target == opts.end() ) {
+            continue;
+        }
+        // Target but no replacement, replace.
+        if( replacement_target == opts.end() ) {
+            target->type = replacement;
+            continue;
+        }
+        // Both target and replacement, remove the target entry and leave the existing replacement.
+        opts.erase( target );
+    }
+}
+
+void requirement_data::replace_item( const itype_id &id, const itype_id &replacement )
+{
+    apply_replacement( tools, id, replacement );
+    apply_replacement( components, id, replacement );
+}
+
 const requirement_data::alter_tool_comp_vector &requirement_data::get_tools() const
 {
     return tools;

src/requirements.h

@@ -208,7 +208,6 @@ struct requirement_data {
             return tools.empty() && components.empty() && qualities.empty();
         }
 
-        /** check if removal of items via @ref blacklist_item left no alternatives in group */
         bool is_blacklisted() const {
             return blacklisted;
         }
@@ -270,6 +269,10 @@ struct requirement_data {
          * will be marked as @ref blacklisted
          */
         void blacklist_item( const itype_id &id );
+        /**
+         * Replace tools or components of the given type.
+         */
+        void replace_item( const itype_id &id, const itype_id &replacement );
 
         const alter_tool_comp_vector &get_tools() const;
         const alter_quali_req_vector &get_qualities() const;