support reverting multiple turns at once

cli_interface.cpp

@@ -140,9 +140,13 @@ namespace Hanabi {
     }
 
     void cli(const std::shared_ptr<HanabiStateIF>& game) {
+        // Set up GNU readline
         rl_attempted_completion_function = cli_command_completion;
         using_history();
+
+        // Tracks the depth of the replay the user explores. We have to ensure that we don't revert too much.
         unsigned depth = 0;
+
         while (true) {
             const std::string prompt = read_line_memory_safe("> ");
             add_history(prompt.c_str());
@@ -153,7 +157,7 @@ namespace Hanabi {
                 std::cout << "play <card>:     play specified card." << std::endl;
                 std::cout << "discard:         discard trash from hand." << std::endl;
                 std::cout << "opt:             take optimal action. In case of ties, prefers plays and discards in that order." << std::endl;
-                std::cout << "revert:      revert last turn of game." << std::endl;
+                std::cout << "revert <turns>:  revert specified number of turns (default 1)." << std::endl;
                 std::cout << "actions:         display list of reasonable actions to take and their winning chances." << std::endl;
                 std::cout << "evaluate:        evaluate current game state recursively. Potentially runtime-expensive." << std::endl;
                 std::cout << "id:              display id of state. Has no inherent meaning, useful for debugging." << std::endl;
@@ -203,9 +207,24 @@ namespace Hanabi {
                     std::cout << "Cannot revert more than base state." << std::endl;
                     continue;
                 }
-                std::cout << "Reverting one turn" << std::endl;
+                unsigned turns_to_revert = 1;
+                if(prompt.length() > 7) {
+                    try {
+                        turns_to_revert = std::stoi(prompt.substr(7));
+                    } catch(const std::invalid_argument&) {
+                        std::cout << "Could not parse number of turns to revert." << std::endl;
+                        continue;
+                    }
+                }
+                if (turns_to_revert > depth) {
+                    turns_to_revert = depth;
+                    std::cout << "Only revererting " << depth << " turns, since this is already the base state." << std::endl;
+                }
+                std::cout << "Reverting " << turns_to_revert << " turn(s)." << std::endl;
+                while(turns_to_revert--) {
                     game->revert();
                     depth--;
+                }
                 continue;
             }
 
@@ -323,6 +342,7 @@ namespace Hanabi {
                     default:
                         break;
                 }
+                depth++;
                 continue;
             }