engine

Introduction

The game engine for the card game Hearthstone written in C++17. Used in AAIA'17 Data Mining Challenge: Helping AI to Play Hearthstone to generate training/validation datasets.

Features

Header-only implementation

• No dependency
• (Free/Automatically) whole program optimization

Modern C++

Use template programming to move workload to compile-time as much as possible. With C++14/17 features like std::variant, SFINAE and much more, we can write structured code with zero overhead.

Components

1. Game state maintains the underlying game state.
2. Flow control makes sure the game follows the rule.
3. Cards implements all the cards.
4. Decks collects all types of deck.

Usage

Action parameter callback

According to Hearthstone's rule, a game is divided into several turns, and a player can perform several main actions at each turn. There are only four main actions:

1. Play a card
2. Attack
3. Use hero power
4. End turn

In a main action, it is sometimes needed to provide further action parameters like choose a spell target or choose where to put the minion. To provide these parameters, we need to implement a callback first.

#include "FlowControl/IActionParameterGetter.h"

class MyActionParameterGetter : public FlowControl::IActionParameterGetter
{
  // implementation
};

Randomness callback

Hearthstone is a game with a lot of randomness. All the random outcomes will be fetched from the provided callback. Once you fix the random outcomes from your random callback, this becomes a deterministic game.

#include "state/IRandomGenerator.h"

class MyRandomGenerator : public state::IRandomGenerator
{
  // implementation
};

Final step!

#include "FlowControl/FlowController.h"

void test()
{
  state::State game_state;
  MyActionParameterGetter action_cb;
  MyRandomGenerator random_cb;
  FlowControl::FlowContext context(random_cb, action_cb);
  Prepare(); // Prepare hero/hero-power/deck/hand...
  FlowControl::FlowController controller(game_state, context);
  controller.PlayCard(0); // Play the first card
}

Refer to e2e test for a full examples.

Build

This library uses some language features only available in the latest C++17, so compiler newer than gcc 7.0+ or Visual Studio 2017 Preview 2.1+ is needed. Please refer to the build folder for working examples.

Troubleshooting

Option /bigobj

Enable the /bigobj option for Visual Studio.

Too slow (re)compilation

This is a header-only implementation. If the compiler is not smart enough, all the headers have to be re-compiled each time. A programmer can always choose to move the implementation detail to another compilation unit.

Refer to the card-dispatcher compilation unit for an example to separate out implementation details for client cards and flow controller.