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Dojo

1. Actions

This chapter will address implementing actions.cairo, which spawns the game & squares containing pieces and also allow players to move pieces.

What is actions contract?

To play chess, you need, to start game, spawn the pieces, and move around the board. The actions contract has two dominant functions spawn function which spawns the game entity, places each piece in its proper position on the board and returns the game_id, and the move funtion which allows pieces to be moved around the board.

Requirements

  1. Write an interface for the actions contract on top of your code. In this case, move and spawn
    use starknet::ContractAddress;
    use chess::models::piece::Vec2;
    #[starknet::interface]
    trait IActions<ContractState> {
        fn move(
            self: @ContractState,
            curr_position: Vec2,
            next_position: Vec2,
            caller: ContractAddress, //player
            game_id: u32
        );
        fn spawn(
            self: @ContractState, white_address: ContractAddress, black_address: ContractAddress
        ) -> u32;
    }
  1. Bring in required imports into the contract like this :
    #[dojo::contract]
    mod actions {
        use chess::models::player::{Player, Color, PlayerTrait};
        use chess::models::piece::{Piece, PieceType, PieceTrait};
        use chess::models::game::{Game, GameTurn, GameTurnTrait};
        use super::{ContractAddress, IActions, Vec2};
    }

Should be noted that actions is the contract name.

  1. Write a spawn function that accepts the white address, and black address as input and set necessary states using set!(...). Implement the player entity from player model. Implement the game entity, comprised of the Game model and GameTurn model we created in the game.cairo and implement the piece entities from a1 to h8 containing the correct PieceType in the spawn fn.
    #[abi(embed_v0)]
    impl IActionsImpl of IActions<ContractState> {
        fn spawn(
            self: @ContractState, white_address: ContractAddress, black_address: ContractAddress
        ) -> u32 {
            let world = self.world_dispatcher.read();
            let game_id = world.uuid();
 
            // set Players
            set!(
                world,
                (
                    Player { game_id, address: black_address, color: Color::Black },
                    Player { game_id, address: white_address, color: Color::White },
                )
            );
 
            // set Game and GameTurn
            set!(
                world,
                (
                    Game {
                        game_id, winner: Color::None, white: white_address, black: black_address
                    },
                    GameTurn { game_id, player_color: Color::White },
                )
            );
 
            // set Pieces
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::White,
                    position: Vec2 { x: 0, y: 0 },
                    piece_type: PieceType::Rook
                })
            );
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::White,
                    position: Vec2 { x: 0, y: 1 },
                    piece_type: PieceType::Pawn
                })
            );
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::Black,
                    position: Vec2 { x: 1, y: 6 },
                    piece_type: PieceType::Pawn
                })
            );
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::White,
                    position: Vec2 { x: 1, y: 0 },
                    piece_type: PieceType::Knight
                })
            );
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::None,
                    position: Vec2 { x: 0, y: 2 },
                    piece_type: PieceType::None
                })
            );
 
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::None,
                    position: Vec2 { x: 0, y: 3 },
                    piece_type: PieceType::None
                })
            );
            set!(
                world,
                (Piece {
                    game_id,
                    color: Color::None,
                    position: Vec2 { x: 1, y: 4 },
                    piece_type: PieceType::None
                })
            );
 
            //the rest of the positions on the board goes here....
 
            game_id
        }
        fn move(
            self: @ContractState,
            curr_position: Vec2,
            next_position: Vec2,
            caller: ContractAddress, //player
            game_id: u32
        )  {
            // Upcoming code
        }
    }