ecs-observable/examples/tetris/main.ts

// ── Tetris: BT-driven game loop with command-based input ──
//
// Architecture:
//   Behaviour Tree (TaskRunner) — controls game flow:
//     root (sequential, repeat)
//       ├── handleInput (leaf)     — reads queued commands, mutates state
//       ├── gravityTick (leaf)     — auto-drop piece on timer
//       └── render (leaf)          — draws via blessed
//
//   CommandQueue — processes input:
//     Keyboard → spawn command entities → CommandQueue.execute()
//     → handlers mutate game state
//
// Usage:
//   npx tsx examples/tetris/main.ts

import { World } from "../../src/index";
import { TaskRunner, Task, ChildOf } from "../../src/bt/index";
import { CommandQueue } from "../../src/commands/index";

import { Board, Piece, Score, GameOver, Paused, TickTimer } from "./components";

import {
  MoveLeft,
  MoveRight,
  Rotate,
  SoftDrop,
  HardDrop,
  TogglePause,
  Restart,
} from "./commands";

import {
  randomPiece,
  collides,
  lockPiece,
  clearLines,
  scoreForLines,
  tryRotate,
  BOARD_W,
} from "./game";

import { createUI, render } from "./render";
import { startInput, type Key } from "./input";

// ── Setup ────────────────────────────────────────────
const world = new World();

// Create the singleton game entity
const game = world.spawn();
world.add(game, Board);
world.add(game, Score);
world.add(game, TickTimer);

// Create blessed UI
const ui = createUI();

// ── Command handlers ─────────────────────────────────
const commands = new CommandQueue(world);

function spawnPiece(): void {
  const p = randomPiece();
  world.add(game, Piece, {
    shape: p.shape,
    color: p.color,
    x: Math.floor((BOARD_W - p.shape[0].length) / 2),
    y: 0,
  });
}

function hasActivePiece(): boolean {
  return world.has(game, Piece);
}

// Move left
commands.handle(MoveLeft, () => {
  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
    return;
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);
  if (!collides(board.grid, piece.shape, piece.x - 1, piece.y)) {
    piece.x--;
  }
});

// Move right
commands.handle(MoveRight, () => {
  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
    return;
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);
  if (!collides(board.grid, piece.shape, piece.x + 1, piece.y)) {
    piece.x++;
  }
});

// Rotate
commands.handle(Rotate, () => {
  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
    return;
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);
  const result = tryRotate(board.grid, piece.shape, piece.x, piece.y);
  if (result) {
    piece.shape = result.shape;
    piece.x = result.x;
  }
});

// Soft drop
commands.handle(SoftDrop, () => {
  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
    return;
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);
  if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
    piece.y++;
  }
});

// Hard drop
commands.handle(HardDrop, () => {
  if (!hasActivePiece() || world.has(game, GameOver) || world.has(game, Paused))
    return;
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);
  while (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
    piece.y++;
  }
  lockAndSpawn();
});

// Toggle pause
commands.handle(TogglePause, () => {
  if (world.has(game, GameOver)) return;
  if (world.has(game, Paused)) {
    world.remove(game, Paused);
  } else {
    world.add(game, Paused);
  }
});

// Restart
commands.handle(Restart, () => {
  if (!world.has(game, GameOver)) return;
  const board = world.get(game, Board);
  for (let r = 0; r < board.grid.length; r++) {
    board.grid[r].fill(0);
  }
  world.set(game, Score, { points: 0, lines: 0, level: 1 });
  world.set(game, TickTimer, { accumulator: 0, interval: 800 });
  world.remove(game, GameOver);
  if (world.has(game, Piece)) world.remove(game, Piece);
  spawnPiece();
});

// ── Lock piece & spawn next ──────────────────────────
function lockAndSpawn(): void {
  const piece = world.get(game, Piece);
  const board = world.get(game, Board);

  lockPiece(board.grid, piece.shape, piece.color, piece.x, piece.y);
  world.remove(game, Piece);

  const cleared = clearLines(board.grid);
  if (cleared > 0) {
    const score = world.get(game, Score);
    score.lines += cleared;
    score.points += scoreForLines(cleared, score.level);
    score.level = Math.floor(score.lines / 10) + 1;
    const timer = world.get(game, TickTimer);
    timer.interval = Math.max(100, 800 - (score.level - 1) * 70);
  }

  spawnPiece();

  const newPiece = world.get(game, Piece);
  if (collides(board.grid, newPiece.shape, newPiece.x, newPiece.y)) {
    world.remove(game, Piece);
    world.add(game, GameOver);
  }
}

// ── Behaviour Tree ───────────────────────────────────
const runner = new TaskRunner(world);

// Build the BT structure:
//   root (repeat)
//     ├── handleInput (leaf)
//     ├── gravityTick (leaf)
//     └── render (leaf)

const root = world.spawn();
world.add(root, Task, { kind: "repeat" });

const handleInputTask = world.spawn();
world.add(handleInputTask, Task, { kind: "leaf" });
world.relate(handleInputTask, ChildOf, root);

const gravityTask = world.spawn();
world.add(gravityTask, Task, { kind: "leaf" });
world.relate(gravityTask, ChildOf, root);

const renderTask = world.spawn();
world.add(renderTask, Task, { kind: "leaf" });
world.relate(renderTask, ChildOf, root);

// ── Leaf handlers ────────────────────────────────────
runner.onLeaf = (_w, entity) => {
  if (entity === handleInputTask) {
    commands.execute();
    runner.succeed(entity);
  } else if (entity === gravityTask) {
    if (world.has(game, GameOver) || world.has(game, Paused)) {
      runner.succeed(entity);
      return;
    }
    const timer = world.get(game, TickTimer);
    timer.accumulator += 16;
    if (timer.accumulator >= timer.interval) {
      timer.accumulator -= timer.interval;
      if (hasActivePiece()) {
        const piece = world.get(game, Piece);
        const board = world.get(game, Board);
        if (!collides(board.grid, piece.shape, piece.x, piece.y + 1)) {
          piece.y++;
        } else {
          lockAndSpawn();
        }
      }
    }
    runner.succeed(entity);
  } else if (entity === renderTask) {
    render(world, game, ui);
    runner.succeed(entity);
  }
};

// ── Input → Command mapping ──────────────────────────
const keyToCommand: Partial<Record<Key, typeof MoveLeft>> = {
  left: MoveLeft,
  right: MoveRight,
  up: Rotate,
  down: SoftDrop,
  space: HardDrop,
  p: TogglePause,
  r: Restart,
};

startInput(ui.screen, (key) => {
  const cmd = keyToCommand[key];
  if (cmd) {
    const cmdEntity = world.spawn();
    world.add(cmdEntity, cmd);
  }
});

// ── Game loop ────────────────────────────────────────
runner.schedule(root);

const TICK_MS = 16;
const interval = setInterval(() => {
  runner.tick();
}, TICK_MS);

// Cleanup on exit
process.on("SIGINT", () => {
  clearInterval(interval);
  ui.screen.destroy();
  process.exit(0);
});