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# Pyxel is an external dependency under its own MIT license.

"""一歩貸してください・教材 5/5。原作1部屋目の仕組みを段階化。
実行: python 05_undo.py
コード・図形: MIT。原作者と条件は隣の LICENSE を参照。
"""
from dataclasses import dataclass

ROWS = ("#######", "#P..G.#", "#.....#", "#E.S..#", "#######")
DIRECTIONS = {"U": (0, -1), "D": (0, 1), "L": (-1, 0), "R": (1, 0), "W": (0, 0)}
TILE = 24


def find(char):
    return next((x, y) for y, row in enumerate(ROWS) for x, cell in enumerate(row) if cell == char)


def move(position, command):
    dx, dy = DIRECTIONS[command]
    x, y = position[0] + dx, position[1] + dy
    if 0 <= y < len(ROWS) and 0 <= x < len(ROWS[y]) and ROWS[y][x] != "#":
        return x, y
    return position


@dataclass(frozen=True)
class State:
    player: tuple = find("P")
    echo: tuple = find("E")
    memory: str = "W"
    status: str = "play"
    turns: int = 0


def step(state, command):
    if command not in DIRECTIONS:
        return state
    if state.status != "play":
        return state
    player = move(state.player, command)
    # 新しい command を保存する前に、一手前の memory を使う。
    echo = move(state.echo, state.memory)
    if player == find("G") and echo != find("S"):
        player = state.player
    # 自分が先に動くので、影がこれから退く場所にも入れない。
    collision = player == state.echo or player == echo
    status = "hit" if collision else "play"
    if not collision and player == find("G") and echo == find("S"):
        status = "win"
    return State(player=player, echo=echo, memory=command, status=status, turns=state.turns + 1)


class Session:
    def __init__(self):
        self.state = State()
        self.history = []

    def act(self, command):
        next_state = step(self.state, command)
        if next_state != self.state:
            self.history.append(self.state)
            self.state = next_state

    def undo(self):
        if self.history:
            self.state = self.history.pop()

    def restart(self):
        self.state = State()
        self.history.clear()


def main(headless=False, screenshot=None):
    import pyxel

    session = Session()
    keys = ((pyxel.KEY_UP, "U"), (pyxel.KEY_DOWN, "D"),
            (pyxel.KEY_LEFT, "L"), (pyxel.KEY_RIGHT, "R"), (pyxel.KEY_SPACE, "W"))

    def update():
        if headless and pyxel.frame_count >= 12:
            if screenshot:
                pyxel.screenshot(screenshot, scale=2)
            pyxel.quit()
            return
        if pyxel.btnp(pyxel.KEY_R):
            session.restart()
            return
        if pyxel.btnp(pyxel.KEY_Z):
            session.undo()
            return
        for key, command in keys:
            if pyxel.btnp(key):
                session.act(command)
                break  # 同じフレームに複数の一手を進めない。

    def draw():
        current = session.state
        pyxel.cls(1)
        pyxel.text(10, 8, "ECHO STEPS / STEP 5", 10)
        pyxel.text(10, 20, f"TURNS {current.turns}", 7)
        for y, row in enumerate(ROWS):
            for x, char in enumerate(row):
                px, py = 10 + x * TILE, 40 + y * TILE
                pyxel.rect(px, py, TILE - 1, TILE - 1, 5 if char == "#" else 0)
                if char == "S":
                    color = 10 if current.echo == (x, y) else 4
                    pyxel.rect(px + 5, py + 5, 14, 14, color)
                    pyxel.text(px + 10, py + 9, "S", 0)
                if char == "G":
                    color = 11 if current.echo == find("S") else 4
                    pyxel.rectb(px + 3, py + 3, 18, 19, color)
                    pyxel.text(px + 10, py + 9, "G", color)
        ex, ey = current.echo
        pyxel.circ(22 + ex * TILE, 52 + ey * TILE, 7, 14)
        pyxel.text(10, 175, f"NEXT ECHO: {current.memory}", 14)
        x, y = current.player
        pyxel.rect(16 + x * TILE, 46 + y * TILE, 12, 12, 12)
        pyxel.text(10, 190, "ARROWS: STEP  SPACE: WAIT", 6)
        pyxel.text(10, 202, "Z: UNDO  R: RESET  ESC: QUIT", 6)
        if current.status == "hit":
            pyxel.text(10, 164, "HIT!  R: RESET", 8)
        elif current.status == "win":
            pyxel.text(10, 164, "CLEAR!  R: PLAY AGAIN", 11)

    pyxel.init(188, 218, title="Echo Steps - Stage 5", fps=30, headless=headless)
    pyxel.run(update, draw)


if __name__ == "__main__":
    import argparse

    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--headless-smoke", action="store_true", help="12 frames then quit; not a playtest")
    parser.add_argument("--screenshot", help="PNG path used with --headless-smoke")
    args = parser.parse_args()
    main(headless=args.headless_smoke, screenshot=args.screenshot)