"""Pit two exported policies against each other and record the result.

Uses the same in-Godot inference path that ships in the game
(AIShipController + PolicyNetwork), so eval strength = in-game strength.
Episodes are golden-goal: first goal wins, timeout is a draw. Half the
episodes are played with sides swapped for fairness. Results are appended to
eval_history.json — the bot-progress-over-time record.

Example:
    .venv/bin/python evaluate.py ../Game/bots/rookie.json checkpoints/run01/candidate.json --episodes 40
"""

import argparse
import datetime
import json
import os
import pathlib
import subprocess

TRAINING_DIR = pathlib.Path(__file__).resolve().parent
GAME_DIR = TRAINING_DIR.parent / "Game"
TRAINING_SCENE = "res://scenes/training.tscn"
DEFAULT_GODOT_MACOS = "/Applications/Godot.app/Contents/MacOS/Godot"


def run_half(godot_bin: str, model_a: str, model_b: str, episodes: int, speedup: int, seed: int) -> dict:
    cmd = [
        godot_bin,
        "--path",
        str(GAME_DIR),
        TRAINING_SCENE,
        "--headless",
        "--disable-render-loop",
        f"--eval_model_a={model_a}",
        f"--eval_model_b={model_b}",
        f"--eval_episodes={episodes}",
        f"--speedup={speedup}",
        f"--env_seed={seed}",
    ]
    timeout = episodes * 30 / speedup * 3 + 120  # worst case: all draws, plus margin
    result = subprocess.run(cmd, capture_output=True, text=True, timeout=timeout)
    for line in result.stdout.splitlines():
        if line.startswith("EVAL_RESULT "):
            return json.loads(line[len("EVAL_RESULT "):])
    raise RuntimeError(f"No EVAL_RESULT in godot output:\n{result.stdout[-2000:]}\n{result.stderr[-2000:]}")


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("model_a", help="Path to first exported policy .json")
    parser.add_argument("model_b", help="Path to second exported policy .json")
    parser.add_argument("--episodes", type=int, default=20, help="Total episodes (split across side swap)")
    parser.add_argument(
        "--godot_bin",
        default=os.environ.get("GODOT_BIN", DEFAULT_GODOT_MACOS),
        help="Path to the Godot binary (or set GODOT_BIN)",
    )
    parser.add_argument("--speedup", type=int, default=16)
    parser.add_argument("--history", default=str(TRAINING_DIR / "eval_history.json"))
    args = parser.parse_args()

    model_a = str(pathlib.Path(args.model_a).resolve())
    model_b = str(pathlib.Path(args.model_b).resolve())
    half = max(args.episodes // 2, 1)

    # Half the episodes on each side to cancel any residual side asymmetry;
    # different seeds so the halves see different randomized episode states.
    first = run_half(args.godot_bin, model_a, model_b, half, args.speedup, seed=1)
    second = run_half(args.godot_bin, model_b, model_a, half, args.speedup, seed=2)

    record = {
        "timestamp": datetime.datetime.now(datetime.timezone.utc).isoformat(timespec="seconds"),
        "model_a": model_a,
        "model_b": model_b,
        "episodes": first["episodes"] + second["episodes"],
        "wins_a": first["goals_a"] + second["goals_b"],
        "wins_b": first["goals_b"] + second["goals_a"],
        "draws": first["draws"] + second["draws"],
    }
    record["win_rate_a"] = round(record["wins_a"] / record["episodes"], 3)

    history_path = pathlib.Path(args.history)
    history = json.loads(history_path.read_text()) if history_path.exists() else []
    history.append(record)
    history_path.write_text(json.dumps(history, indent=2) + "\n")

    print(
        f"{pathlib.Path(model_a).name} vs {pathlib.Path(model_b).name} over {record['episodes']} episodes: "
        f"{record['wins_a']}-{record['wins_b']} ({record['draws']} draws), "
        f"win rate A = {record['win_rate_a']:.0%}"
    )
    print(f"Appended to {history_path}")


if __name__ == "__main__":
    main()