"""
Maze Video Dataset Generator — generates maze puzzle images and solution videos
with checkpoint/resume support, train/test splitting, and JSONL metadata.

Includes an ``eval`` subcommand that takes a directory of result videos,
extracts the last frame from each, parses the red path, and verifies it
against the ground-truth maze text files.

Usage:
    # Generate
    python maze_video_gen.py generate --output-dir maze --sizes 8 16 32 \
        --num-per-size 100 500 1000 --min-path-ratio 0.3 \
        --n-start 5 --m-end 5 --frames 50 --fps 10 --seed 42

    # Evaluate result videos
    python maze_video_gen.py eval result_videos/ --text-dir maze/texts

    # Verify a pre-extracted JSON
    python maze_video_gen.py verify results.json --text-dir maze/texts
"""
import json
import csv
import hashlib
import random
import re
import argparse
from dataclasses import dataclass, asdict
from pathlib import Path
from typing import Dict, List, Optional

import cv2
import numpy as np
from tqdm import tqdm

from maze_processor import MazeProcessor


# ==================== Checkpoint Management ====================

@dataclass
class GenerationState:
    """Tracks generation progress for checkpoint/resume."""
    params_hash: str
    size_progress: Dict[int, int]
    seen_fingerprints: List[str]
    all_samples: List[Dict]
    completed: bool = False

    def to_dict(self) -> Dict:
        return asdict(self)

    @classmethod
    def from_dict(cls, d: Dict) -> "GenerationState":
        return cls(**d)


def _params_hash(params: Dict) -> str:
    """Deterministic hash of generation parameters (excluding output_dir)."""
    key = {k: v for k, v in params.items() if k != "output_dir"}
    return hashlib.md5(json.dumps(key, sort_keys=True).encode()).hexdigest()[:12]


def load_checkpoint(output_dir: Path, params: Dict) -> Optional[GenerationState]:
    """Load checkpoint if it exists and parameters match."""
    meta = output_dir / "metadata.json"
    if not meta.exists():
        return None
    with open(meta) as f:
        data = json.load(f)
    state = GenerationState.from_dict(data["state"])
    expected = _params_hash(params)
    if state.params_hash != expected:
        print(f"⚠️  Parameters changed ({state.params_hash} → {expected}), starting fresh")
        return None
    if state.completed:
        print("✓ Generation already completed")
        return state
    done = sum(state.size_progress.values())
    print(f"✓ Resuming from checkpoint: {done} mazes generated")
    return state


def save_checkpoint(output_dir: Path, state: GenerationState, params: Dict):
    """Atomically write checkpoint to metadata.json."""
    meta = output_dir / "metadata.json"
    tmp = meta.with_suffix(".tmp")
    with open(tmp, "w") as f:
        json.dump({"params": params, "state": state.to_dict()}, f, indent=2)
    tmp.rename(meta)


# ==================== Video I/O ====================

def save_video_cv2(frames: list, path: str, fps: int = 10):
    """Save list of PIL Images as an mp4 video."""
    first = np.array(frames[0])
    h, w = first.shape[:2]
    writer = cv2.VideoWriter(
        str(path), cv2.VideoWriter_fourcc(*"mp4v"), fps, (w, h)
    )
    for frame in frames:
        writer.write(cv2.cvtColor(np.array(frame), cv2.COLOR_RGB2BGR))
    writer.release()


def extract_last_frame(video_path: str) -> Optional[np.ndarray]:
    """
    Extract the last frame from a video file as an RGB numpy array.

    Returns:
        (H, W, 3) uint8 RGB array, or None on failure.
    """
    cap = cv2.VideoCapture(str(video_path))
    if not cap.isOpened():
        return None

    total = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
    if total > 0:
        cap.set(cv2.CAP_PROP_POS_FRAMES, total - 1)

    ret, frame = cap.read()
    cap.release()

    if not ret or frame is None:
        return None
    return cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)


# ==================== Normalisation Helpers ====================

def _normalise_list(val, sizes, name="parameter"):
    """Broadcast a single int to a list, or validate list length."""
    if isinstance(val, int):
        return [val] * len(sizes)
    if len(val) != len(sizes):
        raise ValueError(f"{name} length ({len(val)}) != sizes length ({len(sizes)})")
    return list(val)


# ==================== Core Dataset Generation ====================

def generate_dataset(
    output_dir: str = "maze",
    sizes: List[int] = [8, 16, 32],
    num_per_size: list = [100, 500, 1000],
    min_path_ratio: float = 0.3,
    img_size: int = 1024,
    prompt: str = "Draw a continuous red line from the yellow dot to the blue dot, avoiding all walls.",
    train_ratio: float = 0.9,
    n_start: int = 5,
    m_end: int = 5,
    frames: Optional[int] = None,
    fps: int = 10,
    seed: int = 42,
    checkpoint_interval: int = 50,
):
    """
    Generate maze video dataset with checkpoint/resume support.

    The *frames* parameter controls content frames per video:
      - None   → one content frame per path step (variable length)
      - N > 0  → exactly N content frames (slow-mo / fast-fwd as needed)

    Directory layout::

        output_dir/
            images/       — puzzle PNG (no solution line)
            videos/       — solution MP4 (progressive red line)
            texts/        — maze text files (bitmask format)
            train.jsonl / test.jsonl
            train.csv   / test.csv
            path.json     — UDRL answer key
            metadata.json — checkpoint state
    """
    params = {
        "sizes": sizes, "num_per_size": num_per_size,
        "min_path_ratio": min_path_ratio, "img_size": img_size,
        "prompt": prompt, "train_ratio": train_ratio,
        "n_start": n_start, "m_end": m_end, "frames": frames,
        "fps": fps, "seed": seed,
    }

    out = Path(output_dir)
    img_dir = out / "images"
    vid_dir = out / "videos"
    txt_dir = out / "texts"
    for d in (img_dir, vid_dir, txt_dir):
        d.mkdir(parents=True, exist_ok=True)

    state = load_checkpoint(out, params)
    if state and state.completed:
        return

    num_list = _normalise_list(
        num_per_size[0] if len(num_per_size) == 1 else num_per_size,
        sizes, "num_per_size",
    )
    max_puzzles = max(num_list)
    num_w = len(str(max_puzzles))
    proc = MazeProcessor(img_size=img_size)

    if state is None:
        random.seed(seed)
        state = GenerationState(
            params_hash=_params_hash(params),
            size_progress={sz: 0 for sz in sizes},
            seen_fingerprints=[],
            all_samples=[],
        )
        print(f"Starting fresh generation: sizes={sizes}, counts={num_list}")
        print(f"  frames={'auto (1 per step)' if frames is None else frames}, "
              f"n_start={n_start}, m_end={m_end}, fps={fps}")
    else:
        random.seed(seed)
        for _ in range(sum(state.size_progress.values()) * 10):
            random.random()

    seen = set(state.seen_fingerprints)
    all_samples = list(state.all_samples)
    progress = {int(k): v for k, v in state.size_progress.items()}
    since_ckpt = 0

    total_target = sum(num_list)
    total_done = sum(progress.values())

    with tqdm(total=total_target, initial=total_done, desc="Total", unit="maze") as pbar:
        for maze_size, target in zip(sizes, num_list):
            generated = progress.get(maze_size, 0)
            if generated >= target:
                continue

            min_len = max(1, int(maze_size * maze_size * min_path_ratio))
            max_attempts = (target - generated) * 20

            with tqdm(
                total=target, initial=generated, desc=f"Size {maze_size:3d}",
                unit="maze", leave=False,
            ) as pbar_sz:
                for _ in range(max_attempts):
                    if generated >= target:
                        break

                    try:
                        grid, start, end, path = proc.generate(
                            maze_size, min_path_len=min_len
                        )
                    except RuntimeError:
                        continue

                    fp = proc.fingerprint(grid, start, end)
                    if fp in seen:
                        continue
                    seen.add(fp)

                    idx = generated
                    base = f"size{maze_size}_{idx:0{num_w}d}"
                    img_name = f"{base}.png"
                    vid_name = f"{base}.mp4"
                    txt_name = f"{base}.txt"

                    puzzle_img = proc.render(grid, start, end)
                    puzzle_img.save(str(img_dir / img_name))

                    vid_frames = proc.generate_video_frames(
                        grid, start, end, path,
                        n_start=n_start, m_end=m_end, frames=frames,
                    )
                    save_video_cv2(vid_frames, str(vid_dir / vid_name), fps=fps)

                    proc.save_text(str(txt_dir / txt_name), grid, start, end)

                    udrl = proc.path_to_udrl(path)

                    all_samples.append({
                        "prompt": prompt,
                        "image": img_name,
                        "video": vid_name,
                        "text": txt_name,
                        "maze_size": maze_size,
                        "start": list(start),
                        "end": list(end),
                        "path_udrl": udrl,
                        "path_length": len(path),
                        "frame_count": len(vid_frames),
                    })

                    generated += 1
                    progress[maze_size] = generated
                    since_ckpt += 1
                    pbar_sz.update(1)
                    pbar.update(1)

                    if since_ckpt >= checkpoint_interval:
                        state.size_progress = progress
                        state.seen_fingerprints = list(seen)
                        state.all_samples = all_samples
                        save_checkpoint(out, state, params)
                        since_ckpt = 0

            tqdm.write(
                f"Size {maze_size}: {generated} mazes, "
                f"{sum(1 for s in all_samples if s['maze_size'] == maze_size)} samples"
            )

    # ==================== Final outputs ====================

    path_answers = {s["image"]: s["path_udrl"] for s in all_samples}
    with open(out / "path.json", "w") as f:
        json.dump(dict(sorted(path_answers.items())), f, indent=4)

    random.seed(seed + 1)
    random.shuffle(all_samples)
    split = int(len(all_samples) * train_ratio)

    def _write_jsonl(samples, path):
        with open(path, "w") as f:
            for s in samples:
                f.write(json.dumps(s) + "\n")

    _write_jsonl(all_samples[:split], out / "train.jsonl")
    _write_jsonl(all_samples[split:], out / "test.jsonl")

    for name, samples in [("train", all_samples[:split]), ("test", all_samples[split:])]:
        with open(out / f"{name}.csv", "w", newline="", encoding="utf-8") as f:
            writer = csv.writer(f)
            writer.writerow(["input_image", "video", "prompt"])
            for s in samples:
                writer.writerow([
                    f"images/{s['image']}", f"videos/{s['video']}", s["prompt"]
                ])

    state.size_progress = progress
    state.seen_fingerprints = list(seen)
    state.all_samples = all_samples
    state.completed = True
    save_checkpoint(out, state, params)

    print(f"\n✓ Dataset complete: {out}/")
    print(f"  Sizes: {sizes}")
    print(f"  Mazes: {len(all_samples)}")
    print(f"  Train: {split}, Test: {len(all_samples) - split}")
    lengths = [s["path_length"] for s in all_samples]
    fcounts = [s["frame_count"] for s in all_samples]
    print(f"  Path lengths: avg={np.mean(lengths):.1f}, "
          f"min={min(lengths)}, max={max(lengths)}")
    print(f"  Frame counts: avg={np.mean(fcounts):.1f}, "
          f"min={min(fcounts)}, max={max(fcounts)}")


# ==================== Eval: Video → Last Frame → Verify ====================

def eval_videos(
    video_dir: str,
    text_dir: str,
    output_json: Optional[str] = None,
    gt_json: Optional[str] = None,
):
    """
    Evaluate a directory of result videos against ground-truth mazes.

    Pipeline per video:
        1. Extract last frame from .mp4
        2. Detect red path via pixel analysis
        3. Convert to UDRL action string
        4. Verify against maze .txt (wall-respecting walk from start to end)

    Matching convention:
        Video ``<stem>.mp4``  →  Text ``<stem>.txt``  in *text_dir*.
        Common stems: ``size8_000``, ``size16_042``, etc.

    Args:
        video_dir:   Directory containing result .mp4 files.
        text_dir:    Directory containing ground-truth maze .txt files.
        output_json: Path to save extracted paths as JSON (default: video_dir/0_result.json).
        gt_json:     Optional ground-truth answer JSON for accuracy by path length.
    """
    proc = MazeProcessor()
    vid_root = Path(video_dir)
    txt_root = Path(text_dir)

    if output_json is None:
        output_json = str(vid_root / "0_result.json")

    # Collect videos
    videos = sorted(
        vid_root.glob("*.mp4"),
        key=lambda p: [int(s) if s.isdigit() else s for s in re.split(r"(\d+)", p.stem)],
    )

    if not videos:
        print(f"No .mp4 files found in {vid_root}")
        return

    print(f"Found {len(videos)} result videos in {vid_root}")
    print(f"Text dir: {txt_root}")

    # --- Phase 1: Extract paths from last frames ---
    extracted: Dict[str, str] = {}
    missing_txt = 0
    missing_frame = 0

    for vpath in tqdm(videos, desc="Extracting paths"):
        stem = vpath.stem                        # e.g. "size8_000"
        txt_path = txt_root / f"{stem}.txt"

        if not txt_path.exists():
            missing_txt += 1
            continue

        maze = proc.load_text(str(txt_path))
        if maze is None:
            missing_txt += 1
            continue

        last_frame = extract_last_frame(str(vpath))
        if last_frame is None:
            missing_frame += 1
            continue

        udrl = proc.extract_path_from_pixels(
            last_frame,
            grid_raw=maze["grid_raw"],
            size=maze["size"],
            start=maze["start"],
        )
        extracted[f"{stem}.png"] = udrl   # keyed by image name for consistency

    # Save extracted paths
    with open(output_json, "w", encoding="utf-8") as f:
        json.dump(extracted, f, indent=4)
    print(f"\nExtracted paths saved to: {output_json}")

    # --- Phase 2: Verify ---
    correct = 0
    total_valid = 0
    correctly_solved: List[Dict] = []

    for name, udrl in extracted.items():
        stem = name.replace(".png", "")
        txt_path = txt_root / f"{stem}.txt"
        maze = proc.load_text(str(txt_path))
        if maze is None:
            continue
        total_valid += 1
        if proc.verify_path(maze["grid"], maze["start"], maze["end"], udrl):
            correct += 1
            correctly_solved.append({"name": name, "length": len(udrl)})

    acc = (correct / total_valid * 100) if total_valid else 0

    print(f"\n{'=' * 50}")
    print("Evaluation Summary")
    print(f"{'=' * 50}")
    print(f"Total Videos       : {len(videos)}")
    print(f"Missing .txt       : {missing_txt}")
    print(f"Failed Frame Read  : {missing_frame}")
    print(f"Evaluated          : {total_valid}")
    print(f"Correctly Solved   : {correct}")
    print(f"Accuracy           : {acc:.2f}%")
    print(f"{'-' * 50}")

    # Breakdown by maze size
    size_stats: Dict[int, Dict[str, int]] = {}
    for name, udrl in extracted.items():
        stem = name.replace(".png", "")
        txt_path = txt_root / f"{stem}.txt"
        maze = proc.load_text(str(txt_path))
        if maze is None:
            continue
        sz = maze["size"]
        if sz not in size_stats:
            size_stats[sz] = {"total": 0, "correct": 0}
        size_stats[sz]["total"] += 1
        if proc.verify_path(maze["grid"], maze["start"], maze["end"], udrl):
            size_stats[sz]["correct"] += 1

    if size_stats:
        print("\nAccuracy by maze size:")
        for sz in sorted(size_stats):
            s = size_stats[sz]
            sz_acc = s["correct"] / s["total"] * 100 if s["total"] else 0
            print(f"  Size {sz:3d}: {s['correct']:4d}/{s['total']:4d} ({sz_acc:.2f}%)")

    # Top longest correct
    correctly_solved.sort(key=lambda x: x["length"], reverse=True)
    if correctly_solved:
        print(f"\nTop 3 Longest Correct Paths:")
        for i, item in enumerate(correctly_solved[:3]):
            print(f"  {i+1}. {item['name']} (length: {item['length']})")

    # Optional: compare with ground-truth JSON for path-length-binned accuracy
    if gt_json:
        _compare_with_gt(extracted, gt_json, txt_root, proc)

    print(f"{'=' * 50}")


def _compare_with_gt(
    extracted: Dict[str, str],
    gt_json_path: str,
    txt_root: Path,
    proc: MazeProcessor,
):
    """Print accuracy binned by ground-truth path length."""
    try:
        with open(gt_json_path) as f:
            gt = json.load(f)
    except Exception:
        print(f"  Warning: could not load ground-truth JSON: {gt_json_path}")
        return

    bins: Dict[str, Dict[str, int]] = {}  # "10-19" -> {total, correct}
    for name, pred_udrl in extracted.items():
        if name not in gt:
            continue
        gt_udrl = gt[name]
        gt_len = len(gt_udrl)

        # Bin by path length (decades)
        lo = (gt_len // 10) * 10
        hi = lo + 9
        label = f"{lo:3d}-{hi:3d}"
        if label not in bins:
            bins[label] = {"total": 0, "correct": 0}
        bins[label]["total"] += 1

        stem = name.replace(".png", "")
        maze = proc.load_text(str(txt_root / f"{stem}.txt"))
        if maze and proc.verify_path(maze["grid"], maze["start"], maze["end"], pred_udrl):
            bins[label]["correct"] += 1

    if bins:
        print("\nAccuracy by GT path length:")
        for label in sorted(bins):
            b = bins[label]
            b_acc = b["correct"] / b["total"] * 100 if b["total"] else 0
            print(f"  Length {label}: {b['correct']:4d}/{b['total']:4d} ({b_acc:.2f}%)")


# ==================== Verify: Pre-extracted JSON ====================

def verify_results(json_file: str, text_dir: str):
    """
    Verify pre-extracted UDRL paths (from a JSON file) against maze .txt files.

    Args:
        json_file: Path to JSON with {name: udrl_string} predictions.
        text_dir:  Directory containing maze .txt files.
    """
    proc = MazeProcessor()
    json_path = Path(json_file)
    txt_root = Path(text_dir)

    with open(json_path) as f:
        solutions = json.load(f)

    correct = skipped = valid = 0

    for name, udrl in solutions.items():
        clean = name.replace(".png", "")
        txt_path = txt_root / f"{clean}.txt"
        maze = proc.load_text(str(txt_path))
        if maze is None:
            skipped += 1
            continue
        valid += 1
        if proc.verify_path(maze["grid"], maze["start"], maze["end"], udrl):
            correct += 1

    acc = (correct / valid * 100) if valid else 0
    print(f"\n{'='*40}")
    print(f"Verification: {correct}/{valid} correct ({acc:.2f}%)")
    if skipped:
        print(f"Skipped: {skipped}")
    print(f"{'='*40}")


# ==================== CLI ====================

def parse_args():
    p = argparse.ArgumentParser(
        description="Maze video dataset: generate, eval, verify"
    )
    sub = p.add_subparsers(dest="command", help="Sub-command")

    # --- generate ---
    gen = sub.add_parser("generate", help="Generate dataset")
    gen.add_argument("--output-dir", type=str, default="maze")
    gen.add_argument("--sizes", type=int, nargs="+", default=[8, 16, 24, 32])
    gen.add_argument("--num-per-size", type=int, nargs="+", default=[100, 500, 1000, 2000])
    gen.add_argument("--min-path-ratio", type=float, default=0.3,
                     help="Min path length as fraction of size²")
    gen.add_argument("--img-size", type=int, default=1024)
    gen.add_argument("--prompt", type=str,
                     default="Draw a continuous red line from the yellow dot "
                             "to the blue dot, avoiding all walls.")
    gen.add_argument("--train-ratio", type=float, default=0.9)
    gen.add_argument("--n-start", type=int, default=2,
                     help="Hold frames at video start (blank puzzle)")
    gen.add_argument("--m-end", type=int, default=3,
                     help="Hold frames at video end (completed solution)")
    gen.add_argument("--frames", type=int, default=None,
                     help="Content frames per video (None=auto 1 per step)")
    gen.add_argument("--fps", type=int, default=10)
    gen.add_argument("--seed", type=int, default=42)
    gen.add_argument("--checkpoint-interval", type=int, default=50)

    # --- eval ---
    ev = sub.add_parser("eval",
                        help="Evaluate result videos (last frame → extract → verify)")
    ev.add_argument("video_dir", type=str,
                    help="Directory containing result .mp4 files")
    ev.add_argument("--text-dir", type=str, required=True,
                    help="Directory with ground-truth maze .txt files")
    ev.add_argument("--output-json", type=str, default=None,
                    help="Output JSON for extracted paths (default: video_dir/0_result.json)")
    ev.add_argument("--gt-json", type=str, default=None,
                    help="Optional ground-truth path.json for length-binned accuracy")

    # --- verify ---
    ver = sub.add_parser("verify", help="Verify a pre-extracted JSON of UDRL paths")
    ver.add_argument("json_file", type=str)
    ver.add_argument("--text-dir", type=str, required=True,
                     help="Directory with maze .txt files")

    return p.parse_args()


if __name__ == "__main__":
    args = parse_args()

    if args.command == "generate":
        kwargs = {k: v for k, v in vars(args).items() if k != "command"}
        generate_dataset(**kwargs)

    elif args.command == "eval":
        eval_videos(
            video_dir=args.video_dir,
            text_dir=args.text_dir,
            output_json=args.output_json,
            gt_json=args.gt_json,
        )

    elif args.command == "verify":
        verify_results(args.json_file, args.text_dir)

    else:
        print("Usage: python maze_video_gen.py {generate|eval|verify} [options]")
        print("  python maze_video_gen.py generate --help")
        print("  python maze_video_gen.py eval --help")
        print("  python maze_video_gen.py verify --help")