"""
Sudoku Video Dataset Generator - Supports flexible solution count expressions per puzzle.
With checkpoint/resume support via metadata.json.

The *frames* parameter replaces the old max_frames + k pair:
  - frames=None  → 1 content frame per fill step (variable length)
  - frames=N     → exactly N content frames; fills distributed evenly
                   (slow-motion if N > fills, fast-forward if N < fills)
"""
import json
import re
import random
import argparse
from dataclasses import dataclass, asdict
from pathlib import Path
from typing import List, Tuple, Optional, Dict
import numpy as np
import cv2
from tqdm import tqdm
from sudoku_processor import SudokuProcessor


# ==================== Solution Range ====================

@dataclass
class SolRange:
    """Flexible solution count constraint for puzzle generation."""
    min_sol: int
    max_sol: Optional[int]

    @classmethod
    def parse(cls, expr: str) -> "SolRange":
        expr = expr.strip()
        m = re.fullmatch(r'(\d+)\s*-\s*(\d+)', expr)
        if m:
            lo, hi = int(m.group(1)), int(m.group(2))
            if lo < 1: raise ValueError(f"min_sol must be >= 1, got {lo}")
            if hi < lo: raise ValueError(f"Invalid range: {lo}-{hi}")
            return cls(min_sol=lo, max_sol=hi)
        m = re.fullmatch(r'(>=|>|<=|<|==)\s*(\d+)', expr)
        if m:
            op, n = m.group(1), int(m.group(2))
            if op == '>=': return cls(min_sol=max(1, n), max_sol=None)
            elif op == '>': return cls(min_sol=max(1, n + 1), max_sol=None)
            elif op == '<=': return cls(min_sol=1, max_sol=n)
            elif op == '<': return cls(min_sol=1, max_sol=max(1, n - 1))
            elif op == '==': return cls(min_sol=n, max_sol=n)
        m = re.fullmatch(r'(\d+)', expr)
        if m:
            n = int(m.group(1))
            if n < 1: raise ValueError(f"sol_num must be >= 1, got {n}")
            return cls(min_sol=n, max_sol=n)
        raise ValueError(f"Invalid sol_num expression: '{expr}'")

    @property
    def is_exact(self): return self.max_sol is not None and self.min_sol == self.max_sol
    @property
    def is_unique_only(self): return self.is_exact and self.min_sol == 1
    @property
    def allows_unique(self): return self.min_sol <= 1
    @property
    def requires_multi(self): return self.min_sol > 1
    @property
    def effective_max(self): return self.max_sol if self.max_sol is not None else max(self.min_sol, 10)
    def accepts(self, count):
        if count < self.min_sol: return False
        if self.max_sol is not None and count > self.max_sol: return False
        return True
    def __repr__(self):
        if self.is_exact: return f"SolRange(=={self.min_sol})"
        if self.max_sol is None: return f"SolRange(>={self.min_sol})"
        return f"SolRange({self.min_sol}-{self.max_sol})"


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

@dataclass
class GenerationState:
    """Tracks generation progress for checkpoint/resume."""
    params_hash: str
    clue_progress: Dict[int, int]  # clue_level -> generated_count
    seen_grids: 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 compute_params_hash(params: Dict) -> str:
    """Compute hash of generation parameters for consistency check."""
    import hashlib
    key_params = {k: v for k, v in params.items() if k not in ['output_dir']}
    return hashlib.md5(json.dumps(key_params, sort_keys=True).encode()).hexdigest()[:12]


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


def save_checkpoint(output_dir: Path, state: GenerationState, params: Dict):
    """Save current generation state to metadata.json."""
    meta_path = output_dir / "metadata.json"
    tmp_path = meta_path.with_suffix('.tmp')
    with open(tmp_path, 'w') as f:
        json.dump({"params": params, "state": state.to_dict()}, f, indent=2)
    tmp_path.rename(meta_path)


# ==================== Core Functions ====================

def get_fill_order(puzzle, solution):
    """Return list of (row, col, value) for empty cells in row-major order."""
    return [(i, j, solution[i][j]) for i in range(9) for j in range(9) if puzzle[i][j] == 0]


def create_processor(resolution=None):
    """Create a SudokuProcessor with optional custom resolution."""
    if resolution is None:
        return SudokuProcessor()
    target_size = min(resolution)
    cell_size = target_size // 9
    sf = cell_size / 60
    return SudokuProcessor(
        cell_size=cell_size, font_scale=1.2 * sf, thickness=max(1, int(2 * sf))
    )


def generate_video_frames(proc, puzzle, solution, n_start, m_end, frames=None):
    """
    Generate progressive video frames for a Sudoku solve.

    The *frames* parameter controls the number of **content frames**
    (between the opening and closing holds):

    - frames=None     → 1 content frame per fill step  (n_fills total)
    - frames > fills  → multiple frames per fill step   (slow-motion)
    - frames < fills  → multiple fills per frame         (fast-forward)
    - frames == fills → identical to None

    Total output length = n_start + content_frames + m_end.

    Args:
        proc:      SudokuProcessor instance.
        puzzle:    9×9 puzzle grid (0 = empty).
        solution:  9×9 solved grid.
        n_start:   Hold frames for puzzle at the beginning.
        m_end:     Hold frames for completed solution at the end.
        frames:    Desired number of content frames (None = one per fill).

    Returns:
        List of numpy arrays (RGB images).
    """
    fills = get_fill_order(puzzle, solution)
    n_fills = len(fills)

    if n_fills == 0:
        img = proc.render(solution, original=puzzle)
        return [img.copy() for _ in range(n_start + m_end + 1)]

    content_frames = frames if frames is not None else n_fills
    content_frames = max(1, content_frames)

    result = []
    current = [row[:] for row in puzzle]

    # --- opening hold ---
    img = proc.render(current)
    result.extend([img.copy() for _ in range(n_start)])

    # --- content frames ---
    if content_frames == n_fills:
        # Exact 1:1 mapping
        for r, c, v in fills:
            current[r][c] = v
            result.append(proc.render(current, highlight_new=(r, c), original=puzzle))

    elif content_frames > n_fills:
        # Slow-motion: distribute content_frames evenly across n_fills steps.
        for i, (r, c, v) in enumerate(fills):
            current[r][c] = v
            f_lo = i * content_frames // n_fills
            f_hi = (i + 1) * content_frames // n_fills
            count = f_hi - f_lo  # >= 1

            # First frame of this step shows highlight
            result.append(proc.render(current, highlight_new=(r, c), original=puzzle))
            # Remaining hold frames (no highlight)
            if count > 1:
                img = proc.render(current, original=puzzle)
                result.extend([img.copy() for _ in range(count - 1)])

    else:
        # Fast-forward: each content frame applies multiple fills at once.
        for f in range(content_frames):
            prev_step = f * n_fills // content_frames
            target_step = (f + 1) * n_fills // content_frames
            last_r, last_c = None, None
            for idx in range(prev_step, target_step):
                r, c, v = fills[idx]
                current[r][c] = v
                last_r, last_c = r, c
            if last_r is not None:
                result.append(
                    proc.render(current, highlight_new=(last_r, last_c), original=puzzle)
                )
            else:
                result.append(proc.render(current, original=puzzle))

    # --- closing hold ---
    img = proc.render(solution, original=puzzle)
    result.extend([img.copy() for _ in range(m_end)])

    return result


def save_video(frames, path, fps=10):
    """Save list of numpy RGB frames as mp4."""
    h, w = frames[0].shape[:2]
    writer = cv2.VideoWriter(str(path), cv2.VideoWriter_fourcc(*'mp4v'), fps, (w, h))
    for f in frames:
        writer.write(cv2.cvtColor(f, cv2.COLOR_RGB2BGR))
    writer.release()


def normalize_num_per_clue(num_per_clue, clue_levels):
    """Broadcast single int to list, or validate list length."""
    if isinstance(num_per_clue, int):
        return [num_per_clue] * len(clue_levels)
    if len(num_per_clue) != len(clue_levels):
        raise ValueError(
            f"num_per_clue length ({len(num_per_clue)}) != clue_levels ({len(clue_levels)})"
        )
    return num_per_clue


# ==================== Puzzle Generation with SolRange ====================

def generate_puzzle_with_range(proc, clue, sol_range, min_hamming):
    """Generate one puzzle respecting sol_range. Returns (puzzle, solutions) or None."""
    if sol_range.is_unique_only:
        puzzle, solution = proc.generate(clue, unique=True)
        return puzzle, [solution]

    if sol_range.requires_multi:
        try:
            puzzle, solutions = proc.generate_multi_solution(
                clue, min_solutions=sol_range.min_sol,
                max_solutions=sol_range.effective_max,
                max_attempts=1, min_hamming=min_hamming
            )
            if sol_range.accepts(len(solutions)):
                return puzzle, solutions
        except RuntimeError:
            pass
        return None

    try:
        puzzle, solutions = proc.generate_multi_solution(
            clue, min_solutions=max(2, sol_range.min_sol),
            max_solutions=sol_range.effective_max,
            max_attempts=1, min_hamming=min_hamming
        )
        if sol_range.accepts(len(solutions)):
            return puzzle, solutions
    except RuntimeError:
        pass

    if sol_range.allows_unique:
        puzzle, solution = proc.generate(clue, unique=True)
        return puzzle, [solution]
    return None


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

def generate_dataset(
    output_dir="sudoku", clue_levels=[20, 30, 40, 50, 60, 70],
    num_per_clue=[15000, 10000, 10000, 5000, 2000, 1000],
    sol_num="<=3", min_hamming=10, train_ratio=0.9,
    prompt="Solve this Sudoku puzzle using red font.",
    n_start=2, m_end=3, frames=None, fps=10,
    resolution=None, seed=42, checkpoint_interval=50
):
    """
    Generate Sudoku video dataset with checkpoint/resume support.

    The *frames* parameter controls the number of **content frames** per video:
      - None   → one content frame per fill step (variable length per puzzle)
      - N > 0  → exactly N content frames; fills distributed evenly

    Args:
        checkpoint_interval: Save checkpoint every N puzzles (default: 50)
    """
    params = {
        "clue_levels": clue_levels, "num_per_clue": num_per_clue,
        "sol_num": sol_num, "min_hamming": min_hamming, "train_ratio": train_ratio,
        "prompt": prompt, "n_start": n_start, "m_end": m_end, "frames": frames,
        "fps": fps, "resolution": resolution, "seed": seed
    }

    output_dir = Path(output_dir)
    video_dir = output_dir / "videos"
    image_dir = output_dir / "images"
    video_dir.mkdir(parents=True, exist_ok=True)
    image_dir.mkdir(parents=True, exist_ok=True)

    # Try to resume from checkpoint
    state = load_checkpoint(output_dir, params)
    if state and state.completed:
        return

    sol_range = SolRange.parse(str(sol_num))
    proc = create_processor(resolution)
    actual_size = proc.img_size
    num_per_clue_list = normalize_num_per_clue(num_per_clue, clue_levels)
    max_puzzles = max(num_per_clue_list)
    num_width = len(str(max_puzzles))

    # Initialize or restore state
    if state is None:
        random.seed(seed)
        state = GenerationState(
            params_hash=compute_params_hash(params),
            clue_progress={clue: 0 for clue in clue_levels},
            seen_grids=[],
            all_samples=[]
        )
        print(f"Starting fresh generation with solution range: {sol_range}")
        print(f"  frames={'auto (1 per fill)' 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.clue_progress.values()) * 10):
            random.random()

    seen_grids = set(state.seen_grids)
    all_samples = state.all_samples.copy()
    clue_progress = {int(k): v for k, v in state.clue_progress.items()}

    total_target = sum(num_per_clue_list)
    total_done = sum(clue_progress.values())
    stats_unique = sum(1 for s in all_samples if s["total_solutions"] == 1 and s["sol_idx"] == 0)
    stats_multi = sum(1 for s in all_samples if s["total_solutions"] > 1 and s["sol_idx"] == 0)
    puzzles_since_checkpoint = 0

    with tqdm(total=total_target, initial=total_done, desc="Total", unit="puzzle") as pbar_total:
        for clue, target_count in zip(clue_levels, num_per_clue_list):
            generated = clue_progress.get(clue, 0)
            if generated >= target_count:
                continue

            max_attempts = (target_count - generated) * 20

            with tqdm(total=target_count, initial=generated, desc=f"Clue {clue:2d}",
                      unit="puzzle", leave=False) as pbar_clue:
                for _ in range(max_attempts):
                    if generated >= target_count:
                        break

                    result = generate_puzzle_with_range(proc, clue, sol_range, min_hamming)
                    if result is None:
                        continue
                    puzzle, solutions = result

                    fp = proc.encode(puzzle)
                    if fp in seen_grids:
                        continue
                    seen_grids.add(fp)

                    n_sols = len(solutions)
                    if n_sols == 1:
                        stats_unique += 1
                    else:
                        stats_multi += 1

                    img_name = f"clue{clue}_{generated:0{num_width}d}.png"
                    puzzle_img = proc.render(puzzle)
                    cv2.imwrite(
                        str(image_dir / img_name),
                        cv2.cvtColor(puzzle_img, cv2.COLOR_RGB2BGR),
                    )

                    for si, sol in enumerate(solutions):
                        vid_name = f"clue{clue}_{generated:0{num_width}d}_sol{si}.mp4"
                        vid_frames = generate_video_frames(
                            proc, puzzle, sol, n_start, m_end, frames
                        )
                        save_video(vid_frames, video_dir / vid_name, fps)

                        hdists = [
                            proc._hamming(sol, solutions[j])
                            for j in range(n_sols) if j != si
                        ]
                        all_samples.append({
                            "prompt": prompt, "video": vid_name, "image": img_name,
                            "clue": clue, "puzzle": fp, "solution": proc.encode(sol),
                            "sol_idx": si, "total_solutions": n_sols,
                            "frame_count": len(vid_frames),
                            "min_hamming_to_others": min(hdists) if hdists else 0,
                        })

                    generated += 1
                    clue_progress[clue] = generated
                    puzzles_since_checkpoint += 1
                    pbar_clue.update(1)
                    pbar_total.update(1)

                    if puzzles_since_checkpoint >= checkpoint_interval:
                        state.clue_progress = clue_progress
                        state.seen_grids = list(seen_grids)
                        state.all_samples = all_samples
                        save_checkpoint(output_dir, state, params)
                        puzzles_since_checkpoint = 0

            tqdm.write(
                f"Clue {clue}: {generated} puzzles, "
                f"{sum(1 for s in all_samples if s['clue'] == clue)} videos"
            )

    # Stratified split: ensure each clue level is proportionally represented
    random.seed(seed + 1)
    by_clue: Dict[int, List[Dict]] = {}
    for s in all_samples:
        by_clue.setdefault(s["clue"], []).append(s)

    train_samples, test_samples = [], []
    for clue in sorted(by_clue):
        group = by_clue[clue]
        random.shuffle(group)
        cl_split = int(len(group) * train_ratio)
        train_samples.extend(group[:cl_split])
        test_samples.extend(group[cl_split:])

    random.shuffle(train_samples)
    random.shuffle(test_samples)
    split_idx = len(train_samples)

    def write_jsonl(samples, path):
        with open(path, 'w') as f:
            for s in samples:
                json.dump(s, f)
                f.write('\n')

    write_jsonl(train_samples, output_dir / "train.jsonl")
    write_jsonl(test_samples, output_dir / "test.jsonl")

    # Mark as completed
    state.clue_progress = clue_progress
    state.seen_grids = list(seen_grids)
    state.all_samples = all_samples
    state.completed = True
    save_checkpoint(output_dir, state, params)

    print(f"\n✓ Dataset complete: {output_dir}/")
    print(f"  Resolution: {actual_size}x{actual_size}")
    print(f"  Solution range: {sol_range}")
    print(f"  Puzzles: {len(seen_grids)} ({stats_unique} unique, {stats_multi} multi-sol)")
    print(f"  Videos: {len(all_samples)}")
    print(f"  Train: {split_idx}, Test: {len(all_samples) - split_idx}")

    fcounts = [s["frame_count"] for s in all_samples]
    print(f"  Frame counts: avg={np.mean(fcounts):.1f}, "
          f"min={min(fcounts)}, max={max(fcounts)}")

    hammings = [s["min_hamming_to_others"] for s in all_samples if s["min_hamming_to_others"] > 0]
    if hammings:
        print(f"  Solution diversity: avg={np.mean(hammings):.1f}, "
              f"min={min(hammings)}, max={max(hammings)}")


def parse_resolution(s):
    w, h = map(int, s.lower().split('x'))
    return (w, h)


def parse_args():
    p = argparse.ArgumentParser(
        description="Generate Sudoku video dataset with resume support"
    )
    p.add_argument("--output-dir", type=str, default="sudoku")
    p.add_argument("--clue-levels", type=int, nargs="+",
                   default=[20, 30, 40, 50, 60, 70])
    p.add_argument("--num-per-clue", type=int, nargs="+",
                   default=[15000, 10000, 10000, 5000, 2000, 1000])
    p.add_argument("--sol-num", type=str, default="<=3",
                   help="'1', '3', '>=1', '>1', '<=3', '<3', '2-5'")
    p.add_argument("--min-hamming", type=int, default=10)
    p.add_argument("--train-ratio", type=float, default=0.9)
    p.add_argument("--prompt", type=str,
                   default="Solve this Sudoku puzzle using red font.")
    p.add_argument("--n-start", type=int, default=2,
                   help="Hold frames for puzzle at video start")
    p.add_argument("--m-end", type=int, default=3,
                   help="Hold frames for completed solution at video end")
    p.add_argument("--frames", type=int, default=None,
                   help="Content frames per video. None=1 per fill (auto). "
                        "If > fills: slow-motion. If < fills: fast-forward.")
    p.add_argument("--fps", type=int, default=10)
    p.add_argument("--resolution", type=str, default="1024x1024")
    p.add_argument("--seed", type=int, default=42)
    p.add_argument("--checkpoint-interval", type=int, default=50,
                   help="Save checkpoint every N puzzles (default: 50)")
    return p.parse_args()


if __name__ == "__main__":
    args = parse_args()
    kwargs = vars(args)
    if isinstance(kwargs["num_per_clue"], list) and len(kwargs["num_per_clue"]) == 1:
        kwargs["num_per_clue"] = kwargs["num_per_clue"][0]
    if kwargs["resolution"]:
        kwargs["resolution"] = parse_resolution(kwargs["resolution"])
    generate_dataset(**kwargs)