"""Process a directory of images through NisabaRelief and save as PNG."""

import argparse
import warnings
from concurrent.futures import ThreadPoolExecutor, as_completed
from pathlib import Path

from PIL import Image
from rich.console import Console
from rich.progress import (
    BarColumn,
    MofNCompleteColumn,
    Progress,
    ProgressColumn,
    SpinnerColumn,
    Task,
    TextColumn,
    TimeElapsedColumn,
)
from rich.text import Text

from nisaba_relief import NisabaRelief
from nisaba_relief.constants import MAX_TILE, MIN_IMAGE_DIMENSION

Image.MAX_IMAGE_PIXELS = None

IMAGE_EXTENSIONS = {".jpg", ".jpeg", ".png", ".tif", ".tiff", ".bmp", ".webp", ".gif"}

SKIP_LABELS = {
    "small": "image(s) smaller than {min_size}px",
    "empty": "mostly-empty image(s)",
    "bw": "black-and-white image(s)",
    "corrupt": "corrupt/truncated image(s)",
}


class SimpleTimeRemainingColumn(ProgressColumn):
    """Estimates remaining time from the average duration of recent iterations.

    The window is 0.5% of the task total (minimum 1, maximum 200). Only recomputes when a new
    step completes so the display is stable.
    """

    def __init__(self) -> None:
        super().__init__()
        self._last_completed: float = 0
        self._last_elapsed: float = 0.0
        self._durations: list[float] = []
        self._window: int = 0
        self._cached: Text = Text("-:--:--", style="progress.remaining")

    def render(self, task: Task) -> Text:
        if task.completed <= self._last_completed:
            return self._cached
        if not self._window and task.total:
            self._window = min(max(1, int(task.total * 0.005)), 200)
        elapsed = task.finished_time if task.finished else task.elapsed
        if not elapsed or not task.completed:
            self._last_completed = task.completed
            self._cached = Text("-:--:--", style="progress.remaining")
            return self._cached
        step_duration = elapsed - self._last_elapsed
        steps = task.completed - self._last_completed
        if steps > 0 and self._last_completed > 0:
            per_step = step_duration / steps
            self._durations.append(per_step)
            if self._window and len(self._durations) > self._window:
                self._durations = self._durations[-self._window :]
        self._last_completed = task.completed
        self._last_elapsed = elapsed
        if not self._durations:
            self._cached = Text("-:--:--", style="progress.remaining")
            return self._cached
        avg = sum(self._durations) / len(self._durations)
        remaining = task.total - task.completed
        eta_seconds = avg * remaining
        hours, rem = divmod(int(eta_seconds), 3600)
        minutes, seconds = divmod(rem, 60)
        if hours:
            self._cached = Text(
                f"{hours}:{minutes:02d}:{seconds:02d}", style="progress.remaining"
            )
        else:
            self._cached = Text(f"{minutes}:{seconds:02d}", style="progress.remaining")
        return self._cached


def _make_progress(label: str) -> Progress:
    """Build a Progress bar with the standard column layout."""
    return Progress(
        SpinnerColumn(),
        TextColumn(label),
        BarColumn(),
        MofNCompleteColumn(),
        TimeElapsedColumn(),
        TextColumn("eta"),
        SimpleTimeRemainingColumn(),
    )


def _classify_histogram(
    img: Image.Image,
    uniform_threshold: float,
    sat_threshold: float = 0.03,
    mid_threshold: float = 0.28,
    sample_size: int = 256,
) -> str | None:
    """Classify an image by its grayscale histogram. Returns a skip reason or None.

    Builds a single thumbnail + histogram and runs two checks:
    1. Black and White: lacking saturated colors and mid tones.
    2. Mostly-empty: a single non-black color dominates (±5 sliding window).
    """
    # JPEG: decode at reduced resolution via libjpeg DCT scaling (fast, low memory)
    # Other formats: no-op, thumbnail handles resize after full load
    img.draft("RGB", (sample_size, sample_size))
    img.thumbnail((sample_size, sample_size), Image.NEAREST)
    hist = img.convert("L").histogram()
    total = sum(hist)

    # Check if it contains only black and white with no midtones (eg: lineart, text screenshots)
    sat_hist = img.convert("HSV").split()[1].histogram()
    high_sat = sum(sat_hist[31:]) / total
    if high_sat < sat_threshold and sum(hist[45:205]) / total < mid_threshold:
        return "bw"

    # Check for dominant single color (sliding window of width 11, ±5)
    if uniform_threshold < 1:
        window = 11
        half = window // 2
        running = sum(hist[:window])
        best_count = running
        best_center = half
        for center in range(half + 1, 256 - half):
            running += hist[center + half] - hist[center - half - 1]
            if running > best_count:
                best_count = running
                best_center = center
        if best_center >= 10 and best_count / total >= uniform_threshold:
            return "empty"

    return None


def _check_image(
    src: Path, dst: Path, min_size: int, max_uniform: float
) -> tuple[Path, Path, str]:
    """Classify a single image for filtering. Returns (src, dst, status)."""
    try:
        with warnings.catch_warnings(), Image.open(src) as img:
            warnings.simplefilter("ignore", UserWarning)
            if max(img.size) < min_size or min(img.size) < MIN_IMAGE_DIMENSION:
                return src, dst, "small"
            reason = _classify_histogram(img, max_uniform)
            if reason:
                return src, dst, reason
    except (OSError, SyntaxError):
        return src, dst, "corrupt"
    return src, dst, "process"


def _parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Process images through NisabaRelief and save as PNG."
    )
    parser.add_argument(
        "--input-dir", type=Path, required=True, help="Source image directory"
    )
    parser.add_argument(
        "--output-dir",
        type=Path,
        required=True,
        help="Destination directory (created if needed)",
    )
    parser.add_argument(
        "--max-size",
        type=int,
        default=MAX_TILE * 5,
        help="Downsample images larger than this before processing (default: %(default)s)",
    )
    parser.add_argument(
        "--min-size",
        type=int,
        default=1536,
        help="Skip images where max dimension < this (default: %(default)s)",
    )
    parser.add_argument(
        "--max-uniform",
        type=float,
        default=0.65,
        help="Skip images where this fraction of pixels share a single non-black color (default: %(default)s, set to 1 to disable)",
    )
    parser.add_argument("--seed", type=int, default=None, help="Reproducibility seed")
    parser.add_argument(
        "--weights-dir", type=Path, default=None, help="Local weights directory"
    )
    parser.add_argument("--batch-size", type=int, default=None, help="Tile batch size")
    parser.add_argument(
        "--num-steps", type=int, default=2, help="Solver steps (default: %(default)s)"
    )
    parser.add_argument(
        "--device", default="cuda", help="Torch device (default: %(default)s)"
    )
    parser.add_argument(
        "--overwrite", action="store_true", help="Re-process even if output file exists"
    )
    return parser.parse_args()


def _gather_candidates(
    input_images: list[Path], output_dir: Path, overwrite: bool
) -> tuple[list[tuple[Path, Path]], int]:
    """Scan filesystem for images that need processing. Returns (candidates, skipped_existing)."""
    candidates = []
    skipped_existing = 0
    with _make_progress("Gathering candidates") as progress:
        task = progress.add_task("Scanning", total=len(input_images))
        for src in input_images:
            dst = output_dir / (src.stem + ".png")
            if not overwrite and dst.exists():
                skipped_existing += 1
            else:
                candidates.append((src, dst))
            progress.advance(task)
    return candidates, skipped_existing


def _filter_candidates(
    candidates: list[tuple[Path, Path]], min_size: int, max_uniform: float
) -> tuple[list[tuple[Path, Path]], dict[str, int]]:
    """Run parallel image checks (size + histogram). Returns (to_process, skipped_counts)."""
    to_process = []
    skipped: dict[str, int] = {}
    executor = ThreadPoolExecutor(max_workers=8)
    futures = [
        executor.submit(_check_image, src, dst, min_size, max_uniform)
        for src, dst in candidates
    ]
    with _make_progress("Filtering candidates") as progress:
        task = progress.add_task("Filtering", total=len(futures))
        try:
            for future in as_completed(futures):
                src, dst, status = future.result()
                if status == "process":
                    to_process.append((src, dst))
                else:
                    skipped[status] = skipped.get(status, 0) + 1
                progress.advance(task)
        except KeyboardInterrupt:
            executor.shutdown(wait=False, cancel_futures=True)
            raise
    executor.shutdown()
    to_process.sort()
    return to_process, skipped


def _process_image(src: Path, dst: Path, model: NisabaRelief, max_size: int) -> None:
    """Load, optionally downsample, run model, restore size, and save a single image."""
    image = Image.open(src).convert("RGB")
    original_size = image.size
    if max(image.size) > max_size:
        scale = max_size / max(image.size)
        new_size = (
            round(image.width * scale) // 16 * 16,
            round(image.height * scale) // 16 * 16,
        )
        image = image.resize(new_size, Image.LANCZOS)
    result = model.process(image, show_pbar=False)
    if result.size != original_size:
        result = result.resize(original_size, Image.LANCZOS)
    result.save(dst)


def main():
    args = _parse_args()
    console = Console()

    input_dir: Path = args.input_dir
    output_dir: Path = args.output_dir

    if not input_dir.is_dir():
        console.print(f"[red]Input directory not found:[/red] [cyan]{input_dir}[/cyan]")
        return

    input_images = sorted(
        p for p in input_dir.iterdir() if p.suffix.lower() in IMAGE_EXTENSIONS
    )
    if not input_images:
        console.print(f"[red]No images found in[/red] [cyan]{input_dir}[/cyan]")
        return

    output_dir.mkdir(parents=True, exist_ok=True)

    candidates, skipped_existing = _gather_candidates(
        input_images, output_dir, args.overwrite
    )
    to_process, skipped = _filter_candidates(candidates, args.min_size, args.max_uniform)

    if skipped_existing:
        console.print(
            f"[dim]Skipping {skipped_existing} already-processed image(s)[/dim]"
        )
    for reason, label in SKIP_LABELS.items():
        if count := skipped.get(reason):
            console.print(
                f"[dim]Skipping {count} {label.format(min_size=args.min_size)}[/dim]"
            )

    if not to_process:
        console.print("[green]All images already processed.[/green]")
        return

    console.print(
        f"Processing [bold]{len(to_process)}[/bold] / {len(input_images)} images  "
        f"[dim]({input_dir} → {output_dir})[/dim]"
    )

    model_kwargs = dict(num_steps=args.num_steps, device=args.device)
    if args.seed is not None:
        model_kwargs["seed"] = args.seed
    if args.weights_dir is not None:
        model_kwargs["weights_dir"] = args.weights_dir
    if args.batch_size is not None:
        model_kwargs["batch_size"] = args.batch_size
    model = NisabaRelief(**model_kwargs)

    progress = _make_progress("[progress.description]{task.description}")
    with progress:
        task = progress.add_task("Processing", total=len(to_process))
        for src, dst in to_process:
            progress.update(task, description=f"[cyan]{src.name}[/cyan]")
            _process_image(src, dst, model, args.max_size)
            progress.advance(task)

    console.print(
        f"[green]Done.[/green] {len(to_process)} image(s) saved to [cyan]{output_dir}[/cyan]"
    )


if __name__ == "__main__":
    main()