import asyncio
import inspect
import io
import hashlib
import tempfile
from contextlib import suppress
from pathlib import Path
from typing import Tuple
from fastapi import HTTPException

ALLOWED_EXT = {"jpg", "jpeg", "png", "webp", "gif", "bmp",
               "tiff", "arw", "cr2", "cr3", "nef", "rw2", "orf", "pef", "dng"}
RAW_EXT = {"arw", "cr2", "cr3", "nef", "rw2", "orf", "pef", "dng"}
VIDEO_EXT = {"mp4", "mov", "m4v", "avi", "mkv", "wmv", "flv", "webm", "mpg", "mpeg", "3gp"}
MAX_IMAGE_SOURCE_SIZE = 200 * 1024 * 1024
VIDEO_TAIL_LIMIT = 2 * 1024 * 1024  # 2MB
VIDEO_TAIL_FALLBACK_LIMIT = 4 * 1024 * 1024  # 4MB
VIDEO_HEAD_LIMIT = 2 * 1024 * 1024  # 2MB
VIDEO_HEAD_FALLBACK_LIMIT = 4 * 1024 * 1024  # 4MB
VIDEO_THUMB_SEEK_SECONDS = (15, 10, 5, 3, 1, 0)
VIDEO_BLACK_FRAME_MEAN_THRESHOLD = 12.0
CACHE_ROOT = Path('data/.thumb_cache')


def is_image_filename(name: str) -> bool:
    parts = name.rsplit('.', 1)
    if len(parts) < 2:
        return False
    return parts[1].lower() in ALLOWED_EXT


def is_raw_filename(name: str) -> bool:
    parts = name.rsplit('.', 1)
    if len(parts) < 2:
        return False
    return parts[1].lower() in RAW_EXT


def is_video_filename(name: str) -> bool:
    parts = name.rsplit('.', 1)
    if len(parts) < 2:
        return False
    return parts[1].lower() in VIDEO_EXT


def _cache_key(adapter_id: int, rel: str, size: int, mtime: int, w: int, h: int, fit: str) -> str:
    raw = f"{adapter_id}|{rel}|{size}|{mtime}|{w}x{h}|{fit}".encode()
    return hashlib.sha1(raw).hexdigest()


def _cache_path(key: str) -> Path:
    sub = Path(key[:2]) / key[2:4]
    return CACHE_ROOT / sub / f"{key}.webp"


def _ensure_cache_dir(p: Path):
    p.parent.mkdir(parents=True, exist_ok=True)


def _image_to_webp(im, w: int, h: int, fit: str) -> Tuple[bytes, str]:
    from PIL import Image
    if im.mode not in ("RGB", "RGBA"):
        im = im.convert("RGBA" if im.mode in ("P", "LA") else "RGB")
    if fit == 'cover':
        im_ratio = im.width / im.height
        target_ratio = w / h
        if im_ratio > target_ratio:
            new_h = h
            new_w = int(h * im_ratio)
        else:
            new_w = w
            new_h = int(w / im_ratio)
        im = im.resize((new_w, new_h))
        left = max(0, (im.width - w)//2)
        top = max(0, (im.height - h)//2)
        im = im.crop((left, top, left + w, top + h))
    else:
        im.thumbnail((w, h))
    buf = io.BytesIO()
    im.save(buf, 'WEBP', quality=80)
    return buf.getvalue(), 'image/webp'


def generate_thumb(data: bytes, w: int, h: int, fit: str, is_raw: bool = False) -> Tuple[bytes, str]:
    from PIL import Image
    if is_raw:
        try:
            import rawpy
            with rawpy.imread(io.BytesIO(data)) as raw:
                try:
                    thumb = raw.extract_thumb()
                except rawpy.LibRawNoThumbnailError:
                    thumb = None

                if thumb is not None and thumb.format in [rawpy.ThumbFormat.JPEG, rawpy.ThumbFormat.BITMAP]:
                    im = Image.open(io.BytesIO(thumb.data))
                else:
                    rgb = raw.postprocess(
                        use_camera_wb=False, use_auto_wb=True, output_bps=8)
                    im = Image.fromarray(rgb)
        except Exception as e:
            print(f"rawpy processing failed: {e}")
            raise e

    else:
        im = Image.open(io.BytesIO(data))

    return _image_to_webp(im, w, h, fit)


async def _collect_response_bytes(response, limit: int) -> bytes:
    if response is None:
        return b""

    try:
        if isinstance(response, (bytes, bytearray)):
            return bytes(response[:limit])

        body = getattr(response, "body", None)
        if body is not None:
            return bytes(body[:limit])

        iterator = getattr(response, "body_iterator", None)
        if iterator is not None:
            data = bytearray()
            async for chunk in iterator:
                if not chunk:
                    continue
                need = limit - len(data)
                if need <= 0:
                    break
                data.extend(chunk[:need])
                if len(data) >= limit:
                    break
            return bytes(data)

        if hasattr(response, "__aiter__"):
            data = bytearray()
            async for chunk in response:
                if not chunk:
                    continue
                need = limit - len(data)
                if need <= 0:
                    break
                data.extend(chunk[:need])
                if len(data) >= limit:
                    break
            return bytes(data)
    finally:
        close_func = getattr(response, "close", None)
        if callable(close_func):
            result = close_func()
            if inspect.isawaitable(result):
                await result

    return b""


async def _read_range_slice(adapter, root: str, rel: str, start: int, end: int) -> bytes:
    read_range = getattr(adapter, "read_file_range", None)
    if callable(read_range):
        try:
            return await read_range(root, rel, start, end)
        except TypeError:
            return await read_range(root, rel, start, end=end)

    stream_impl = getattr(adapter, "stream_file", None)
    if callable(stream_impl):
        range_header = f"bytes={start}-{end}"
        response = await stream_impl(root, rel, range_header)
        expected = end - start + 1
        return await _collect_response_bytes(response, expected)

    read_file = getattr(adapter, "read_file", None)
    if callable(read_file) and start == 0:
        data = await read_file(root, rel)
        slice_end = end + 1
        return data[:slice_end]

    return b""


async def _read_video_head(adapter, root: str, rel: str, size: int, limit: int = VIDEO_HEAD_LIMIT) -> bytes:
    end = limit - 1
    if size > 0:
        end = min(end, size - 1)
    if end < 0:
        return b""
    return await _read_range_slice(adapter, root, rel, 0, end)


async def _read_video_tail(adapter, root: str, rel: str, size: int, limit: int) -> Tuple[bytes, int]:
    if size <= 0:
        return b"", 0
    start = max(0, size - limit)
    end = size - 1
    data = await _read_range_slice(adapter, root, rel, start, end)
    return data, start


def _write_video_sparse_file(rel: str, head_bytes: bytes, tail_bytes: bytes, tail_offset: int) -> str:
    suffix = Path(rel).suffix or ".mp4"
    src_tmp = tempfile.NamedTemporaryFile(suffix=suffix, delete=False)
    src_path = src_tmp.name
    try:
        if head_bytes:
            src_tmp.write(head_bytes)
            src_tmp.flush()
    finally:
        src_tmp.close()

    if tail_bytes:
        with open(src_path, "r+b") as f:
            f.seek(max(0, int(tail_offset)))
            f.write(tail_bytes)
            f.flush()
    return src_path


async def _run_ffmpeg_extract_frame(src_path: str, dst_path: str, *, seek_seconds: float | None = None):
    cmd = [
        "ffmpeg",
        "-y",
        "-hide_banner",
        "-loglevel", "error",
    ]
    is_http_input = src_path.startswith(("http://", "https://"))
    if is_http_input and seek_seconds is not None:
        cmd += ["-ss", str(seek_seconds), "-i", src_path]
    else:
        cmd += ["-i", src_path]
        if seek_seconds is not None:
            cmd += ["-ss", str(seek_seconds)]
    cmd += [
        "-frames:v", "1",
        dst_path,
    ]
    try:
        proc = await asyncio.create_subprocess_exec(
            *cmd,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.PIPE,
        )
    except FileNotFoundError as e:
        raise RuntimeError("未找到 ffmpeg，可执行文件需要在 PATH 中") from e

    stdout, stderr = await proc.communicate()
    if proc.returncode != 0:
        message = stderr.decode().strip() or stdout.decode().strip() or "ffmpeg 执行失败"
        raise RuntimeError(message)


def _frame_mean_luma(im) -> float:
    from PIL import ImageStat
    gray = im.convert("L").resize((64, 64))
    return float(ImageStat.Stat(gray).mean[0])


def _is_black_image_bytes(image_bytes: bytes) -> bool:
    from PIL import Image
    with Image.open(io.BytesIO(image_bytes)) as im:
        im.load()
        return _frame_mean_luma(im) < VIDEO_BLACK_FRAME_MEAN_THRESHOLD


async def _generate_video_thumb_from_src_path(src_path: str, w: int, h: int, fit: str) -> Tuple[bytes, str]:
    from PIL import Image

    dst_tmp = tempfile.NamedTemporaryFile(suffix=".png", delete=False)
    dst_path = dst_tmp.name
    dst_tmp.close()

    best: tuple[float, bytes, str] | None = None
    last_error: Exception | None = None
    try:
        for seek_seconds in VIDEO_THUMB_SEEK_SECONDS:
            try:
                with suppress(FileNotFoundError):
                    Path(dst_path).unlink()
                await _run_ffmpeg_extract_frame(src_path, dst_path, seek_seconds=seek_seconds)
                with Image.open(dst_path) as im:
                    im.load()
                    mean = _frame_mean_luma(im)
                    webp_bytes, mime = _image_to_webp(im, w, h, fit)

                if best is None or mean > best[0]:
                    best = (mean, webp_bytes, mime)
                if mean >= VIDEO_BLACK_FRAME_MEAN_THRESHOLD:
                    return webp_bytes, mime
            except Exception as e:
                last_error = e
                continue

        if best is not None:
            return best[1], best[2]
        if last_error is not None:
            raise last_error
        raise RuntimeError("ffmpeg 截帧失败")
    finally:
        with suppress(FileNotFoundError):
            Path(dst_path).unlink()


async def _generate_video_thumb_from_segments(
    head_bytes: bytes,
    tail_bytes: bytes,
    tail_offset: int,
    rel: str,
    w: int,
    h: int,
    fit: str,
) -> Tuple[bytes, str]:
    src_path = _write_video_sparse_file(rel, head_bytes, tail_bytes, tail_offset)
    try:
        return await _generate_video_thumb_from_src_path(src_path, w, h, fit)
    finally:
        with suppress(FileNotFoundError):
            Path(src_path).unlink()


async def get_or_create_thumb(adapter, adapter_id: int, root: str, rel: str, w: int, h: int, fit: str = 'cover'):
    stat = await adapter.stat_file(root, rel)
    size = int(stat.get('size') or 0)
    is_video = is_video_filename(rel)
    if not is_video and size > MAX_IMAGE_SOURCE_SIZE:
        raise HTTPException(400, detail="Image too large for thumbnail")

    key = _cache_key(adapter_id, rel, size, int(
        stat.get('mtime', 0)), w, h, fit)
    path = _cache_path(key)
    if path.exists():
        return path.read_bytes(), 'image/webp', key

    _ensure_cache_dir(path)
    thumb_bytes, mime = None, None

    get_thumb_impl = getattr(adapter, "get_thumbnail", None)
    if callable(get_thumb_impl):
        size_str = "large" if w > 400 else "medium" if w > 100 else "small"
        native_thumb_bytes = await get_thumb_impl(root, rel, size_str)

        if native_thumb_bytes:
            try:
                from PIL import Image
                im = Image.open(io.BytesIO(native_thumb_bytes))
                buf = io.BytesIO()
                im.save(buf, 'WEBP', quality=85)
                thumb_bytes = buf.getvalue()
                mime = 'image/webp'
            except Exception as e:
                print(
                    f"Failed to convert native thumbnail to WebP: {e}, falling back.")
                thumb_bytes, mime = None, None

    if not thumb_bytes:
        if is_video:
            async def _maybe_transcoding_thumb() -> Tuple[bytes, str] | None:
                fid = (stat or {}).get("fid") if isinstance(stat, dict) else None
                get_url = getattr(adapter, "get_video_transcoding_url", None)
                if not fid or not callable(get_url):
                    return None
                try:
                    url = await get_url(str(fid))
                except Exception as e:
                    print(f"Video transcoding url fetch failed: {e}")
                    return None
                if not url:
                    return None
                try:
                    return await _generate_video_thumb_from_src_path(url, w, h, fit)
                except Exception as e:
                    print(f"Video transcoding thumbnail generation failed: {e}")
                    return None

            def _is_hevc_decoder_missing(exc: Exception) -> bool:
                msg = str(exc).lower()
                return ("no decoder found" in msg) and ("hevc" in msg or "h265" in msg)

            async def _read_head(limit: int) -> bytes:
                try:
                    return await _read_video_head(adapter, root, rel, size, limit=limit)
                except HTTPException:
                    raise
                except Exception as e:
                    print(f"Video head read failed: {e}")
                    raise HTTPException(500, detail=f"Video read failed: {e}")

            async def _read_tail(limit: int) -> Tuple[bytes, int]:
                try:
                    return await _read_video_tail(adapter, root, rel, size, limit=limit)
                except HTTPException:
                    raise
                except Exception as e:
                    print(f"Video tail read failed: {e}")
                    raise HTTPException(500, detail=f"Video read failed: {e}")

            head_bytes = await _read_head(VIDEO_HEAD_LIMIT)
            tail_bytes, tail_offset = await _read_tail(VIDEO_TAIL_LIMIT)
            if not head_bytes and not tail_bytes:
                raise HTTPException(500, detail="Unable to read video data for thumbnail")

            try:
                thumb_bytes, mime = await _generate_video_thumb_from_segments(
                    head_bytes, tail_bytes, tail_offset, rel, w, h, fit
                )
            except Exception as e1:
                if _is_hevc_decoder_missing(e1):
                    got = await _maybe_transcoding_thumb()
                    if got is not None:
                        thumb_bytes, mime = got
                if not thumb_bytes:
                    try:
                        tail_bytes, tail_offset = await _read_tail(VIDEO_TAIL_FALLBACK_LIMIT)
                        thumb_bytes, mime = await _generate_video_thumb_from_segments(
                            head_bytes, tail_bytes, tail_offset, rel, w, h, fit
                        )
                    except HTTPException:
                        raise
                    except Exception as e2:
                        print(f"Video thumbnail generation failed: {e2}")
                        raise HTTPException(500, detail=f"Video thumbnail generation failed: {e2}")

            if thumb_bytes and _is_black_image_bytes(thumb_bytes):
                try:
                    head_bytes = await _read_head(VIDEO_HEAD_FALLBACK_LIMIT)
                    retry_thumb, retry_mime = await _generate_video_thumb_from_segments(
                        head_bytes, tail_bytes, tail_offset, rel, w, h, fit
                    )
                    if retry_thumb and not _is_black_image_bytes(retry_thumb):
                        thumb_bytes, mime = retry_thumb, retry_mime
                except Exception:
                    pass
        else:
            read_data = await adapter.read_file(root, rel)
            try:
                thumb_bytes, mime = generate_thumb(
                    read_data, w, h, fit, is_raw=is_raw_filename(rel))
            except Exception as e:
                print(e)
                raise HTTPException(
                    500, detail=f"Thumbnail generation failed: {e}")

    if thumb_bytes:
        path.write_bytes(thumb_bytes)
        return thumb_bytes, mime, key

    raise HTTPException(
        500, detail="Failed to generate thumbnail by any means")