import hashlib
import logging
import mimetypes
import uuid
from pathlib import Path

from fastapi import HTTPException, Response
from .config import settings


logger = logging.getLogger(__name__)


def _safe_extension(filename: str, content_type: str) -> str:
    extension = Path(filename or "").suffix.lower()
    if extension in {".jpg", ".jpeg", ".png", ".webp"}:
        return extension
    guessed = mimetypes.guess_extension(content_type or "") or ".bin"
    return ".jpg" if guessed == ".jpe" else guessed


def _absolute_path(relative_path: str) -> Path:
    root = settings.screenshot_storage_dir.resolve()
    candidate = (root / relative_path).resolve()
    if root != candidate and root not in candidate.parents:
        raise ValueError("非法截图文件路径")
    return candidate


def store_screenshot(data: bytes, filename: str, content_type: str, category: str) -> str:
    if not data:
        raise ValueError("截图内容不能为空")
    now_path = Path(category) / uuid.uuid4().hex[:2]
    relative_path = now_path / f"{uuid.uuid4().hex}{_safe_extension(filename, content_type)}"
    target = _absolute_path(relative_path.as_posix())
    target.parent.mkdir(parents=True, exist_ok=True)
    temporary = target.with_suffix(target.suffix + ".tmp")
    temporary.write_bytes(data)
    if temporary.stat().st_size != len(data):
        temporary.unlink(missing_ok=True)
        raise OSError("截图写入不完整")
    temporary.replace(target)
    return relative_path.as_posix()


def screenshot_fields(data: bytes, filename: str, content_type: str, category: str) -> dict:
    try:
        file_path = store_screenshot(data, filename, content_type, category)
    except (OSError, ValueError) as exc:
        logger.exception(
            "Screenshot file write failed: category=%s filename=%s storage_dir=%s",
            category,
            filename,
            settings.screenshot_storage_dir,
        )
        raise HTTPException(
            status_code=503,
            detail="图片存储目录不可用，请联系管理员检查目录配置和写入权限",
        ) from exc
    return {
        "filename": filename,
        "content_type": content_type,
        "file_path": file_path,
        "image_data": None,
    }


def screenshot_bytes(image) -> bytes:
    if image.file_path:
        try:
            path = _absolute_path(image.file_path)
            if path.is_file():
                return path.read_bytes()
        except (OSError, ValueError):
            pass
    if image.image_data:
        return bytes(image.image_data)
    raise HTTPException(status_code=404, detail="截图文件不存在")


def screenshot_response(image) -> Response:
    return Response(
        content=screenshot_bytes(image),
        media_type=image.content_type or "application/octet-stream",
        headers={"Cache-Control": "private, max-age=600"},
    )


def screenshot_data_url(image) -> str:
    import base64

    encoded = base64.b64encode(screenshot_bytes(image)).decode()
    return f"data:{image.content_type};base64,{encoded}"


def file_digest(relative_path: str) -> tuple[int, str]:
    data = _absolute_path(relative_path).read_bytes()
    return len(data), hashlib.sha256(data).hexdigest()