from datetime import datetime, timedelta
from io import BytesIO
from pathlib import Path
from uuid import uuid4

from fastapi import HTTPException, UploadFile, status
from PIL import Image, ImageStat, UnidentifiedImageError

from app.core.config import settings

ALLOWED_CONTENT_TYPES = {"image/jpeg", "image/png", "image/webp"}


class ImageService:
    def __init__(self) -> None:
        self.upload_dir = Path(settings.upload_dir)
        self.upload_dir.mkdir(parents=True, exist_ok=True)

    async def validate_and_store(self, file: UploadFile, user_id: str) -> tuple[str, int, datetime, dict]:
        content_type = file.content_type or ""
        if content_type not in ALLOWED_CONTENT_TYPES:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Only jpg, png and webp images are supported")

        data = await file.read()
        max_bytes = settings.max_image_mb * 1024 * 1024
        if len(data) > max_bytes:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=f"Image must be smaller than {settings.max_image_mb}MB")

        quality_check = self._inspect_image(data)
        if not quality_check["is_acceptable"]:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=quality_check["reason"])

        suffix = self._suffix_for_type(content_type)
        storage_key = f"{user_id}/{uuid4()}{suffix}"
        path = self.upload_dir / storage_key
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_bytes(data)
        expires_at = datetime.utcnow() + timedelta(days=settings.image_retention_days)
        return storage_key, len(data), expires_at, quality_check

    def read_bytes(self, storage_key: str) -> bytes:
        return (self.upload_dir / storage_key).read_bytes()

    def delete(self, storage_key: str) -> None:
        path = self.upload_dir / storage_key
        if path.exists():
            path.unlink()

    def _inspect_image(self, data: bytes) -> dict:
        try:
            with Image.open(BytesIO(data)) as image:
                image.verify()
            with Image.open(BytesIO(data)) as image:
                width, height = image.size
                rgb = image.convert("RGB")
                gray = image.convert("L")
                brightness = ImageStat.Stat(gray).mean[0]
                resized = gray.resize((64, 64))
                variance = ImageStat.Stat(resized).var[0]
        except UnidentifiedImageError as exc:
            raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Invalid image file") from exc

        checks = {
            "width": width,
            "height": height,
            "brightness": round(brightness, 2),
            "sharpness_score": round(variance, 2),
        }
        if width < 640 or height < 640:
            return {**checks, "is_acceptable": False, "reason": "照片分辨率太低，请上传更清晰的掌心照片"}
        if brightness < 35:
            return {**checks, "is_acceptable": False, "reason": "照片过暗，请在光线更充足的环境重拍"}
        if variance < 80:
            return {**checks, "is_acceptable": False, "reason": "照片可能过于模糊，请保持手掌和镜头稳定后重拍"}
        return {**checks, "is_acceptable": True, "reason": "ok"}

    def _suffix_for_type(self, content_type: str) -> str:
        return {"image/jpeg": ".jpg", "image/png": ".png", "image/webp": ".webp"}[content_type]