"""C-04 Provider 抽象层：本地 Pillow 实现 + HTTP 预留。"""
from __future__ import annotations

import io
import os

from PIL import Image


class BaseProvider:
    name = 'base'

    def upscale(self, raw: bytes, scale: int) -> bytes:  # pragma: no cover
        raise NotImplementedError


class PillowProvider(BaseProvider):
    """本地放大：LANCZOS 重采样。零 key、零外部调用，mock 链路即生产链路。"""
    name = 'pillow'
    MAX_INPUT_BYTES = 10 * 1024 * 1024
    MAX_DIM = 4096

    def upscale(self, raw: bytes, scale: int) -> bytes:
        if scale not in (2, 4):
            raise ValueError('仅支持 2x / 4x')
        if len(raw) > self.MAX_INPUT_BYTES:
            raise ValueError('图片过大（>10MB）')
        img = Image.open(io.BytesIO(raw))
        img.load()
        if img.width > self.MAX_DIM or img.height > self.MAX_DIM:
            raise ValueError('图片尺寸过大')
        out = img.resize((img.width * scale, img.height * scale), Image.Resampling.LANCZOS)
        buf = io.BytesIO()
        fmt = (img.format or 'PNG').upper()
        if fmt in ('JPEG', 'JPG'):
            if out.mode in ('RGBA', 'P'):
                out = out.convert('RGB')
            out.save(buf, 'JPEG', quality=95, optimize=True)
            return buf.getvalue()
        out.save(buf, 'PNG', optimize=True)
        return buf.getvalue()


class HTTPProvider(BaseProvider):
    """预留第三方网关：baseURL/key 全走环境变量。未配置时直接抛错（由视图转 503）。"""
    name = 'http'

    def __init__(self) -> None:
        self.base = os.environ.get('AITOOL_API_BASE', '')
        self.key = os.environ.get('AITOOL_API_KEY', '')

    def upscale(self, raw: bytes, scale: int) -> bytes:  # pragma: no cover
        import urllib.request
        if not self.base or not self.key:
            raise RuntimeError('AITOOL_API_BASE / AITOOL_API_KEY 未配置')
        req = urllib.request.Request(
            f'{self.base.rstrip("/")}/upscale',
            data=raw,
            headers={'Authorization': f'Bearer {self.key}', 'X-Scale': str(scale)},
            method='POST',
        )
        with urllib.request.urlopen(req, timeout=30) as resp:
            return resp.read()


def get_provider() -> BaseProvider:
    which = os.environ.get('AITOOL_PROVIDER', 'pillow').lower()
    if which == 'http':
        return HTTPProvider()
    return PillowProvider()