from pathlib import Path
import uuid

import requests
from django.db import transaction
from django.http import StreamingHttpResponse
from rest_framework import status
from rest_framework.decorators import action
from rest_framework.pagination import PageNumberPagination
from rest_framework.parsers import FormParser, MultiPartParser
from rest_framework.response import Response
from rest_framework.views import APIView
from rest_framework.viewsets import ModelViewSet

from apps.common.api import TeamScopedViewSetMixin, get_current_team

from .models import Asset, AssetFile
from .serializers import AssetSerializer, AssetUploadSerializer
from .storage import TosStorage


class AssetPagination(PageNumberPagination):
    """允许前端用 ?page_size= 覆盖(默认 20,上限 200)。前端「取全部资产」一次大页拉完,
    不再逐页串行(原来 20/页 → 资产多时每次刷新要串十几个请求,整页很慢)。"""

    page_size_query_param = "page_size"
    max_page_size = 200


class AssetViewSet(TeamScopedViewSetMixin, ModelViewSet):
    # select_related 回溯链:asset → origin_task → project,供序列化器解析资产归属商品(避免 N+1)。
    # ★ defer 掉 AITask 的两个巨型 JSON 列(request/response payload):列表序列化只需 project.product_id,
    #   不 defer 的话 select_related 会把每个资产关联 AITask 的完整 AI 请求/响应 payload 全拖出来,
    #   200 个资产实测 100s+(数据越多越慢);defer 后 <1s、product 仍正常解析、无额外查询。
    queryset = (
        Asset.objects.prefetch_related("files")
        .select_related("origin_task__project")
        .defer("origin_task__request_payload", "origin_task__response_payload")
        .all()
    )
    serializer_class = AssetSerializer
    pagination_class = AssetPagination
    search_fields = ["name", "description"]
    ordering_fields = ["created_at", "updated_at", "name"]

    @action(detail=True, methods=["get"], url_path="raw")
    def raw(self, request, pk=None):
        """同源流式代理资产主文件。TOS 桶未配 CORS,浏览器 JS 读不到跨域媒体数据——
        编辑器抽视频缩略图(canvas 会被 taint)/解码音频波形(fetch 被拦)都需要走这里。"""
        asset = self.get_object()
        primary = asset.files.filter(is_primary=True).first() or asset.files.first()
        if primary is None:
            return Response({"detail": "asset has no file"}, status=status.HTTP_404_NOT_FOUND)
        url = TosStorage().presigned_get_url(object_key=primary.object_key, expires_in=600)
        upstream_headers = {}
        if request.META.get("HTTP_RANGE"):
            upstream_headers["Range"] = request.META["HTTP_RANGE"]
        upstream = requests.get(url, headers=upstream_headers, stream=True, timeout=120)
        response = StreamingHttpResponse(
            upstream.iter_content(chunk_size=256 * 1024),
            status=upstream.status_code,
            content_type=primary.content_type or "application/octet-stream",
        )
        for header in ("Content-Length", "Content-Range", "Accept-Ranges"):
            if header in upstream.headers:
                response[header] = upstream.headers[header]
        return response


class AssetUploadView(APIView):
    parser_classes = [MultiPartParser, FormParser]

    @transaction.atomic
    def post(self, request):
        serializer = AssetUploadSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        team = get_current_team(request.user)
        upload = serializer.validated_data["file"]
        suffix = Path(upload.name).suffix.lower()
        asset_id = uuid.uuid4()
        object_key = f"teams/{team.id}/uploads/{asset_id}{suffix}"

        stored = TosStorage().upload_fileobj(
            fileobj=upload.file,
            object_key=object_key,
            content_type=upload.content_type or "application/octet-stream",
        )
        asset = Asset.objects.create(
            id=asset_id,
            team=team,
            created_by=request.user,
            name=serializer.validated_data.get("name") or upload.name,
            asset_type=serializer.validated_data["asset_type"],
            source=Asset.Source.UPLOAD,
            category=serializer.validated_data["category"],
            description=serializer.validated_data.get("description", ""),
        )
        AssetFile.objects.create(
            asset=asset,
            object_key=stored.object_key,
            bucket=stored.bucket,
            content_type=stored.content_type,
            size_bytes=stored.size_bytes,
            is_primary=True,
        )
        return Response(AssetSerializer(asset).data, status=status.HTTP_201_CREATED)