import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/app/(auth)/auth";
import {
  buildAttachmentContentDisposition,
  fetchCanvasDownloadAsset,
  sanitizeCanvasDownloadFileName,
} from "@/lib/canvas/photoshop-safe-download";

export const runtime = "nodejs";
export const maxDuration = 120;

function getRequestOrigin(request: NextRequest): string {
  const forwardedHost = (request.headers.get("x-forwarded-host") || "").split(",")[0]?.trim();
  const forwardedProto = (request.headers.get("x-forwarded-proto") || "").split(",")[0]?.trim();
  if (forwardedHost && forwardedProto) {
    return `${forwardedProto}://${forwardedHost}`;
  }
  return new URL(request.url).origin;
}

function resolveDownloadUrl(rawUrl: unknown, origin: string): string {
  const value = String(rawUrl || "").trim();
  if (!value) return "";
  try {
    const parsed = new URL(value, origin);
    if (!/^https?:$/i.test(parsed.protocol)) return "";
    return parsed.toString();
  } catch (_error) {
    return "";
  }
}

function resolveDownloadUrls(body: Record<string, unknown>, origin: string): string[] {
  const rawCandidates = Array.isArray(body.urls) ? body.urls : [body.url];
  const urls: string[] = [];
  const seen = new Set<string>();

  for (const rawUrl of rawCandidates) {
    const url = resolveDownloadUrl(rawUrl, origin);
    if (!url || seen.has(url)) continue;
    seen.add(url);
    urls.push(url);
  }

  return urls.slice(0, 6);
}

export async function POST(request: NextRequest) {
  try {
    const session = await auth();
    if (!session?.user?.id) {
      return NextResponse.json({ success: false, error: "未登录" }, { status: 401 });
    }

    const body = (await request.json().catch(() => ({}))) as Record<string, unknown>;
    const requestOrigin = getRequestOrigin(request);
    const urls = resolveDownloadUrls(body, requestOrigin);
    if (urls.length === 0) {
      return NextResponse.json({ success: false, error: "图片地址无效" }, { status: 400 });
    }

    const name = sanitizeCanvasDownloadFileName(String(body.name || ""), "canvas-image");
    const cookie = request.headers.get("cookie") || "";
    let result: Awaited<ReturnType<typeof fetchCanvasDownloadAsset>> | null = null;
    const failures: string[] = [];

    for (const url of urls) {
      result = await fetchCanvasDownloadAsset({
        file: { url, name },
        index: 0,
        requestOrigin,
        cookie,
        includeSequencePrefix: false,
      });
      if (result.ok) break;
      failures.push(`${url}: ${result.error}`);
    }

    if (!result?.ok) {
      if (failures.length > 0) {
        console.warn("[CanvasDownloadImage] All candidates failed:", failures);
      }
      return NextResponse.json(
        { success: false, error: result?.error || "图片源文件暂时不可访问" },
        { status: 502 }
      );
    }

    return new NextResponse(result.bytes, {
      status: 200,
      headers: {
        "Content-Type": result.contentType,
        "Content-Length": String(result.bytes.length),
        "Content-Disposition": buildAttachmentContentDisposition(result.filename),
        "Cache-Control": "no-store",
      },
    });
  } catch (error) {
    console.error("[CanvasDownloadImage] Failed:", error);
    return NextResponse.json({ success: false, error: "图片下载失败" }, { status: 500 });
  }
}