import { NextResponse } from "next/server";
import { readFileSync } from "fs";
import { auth } from "@/lib/auth";
import { MOD_METADATA_FILE } from "@/lib/constants";
import { memoAsync } from "@/lib/cache";

export const dynamic = "force-dynamic";

const API = "https://api.modrinth.com/v2";
const GAME_VERSION = "1.20.1";
const LOADER = "forge";
const UA = "HurkiCorgiMC/1.0 (minecraft.hurkicorgi.com)";

type ModMetadataEntry = { projectId: string; side: string };

type UpdateInfo = {
  filename: string;
  projectId: string;
  latestFilename: string;
  latestVersionId: string;
  dateModified: string;
  hasUpdate: boolean;
};

async function checkUpdates(): Promise<UpdateInfo[]> {
  let metadata: Record<string, ModMetadataEntry>;
  try {
    metadata = JSON.parse(readFileSync(MOD_METADATA_FILE, "utf8"));
  } catch {
    return [];
  }

  const entries = Object.entries(metadata).filter(([, m]) => m?.projectId);
  if (entries.length === 0) return [];

  const results = await Promise.all(
    entries.map(async ([filename, entry]) => {
      try {
        const url = `${API}/project/${entry.projectId}/version?game_versions=["${GAME_VERSION}"]&loaders=["${LOADER}"]`;
        const res = await fetch(url, {
          headers: { "User-Agent": UA },
          signal: AbortSignal.timeout(10_000),
        });
        if (!res.ok) return null;
        const versions: Array<{
          id: string;
          date_published: string;
          files: Array<{ filename: string }>;
        }> = await res.json();
        const latest = versions[0];
        if (!latest || !latest.files?.[0]) return null;
        const latestFilename = latest.files[0].filename;
        return {
          filename,
          projectId: entry.projectId,
          latestFilename,
          latestVersionId: latest.id,
          dateModified: latest.date_published,
          hasUpdate: latestFilename !== filename,
        } satisfies UpdateInfo;
      } catch {
        return null;
      }
    })
  );

  return results.filter((r): r is UpdateInfo => r !== null && r.hasUpdate);
}

export async function GET() {
  const session = await auth();
  if (!session) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 403 });
  }

  try {
    const updates = await memoAsync("mods:updates", 30 * 60 * 1000, checkUpdates);
    return NextResponse.json(updates, {
      headers: { "Cache-Control": "private, max-age=300" },
    });
  } catch (e) {
    return NextResponse.json(
      { error: (e as Error).message },
      { status: 500 }
    );
  }
}