import { NextRequest } from "next/server";
import { auth } from "@/lib/auth";
import { downloadMod } from "@/lib/modrinth";
import type { ModSide } from "@/lib/modrinth";
import { createSnapshot, restoreSnapshot, listSnapshots } from "@/lib/snapshots";
import { waitForServerAdaptive, rebuildModpack, addModMetadata } from "@/lib/mods";
import { exec } from "child_process";

export const dynamic = "force-dynamic";

type ModToInstall = {
  projectId: string;
  versionId: string;
  filename: string;
  url: string;
  title: string;
  side: ModSide;
};

function restartServer(): Promise<void> {
  return new Promise((resolve, reject) => {
    exec("sudo systemctl restart minecraft.service", (err) => {
      if (err) reject(err);
      else resolve();
    });
  });
}

export async function POST(req: NextRequest) {
  const session = await auth();
  if (!session) {
    return new Response(JSON.stringify({ error: "Unauthorized" }), {
      status: 403,
      headers: { "Content-Type": "application/json" },
    });
  }

  const { mods, snapshotName } = (await req.json()) as {
    mods: ModToInstall[];
    snapshotName: string;
  };

  if (!Array.isArray(mods) || mods.length === 0) {
    return new Response(JSON.stringify({ error: "No mods to install" }), {
      status: 400,
      headers: { "Content-Type": "application/json" },
    });
  }

  const stream = new TransformStream();
  const writer = stream.writable.getWriter();
  const encoder = new TextEncoder();

  async function send(event: string, data: object) {
    try {
      await writer.write(encoder.encode(`event: ${event}\ndata: ${JSON.stringify(data)}\n\n`));
    } catch {}
  }

  // Run the pipeline in the background, streaming events as we go
  (async () => {
    const name = snapshotName || `before-install-${Date.now()}`;

    try {
      // 1. Create snapshot
      await send("step", { id: "snapshot", status: "active", message: "Creating safety snapshot..." });
      try {
        createSnapshot(name);
      } catch (e) {
        await send("step", { id: "snapshot", status: "error", message: (e as Error).message });
        await send("done", { success: false, message: `Failed to create snapshot: ${(e as Error).message}` });
        return;
      }
      await send("step", { id: "snapshot", status: "done", message: "Snapshot created" });

      // 2. Download mods
      await send("step", { id: "download", status: "active", message: `Downloading ${mods.length} mod(s)...` });
      try {
        for (const mod of mods) {
          await downloadMod(mod.url, mod.filename, mod.side);
          addModMetadata(mod.filename, { projectId: mod.projectId, side: mod.side });
        }
      } catch (e) {
        await send("step", { id: "download", status: "error", message: (e as Error).message });
        await send("step", { id: "rollback", status: "active", message: "Rolling back..." });
        try {
          const snaps = listSnapshots();
          if (snaps.length > 0) restoreSnapshot(snaps[0].dirName);
        } catch {}
        await send("step", { id: "rollback", status: "done", message: "Rolled back to snapshot" });
        await send("done", { success: false, message: `Download failed: ${(e as Error).message}`, rolledBack: true });
        return;
      }
      await send("step", { id: "download", status: "done", message: "All mods downloaded" });

      // 3. Check if server-side mods need a restart
      const hasServerMods = mods.some((m) => m.side !== "client");

      if (!hasServerMods) {
        await send("step", { id: "modpack", status: "active", message: "Rebuilding modpack..." });
        try { rebuildModpack(); } catch {}
        await send("step", { id: "modpack", status: "done", message: "Modpack updated" });
        await send("done", {
          success: true,
          message: `Installed ${mods.length} client-only mod(s). No server restart needed.`,
          installed: mods.map((m) => m.filename),
        });
        return;
      }

      // 4. Restart server
      await send("step", { id: "restart", status: "active", message: "Restarting server..." });
      try {
        await restartServer();
      } catch (e) {
        await send("step", { id: "restart", status: "error", message: (e as Error).message });
        await send("step", { id: "rollback", status: "active", message: "Rolling back..." });
        try {
          const snaps = listSnapshots();
          if (snaps.length > 0) restoreSnapshot(snaps[0].dirName);
        } catch {}
        await send("step", { id: "rollback", status: "done", message: "Rolled back to snapshot" });
        await send("done", { success: false, message: `Server restart failed: ${(e as Error).message}`, rolledBack: true });
        return;
      }
      await send("step", { id: "restart", status: "done", message: "Restart command sent" });

      // 5. Wait for server with progress reporting
      await send("step", { id: "health", status: "active", message: "Waiting for server..." });
      const online = await waitForServerAdaptive(async (progress) => {
        await send("step", { id: "health", status: "active", message: progress.message });
      });

      if (online) {
        await send("step", { id: "health", status: "done", message: "Server is online" });
        await send("step", { id: "modpack", status: "active", message: "Rebuilding modpack..." });
        try { rebuildModpack(); } catch {}
        await send("step", { id: "modpack", status: "done", message: "Modpack updated" });
        await send("done", {
          success: true,
          message: `Installed ${mods.length} mod(s). Server is online.`,
          installed: mods.map((m) => m.filename),
        });
      } else {
        await send("step", { id: "health", status: "error", message: "Server failed to start" });
        await send("step", { id: "rollback", status: "active", message: "Rolling back to snapshot..." });
        try {
          const snaps = listSnapshots();
          if (snaps.length > 0) {
            restoreSnapshot(snaps[0].dirName);
            await restartServer();
            await waitForServerAdaptive(async (progress) => {
              await send("step", { id: "rollback", status: "active", message: `Rollback: ${progress.message}` });
            });
            try { rebuildModpack(); } catch {}
          }
        } catch {}
        await send("step", { id: "rollback", status: "done", message: "Rolled back and server restarted" });
        await send("done", {
          success: false,
          message: `Server failed to start after installing ${mods.length} mod(s). Rolled back to snapshot.`,
          rolledBack: true,
        });
      }
    } catch (e) {
      await send("done", { success: false, message: (e as Error).message });
    } finally {
      try { writer.close(); } catch {}
    }
  })();

  return new Response(stream.readable, {
    headers: {
      "Content-Type": "text/event-stream",
      "Cache-Control": "no-cache",
      Connection: "keep-alive",
      "X-Accel-Buffering": "no",
    },
  });
}