import { NextRequest, NextResponse } from "next/server";
import { existsSync } from "fs";
import { join } from "path";
import { exec } from "child_process";
import { auth } from "@/lib/auth";
import { removeMod, isClientOnlyMod, waitForServer, rebuildModpack } from "@/lib/mods";
import { createSnapshot, restoreSnapshot, listSnapshots } from "@/lib/snapshots";
import { MODS_DIR, CLIENT_MODS_DIR } from "@/lib/constants";

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 NextResponse.json({ error: "Unauthorized" }, { status: 403 });
  }

  const { filename } = await req.json();

  if (!filename || !filename.endsWith(".jar")) {
    return NextResponse.json({ error: "Invalid filename" }, { status: 400 });
  }

  if (filename.includes("/") || filename.includes("\\")) {
    return NextResponse.json({ error: "Invalid filename" }, { status: 400 });
  }

  const inServerDir = existsSync(join(MODS_DIR, filename));
  const inClientDir = existsSync(join(CLIENT_MODS_DIR, filename));

  if (!inServerDir && !inClientDir) {
    return NextResponse.json({ error: "Mod not found" }, { status: 404 });
  }

  // Create snapshot before removing
  const snapName = `before-remove-${filename.replace(".jar", "")}`;
  createSnapshot(snapName);

  const clientOnly = !inServerDir && inClientDir;

  // Remove the mod
  removeMod(filename);

  if (clientOnly) {
    // Client-only mod — no restart needed
    try { rebuildModpack(); } catch {}
    return NextResponse.json({
      success: true,
      message: `Removed client-only mod "${filename}". No server restart needed.`,
    });
  }

  // Server mod — restart and verify
  try {
    await restartServer();
  } catch (e) {
    const snaps = listSnapshots();
    const snap = snaps[0];
    if (snap) restoreSnapshot(snap.dirName);
    return NextResponse.json({
      success: false,
      message: `Restart failed: ${(e as Error).message}`,
      rolledBack: true,
    });
  }

  const online = await waitForServer(90000);

  if (online) {
    try { rebuildModpack(); } catch {}
    return NextResponse.json({
      success: true,
      message: `Removed "${filename}". Server is online.`,
    });
  } else {
    // Rollback
    const snaps = listSnapshots();
    const snap = snaps[0];
    if (snap) {
      restoreSnapshot(snap.dirName);
      try {
        await restartServer();
        await waitForServer(90000);
        try { rebuildModpack(); } catch {}
      } catch {}
    }

    return NextResponse.json({
      success: false,
      message: `Server failed after removing "${filename}". Rolled back.`,
      rolledBack: true,
    });
  }
}