import { NextRequest, NextResponse } from "next/server";
import { prisma } from "@/lib/db";
import { createSession } from "@/lib/auth";
import { checkRateLimit } from "@/lib/rateLimiter";

// Progressive lockout thresholds from Section 4
function getLockoutDuration(failedAttempts: number): number {
  if (failedAttempts >= 20) return 24 * 60 * 60 * 1000; // 24 hours
  if (failedAttempts >= 15) return 30 * 60 * 1000; // 30 minutes
  if (failedAttempts >= 10) return 5 * 60 * 1000; // 5 minutes
  if (failedAttempts >= 5) return 1 * 60 * 1000; // 1 minute
  return 0;
}

export async function POST(request: NextRequest) {
  // Rate limit by IP
  const forwarded = request.headers.get("x-forwarded-for");
  const ip = forwarded?.split(",")[0]?.trim() ?? "unknown";
  const rateCheck = checkRateLimit(ip);

  if (!rateCheck.allowed) {
    return NextResponse.json(
      { error: "Too many requests. Try again shortly." },
      { status: 429 }
    );
  }

  const body = await request.json().catch(() => null);
  if (!body?.password || typeof body.password !== "string") {
    return NextResponse.json(
      { error: "Password is required" },
      { status: 400 }
    );
  }

  // Check lockout state
  let security = await prisma.authSecurity.findUnique({ where: { id: 1 } });
  if (!security) {
    security = await prisma.authSecurity.create({ data: { id: 1 } });
  }

  if (security.lockedUntil && security.lockedUntil > new Date()) {
    const remainingMs =
      security.lockedUntil.getTime() - Date.now();
    const remainingMin = Math.ceil(remainingMs / 60000);
    return NextResponse.json(
      {
        error: `Account locked. Try again in ${remainingMin} minute${remainingMin !== 1 ? "s" : ""}.`,
      },
      { status: 423 }
    );
  }

  // Verify password
  const setting = await prisma.setting.findUnique({
    where: { key: "admin_password_hash" },
  });

  let isValid = false;

  if (!setting) {
    // Initial setup: hash and save the new password
    const argon2 = await import("argon2");
    const newHash = await argon2.hash(body.password);
    await prisma.setting.create({
      data: {
        key: "admin_password_hash",
        value: newHash,
      },
    });
    isValid = true;
  } else {
    // Verify existing password
    const passwordHash = setting.value;
    try {
      const argon2 = await import("argon2");
      isValid = await argon2.verify(passwordHash, body.password);
    } catch {
      isValid = body.password === passwordHash;
    }
  }

  if (!isValid) {
    const newFailedAttempts = security.failedAttempts + 1;
    const lockoutMs = getLockoutDuration(newFailedAttempts);
    const lockedUntil = lockoutMs > 0 ? new Date(Date.now() + lockoutMs) : null;

    await prisma.authSecurity.update({
      where: { id: 1 },
      data: {
        failedAttempts: newFailedAttempts,
        lockedUntil,
        lastAttemptAt: new Date(),
      },
    });

    return NextResponse.json(
      { error: "Invalid password" },
      { status: 401 }
    );
  }

  // Success — reset lockout, create session
  await prisma.authSecurity.update({
    where: { id: 1 },
    data: {
      failedAttempts: 0,
      lockedUntil: null,
      lastAttemptAt: new Date(),
    },
  });

  await createSession();

  return NextResponse.json({ success: true });
}