import prisma from "@shieldai/db";
import { SubscriptionTier } from "@shieldai/types";

const TIER_CONFIG = {
  [SubscriptionTier.BASIC]: { intervalMinutes: 1440, cron: "0 0 * * *" },
  [SubscriptionTier.PLUS]: { intervalMinutes: 360, cron: "0 */6 * * *" },
  [SubscriptionTier.PREMIUM]: { intervalMinutes: 60, cron: "0 * * * *" },
} as const;

export class ScanScheduler {
  /**
   * Get the scan interval (in minutes) for a given subscription tier.
   */
  public static getIntervalForTier(tier: SubscriptionTier): number {
    return TIER_CONFIG[tier]?.intervalMinutes ?? TIER_CONFIG[SubscriptionTier.BASIC].intervalMinutes;
  }

  /**
   * Get the cron expression for a given subscription tier.
   */
  public static getCronForTier(tier: SubscriptionTier): string {
    return TIER_CONFIG[tier]?.cron ?? TIER_CONFIG[SubscriptionTier.BASIC].cron;
  }

  /**
   * Ensure a user has an active scan schedule based on their subscription tier.
   * Creates or updates the schedule record.
   */
  async ensureScheduleForUser(userId: string): Promise<{ scheduled: boolean; intervalMinutes: number }> {
    const user = await prisma.user.findUnique({
      where: { id: userId },
      select: { subscriptionTier: true },
    });

    if (!user) {
      return { scheduled: false, intervalMinutes: 0 };
    }

    const tier = user.subscriptionTier ?? SubscriptionTier.BASIC;
    const config = TIER_CONFIG[tier];
    const nextScan = this.calculateNextScan();

    const schedule = await prisma.scanSchedule.upsert({
      where: { userId },
      update: {
        intervalMinutes: config.intervalMinutes,
        cronExpression: config.cron,
        nextScanAt: nextScan,
      },
      create: {
        userId,
        intervalMinutes: config.intervalMinutes,
        cronExpression: config.cron,
        status: "ACTIVE",
        nextScanAt: nextScan,
      },
    });

    return {
      scheduled: schedule.status === "ACTIVE",
      intervalMinutes: schedule.intervalMinutes,
    };
  }

  /**
   * Get all active schedules that are due for scanning.
   */
  async getDueSchedules(): Promise<Array<{ userId: string; intervalMinutes: number; cronExpression: string }>> {
    const now = new Date();

    const due = await prisma.scanSchedule.findMany({
      where: {
        status: "ACTIVE",
        OR: [
          { nextScanAt: { lte: now } },
          { nextScanAt: null },
        ],
      },
      select: {
        userId: true,
        intervalMinutes: true,
        cronExpression: true,
      },
    });

    return due;
  }

  /**
   * Mark a schedule as scanned and compute the next scan time.
   */
  async markScanned(userId: string): Promise<Date> {
    const schedule = await prisma.scanSchedule.findUnique({ where: { userId } });

    if (!schedule) {
      throw new Error(`ScanSchedule not found for user ${userId}`);
    }

    const nextScan = this.calculateNextScan(schedule.intervalMinutes);

    await prisma.scanSchedule.update({
      where: { userId },
      data: {
        lastScanAt: new Date(),
        nextScanAt: nextScan,
      },
    });

    return nextScan;
  }

  /**
   * Pause scheduling for a user (e.g., on subscription downgrade or pause).
   */
  async pauseSchedule(userId: string): Promise<void> {
    await prisma.scanSchedule.updateMany({
      where: { userId, status: "ACTIVE" },
      data: { status: "PAUSED" },
    });
  }

  /**
   * Resume scheduling for a user and recalculate based on current tier.
   */
  async resumeSchedule(userId: string): Promise<void> {
    await this.ensureScheduleForUser(userId);
  }

  /**
   * Get the current schedule for a user.
   */
  async getSchedule(userId: string) {
    return prisma.scanSchedule.findUnique({
      where: { userId },
    });
  }

  /**
   * List all active schedules (for admin/monitoring).
   */
  async listActiveSchedules(limit = 100, offset = 0) {
    return prisma.scanSchedule.findMany({
      where: { status: "ACTIVE" },
      include: {
        user: {
          select: {
            id: true,
            email: true,
            subscriptionTier: true,
          },
        },
      },
      orderBy: { nextScanAt: "asc" },
      take: limit,
      skip: offset,
    });
  }

  /**
   * Calculate the next scan time based on interval.
   */
  private calculateNextScan(intervalMinutes?: number): Date {
    const minutes = intervalMinutes ?? 60;
    const next = new Date();
    next.setMinutes(next.getMinutes() + minutes);
    return next;
  }
}