import { Injectable, Logger, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository, LessThanOrEqual, In } from 'typeorm';
import { ConfigService } from '@nestjs/config';
import { Application } from '../applications/entities/application.entity';
import { PlatformSetting } from '../billing/entities/platform-setting.entity';
import { KubernetesService } from '../kubernetes/kubernetes.service';
import { BillingService } from '../billing/billing.service';
import { AppLifecycleStatus, BillingCycle, DeploymentStatus } from '../common/enums';

/**
 * Manages the full lifecycle of applications based on their billing plan:
 *
 *  ACTIVE  ──(plan expires)──►  SUSPENDED  ──(grace period)──►  PENDING_DELETION ──► DELETED
 *     ▲                              │                                │
 *     └──────── payment ─────────────┘                                │
 *     └──────── payment (if still within grace) ──────────────────────┘
 *
 * Runs a periodic scan (configurable interval, default 60s) that:
 *   1. Finds ACTIVE apps whose planExpiresAt has passed → suspends them
 *   2. Finds SUSPENDED apps past their grace period → marks PENDING_DELETION
 *   3. Finds PENDING_DELETION apps past scheduledDeletionAt → fully deletes
 */
@Injectable()
export class AppLifecycleService implements OnModuleInit, OnModuleDestroy {
  private readonly logger = new Logger(AppLifecycleService.name);
  private scanTimer: NodeJS.Timeout | null = null;

  constructor(
    @InjectRepository(Application)
    private appRepo: Repository<Application>,
    @InjectRepository(PlatformSetting)
    private settingsRepo: Repository<PlatformSetting>,
    private configService: ConfigService,
    private kubernetesService: KubernetesService,
    private billingService: BillingService,
  ) {}

  onModuleInit() {
    const interval = this.configService.get<number>('lifecycle.scanIntervalMs') || 60_000;
    this.logger.log(`Lifecycle scanner starting — interval: ${interval / 1000}s`);
    this.scanTimer = setInterval(() => this.runScan(), interval);
    // Run once immediately after a short delay to catch up on startup
    setTimeout(() => this.runScan(), 5_000);
  }

  onModuleDestroy() {
    if (this.scanTimer) clearInterval(this.scanTimer);
  }

  // ─── Public API (called by billing on payment) ────────────────────

  /**
   * Activate or reactivate an application after successful payment.
   * Calculates the new expiry based on billing cycle and scales pods back up.
   */
  async activateApp(appId: string, billingCycle: BillingCycle, planId: string): Promise<Application> {
    const app = await this.appRepo.findOne({ where: { id: appId } });
    if (!app) throw new Error(`Application ${appId} not found`);

    const now = new Date();
    const expiresAt = this.calculateExpiry(now, billingCycle);

    app.planId = planId;
    app.billingCycle = billingCycle;
    app.lifecycleStatus = AppLifecycleStatus.ACTIVE;
    app.planExpiresAt = expiresAt;
    app.suspendedAt = null as any;
    app.scheduledDeletionAt = null as any;

    const saved = await this.appRepo.save(app);

    // If the app was suspended, scale it back up
    if (app.latestImageTag) {
      try {
        await this.kubernetesService.scaleDeployment(app, app.replicas || 1);
        this.logger.log(`Reactivated ${app.name} — scaled to ${app.replicas} replicas, expires ${expiresAt.toISOString()}`);
      } catch (e: any) {
        this.logger.warn(`Failed to scale up ${app.name} on reactivation: ${e.message}`);
      }
    }

    return saved;
  }

  /**
   * Renew an app for another billing period (used for auto-renew or manual renewal).
   */
  async renewApp(appId: string): Promise<Application> {
    const app = await this.appRepo.findOne({ where: { id: appId } });
    if (!app || !app.billingCycle) throw new Error('Application not found or has no billing cycle');

    const baseDate = app.planExpiresAt && app.planExpiresAt > new Date()
      ? app.planExpiresAt  // extend from current expiry
      : new Date();        // expired — extend from now

    app.planExpiresAt = this.calculateExpiry(baseDate, app.billingCycle);
    app.lifecycleStatus = AppLifecycleStatus.ACTIVE;
    app.suspendedAt = null as any;
    app.scheduledDeletionAt = null as any;

    return this.appRepo.save(app);
  }

  // ─── Periodic Scanner ─────────────────────────────────────────────

  private async runScan() {
    try {
      const now = new Date();
      await this.suspendExpiredApps(now);
      await this.markForDeletion(now);
      await this.deleteExpiredApps(now);
    } catch (e: any) {
      this.logger.error(`Lifecycle scan error: ${e.message}`, e.stack);
    }
  }

  /**
   * Step 1: Find ACTIVE apps whose planExpiresAt has passed → SUSPEND
   */
  private async suspendExpiredApps(now: Date) {
    const expiredApps = await this.appRepo.find({
      where: {
        lifecycleStatus: AppLifecycleStatus.ACTIVE,
        planExpiresAt: LessThanOrEqual(now),
      },
    });

    for (const app of expiredApps) {
      if (!app.billingCycle) continue; // No billing plan — skip (free/unmanaged app)

      try {
        // For hourly plans: try auto-deduct from wallet for renewal
        if (app.billingCycle === BillingCycle.HOURLY) {
          const renewed = await this.tryAutoRenew(app);
          if (renewed) continue;
        }

        // Suspend: scale to 0
        try {
          await this.kubernetesService.scaleDeployment(app, 0);
        } catch (e: any) {
          this.logger.warn(`Failed to scale down ${app.name}: ${e.message}`);
        }

        app.lifecycleStatus = AppLifecycleStatus.SUSPENDED;
        app.suspendedAt = now;

        // Calculate when deletion should happen
        const deleteAfterMs = await this.getDeleteGracePeriod(app.billingCycle);
        app.scheduledDeletionAt = new Date(now.getTime() + deleteAfterMs);

        await this.appRepo.save(app);
        this.logger.warn(
          `SUSPENDED ${app.name} (${app.billingCycle} plan expired). ` +
          `Scheduled deletion: ${app.scheduledDeletionAt.toISOString()}`,
        );
      } catch (e: any) {
        this.logger.error(`Failed to suspend ${app.name}: ${e.message}`);
      }
    }
  }

  /**
   * Step 2: Find SUSPENDED apps past their scheduledDeletionAt → PENDING_DELETION
   */
  private async markForDeletion(now: Date) {
    const apps = await this.appRepo.find({
      where: {
        lifecycleStatus: AppLifecycleStatus.SUSPENDED,
        scheduledDeletionAt: LessThanOrEqual(now),
      },
    });

    for (const app of apps) {
      app.lifecycleStatus = AppLifecycleStatus.PENDING_DELETION;
      await this.appRepo.save(app);
      this.logger.warn(`PENDING_DELETION: ${app.name} — grace period ended, will be deleted`);
    }
  }

  /**
   * Step 3: Find PENDING_DELETION apps → fully delete from K8s and DB
   */
  private async deleteExpiredApps(now: Date) {
    const apps = await this.appRepo.find({
      where: {
        lifecycleStatus: AppLifecycleStatus.PENDING_DELETION,
      },
    });

    for (const app of apps) {
      try {
        // Delete all K8s resources
        await this.kubernetesService.deleteApplication(app);
        this.logger.log(`Deleted K8s resources for expired app ${app.name}`);
      } catch (e: any) {
        this.logger.warn(`K8s cleanup failed for expired ${app.name}: ${e.message}`);
      }

      try {
        // Mark as deleted (soft-delete approach — keep record for audit)
        app.lifecycleStatus = AppLifecycleStatus.DELETED;
        await this.appRepo.save(app);
        this.logger.warn(`DELETED: ${app.name} — all resources removed`);
      } catch (e: any) {
        this.logger.error(`Failed to mark ${app.name} as deleted: ${e.message}`);
      }
    }
  }

  // ─── Auto-renew for hourly plans ──────────────────────────────────

  private async tryAutoRenew(app: Application): Promise<boolean> {
    if (!app.planId) return false;

    try {
      const cost = await this.billingService.calculateCostForApp(app);
      const hourlyAmount = cost.hourly;
      if (hourlyAmount <= 0) return false;

      // Check wallet balance
      const { balance } = await this.billingService.getBalance(app.userId);
      if (balance < hourlyAmount) return false;

      // Deduct and renew
      await this.billingService.deductWallet(
        app.userId,
        hourlyAmount,
        `Auto-renew hourly: ${app.name}`,
        app.id,
      );

      app.planExpiresAt = this.calculateExpiry(new Date(), BillingCycle.HOURLY);
      app.lifecycleStatus = AppLifecycleStatus.ACTIVE;
      await this.appRepo.save(app);

      this.logger.log(`Auto-renewed hourly plan for ${app.name} — deducted ${hourlyAmount} Toman`);
      return true;
    } catch (e: any) {
      this.logger.warn(`Auto-renew failed for ${app.name}: ${e.message}`);
      return false;
    }
  }

  // ─── Helpers ──────────────────────────────────────────────────────

  private calculateExpiry(from: Date, cycle: BillingCycle): Date {
    const expiry = new Date(from);
    switch (cycle) {
      case BillingCycle.HOURLY:
        expiry.setHours(expiry.getHours() + 1);
        break;
      case BillingCycle.MONTHLY:
        expiry.setMonth(expiry.getMonth() + 1);
        break;
      case BillingCycle.YEARLY:
        expiry.setFullYear(expiry.getFullYear() + 1);
        break;
    }
    return expiry;
  }

  /**
   * Get the grace period (ms) before a suspended app is deleted.
   * First checks PlatformSettings (admin-editable), then falls back to config file defaults.
   */
  private async getDeleteGracePeriod(cycle: BillingCycle): Promise<number> {
    const settingKey = `lifecycle.${cycle}.deleteAfterMs`;

    // Check admin-editable settings first
    try {
      const setting = await this.settingsRepo.findOne({ where: { key: settingKey } });
      if (setting) return parseInt(setting.value, 10);
    } catch {}

    // Fall back to config file
    return this.configService.get<number>(`lifecycle.${cycle}.deleteAfterMs`) || 24 * 3600 * 1000;
  }

  // ─── Admin API ────────────────────────────────────────────────────

  async getLifecycleSettings(): Promise<Record<string, any>> {
    const settings = await this.settingsRepo.find({
      where: { key: In([
        'lifecycle.hourly.deleteAfterMs',
        'lifecycle.monthly.deleteAfterMs',
        'lifecycle.yearly.deleteAfterMs',
      ]) },
    });

    const defaults = {
      'lifecycle.hourly.deleteAfterMs': this.configService.get<number>('lifecycle.hourly.deleteAfterMs'),
      'lifecycle.monthly.deleteAfterMs': this.configService.get<number>('lifecycle.monthly.deleteAfterMs'),
      'lifecycle.yearly.deleteAfterMs': this.configService.get<number>('lifecycle.yearly.deleteAfterMs'),
    };

    const result: Record<string, any> = { ...defaults };
    for (const s of settings) {
      result[s.key] = parseInt(s.value, 10);
    }

    return {
      hourly: { deleteAfterMs: result['lifecycle.hourly.deleteAfterMs'], deleteAfterHours: result['lifecycle.hourly.deleteAfterMs'] / 3600000 },
      monthly: { deleteAfterMs: result['lifecycle.monthly.deleteAfterMs'], deleteAfterDays: result['lifecycle.monthly.deleteAfterMs'] / 86400000 },
      yearly: { deleteAfterMs: result['lifecycle.yearly.deleteAfterMs'], deleteAfterDays: result['lifecycle.yearly.deleteAfterMs'] / 86400000 },
    };
  }

  async updateLifecycleSetting(key: string, value: number, description?: string): Promise<PlatformSetting> {
    let setting = await this.settingsRepo.findOne({ where: { key } });
    if (setting) {
      setting.value = String(value);
      if (description) setting.description = description;
    } else {
      setting = this.settingsRepo.create({ key, value: String(value), description });
    }
    return this.settingsRepo.save(setting);
  }
}