import { Injectable, Logger } from '@nestjs/common';
import { Knex, knex } from 'knex';
import { getCentralPrisma } from '../prisma/central-prisma.service';
import * as crypto from 'crypto';

@Injectable()
export class TenantDatabaseService {
  private readonly logger = new Logger(TenantDatabaseService.name);
  private tenantConnections: Map<string, Knex> = new Map();

  /**
   * Get tenant database connection by domain (for subdomain-based authentication)
   * This is used when users log in via tenant subdomains
   */
  async getTenantKnexByDomain(domain: string): Promise<Knex> {
    const cacheKey = `domain:${domain}`;
    
    // Check if we have a cached connection
    if (this.tenantConnections.has(cacheKey)) {
      // Validate the domain still exists before returning cached connection
      const centralPrisma = getCentralPrisma();
      
      try {
        const domainRecord = await centralPrisma.domain.findUnique({
          where: { domain },
        });
        
        // If domain no longer exists, remove cached connection
        if (!domainRecord) {
          this.logger.warn(`Domain ${domain} no longer exists, removing cached connection`);
          await this.disconnectTenant(cacheKey);
          throw new Error(`Domain ${domain} not found`);
        }
      } catch (error) {
        // If domain doesn't exist, remove from cache and re-throw
        if (error.message.includes('not found')) {
          throw error;
        }
        // For other errors, log but continue with cached connection
        this.logger.warn(`Error validating domain ${domain}:`, error.message);
      }
      
      return this.tenantConnections.get(cacheKey);
    }

    const centralPrisma = getCentralPrisma();
    
    // Find tenant by domain
    const domainRecord = await centralPrisma.domain.findUnique({
      where: { domain },
      include: { tenant: true },
    });

    if (!domainRecord) {
      throw new Error(`Domain ${domain} not found`);
    }

    const tenant = domainRecord.tenant;
    this.logger.log(`Found tenant by domain: ${domain} -> ${tenant.name}`);

    if (tenant.status !== 'active') {
      throw new Error(`Tenant ${tenant.name} is not active`);
    }

    // Create connection and cache it
    const tenantKnex = await this.createTenantConnection(tenant);
    this.tenantConnections.set(cacheKey, tenantKnex);
    
    return tenantKnex;
  }

  /**
   * Get tenant database connection by tenant ID (for central admin operations)
   * This is used when central admin needs to access tenant databases
   */
  async getTenantKnexById(tenantId: string): Promise<Knex> {
    const cacheKey = `id:${tenantId}`;
    
    // Check if we have a cached connection (no validation needed for ID-based lookups)
    if (this.tenantConnections.has(cacheKey)) {
      return this.tenantConnections.get(cacheKey);
    }

    const centralPrisma = getCentralPrisma();
    
    // Find tenant by ID
    const tenant = await centralPrisma.tenant.findUnique({
      where: { id: tenantId },
    });

    if (!tenant) {
      throw new Error(`Tenant ${tenantId} not found`);
    }

    if (tenant.status !== 'active') {
      throw new Error(`Tenant ${tenant.name} is not active`);
    }

    this.logger.log(`Connecting to tenant database by ID: ${tenant.name}`);

    // Create connection and cache it
    const tenantKnex = await this.createTenantConnection(tenant);
    this.tenantConnections.set(cacheKey, tenantKnex);
    
    return tenantKnex;
  }

  /**
   * Legacy method - delegates to domain-based lookup
   * @deprecated Use getTenantKnexByDomain or getTenantKnexById instead
   */
  async getTenantKnex(tenantIdOrSlug: string): Promise<Knex> {
    // Assume it's a domain if it contains a dot
    return this.getTenantKnexByDomain(tenantIdOrSlug);
  }

  /**
   * Create a new Knex connection to a tenant database
   */
  private async createTenantConnection(tenant: any): Promise<Knex> {
    // Decrypt password
    const decryptedPassword = this.decryptPassword(tenant.dbPassword);

    const tenantKnex = knex({
      client: 'mysql2',
      connection: {
        host: tenant.dbHost,
        port: tenant.dbPort,
        user: tenant.dbUsername,
        password: decryptedPassword,
        database: tenant.dbName,
      },
      pool: {
        min: 2,
        max: 10,
      },
    });

    // Test connection
    try {
      await tenantKnex.raw('SELECT 1');
      this.logger.log(`Connected to tenant database: ${tenant.dbName}`);
    } catch (error) {
      this.logger.error(
        `Failed to connect to tenant database: ${tenant.dbName}`,
        error,
      );
      throw error;
    }

    return tenantKnex;
  }

  async getTenantByDomain(domain: string): Promise<any> {
    const centralPrisma = getCentralPrisma();
    const domainRecord = await centralPrisma.domain.findUnique({
      where: { domain },
      include: { tenant: true },
    });

    if (!domainRecord) {
      throw new Error(`Domain ${domain} not found`);
    }

    if (domainRecord.tenant.status !== 'active') {
      throw new Error(`Tenant for domain ${domain} is not active`);
    }

    return domainRecord.tenant;
  }

  /**
   * Resolve tenant by ID or slug
   * Tries ID first, then falls back to slug
   */
  async resolveTenantId(idOrSlug: string): Promise<string> {
    const centralPrisma = getCentralPrisma();
    
    // Try by ID first
    let tenant = await centralPrisma.tenant.findUnique({
      where: { id: idOrSlug },
    });

    // If not found, try by slug
    if (!tenant) {
      tenant = await centralPrisma.tenant.findUnique({
        where: { slug: idOrSlug },
      });
    }

    if (!tenant) {
      throw new Error(`Tenant ${idOrSlug} not found`);
    }

    if (tenant.status !== 'active') {
      throw new Error(`Tenant ${tenant.name} is not active`);
    }

    return tenant.id;
  }

  async disconnectTenant(tenantId: string) {
    const connection = this.tenantConnections.get(tenantId);
    if (connection) {
      await connection.destroy();
      this.tenantConnections.delete(tenantId);
      this.logger.log(`Disconnected tenant: ${tenantId}`);
    }
  }

  removeTenantConnection(tenantId: string) {
    this.tenantConnections.delete(tenantId);
    this.logger.log(`Removed tenant connection from cache: ${tenantId}`);
  }

  async disconnectAll() {
    for (const [tenantId, connection] of this.tenantConnections.entries()) {
      await connection.destroy();
    }
    this.tenantConnections.clear();
    this.logger.log('Disconnected all tenant connections');
  }

  encryptPassword(password: string): string {
    const algorithm = 'aes-256-cbc';
    const key = Buffer.from(process.env.ENCRYPTION_KEY, 'hex');
    const iv = crypto.randomBytes(16);
    const cipher = crypto.createCipheriv(algorithm, key, iv);
    let encrypted = cipher.update(password, 'utf8', 'hex');
    encrypted += cipher.final('hex');
    return iv.toString('hex') + ':' + encrypted;
  }

  private decryptPassword(encryptedPassword: string): string {
    const algorithm = 'aes-256-cbc';
    const key = Buffer.from(process.env.ENCRYPTION_KEY, 'hex');
    const parts = encryptedPassword.split(':');
    const iv = Buffer.from(parts[0], 'hex');
    const encrypted = parts[1];
    const decipher = crypto.createDecipheriv(algorithm, key, iv);
    let decrypted = decipher.update(encrypted, 'hex', 'utf8');
    decrypted += decipher.final('utf8');
    return decrypted;
  }
}