import * as plugins from './smartmail.plugins.js';
import * as paths from './smartmail.paths.js';

export interface IEmailValidationResult {
  valid: boolean;
  disposable: boolean;
  freemail: boolean;
  reason: string;
  formatValid: boolean;
  mxValid: boolean;
  localPartValid: boolean;
  domainPartValid: boolean;
}

export interface IEmailAddressValidatorOptions {
  skipOnlineDomainFetch?: boolean;
  cacheDnsResults?: boolean;
  cacheExpiryMs?: number;
}

export class EmailAddressValidator {
  public domainMap: { [key: string]: 'disposable' | 'freemail' };
  public smartdns = new plugins.smartdns.Smartdns({});
  private dnsCache: Map<string, { result: any; timestamp: number }> = new Map();
  private options: IEmailAddressValidatorOptions;

  constructor(optionsArg: IEmailAddressValidatorOptions = {}) {
    this.options = {
      skipOnlineDomainFetch: false,
      cacheDnsResults: true,
      cacheExpiryMs: 3600000, // 1 hour
      ...optionsArg
    };
  }

  /**
   * Validates an email address format according to RFC 5322
   * @param emailArg The email address to validate
   * @returns True if the format is valid
   */
  public isValidEmailFormat(emailArg: string): boolean {
    if (!emailArg) return false;
    
    // RFC 5322 compliant regex pattern
    const emailRegex = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return emailRegex.test(emailArg);
  }

  /**
   * Validates the local part of an email address (before the @)
   * @param localPart The local part of the email address
   * @returns True if the local part is valid
   */
  public isValidLocalPart(localPart: string): boolean {
    if (!localPart) return false;
    if (localPart.length > 64) return false;
    
    // Check for illegal characters and patterns
    const illegalChars = /[^\w.!#$%&'*+/=?^`{|}~-]/;
    if (illegalChars.test(localPart)) return false;
    
    // Check for consecutive dots or leading/trailing dots
    if (localPart.includes('..') || localPart.startsWith('.') || localPart.endsWith('.')) return false;
    
    return true;
  }

  /**
   * Validates the domain part of an email address (after the @)
   * @param domainPart The domain part of the email address
   * @returns True if the domain part is valid
   */
  public isValidDomainPart(domainPart: string): boolean {
    if (!domainPart) return false;
    if (domainPart.length > 255) return false;
    
    // Domain name validation regex
    const domainRegex = /^[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(\.[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/;
    
    // Must have at least one dot
    if (!domainPart.includes('.')) return false;
    
    // Must end with a valid TLD (at least 2 chars)
    const parts = domainPart.split('.');
    const tld = parts[parts.length - 1];
    if (tld.length < 2) return false;
    
    return domainRegex.test(domainPart);
  }

  /**
   * Performs DNS MX record lookup for a domain
   * @param domain The domain to check
   * @returns MX records or null if none exist
   */
  public async checkMxRecords(domain: string): Promise<any> {
    if (this.options.cacheDnsResults) {
      const cached = this.dnsCache.get(domain);
      if (cached && (Date.now() - cached.timestamp) < this.options.cacheExpiryMs!) {
        return cached.result;
      }
    }
    
    const result = await this.smartdns.getRecords(domain, 'MX');
    
    if (this.options.cacheDnsResults) {
      this.dnsCache.set(domain, { result, timestamp: Date.now() });
    }
    
    return result;
  }
  
  /**
   * Gets the MX records for a domain
   * @param domain The domain to get MX records for
   * @returns Array of MX records as strings
   */
  public async getMxRecords(domain: string): Promise<string[]> {
    const mxRecords = await this.checkMxRecords(domain);
    
    if (!mxRecords || !Array.isArray(mxRecords)) {
      return [];
    }
    
    // Extract exchange values from MX records
    return mxRecords.map((record: any) => {
      if (record && record.exchange) {
        return record.exchange;
      }
      return '';
    }).filter(Boolean);
  }

  /**
   * Checks if an email is from a disposable domain
   * @param email The email address to check
   * @returns True if the email is from a disposable domain
   */
  public async isDisposableEmail(email: string): Promise<boolean> {
    await this.fetchDomains();
    
    if (!this.isValidEmailFormat(email)) {
      return false;
    }
    
    const domainPart = email.split('@')[1];
    return this.domainMap[domainPart] === 'disposable';
  }
  
  /**
   * Checks if an email is a role account (e.g. info@, support@, etc.)
   * @param email The email address to check
   * @returns True if the email is a role account
   */
  public isRoleAccount(email: string): boolean {
    if (!this.isValidEmailFormat(email)) {
      return false;
    }
    
    const localPart = email.split('@')[0].toLowerCase();
    const roleAccounts = [
      'admin', 'administrator', 'webmaster', 'hostmaster', 'postmaster',
      'info', 'support', 'sales', 'marketing', 'contact', 'help',
      'abuse', 'noc', 'security', 'billing', 'donations', 'donate',
      'staff', 'office', 'hr', 'jobs', 'careers', 'team',
      'enquiry', 'enquiries', 'feedback', 'no-reply', 'noreply'
    ];
    
    return roleAccounts.includes(localPart);
  }

  /**
   * Validates an email address
   * @param emailArg The email address to validate
   * @returns Validation result with details
   */
  public async validate(emailArg: string): Promise<IEmailValidationResult> {
    await this.fetchDomains();
    
    // Initialize result
    const result: IEmailValidationResult = {
      valid: false,
      reason: '',
      disposable: false,
      freemail: false,
      formatValid: false,
      mxValid: false,
      localPartValid: false,
      domainPartValid: false
    };
    
    // Check overall email format
    const formatValid = this.isValidEmailFormat(emailArg);
    result.formatValid = formatValid;
    
    if (!formatValid) {
      result.reason = 'Invalid email format';
      return result;
    }
    
    // Split email into local and domain parts
    const [localPart, domainPart] = emailArg.split('@');
    
    // Validate local part
    const localPartValid = this.isValidLocalPart(localPart);
    result.localPartValid = localPartValid;
    
    if (!localPartValid) {
      result.reason = 'Invalid local part (username)';
      return result;
    }
    
    // Validate domain part
    const domainPartValid = this.isValidDomainPart(domainPart);
    result.domainPartValid = domainPartValid;
    
    if (!domainPartValid) {
      result.reason = 'Invalid domain part';
      return result;
    }
    
    // Check MX records
    const mxRecords = await this.checkMxRecords(domainPart);
    result.mxValid = !!mxRecords;
    
    if (!mxRecords) {
      result.reason = 'Domain does not have valid MX records';
      return result;
    }
    
    // Check if domain is disposable or free
    result.disposable = this.domainMap[domainPart] === 'disposable';
    result.freemail = this.domainMap[domainPart] === 'freemail';
    
    if (result.disposable) {
      result.reason = 'Domain is a disposable email provider';
    } else if (result.freemail) {
      result.reason = 'Domain is a free email provider';
    } else {
      result.reason = 'Email is valid';
    }
    
    // Email is valid if it has proper format and MX records
    result.valid = result.formatValid && result.mxValid;
    
    return result;
  }

  /**
   * Fetches the domain list for checking disposable and free email providers
   */
  public async fetchDomains() {
    if (!this.domainMap) {
      const localFileString = plugins.smartfile.fs.toStringSync(
        plugins.path.join(paths.assetDir, 'domains.json')
      );
      const localFileObject = JSON.parse(localFileString);

      if (this.options.skipOnlineDomainFetch) {
        this.domainMap = localFileObject;
        return;
      }

      try {
        const onlineFileObject = (
          await plugins.smartrequest.getJson(
            'https://raw.githubusercontent.com/romainsimon/emailvalid/master/domains.json'
          )
        ).body;
        this.domainMap = onlineFileObject;
      } catch (e) {
        this.domainMap = localFileObject;
      }
    }
  }
}