import { Injectable, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { MailerService } from '@nestjs-modules/mailer';

@Injectable()
export class MailService {
  private readonly logger = new Logger(MailService.name);
  private readonly appUrl: string;

  constructor(
    private mailerService: MailerService,
    private configService: ConfigService,
  ) {
    this.appUrl = this.configService.get<string>(
      'TESSERA_APP_URL',
      'http://localhost:3000',
    );
  }

  /**
   * Send a password reset email with a time-limited token link.
   * T-02-12: The caller always returns 200 regardless of whether this succeeds
   * (no email enumeration).
   */
  async sendPasswordResetEmail(
    email: string,
    token: string,
    locale: string = 'de',
  ): Promise<void> {
    const resetLink = `${this.appUrl}/reset-password/${token}`;

    const isGerman = locale === 'de';
    const subject = isGerman
      ? 'Passwort zurücksetzen - Tessera'
      : 'Reset your password - Tessera';

    const text = isGerman
      ? [
          'Hallo,',
          '',
          'Sie haben eine Passwortzurücksetzung für Ihren Tessera-Account angefordert.',
          '',
          `Klicken Sie auf den folgenden Link, um Ihr Passwort zurückzusetzen:`,
          resetLink,
          '',
          'Dieser Link ist 1 Stunde gültig und kann nur einmal verwendet werden.',
          '',
          'Falls Sie diese Anfrage nicht gestellt haben, können Sie diese E-Mail ignorieren.',
          '',
          'Mit freundlichen Grüßen,',
          'Ihr Tessera-Team',
        ].join('\n')
      : [
          'Hello,',
          '',
          'You have requested a password reset for your Tessera account.',
          '',
          'Click the following link to reset your password:',
          resetLink,
          '',
          'This link is valid for 1 hour and can only be used once.',
          '',
          'If you did not request this, you can safely ignore this email.',
          '',
          'Best regards,',
          'The Tessera Team',
        ].join('\n');

    try {
      await this.mailerService.sendMail({
        to: email,
        subject,
        text,
      });
      this.logger.log(`Password reset email sent to ${email}`);
    } catch (error) {
      // Log but don't throw -- caller returns 200 regardless (T-02-12)
      this.logger.error(
        `Failed to send password reset email to ${email}`,
        error instanceof Error ? error.stack : String(error),
      );
    }
  }

  /**
   * Send a welcome email to a newly created user (optional).
   */
  async sendWelcomeEmail(
    email: string,
    username: string,
    locale: string = 'de',
  ): Promise<void> {
    const isGerman = locale === 'de';
    const subject = isGerman
      ? 'Willkommen bei Tessera'
      : 'Welcome to Tessera';

    const text = isGerman
      ? [
          `Hallo ${username},`,
          '',
          'Ihr Tessera-Account wurde erstellt.',
          '',
          `Sie können sich unter ${this.appUrl}/login anmelden.`,
          '',
          'Mit freundlichen Grüßen,',
          'Ihr Tessera-Team',
        ].join('\n')
      : [
          `Hello ${username},`,
          '',
          'Your Tessera account has been created.',
          '',
          `You can sign in at ${this.appUrl}/login.`,
          '',
          'Best regards,',
          'The Tessera Team',
        ].join('\n');

    try {
      await this.mailerService.sendMail({
        to: email,
        subject,
        text,
      });
      this.logger.log(`Welcome email sent to ${email}`);
    } catch (error) {
      this.logger.error(
        `Failed to send welcome email to ${email}`,
        error instanceof Error ? error.stack : String(error),
      );
    }
  }
}