import { Injectable, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { DataSource } from 'typeorm';
import { Resend } from 'resend';

@Injectable()
export class EmailService {
  private readonly logger = new Logger(EmailService.name);
  private resend: Resend | null = null;
  private fromAddress: string;
  private replyToAddress: string;

  constructor(
    private configService: ConfigService,
    private dataSource: DataSource,
  ) {
    const apiKey = this.configService.get<string>('RESEND_API_KEY');
    if (apiKey && !apiKey.includes('placeholder')) {
      this.resend = new Resend(apiKey);
      this.logger.log('Resend email service initialized');
    } else {
      this.logger.warn('Resend not configured — emails will be logged only (stub mode)');
    }
    this.fromAddress = this.configService.get<string>('RESEND_FROM_ADDRESS') || 'noreply@hoaledgeriq.com';
    this.replyToAddress = this.configService.get<string>('RESEND_REPLY_TO') || '';
  }

  // ─── Public API ──────────────────────────────────────────────

  async sendActivationEmail(email: string, businessName: string, activationUrl: string): Promise<void> {
    const subject = `Activate your ${businessName} account on HOA LedgerIQ`;
    const html = this.buildTemplate({
      preheader: 'Your HOA LedgerIQ account is ready to activate.',
      heading: 'Welcome to HOA LedgerIQ!',
      body: `
        <p>Your organization <strong>${this.esc(businessName)}</strong> has been created and is ready to go.</p>
        <p>Click the button below to set your password and activate your account:</p>
      `,
      ctaText: 'Activate My Account',
      ctaUrl: activationUrl,
      footer: 'This activation link expires in 72 hours. If you did not sign up for HOA LedgerIQ, please ignore this email.',
    });

    await this.send(email, subject, html, 'activation', { businessName, activationUrl });
  }

  async sendWelcomeEmail(email: string, businessName: string): Promise<void> {
    const appUrl = this.configService.get<string>('APP_URL') || 'https://app.hoaledgeriq.com';
    const subject = `Welcome to HOA LedgerIQ — ${businessName}`;
    const html = this.buildTemplate({
      preheader: `${businessName} is all set up on HOA LedgerIQ.`,
      heading: `You're all set!`,
      body: `
        <p>Your account for <strong>${this.esc(businessName)}</strong> is now active.</p>
        <p>Log in to start managing your HOA's finances, assessments, and investments — all in one place.</p>
      `,
      ctaText: 'Go to Dashboard',
      ctaUrl: `${appUrl}/dashboard`,
      footer: 'If you have any questions, just reply to this email and we\'ll help you get started.',
    });

    await this.send(email, subject, html, 'welcome', { businessName });
  }

  async sendPaymentFailedEmail(email: string, businessName: string): Promise<void> {
    const subject = `Action required: Payment failed for ${businessName}`;
    const html = this.buildTemplate({
      preheader: 'We were unable to process your payment.',
      heading: 'Payment Failed',
      body: `
        <p>We were unable to process the latest payment for <strong>${this.esc(businessName)}</strong>.</p>
        <p>Please update your payment method to avoid any interruption to your service.</p>
      `,
      ctaText: 'Update Payment Method',
      ctaUrl: `${this.configService.get<string>('APP_URL') || 'https://app.hoaledgeriq.com'}/settings`,
      footer: 'If you believe this is an error, please reply to this email and we\'ll look into it.',
    });

    await this.send(email, subject, html, 'payment_failed', { businessName });
  }

  async sendInviteMemberEmail(email: string, orgName: string, inviteUrl: string): Promise<void> {
    const subject = `You've been invited to ${orgName} on HOA LedgerIQ`;
    const html = this.buildTemplate({
      preheader: `Join ${orgName} on HOA LedgerIQ.`,
      heading: 'You\'re Invited!',
      body: `
        <p>You've been invited to join <strong>${this.esc(orgName)}</strong> on HOA LedgerIQ.</p>
        <p>Click below to accept the invitation and set up your account:</p>
      `,
      ctaText: 'Accept Invitation',
      ctaUrl: inviteUrl,
      footer: 'This invitation link expires in 7 days. If you were not expecting this, please ignore this email.',
    });

    await this.send(email, subject, html, 'invite_member', { orgName, inviteUrl });
  }

  async sendTrialEndingEmail(email: string, businessName: string, daysRemaining: number, settingsUrl: string): Promise<void> {
    const subject = `Your free trial ends in ${daysRemaining} days — ${businessName}`;
    const html = this.buildTemplate({
      preheader: `Your HOA LedgerIQ trial for ${businessName} is ending soon.`,
      heading: `Your Trial Ends in ${daysRemaining} Days`,
      body: `
        <p>Your free trial for <strong>${this.esc(businessName)}</strong> on HOA LedgerIQ ends in <strong>${daysRemaining} days</strong>.</p>
        <p>To continue using all features without interruption, add a payment method before your trial expires.</p>
        <p>If you don't add a payment method, your account will become read-only and you won't be able to make changes to your data.</p>
      `,
      ctaText: 'Add Payment Method',
      ctaUrl: settingsUrl,
      footer: 'If you have any questions about plans or pricing, just reply to this email.',
    });

    await this.send(email, subject, html, 'trial_ending', { businessName, daysRemaining, settingsUrl });
  }

  async sendTrialExpiredEmail(email: string, businessName: string): Promise<void> {
    const appUrl = this.configService.get<string>('APP_URL') || 'https://app.hoaledgeriq.com';
    const subject = `Your free trial has ended — ${businessName}`;
    const html = this.buildTemplate({
      preheader: `Your HOA LedgerIQ trial for ${businessName} has ended.`,
      heading: 'Your Trial Has Ended',
      body: `
        <p>The free trial for <strong>${this.esc(businessName)}</strong> on HOA LedgerIQ has ended.</p>
        <p>Your data is safe and your account is preserved. Subscribe to a plan to regain full access to your HOA financial management tools.</p>
      `,
      ctaText: 'Choose a Plan',
      ctaUrl: `${appUrl}/pricing`,
      footer: 'Your data will be preserved. You can reactivate your account at any time by subscribing to a plan.',
    });

    await this.send(email, subject, html, 'trial_expired', { businessName });
  }

  async sendPasswordResetEmail(email: string, resetUrl: string): Promise<void> {
    const subject = 'Reset your HOA LedgerIQ password';
    const html = this.buildTemplate({
      preheader: 'Password reset requested for your HOA LedgerIQ account.',
      heading: 'Password Reset',
      body: `
        <p>We received a request to reset your password. Click the button below to choose a new one:</p>
      `,
      ctaText: 'Reset Password',
      ctaUrl: resetUrl,
      footer: 'This link expires in 1 hour. If you did not request a password reset, please ignore this email — your password will remain unchanged.',
    });

    await this.send(email, subject, html, 'password_reset', { resetUrl });
  }

  // ─── Core send logic ────────────────────────────────────────

  private async send(
    toEmail: string,
    subject: string,
    html: string,
    template: string,
    metadata: Record<string, any>,
  ): Promise<void> {
    // Always log to the database
    await this.log(toEmail, subject, html, template, metadata);

    if (!this.resend) {
      this.logger.log(`📧 EMAIL STUB → ${toEmail}`);
      this.logger.log(`   Subject: ${subject}`);
      return;
    }

    try {
      const result = await this.resend.emails.send({
        from: this.fromAddress,
        to: [toEmail],
        replyTo: this.replyToAddress || undefined,
        subject,
        html,
      });

      if (result.error) {
        this.logger.error(`Resend error for ${toEmail}: ${JSON.stringify(result.error)}`);
        await this.updateLogStatus(toEmail, template, 'failed', result.error.message);
      } else {
        this.logger.log(`✅ Email sent to ${toEmail} (id: ${result.data?.id})`);
        await this.updateLogStatus(toEmail, template, 'sent', result.data?.id);
      }
    } catch (err: any) {
      this.logger.error(`Failed to send email to ${toEmail}: ${err.message}`);
      await this.updateLogStatus(toEmail, template, 'failed', err.message);
    }
  }

  // ─── Database logging ───────────────────────────────────────

  private async log(
    toEmail: string,
    subject: string,
    body: string,
    template: string,
    metadata: Record<string, any>,
  ): Promise<void> {
    try {
      await this.dataSource.query(
        `INSERT INTO shared.email_log (to_email, subject, body, template, metadata)
         VALUES ($1, $2, $3, $4, $5)`,
        [toEmail, subject, body, template, JSON.stringify(metadata)],
      );
    } catch (err) {
      this.logger.warn(`Failed to log email: ${err}`);
    }
  }

  private async updateLogStatus(toEmail: string, template: string, status: string, detail?: string): Promise<void> {
    try {
      await this.dataSource.query(
        `UPDATE shared.email_log
         SET metadata = metadata || $1::jsonb
         WHERE to_email = $2 AND template = $3
           AND created_at = (
             SELECT MAX(created_at) FROM shared.email_log
             WHERE to_email = $2 AND template = $3
           )`,
        [JSON.stringify({ send_status: status, send_detail: detail || '' }), toEmail, template],
      );
    } catch {
      // Best effort — don't block the flow
    }
  }

  // ─── HTML email template ────────────────────────────────────

  private esc(text: string): string {
    return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
  }

  private buildTemplate(opts: {
    preheader: string;
    heading: string;
    body: string;
    ctaText: string;
    ctaUrl: string;
    footer: string;
  }): string {
    return `<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>${this.esc(opts.heading)}</title>
  <!--[if mso]><noscript><xml><o:OfficeDocumentSettings><o:PixelsPerInch>96</o:PixelsPerInch></o:OfficeDocumentSettings></xml></noscript><![endif]-->
</head>
<body style="margin:0;padding:0;background-color:#f4f5f7;font-family:-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;">
  <!-- Preheader (hidden preview text) -->
  <div style="display:none;max-height:0;overflow:hidden;">${this.esc(opts.preheader)}</div>

  <table role="presentation" width="100%" cellpadding="0" cellspacing="0" style="background-color:#f4f5f7;padding:24px 0;">
    <tr>
      <td align="center">
        <table role="presentation" width="600" cellpadding="0" cellspacing="0" style="max-width:600px;width:100%;">

          <!-- Logo bar -->
          <tr>
            <td align="center" style="padding:24px 0 16px;">
              <span style="font-size:22px;font-weight:700;color:#1a73e8;letter-spacing:-0.5px;">
                HOA LedgerIQ
              </span>
            </td>
          </tr>

          <!-- Main card -->
          <tr>
            <td>
              <table role="presentation" width="100%" cellpadding="0" cellspacing="0"
                style="background-color:#ffffff;border-radius:8px;overflow:hidden;box-shadow:0 1px 3px rgba(0,0,0,0.08);">
                <tr>
                  <td style="padding:40px 32px;">
                    <h1 style="margin:0 0 16px;font-size:24px;font-weight:700;color:#1a1a2e;">
                      ${this.esc(opts.heading)}
                    </h1>
                    <div style="font-size:15px;line-height:1.6;color:#4a4a68;">
                      ${opts.body}
                    </div>

                    <!-- CTA Button -->
                    <table role="presentation" cellpadding="0" cellspacing="0" style="margin:28px 0 8px;">
                      <tr>
                        <td align="center" style="background-color:#1a73e8;border-radius:6px;">
                          <a href="${opts.ctaUrl}"
                            target="_blank"
                            style="display:inline-block;padding:14px 32px;color:#ffffff;font-size:15px;font-weight:600;text-decoration:none;border-radius:6px;">
                            ${this.esc(opts.ctaText)}
                          </a>
                        </td>
                      </tr>
                    </table>

                    <!-- Fallback URL -->
                    <p style="font-size:12px;color:#999;word-break:break-all;margin-top:16px;">
                      If the button doesn't work, copy and paste this link into your browser:<br>
                      <a href="${opts.ctaUrl}" style="color:#1a73e8;">${opts.ctaUrl}</a>
                    </p>
                  </td>
                </tr>
              </table>
            </td>
          </tr>

          <!-- Footer -->
          <tr>
            <td style="padding:24px 32px;text-align:center;">
              <p style="font-size:12px;color:#999;line-height:1.5;margin:0;">
                ${this.esc(opts.footer)}
              </p>
              <p style="font-size:12px;color:#bbb;margin:12px 0 0;">
                &copy; ${new Date().getFullYear()} HOA LedgerIQ &mdash; Smart Financial Management for HOAs
              </p>
            </td>
          </tr>

        </table>
      </td>
    </tr>
  </table>
</body>
</html>`;
  }
}