import { Injectable, BadRequestException, NotFoundException } from '@nestjs/common';
import { PrismaService } from '../prisma/prisma.service';

// Tabs stay open per customer (closing only settles them), so a customer can be reminded again
// once this many days have passed since their last reminder.
const REMINDER_COOLDOWN_DAYS = 7;

function escapeHtml(value: string): string {
  return value
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#39;');
}

@Injectable()
export class RemindersService {
  private resendApiKey: string;
  private fromEmail: string;

  constructor(private prisma: PrismaService) {
    this.resendApiKey = process.env.RESEND_API_KEY || '';
    this.fromEmail = process.env.RESEND_FROM_EMAIL || 'KoolTab <onboarding@resend.dev>';
  }

  async listCandidates(venueId: string) {
    const ownerships = await this.prisma.tabOwnership.findMany({
      where: { venueId },
    });

    // Only the owning device's snapshot is authoritative for a tab
    const snapshots = ownerships.length === 0 ? [] : await this.prisma.openTabSnapshot.findMany({
      where: {
        OR: ownerships.map((o) => ({ deviceId: o.deviceId, tabId: o.tabId })),
      },
    });
    const latestByTab = new Map(snapshots.map((s) => [s.tabId, s]));

    const emailMap = new Map<string, string>();
    try {
      const plannedTabs = await this.prisma.plannedTab.findMany({
        where: { venueId, email: { not: null } },
        select: { customerName: true, email: true },
      });
      for (const pt of plannedTabs) {
        if (pt.email) emailMap.set(pt.customerName.toLowerCase(), pt.email);
      }
    } catch {
      // email column may not exist yet if migration hasn't been applied
    }

    let sentTabIds = new Set<string>();
    try {
      const alreadySent = await this.prisma.tabReminder.findMany({
        where: { venueId, sentAt: { gt: new Date(Date.now() - REMINDER_COOLDOWN_DAYS * 24 * 60 * 60 * 1000) } },
        select: { tabId: true },
      });
      sentTabIds = new Set(alreadySent.map((r) => r.tabId));
    } catch {
      // Table may not exist yet if migration hasn't been applied
    }

    const candidates = [];
    for (const snap of latestByTab.values()) {
      if (snap.totalInCents <= 0) continue;
      if (sentTabIds.has(snap.tabId)) continue;
      const email = emailMap.get(snap.customerName.toLowerCase());
      if (!email) continue;
      candidates.push({
        tabId: snap.tabId,
        customerName: snap.customerName,
        email,
        amountInCents: snap.totalInCents,
        itemCount: snap.itemCount,
      });
    }

    return { candidates };
  }

  async sendReminders(venueId: string, requestorEmail: string) {
    const { candidates } = await this.listCandidates(venueId);

    if (candidates.length === 0) {
      return { sent: 0, message: 'No candidates to remind' };
    }

    if (!this.resendApiKey) {
      throw new BadRequestException({
        code: 'resend_not_configured',
        message: 'Resend API key is not configured. Set RESEND_API_KEY environment variable.',
      });
    }

    let sent = 0;
    const errors: { customerName: string; error: string }[] = [];

    for (const candidate of candidates) {
      try {
        const res = await fetch('https://api.resend.com/emails', {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
            Authorization: `Bearer ${this.resendApiKey}`,
          },
          body: JSON.stringify({
            from: this.fromEmail,
            to: candidate.email,
            subject: `Payment reminder for your tab at the bar`,
            html: `<p>Hi ${escapeHtml(candidate.customerName)},</p>
<p>This is a friendly reminder that you have an open tab of <strong>&euro;${(candidate.amountInCents / 100).toFixed(2)}</strong> (${candidate.itemCount} item${candidate.itemCount !== 1 ? 's' : ''}).</p>
<p>Please settle your tab at the bar at your earliest convenience.</p>
<p>Thank you!</p>`,
          }),
        });

        if (!res.ok) {
          const errBody = await res.text();
          errors.push({ customerName: candidate.customerName, error: errBody });
          continue;
        }

        await this.prisma.tabReminder.create({
          data: {
            venueId,
            tabId: candidate.tabId,
            customerName: candidate.customerName,
            email: candidate.email,
            amountInCents: candidate.amountInCents,
          },
        });

        sent++;
      } catch (err: any) {
        errors.push({ customerName: candidate.customerName, error: err.message });
      }
    }

    return { sent, total: candidates.length, errors: errors.length > 0 ? errors : undefined };
  }

  async history(venueId: string) {
    try {
      const reminders = await this.prisma.tabReminder.findMany({
        where: { venueId },
        orderBy: { sentAt: 'desc' },
        take: 100,
      });
      return { reminders };
    } catch {
      return { reminders: [] };
    }
  }

  async sendTestEmail(venueId: string, plannedTabId: string) {
    if (!this.resendApiKey) {
      throw new BadRequestException({
        code: 'resend_not_configured',
        message: 'Resend API key is not configured. Set RESEND_API_KEY environment variable.',
      });
    }

    const tab = await this.prisma.plannedTab.findFirst({
      where: { id: plannedTabId, venueId },
    });

    if (!tab) {
      throw new NotFoundException({ code: 'not_found', message: 'Planned customer not found' });
    }

    if (!tab.email) {
      throw new BadRequestException({ code: 'no_email', message: 'This customer has no email address set' });
    }

    const res = await fetch('https://api.resend.com/emails', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${this.resendApiKey}`,
      },
      body: JSON.stringify({
        from: this.fromEmail,
        to: tab.email,
        subject: `Test email from KoolTab`,
        html: `<p>Hi ${escapeHtml(tab.customerName)},</p>
<p>This is a test email from KoolTab to verify that email reminders are working correctly.</p>
<p>If you received this, the email configuration is working!</p>
<hr>
<p style="color: #888; font-size: 12px;">This is a test — no action needed.</p>`,
      }),
    });

    if (!res.ok) {
      const errBody = await res.text();
      throw new BadRequestException({
        code: 'email_failed',
        message: `Failed to send test email: ${errBody}`,
      });
    }

    return { ok: true, email: tab.email, customerName: tab.customerName };
  }
}