import prisma from "../config/database";
import { config } from "../config/env";
import { sendMail } from "./mailer";
import { localDateCzStr, localDateStr } from "../utils/date";
import { getSystemSettings } from "./system-settings";

interface AlertInvoice {
  id: number;
  type: "created" | "received";
  number: string;
  counterparty: string;
  amount: string;
  currency: string;
  due_date: string;
  days_label: string;
}

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

function formatAmount(n: number | { toNumber?: () => number }): string {
  const num = typeof n === "number" ? n : Number(n);
  return num.toLocaleString("cs-CZ", {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2,
  });
}

export async function checkInvoiceAlerts(): Promise<void> {
  const settings = await getSystemSettings();
  const alertEmail = settings.invoice_alert_email || config.email.invoiceAlert;
  if (!alertEmail) return;

  const today = new Date();
  const todayStr = localDateStr(today);
  const in3days = new Date(today);
  in3days.setDate(in3days.getDate() + 3);
  const in3daysStr = localDateStr(in3days);

  const alerts: AlertInvoice[] = [];

  // --- Created invoices (customer owes us) ---
  const createdInvoices = await prisma.invoices.findMany({
    where: {
      status: { in: ["issued", "overdue"] },
      due_date: { not: null },
    },
    include: {
      customers: { select: { name: true } },
      invoice_items: true,
    },
  });

  for (const inv of createdInvoices) {
    if (!inv.due_date) continue;
    const dueDateStr = localDateStr(new Date(inv.due_date));

    let alertType: string | null = null;
    let daysLabel = "";

    if (dueDateStr === todayStr) {
      alertType = "due";
      daysLabel = "splatnost dnes";
    } else if (dueDateStr === in3daysStr) {
      alertType = "3days";
      daysLabel = "splatnost za 3 dny";
    }

    if (!alertType) continue;

    const alreadySent = await prisma.invoice_alert_log.findUnique({
      where: {
        invoice_type_invoice_id_alert_type: {
          invoice_type: "created",
          invoice_id: inv.id,
          alert_type: alertType,
        },
      },
    });
    if (alreadySent) continue;

    const subtotal = inv.invoice_items.reduce(
      (sum, item) => sum + Number(item.quantity) * Number(item.unit_price),
      0,
    );

    alerts.push({
      id: inv.id,
      type: "created",
      number: inv.invoice_number || `#${inv.id}`,
      counterparty: inv.customers?.name || "—",
      amount: formatAmount(subtotal),
      currency: inv.currency || "CZK",
      due_date: localDateCzStr(new Date(inv.due_date)),
      days_label: daysLabel,
    });

    await prisma.invoice_alert_log.create({
      data: {
        invoice_type: "created",
        invoice_id: inv.id,
        alert_type: alertType,
      },
    });
  }

  // --- Received invoices (we owe supplier) ---
  const receivedInvoices = await prisma.received_invoices.findMany({
    where: {
      status: "unpaid",
      due_date: { not: null },
    },
  });

  for (const inv of receivedInvoices) {
    if (!inv.due_date) continue;
    const dueDateStr = localDateStr(new Date(inv.due_date));

    let alertType: string | null = null;
    let daysLabel = "";

    if (dueDateStr === todayStr) {
      alertType = "due";
      daysLabel = "splatnost dnes";
    } else if (dueDateStr === in3daysStr) {
      alertType = "3days";
      daysLabel = "splatnost za 3 dny";
    }

    if (!alertType) continue;

    const alreadySent = await prisma.invoice_alert_log.findUnique({
      where: {
        invoice_type_invoice_id_alert_type: {
          invoice_type: "received",
          invoice_id: inv.id,
          alert_type: alertType,
        },
      },
    });
    if (alreadySent) continue;

    alerts.push({
      id: inv.id,
      type: "received",
      number: inv.invoice_number || inv.supplier_name,
      counterparty: inv.supplier_name,
      amount: formatAmount(inv.amount),
      currency: inv.currency,
      due_date: localDateCzStr(new Date(inv.due_date)),
      days_label: daysLabel,
    });

    await prisma.invoice_alert_log.create({
      data: {
        invoice_type: "received",
        invoice_id: inv.id,
        alert_type: alertType,
      },
    });
  }

  if (alerts.length === 0) return;

  // --- Build summary email ---
  const createdAlerts = alerts.filter((a) => a.type === "created");
  const receivedAlerts = alerts.filter((a) => a.type === "received");

  const subject = `Upozornění na splatnost faktur (${alerts.length})`;

  const buildTable = (items: AlertInvoice[], title: string) => {
    if (items.length === 0) return "";
    const rows = items
      .map(
        (a) => `
        <tr>
          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${escapeHtml(a.number)}</td>
          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${escapeHtml(a.counterparty)}</td>
          <td style="padding: 8px; border-bottom: 1px solid #ddd; text-align: right;">${a.amount} ${a.currency}</td>
          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${a.due_date}</td>
          <td style="padding: 8px; border-bottom: 1px solid #ddd; color: ${a.days_label.includes("dnes") ? "#dc3545" : "#e67e22"}; font-weight: bold;">${a.days_label}</td>
        </tr>`,
      )
      .join("");

    return `
      <h3 style="color: #333; margin-top: 24px;">${escapeHtml(title)} (${items.length})</h3>
      <table style="width: 100%; border-collapse: collapse; margin: 12px 0;">
        <thead>
          <tr style="background: #f5f5f5;">
            <th style="padding: 8px; text-align: left;">Číslo</th>
            <th style="padding: 8px; text-align: left;">Firma</th>
            <th style="padding: 8px; text-align: right;">Částka</th>
            <th style="padding: 8px; text-align: left;">Splatnost</th>
            <th style="padding: 8px; text-align: left;">Stav</th>
          </tr>
        </thead>
        <tbody>${rows}</tbody>
      </table>`;
  };

  const html = `
    <html>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
      <h2 style="color: #dc3545;">Upozornění na splatnost faktur</h2>
      <p>Následující faktury se blíží ke splatnosti nebo jsou dnes splatné:</p>
      ${buildTable(createdAlerts, "Vydané faktury (neuhrazené zákazníkem)")}
      ${buildTable(receivedAlerts, "Přijaté faktury (k úhradě)")}
      <hr style="margin: 30px 0; border: none; border-top: 1px solid #ddd;">
      <p style="font-size: 12px; color: #999;">
        Automatické upozornění vygenerováno ${localDateCzStr(today)}.
      </p>
    </body>
    </html>`;

  const sent = await sendMail(alertEmail, subject, html);
  if (!sent) {
    console.error(`InvoiceAlerts: Failed to send alert to ${alertEmail}`);
  } else {
    console.log(
      `InvoiceAlerts: Sent ${alerts.length} alert(s) to ${alertEmail}`,
    );
  }
}