import nodemailer from "nodemailer";
import type { Transporter } from "nodemailer";
import type { ShopSettings } from "@prisma/client";

import db from "../../db.server";
import { getStrings, pickLanguage } from "./i18n";
import {
  DEFAULT_EMAIL_BODY_DE,
  DEFAULT_EMAIL_BODY_EN,
  DEFAULT_EMAIL_SUBJECT_DE,
  DEFAULT_EMAIL_SUBJECT_EN,
} from "./emailTemplates";
import { STORED_LOGO_SENTINEL } from "./logoCache.constants";

export interface SendInvoiceEmailArgs {
  shopDomain: string;
  invoiceId: string;
  toAddress?: string;
  /** Customer locale (e.g. "de-AT" or "en"); used to pick subject/body language. */
  customerLocale?: string;
  /**
   * Override the underlying transport (test only). Production code should
   * leave this undefined so SMTP creds from `ShopSettings` are used.
   */
  transportOverride?: Transporter;
}

export interface SendInvoiceEmailResult {
  ok: boolean;
  toAddress: string;
  messageId?: string;
  errorMessage?: string;
}

/**
 * Sends the invoice PDF as an email attachment to the customer using the
 * shop's configured SMTP credentials. On success, marks the invoice
 * `sentAt = now()` and `status = 'sent'`, which locks it from in-place
 * regeneration (cancel-and-reissue is required to correct it after this).
 */
export async function sendInvoiceEmail(
  args: SendInvoiceEmailArgs,
): Promise<SendInvoiceEmailResult> {
  const settings = await db.shopSettings.findUnique({
    where: { shopDomain: args.shopDomain },
  });
  if (!settings) {
    return failLog(args, "ShopSettings missing for this shop.");
  }

  const invoice = await db.invoice.findUnique({ where: { id: args.invoiceId } });
  if (!invoice) return failLog(args, `Invoice ${args.invoiceId} not found.`);
  if (invoice.shopDomain !== args.shopDomain) {
    return failLog(args, "Invoice does not belong to this shop.");
  }
  if (!invoice.pdfUrl) return failLog(args, "Invoice has no PDF URL.");

  // Resolve recipient: explicit override > customer email captured on the invoice.
  let to = args.toAddress?.trim();
  if (!to) {
    try {
      const customer = JSON.parse(invoice.customerJson) as { customerEmail?: string };
      to = customer.customerEmail?.trim();
    } catch {
      // ignore
    }
  }
  if (!to) return failLog(args, "No recipient email available.", invoice.id);

  // Build email content.
  const language = pickLanguage(args.customerLocale ?? settings.defaultLanguage);
  const t = getStrings(language);
  const customer = parseCustomer(invoice.customerJson);
  const totals = parseTotals(invoice.totalsJson);
  const vars = buildTemplateVars({
    invoice,
    settings,
    customerName: customer.customerName ?? "",
    customerFirstName: (customer.customerName ?? "").split(/\s+/)[0] ?? "",
    totalGross: totals.totalGross ?? "",
  });

  const customSubject =
    (language === "en" ? settings.emailSubjectEn : settings.emailSubjectDe) ||
    (language === "en" ? DEFAULT_EMAIL_SUBJECT_EN : DEFAULT_EMAIL_SUBJECT_DE);
  const subject = renderTemplate(customSubject, vars);

  const customBodyHtml =
    (language === "en" ? settings.emailBodyHtmlEn : settings.emailBodyHtmlDe) ||
    (language === "en" ? DEFAULT_EMAIL_BODY_EN : DEFAULT_EMAIL_BODY_DE);
  const body = renderHtmlBody(renderTemplate(customBodyHtml, vars));

  // If the rendered body references the inline logo, attach it.
  const inlineLogo = body.html.includes("cid:invoice-logo")
    ? await loadInlineLogo(args.shopDomain, settings)
    : null;

  // Download the PDF (Shopify Files URLs are public CDN URLs).
  let pdfBytes: Uint8Array;
  try {
    const res = await fetch(invoice.pdfUrl);
    if (!res.ok) throw new Error(`HTTP ${res.status}`);
    pdfBytes = new Uint8Array(await res.arrayBuffer());
  } catch (err) {
    const m = err instanceof Error ? err.message : String(err);
    return failLog(args, `Failed to download invoice PDF: ${m}`, invoice.id);
  }

  const transporter = args.transportOverride ?? buildTransport(settings);

  const fromName = settings.smtpFromName || settings.companyName || "Invoices";
  const fromEmail = settings.smtpFromEmail || settings.smtpUser || settings.email;
  if (!fromEmail) {
    return failLog(args, "No SMTP From address configured.", invoice.id);
  }

  try {
    const info = await transporter.sendMail({
      from: `"${fromName}" <${fromEmail}>`,
      to,
      bcc: "shop@linumiq.com",
      replyTo: settings.smtpReplyTo || undefined,
      subject,
      text: body.text,
      html: body.html,
      attachments: [
        {
          filename: `${invoice.kind === "storno" ? "Stornorechnung" : "Rechnung"}-${invoice.invoiceNumber}.pdf`,
          content: Buffer.from(pdfBytes),
          contentType: "application/pdf",
        },
        ...(inlineLogo
          ? [
              {
                filename: "logo",
                content: Buffer.from(inlineLogo.bytes),
                contentType: inlineLogo.contentType,
                cid: "invoice-logo",
              },
            ]
          : []),
      ],
    });

    await db.$transaction(async (tx) => {
      await tx.invoice.update({
        where: { id: invoice.id },
        data: { sentAt: new Date(), status: "sent" },
      });
      await tx.emailLog.create({
        data: {
          shopDomain: args.shopDomain,
          invoiceId: invoice.id,
          toAddress: to!,
          subject,
          status: "sent",
        },
      });
    });

    return { ok: true, toAddress: to, messageId: info.messageId };
  } catch (err) {
    const m = err instanceof Error ? err.message : String(err);
    return failLog(args, `SMTP send failed: ${m}`, invoice.id, to);
  }
}

function buildTransport(settings: ShopSettings): Transporter {
  return nodemailer.createTransport({
    host: settings.smtpHost,
    port: settings.smtpPort,
    secure: settings.smtpSecure,
    auth: settings.smtpUser
      ? { user: settings.smtpUser, pass: settings.smtpPassword }
      : undefined,
  });
}

async function failLog(
  args: SendInvoiceEmailArgs,
  message: string,
  invoiceId?: string,
  to?: string,
): Promise<SendInvoiceEmailResult> {
  if (invoiceId) {
    try {
      await db.emailLog.create({
        data: {
          shopDomain: args.shopDomain,
          invoiceId,
          toAddress: to ?? args.toAddress ?? "",
          subject: "(failed)",
          status: "failed",
          error: message,
        },
      });
    } catch {
      // best-effort
    }
  }
  return { ok: false, toAddress: to ?? args.toAddress ?? "", errorMessage: message };
}

function renderEmailBody({
  settings,
  invoiceNumber,
  language,
}: {
  settings: ShopSettings;
  invoiceNumber: string;
  language: "de" | "en";
}): { text: string; html: string } {
  if (language === "en") {
    const text =
      `Dear customer,\n\n` +
      `Please find attached invoice ${invoiceNumber}.\n\n` +
      `Thank you for your purchase.`;
    const html =
      `<p>Dear customer,</p>` +
      `<p>Please find attached invoice <strong>${escapeHtml(invoiceNumber)}</strong>.</p>` +
      `<p>Thank you for your purchase.</p>`;
    return { text, html };
  }
  const text =
    `Hallo,\n\n` +
    `anbei finden Sie die Rechnung ${invoiceNumber}.\n\n` +
    `Danke für deinen Einkauf.`;
  const html =
    `<p>Hallo,</p>` +
    `<p>anbei finden Sie die Rechnung <strong>${escapeHtml(invoiceNumber)}</strong>.</p>` +
    `<p>Danke für deinen Einkauf.</p>`;
  return { text, html };
}

function escapeHtml(s: string): string {
  return s.replace(/[&<>"']/g, (c) =>
    ({ "&": "&amp;", "<": "&lt;", ">": "&gt;", '"': "&quot;", "'": "&#39;" })[c]!,
  );
}

// --- Template variables ----------------------------------------------------

interface TemplateVars {
  invoiceNumber: string;
  customerName: string;
  customerFirstName: string;
  orderName: string;
  totalGross: string;
  dueDate: string;
  companyName: string;
  ownerName: string;
  shopEmail: string;
  shopWebsite: string;
}

function buildTemplateVars(args: {
  invoice: { invoiceNumber: string; orderName: string };
  settings: ShopSettings;
  customerName: string;
  customerFirstName: string;
  totalGross: string;
}): TemplateVars {
  const dueMs = Number((args.invoice as unknown as { dueDate?: string | Date }).dueDate ?? 0);
  return {
    invoiceNumber: args.invoice.invoiceNumber,
    orderName: args.invoice.orderName,
    customerName: args.customerName,
    customerFirstName: args.customerFirstName,
    totalGross: args.totalGross,
    dueDate: dueMs ? new Date(dueMs).toLocaleDateString() : "",
    companyName: args.settings.companyName,
    ownerName: args.settings.ownerName,
    shopEmail: args.settings.email,
    shopWebsite: args.settings.website,
  };
}

/**
 * Substitutes {{token}} placeholders in `template`. Unknown tokens are left
 * in place so the user notices typos instead of silent blanks. Values are
 * inserted verbatim — callers are responsible for HTML-escaping if needed.
 */
function renderTemplate(template: string, vars: TemplateVars): string {
  return template.replace(/\{\{\s*([a-zA-Z_][a-zA-Z0-9_]*)\s*\}\}/g, (full, key) => {
    const v = (vars as unknown as Record<string, string | undefined>)[key];
    return v === undefined ? full : v;
  });
}

/** Strips HTML tags to produce a plain-text fallback for the multipart email. */
function htmlToText(html: string): string {
  return html
    .replace(/<br\s*\/?>(?=\s|$)/gi, "\n")
    .replace(/<\/p>/gi, "\n\n")
    .replace(/<[^>]+>/g, "")
    .replace(/&nbsp;/g, " ")
    .replace(/&amp;/g, "&")
    .replace(/&lt;/g, "<")
    .replace(/&gt;/g, ">")
    .replace(/&quot;/g, '"')
    .replace(/&#39;/g, "'")
    .replace(/\n{3,}/g, "\n\n")
    .trim();
}

function renderHtmlBody(html: string): { text: string; html: string } {
  return { html, text: htmlToText(html) };
}

interface InvoiceCustomerSnapshot {
  customerEmail?: string;
  customerName?: string;
}
function parseCustomer(json: string): InvoiceCustomerSnapshot {
  try {
    return JSON.parse(json) as InvoiceCustomerSnapshot;
  } catch {
    return {};
  }
}

interface InvoiceTotalsSnapshot {
  totalGross?: string;
}
function parseTotals(json: string): InvoiceTotalsSnapshot {
  try {
    return JSON.parse(json) as InvoiceTotalsSnapshot;
  } catch {
    return {};
  }
}

/**
 * Resolves the shop logo bytes for inline embedding. Returns null if no
 * logo is configured or the lookup fails — the email is still sent, just
 * without the inline image (the alt text remains visible).
 */
async function loadInlineLogo(
  shopDomain: string,
  settings: ShopSettings,
): Promise<{ bytes: Uint8Array; contentType: string } | null> {
  if (!settings.logoUrl) return null;
  try {
    if (settings.logoUrl === STORED_LOGO_SENTINEL) {
      const cached = await db.logoCache.findUnique({ where: { shopDomain } });
      if (!cached) return null;
      return { bytes: new Uint8Array(cached.bytes), contentType: cached.contentType };
    }
    const res = await fetch(settings.logoUrl);
    if (!res.ok) return null;
    const ct = res.headers.get("content-type") ?? "image/png";
    return { bytes: new Uint8Array(await res.arrayBuffer()), contentType: ct };
  } catch {
    return null;
  }
}