type SendEmailParams = {
  to: string | string[];
  subject: string;
  text?: string;
  html?: string;
  from?: string;
  cc?: string | string[];
  bcc?: string | string[];
  replyTo?: string | string[];
  attachments?: Array<{
    filename: string;
    content: string; // base64 encoded
    type?: string;
  }>;
};

import { readFile } from "node:fs/promises";
import { fileURLToPath } from "node:url";
import { dirname, resolve } from "node:path";

const RESEND_API_KEY = process.env.RESEND_API_KEY;
const DEFAULT_FROM = process.env.EMAIL_FROM || "Stargirlnails <no-reply@stargirlnails.de>";

// Helper function to format dates for ICS files (YYYYMMDDTHHMMSS)
function formatDateForICS(date: string, time: string): string {
  // date is in YYYY-MM-DD format, time is in HH:MM format
  const [year, month, day] = date.split('-');
  const [hours, minutes] = time.split(':');
  return `${year}${month}${day}T${hours}${minutes}00`;
}

// Helper function to create ICS (iCalendar) file content
function createICSFile(params: {
  date: string; // YYYY-MM-DD
  time: string; // HH:MM
  durationMinutes: number;
  customerName: string;
  treatmentName: string;
}): string {
  const { date, time, durationMinutes, customerName, treatmentName } = params;
  
  // Calculate start and end times in Europe/Berlin timezone
  const dtStart = formatDateForICS(date, time);
  
  // Calculate end time
  const [hours, minutes] = time.split(':').map(Number);
  const startDate = new Date(`${date}T${time}:00`);
  const endDate = new Date(startDate.getTime() + durationMinutes * 60000);
  const endHours = String(endDate.getHours()).padStart(2, '0');
  const endMinutes = String(endDate.getMinutes()).padStart(2, '0');
  const dtEnd = formatDateForICS(date, `${endHours}:${endMinutes}`);
  
  // Create unique ID for this event
  const uid = `booking-${Date.now()}-${Math.random().toString(36).substr(2, 9)}@stargirlnails.de`;
  
  // Current timestamp for DTSTAMP
  const now = new Date();
  const dtstamp = now.toISOString().replace(/[-:]/g, '').split('.')[0] + 'Z';
  
  // ICS content
  const icsContent = [
    'BEGIN:VCALENDAR',
    'VERSION:2.0',
    'PRODID:-//Stargirlnails Kiel//Booking System//DE',
    'CALSCALE:GREGORIAN',
    'METHOD:REQUEST',
    'BEGIN:VEVENT',
    `UID:${uid}`,
    `DTSTAMP:${dtstamp}`,
    `DTSTART;TZID=Europe/Berlin:${dtStart}`,
    `DTEND;TZID=Europe/Berlin:${dtEnd}`,
    `SUMMARY:${treatmentName} - Stargirlnails Kiel`,
    `DESCRIPTION:Termin für ${treatmentName} bei Stargirlnails Kiel`,
    'LOCATION:Stargirlnails Kiel',
    `ORGANIZER;CN=Stargirlnails Kiel:mailto:${process.env.EMAIL_FROM?.match(/<(.+)>/)?.[1] || 'no-reply@stargirlnails.de'}`,
    `ATTENDEE;CN=${customerName};RSVP=TRUE:mailto:${customerName}`,
    'STATUS:CONFIRMED',
    'SEQUENCE:0',
    'BEGIN:VALARM',
    'TRIGGER:-PT24H',
    'ACTION:DISPLAY',
    'DESCRIPTION:Erinnerung: Termin morgen bei Stargirlnails Kiel',
    'END:VALARM',
    'END:VEVENT',
    'BEGIN:VTIMEZONE',
    'TZID:Europe/Berlin',
    'BEGIN:DAYLIGHT',
    'TZOFFSETFROM:+0100',
    'TZOFFSETTO:+0200',
    'TZNAME:CEST',
    'DTSTART:19700329T020000',
    'RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU',
    'END:DAYLIGHT',
    'BEGIN:STANDARD',
    'TZOFFSETFROM:+0200',
    'TZOFFSETTO:+0100',
    'TZNAME:CET',
    'DTSTART:19701025T030000',
    'RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU',
    'END:STANDARD',
    'END:VTIMEZONE',
    'END:VCALENDAR'
  ].join('\r\n');
  
  return icsContent;
}

// Cache for AGB PDF to avoid reading it multiple times
let cachedAGBPDF: string | null = null;

async function getAGBPDFBase64(): Promise<string | null> {
  if (cachedAGBPDF) return cachedAGBPDF;
  
  try {
    const __filename = fileURLToPath(import.meta.url);
    const __dirname = dirname(__filename);
    const agbPath = resolve(__dirname, "../../../AGB.pdf");
    const buf = await readFile(agbPath);
    cachedAGBPDF = buf.toString('base64');
    return cachedAGBPDF;
  } catch (error) {
    console.warn("Could not read AGB.pdf:", error);
    return null;
  }
}

export async function sendEmail(params: SendEmailParams): Promise<{ success: boolean }> {
  if (!RESEND_API_KEY) {
    // In development or if not configured, skip sending but don't fail the flow
    console.warn("Resend API key not configured. Skipping email send.");
    return { success: false };
  }

  const payload = {
    from: params.from || DEFAULT_FROM,
    to: Array.isArray(params.to) ? params.to : [params.to],
    subject: params.subject,
    text: params.text,
    html: params.html,
    cc: params.cc ? (Array.isArray(params.cc) ? params.cc : [params.cc]) : undefined,
    bcc: params.bcc ? (Array.isArray(params.bcc) ? params.bcc : [params.bcc]) : undefined,
    reply_to: params.replyTo ? (Array.isArray(params.replyTo) ? params.replyTo : [params.replyTo]) : undefined,
    attachments: params.attachments,
  };

  console.log(`Sending email via Resend: to=${JSON.stringify(payload.to)}, subject="${params.subject}"`);

  const response = await fetch("https://api.resend.com/emails", {
    method: "POST",
    headers: {
      "Authorization": `Bearer ${RESEND_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify(payload),
  });

  if (!response.ok) {
    const body = await response.text().catch(() => "");
    console.error("Resend send error:", response.status, body);
    return { success: false };
  }
  
  const responseData = await response.json().catch(() => ({}));
  console.log("Resend email sent successfully:", responseData);
  return { success: true };
}

export async function sendEmailWithAGB(params: SendEmailParams): Promise<{ success: boolean }> {
  const agbBase64 = await getAGBPDFBase64();
  
  if (agbBase64) {
    params.attachments = [
      ...(params.attachments || []),
      {
        filename: "AGB_Stargirlnails_Kiel.pdf",
        content: agbBase64,
        type: "application/pdf"
      }
    ];
  }
  
  return sendEmail(params);
}

export async function sendEmailWithAGBAndCalendar(
  params: SendEmailParams,
  calendarParams: {
    date: string;
    time: string;
    durationMinutes: number;
    customerName: string;
    treatmentName: string;
  }
): Promise<{ success: boolean }> {
  const agbBase64 = await getAGBPDFBase64();
  
  // Create ICS file content
  const icsContent = createICSFile(calendarParams);
  const icsBase64 = Buffer.from(icsContent, 'utf-8').toString('base64');
  
  // Attach both AGB and ICS file
  params.attachments = [...(params.attachments || [])];
  
  if (agbBase64) {
    params.attachments.push({
      filename: "AGB_Stargirlnails_Kiel.pdf",
      content: agbBase64,
      type: "application/pdf"
    });
  }
  
  params.attachments.push({
    filename: "Termin_Stargirlnails.ics",
    content: icsBase64,
    type: "text/calendar"
  });
  
  return sendEmail(params);
}

export async function sendEmailWithInspirationPhoto(
  params: SendEmailParams, 
  photoData: string, 
  customerName: string
): Promise<{ success: boolean }> {
  if (!photoData) {
    return sendEmail(params);
  }

  // Extract file extension from base64 data URL
  const match = photoData.match(/data:image\/([^;]+);base64,(.+)/);
  if (!match) {
    console.warn("Invalid photo data format");
    return sendEmail(params);
  }

  const [, extension, base64Content] = match;
  const filename = `inspiration_${customerName.replace(/[^a-zA-Z0-9]/g, '_')}_${Date.now()}.${extension}`;

  // Check if attachment is too large (max 1MB base64 content)
  if (base64Content.length > 1024 * 1024) {
    console.warn(`Photo attachment too large: ${base64Content.length} chars, skipping attachment`);
    return sendEmail(params);
  }

  // console.log(`Sending email with photo attachment: ${filename}, size: ${base64Content.length} chars`);

  params.attachments = [
    ...(params.attachments || []),
    {
      filename,
      content: base64Content,
      type: `image/${extension}`
    }
  ];
  
  return sendEmail(params);
}