const fs = require('fs/promises');
const path = require('path');
const QRCode = require('qrcode');
const { PDFDocument, PDFArray, PDFName, PDFNumber, rgb, StandardFonts } = require('pdf-lib');
const { pdflibAddPlaceholder } = require('@signpdf/placeholder-pdf-lib');
const { SignPdf } = require('@signpdf/signpdf');
const { P12Signer } = require('@signpdf/signer-p12');
const { getSignedDocumentPath } = require('../../utils/storagePath');

// ── Color helpers ──────────────────────────────────────────────────────────────
const C = {
  primary:   rgb(0.31, 0.27, 0.90),
  dark:      rgb(0.10, 0.10, 0.30),
  gray:      rgb(0.35, 0.35, 0.45),
  lightGray: rgb(0.60, 0.60, 0.65),
  bgBlue:    rgb(0.95, 0.97, 1.00),
  bgDark:    rgb(0.12, 0.14, 0.25),
  bgGray:    rgb(0.96, 0.96, 0.97),
  white:     rgb(1.00, 1.00, 1.00),
  accent:    rgb(0.20, 0.60, 0.85),
  green:     rgb(0.10, 0.55, 0.30),
  bgGreen:   rgb(0.93, 0.98, 0.94),
};

// ── Shared text truncation ─────────────────────────────────────────────────────
function truncate(text, font, size, maxWidth) {
  if (!text) return '';
  const ellipsis = '...';
  if (font.widthOfTextAtSize(text, size) <= maxWidth) return text;
  let t = text;
  while (t.length > 0 && font.widthOfTextAtSize(t + ellipsis, size) > maxWidth) t = t.slice(0, -1);
  return t + ellipsis;
}

function getSignatureWidth(style, signerName = '') {
  if (style === 'qr' || style === 'firmaec') {
    const normalizedName = String(signerName).trim();
    const calculatedWidth = 78 + (normalizedName.length * 4.9);
    return Math.max(170, Math.min(270, Math.round(calculatedWidth)));
  }
  return 200;
}

function wrapToLines(text, font, size, maxWidth, maxLines) {
  const words = text.split(' ');
  const lines = [];
  let current = '';
  for (const word of words) {
    if (lines.length >= maxLines) break;
    const test = current ? `${current} ${word}` : word;
    if (font.widthOfTextAtSize(test, size) <= maxWidth) {
      current = test;
    } else {
      if (current) lines.push(current);
      current = truncate(word, font, size, maxWidth);
    }
  }
  if (current && lines.length < maxLines) lines.push(current);
  return lines;
}

function buildLocalizedSignatureTimestamp({ locale, timeZone } = {}) {
  const now = new Date();
  const normalizedLocale = locale || 'es-EC';
  const options = timeZone ? { timeZone } : {};

  try {
    return {
      dateStr: now.toLocaleDateString(normalizedLocale, {
        day: '2-digit',
        month: '2-digit',
        year: 'numeric',
        ...options,
      }),
      timeStr: now.toLocaleTimeString(normalizedLocale, {
        hour: '2-digit',
        minute: '2-digit',
        hour12: true,
        ...options,
      }),
    };
  } catch {
    return {
      dateStr: now.toLocaleDateString('es-EC', { day: '2-digit', month: '2-digit', year: 'numeric' }),
      timeStr: now.toLocaleTimeString('es-EC', { hour: '2-digit', minute: '2-digit', hour12: true }),
    };
  }
}

function hideSignatureWidgetBorder(pdfDoc, pageIndex) {
  const page = pdfDoc.getPages()[pageIndex];
  if (!page) return;

  const annotations = page.node.lookupMaybe(PDFName.of('Annots'), PDFArray);
  if (!annotations || annotations.size() === 0) return;

  const widgetRef = annotations.get(annotations.size() - 1);
  const widget = pdfDoc.context.lookup(widgetRef);
  if (!widget) return;

  const zeroBorder = PDFArray.withContext(pdfDoc.context);
  zeroBorder.push(PDFNumber.of(0));
  zeroBorder.push(PDFNumber.of(0));
  zeroBorder.push(PDFNumber.of(0));

  widget.set(PDFName.of('Border'), zeroBorder);
  widget.set(PDFName.of('BS'), pdfDoc.context.obj({
    Type: 'Border',
    W: 0,
    S: 'S',
  }));
  widget.set(PDFName.of('MK'), pdfDoc.context.obj({
    BC: [],
    BG: [],
  }));
}

// ── Style: CLASSIC (blue bar + DS badge) ──────────────────────────────────────
async function drawStyleClassic(pdfDoc, page, sx, sy, sw, sh, { signerName, reason, dateStr, timeStr, location }) {
  const f1 = await pdfDoc.embedFont(StandardFonts.HelveticaBold);
  const f2 = await pdfDoc.embedFont(StandardFonts.Helvetica);

  page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, color: C.bgBlue, borderColor: C.primary, borderWidth: 1 });
  page.drawRectangle({ x: sx, y: sy, width: 4,  height: sh, color: C.primary });

  const nameSize = signerName.length > 24 ? 7 : 8.5;
  page.drawText('DS', { x: sx + 7, y: sy + sh - 18, size: 9, font: f1, color: C.primary });
  page.drawText(truncate(signerName, f1, nameSize, sw - 30), { x: sx + 22, y: sy + sh - 17, size: nameSize, font: f1, color: C.dark });
  if (reason) page.drawText(`Razon: ${truncate(reason, f2, 7, sw - 60)}`, { x: sx + 8, y: sy + sh - 30, size: 7, font: f2, color: C.gray });
  page.drawText(`Fecha: ${dateStr} ${timeStr}`,     { x: sx + 8, y: sy + sh - 41, size: 7, font: f2, color: C.gray });
  if (location) page.drawText(`Lugar: ${truncate(location, f2, 7, sw - 60)}`, { x: sx + 8, y: sy + sh - 52, size: 7, font: f2, color: C.gray });
  page.drawText('Firma digital', { x: sx + sw - 54, y: sy + 4, size: 6, font: f2, color: C.lightGray });
}

// ── Style: QR CODE ─────────────────────────────────────────────────────────────
async function drawStyleQR(pdfDoc, page, sx, sy, sw, sh, { signerName, reason, dateStr, timeStr, location, verificationUrl, qrPosition, qrBackground, qrBorder }) {
  const f1 = await pdfDoc.embedFont(StandardFonts.Helvetica);
  const f2 = await pdfDoc.embedFont(StandardFonts.Helvetica);
  const useSoftBackground = qrBackground === 'soft';
  const useBorder = qrBorder === 'line';

  const qrContent = verificationUrl || [
    'FIRMA DIGITAL VERIFICADA',
    `Firmante: ${signerName}`,
    reason ? `Razon: ${reason}` : '',
    `Fecha: ${dateStr} ${timeStr}`,
    location ? `Lugar: ${location}` : '',
  ].filter(Boolean).join('\n');

  // Generate QR as PNG buffer
  const qrPng = await QRCode.toBuffer(qrContent, {
    type: 'png',
    width: 100,
    margin: 1,
    color: { dark: '#1f1b6e', light: useSoftBackground ? '#f2f4ff' : '#0000' },
  });

  const qrImage = await pdfDoc.embedPng(qrPng);
  const qrSize = Math.min(sh - 10, 44);
  const qrOnRight = qrPosition === 'right';
  const textPadding = 6;
  const textX = qrOnRight ? sx + textPadding : sx + qrSize + 6;
  const textW = sw - qrSize - 10;

  // Background
  if (useSoftBackground) {
    page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, color: C.bgBlue });
  }
  if (useBorder) {
    page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, borderColor: C.primary, borderWidth: 1 });
  }
  const qrX = qrOnRight ? sx + sw - qrSize - 2 : sx + 2;
  if (useSoftBackground) {
    page.drawRectangle({ x: qrOnRight ? sx + sw - qrSize - 4 : sx, y: sy, width: qrSize + 4, height: sh, color: C.bgBlue });
  }
  page.drawImage(qrImage, { x: qrX, y: sy + 4, width: qrSize, height: qrSize });

  const dividerX = qrOnRight ? sx + sw - qrSize - 4 : textX - 2;
  page.drawLine({ start: { x: dividerX, y: sy + 4 }, end: { x: dividerX, y: sy + sh - 4 }, thickness: 0.5, color: C.primary, opacity: 0.4 });

  // Text on right
  const nameSize = signerName.length > 26 ? 6.8 : 7.6;
  page.drawText(truncate(signerName, f1, nameSize, textW), { x: textX, y: sy + sh - 13, size: nameSize, font: f1, color: C.dark });
  if (reason) page.drawText(truncate(reason, f2, 6.2, textW), { x: textX, y: sy + sh - 23, size: 6.2, font: f2, color: C.gray });
  page.drawText(`${dateStr}`, { x: textX, y: sy + sh - 33, size: 6.2, font: f2, color: C.gray });
  page.drawText(`${timeStr}`, { x: textX, y: sy + sh - 43, size: 6.2, font: f2, color: C.gray });
  if (location) page.drawText(truncate(location, f2, 5.6, textW), { x: textX, y: sy + sh - 52, size: 5.6, font: f2, color: C.lightGray });
  page.drawText('Escanee el QR para verificar', { x: sx + 2, y: sy + 2, size: 5, font: f2, color: C.lightGray });
}

// ── Style: PROFESSIONAL (dark header + fields) ────────────────────────────────
async function drawStyleProfessional(pdfDoc, page, sx, sy, sw, sh, { signerName, reason, dateStr, timeStr, location }) {
  const f1 = await pdfDoc.embedFont(StandardFonts.HelveticaBold);
  const f2 = await pdfDoc.embedFont(StandardFonts.Helvetica);

  const headerH = 16;

  // Background
  page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, color: C.bgGray, borderColor: rgb(0.70, 0.72, 0.78), borderWidth: 0.75 });
  // Dark header bar
  page.drawRectangle({ x: sx, y: sy + sh - headerH, width: sw, height: headerH, color: C.bgDark });

  page.drawText('FIRMA DIGITAL', { x: sx + 6, y: sy + sh - headerH + 4, size: 7.5, font: f1, color: C.white });
  page.drawText('Firmado electronicamente', { x: sx + sw - 88, y: sy + sh - headerH + 4, size: 5.5, font: f2, color: rgb(0.7, 0.7, 0.85) });

  // Separator line below header
  page.drawLine({ start: { x: sx, y: sy + sh - headerH - 1 }, end: { x: sx + sw, y: sy + sh - headerH - 1 }, thickness: 0.5, color: C.primary, opacity: 0.3 });

  // Signer name (prominent)
  const nameSize = signerName.length > 28 ? 7.5 : 9;
  page.drawText(truncate(signerName, f1, nameSize, sw - 10), { x: sx + 6, y: sy + sh - headerH - 14, size: nameSize, font: f1, color: C.dark });

  // Separator line
  const lineY = sy + sh - headerH - 20;
  page.drawLine({ start: { x: sx + 4, y: lineY }, end: { x: sx + sw - 4, y: lineY }, thickness: 0.4, color: C.lightGray, opacity: 0.6 });

  // Fields in two columns
  const col1X = sx + 6;
  const col2X = sx + sw / 2 + 2;
  const fieldW = sw / 2 - 10;

  page.drawText('Razon:', { x: col1X, y: lineY - 11, size: 5.5, font: f1, color: C.gray });
  page.drawText(truncate(reason || 'Firmado digitalmente', f2, 6, fieldW), { x: col1X, y: lineY - 20, size: 6, font: f2, color: C.dark });

  page.drawText('Fecha:', { x: col2X, y: lineY - 11, size: 5.5, font: f1, color: C.gray });
  page.drawText(`${dateStr}`, { x: col2X, y: lineY - 20, size: 6, font: f2, color: C.dark });
  page.drawText(`${timeStr}`, { x: col2X, y: lineY - 28, size: 6, font: f2, color: C.dark });

  if (location) {
    page.drawText('Lugar:', { x: col1X, y: lineY - 30, size: 5.5, font: f1, color: C.gray });
    page.drawText(truncate(location, f2, 6, fieldW), { x: col1X, y: lineY - 39, size: 6, font: f2, color: C.dark });
  }
}

// ── Style: IMAGE (custom handwritten image + info) ────────────────────────────
async function drawStyleImage(pdfDoc, page, sx, sy, sw, sh, { signerName, reason, dateStr, timeStr, location, signatureImageBase64 }) {
  const f1 = await pdfDoc.embedFont(StandardFonts.HelveticaBold);
  const f2 = await pdfDoc.embedFont(StandardFonts.Helvetica);

  // Background
  page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, color: C.white, borderColor: rgb(0.75, 0.75, 0.80), borderWidth: 0.75 });
  page.drawRectangle({ x: sx, y: sy, width: 4, height: sh, color: C.green });

  const imgAreaW = sw * 0.45;
  const imgAreaH = sh - 10;

  if (signatureImageBase64) {
    try {
      // Strip data URL prefix if present
      const base64Data = signatureImageBase64.replace(/^data:image\/\w+;base64,/, '');
      const imgBuf = Buffer.from(base64Data, 'base64');

      let embeddedImg;
      try {
        embeddedImg = await pdfDoc.embedPng(imgBuf);
      } catch {
        embeddedImg = await pdfDoc.embedJpg(imgBuf);
      }

      const scale = Math.min(imgAreaW / embeddedImg.width, imgAreaH / embeddedImg.height);
      const drawW = embeddedImg.width * scale;
      const drawH = embeddedImg.height * scale;
      page.drawImage(embeddedImg, {
        x: sx + 6 + (imgAreaW - drawW) / 2,
        y: sy + (sh - drawH) / 2,
        width: drawW, height: drawH,
      });
    } catch { /* ignore embed errors */ }
  } else {
    // Placeholder if no image provided
    page.drawRectangle({ x: sx + 6, y: sy + 8, width: imgAreaW, height: imgAreaH, color: C.bgGray, borderColor: rgb(0.8, 0.8, 0.85), borderWidth: 0.5 });
    page.drawText('Firma', { x: sx + 6 + imgAreaW / 2 - 10, y: sy + sh / 2 - 4, size: 7, font: f2, color: C.lightGray });
  }

  // Vertical divider
  const divX = sx + imgAreaW + 8;
  page.drawLine({ start: { x: divX, y: sy + 4 }, end: { x: divX, y: sy + sh - 4 }, thickness: 0.5, color: rgb(0.8, 0.8, 0.85) });

  // Text right side
  const textX = divX + 5;
  const textW  = sw - imgAreaW - 16;
  const nameSize = signerName.length > 20 ? 7 : 8.5;
  page.drawText(truncate(signerName, f1, nameSize, textW), { x: textX, y: sy + sh - 14, size: nameSize, font: f1, color: C.dark });
  page.drawLine({ start: { x: textX, y: sy + sh - 18 }, end: { x: textX + textW, y: sy + sh - 18 }, thickness: 0.4, color: C.green, opacity: 0.5 });
  if (reason) page.drawText(truncate(reason, f2, 6.5, textW), { x: textX, y: sy + sh - 29, size: 6.5, font: f2, color: C.gray });
  page.drawText(`${dateStr}`, { x: textX, y: sy + sh - 39, size: 6.5, font: f2, color: C.gray });
  page.drawText(`${timeStr}`, { x: textX, y: sy + sh - 49, size: 6.5, font: f2, color: C.gray });
  if (location) page.drawText(truncate(location, f2, 6, textW), { x: textX, y: sy + sh - 59, size: 6, font: f2, color: C.lightGray });
}

// ── Style: FIRMAEC (QR izquierda + texto monoespaciado estilo FirmaEC Ecuador) ─
async function drawStyleFirmaEC(pdfDoc, page, sx, sy, sw, sh, { signerName, verificationUrl, qrPosition, qrBackground, qrBorder }) {
  const fBold = await pdfDoc.embedFont(StandardFonts.CourierBold);
  const fReg  = await pdfDoc.embedFont(StandardFonts.Courier);
  const useSoftBackground = qrBackground === 'soft';
  const useBorder = qrBorder === 'line';
  const qrOnRight = qrPosition === 'right';

  const qrContent = verificationUrl || [
    'FIRMA DIGITAL VERIFICADA',
    `Firmante: ${signerName}`,
  ].join('\n');

  const qrPng = await QRCode.toBuffer(qrContent, {
    type: 'png',
    width: 120,
    margin: 1,
    color: { dark: '#000000', light: '#ffffff' },
  });
  const qrImage = await pdfDoc.embedPng(qrPng);
  const qrSize = Math.min(sh - 10, 50);

  // Background
  const bgColor = useSoftBackground ? C.bgBlue : C.white;
  page.drawRectangle({ x: sx, y: sy, width: sw, height: sh, color: bgColor });
  if (useBorder) {
    page.drawRectangle({
      x: sx,
      y: sy,
      width: sw,
      height: sh,
      borderColor: rgb(0.15, 0.15, 0.15),
      borderWidth: 0.85,
    });
  }

  // QR image
  const qrX = qrOnRight ? sx + sw - qrSize - 4 : sx + 4;
  const qrY = sy + (sh - qrSize) / 2;
  page.drawImage(qrImage, { x: qrX, y: qrY, width: qrSize, height: qrSize });

  // Vertical divider belongs to the bordered variant only.
  const divX = qrOnRight ? qrX - 4 : sx + qrSize + 8;
  if (useBorder) {
    page.drawLine({ start: { x: divX, y: sy + 6 }, end: { x: divX, y: sy + sh - 6 }, thickness: 0.5, color: rgb(0.55, 0.55, 0.58) });
  }

  // Text column
  const textX = qrOnRight ? sx + 6 : divX + 5;
  const textW  = sw - qrSize - 18;

  page.drawText('Validar unicamente en FirmaEC.', { x: textX, y: sy + sh - 12, size: 6, font: fReg, color: rgb(0.12, 0.12, 0.14) });
  page.drawText('Firmado electronicamente por:', { x: textX, y: sy + sh - 21, size: 6, font: fReg, color: rgb(0.12, 0.12, 0.14) });

  // Name — bold, uppercase, word-wrapped up to 2 lines
  const nameUpper = signerName.toUpperCase();
  const nameSize  = 8.5;
  const nameLines = wrapToLines(nameUpper, fBold, nameSize, textW, 2);
  nameLines.forEach((line, i) => {
    page.drawText(line, { x: textX, y: sy + sh - 34 - (i * 13), size: nameSize, font: fBold, color: rgb(0.05, 0.05, 0.07) });
  });
}

// ── Main sign function ─────────────────────────────────────────────────────────
const signPdf = async ({
  pdfPath, p12Buffer, p12Password,
  signerName, reason = '', location = '',
  page = 0, rect = null,
  signatureStyle = 'classic', signatureImageBase64 = null,
  qrPosition = 'left',
  qrBackground = 'transparent',
  qrBorder = 'none',
  verificationUrl = null,
  clientLocale = null,
  clientTimeZone = null,
  outputDir = null,
  outputBaseName = null,
}) => {
  const pdfBytes = await fs.readFile(pdfPath);
  const pdfDoc   = await PDFDocument.load(pdfBytes, { ignoreEncryption: true });
  const pages    = pdfDoc.getPages();
  const tp       = pages[Math.min(page, pages.length - 1)];
  const { width: pw, height: ph } = tp.getSize();
  const cropBox = typeof tp.getCropBox === 'function'
    ? tp.getCropBox()
    : { x: 0, y: 0, width: pw, height: ph };

  const defaultWidth = getSignatureWidth(signatureStyle, signerName);
  const requestedRect = rect || {
    x: cropBox.width - (defaultWidth + 22),
    y: 18,
    width: defaultWidth,
    height: 65,
  };
  const resolvedWidth = requestedRect.width || defaultWidth;
  const resolvedX = Math.min(
    Math.max(requestedRect.x, 0),
    Math.max(0, cropBox.width - resolvedWidth - 4)
  );
  const resolvedY = Math.min(
    Math.max(requestedRect.y, 0),
    Math.max(0, cropBox.height - (requestedRect.height || 65) - 4)
  );
  const sigRect = {
    ...requestedRect,
    x: resolvedX + cropBox.x,
    y: resolvedY + cropBox.y,
    width: resolvedWidth,
  };
  const { x: sx, y: sy, width: sw, height: sh } = sigRect;

  const { dateStr, timeStr } = buildLocalizedSignatureTimestamp({
    locale: clientLocale,
    timeZone: clientTimeZone,
  });

  const info = { signerName, reason, dateStr, timeStr, location, signatureImageBase64, verificationUrl, qrPosition, qrBackground, qrBorder };

  // ── Draw visual stamp on page content stream ─────────────────────
  const style = signatureStyle || 'classic';
  if      (style === 'qr')           await drawStyleQR(pdfDoc, tp, sx, sy, sw, sh, info);
  else if (style === 'professional') await drawStyleProfessional(pdfDoc, tp, sx, sy, sw, sh, info);
  else if (style === 'image')        await drawStyleImage(pdfDoc, tp, sx, sy, sw, sh, info);
  else if (style === 'firmaec')      await drawStyleFirmaEC(pdfDoc, tp, sx, sy, sw, sh, info);
  else                               await drawStyleClassic(pdfDoc, tp, sx, sy, sw, sh, info);

  // ── Save page with visual stamp ───────────────────────────────────
  const pdfWithStamp = Buffer.from(await pdfDoc.save({ useObjectStreams: false }));

  // ── Add cryptographic signature placeholder ───────────────────────
  const pdfDocForSign = await PDFDocument.load(pdfWithStamp);
  const placeholderPageIndex = Math.min(page, pdfDocForSign.getPageCount() - 1);
  pdflibAddPlaceholder({
    pdfDoc: pdfDocForSign,
    reason: reason || 'Firma digital',
    contactInfo: signerName,
    name: signerName,
    location: location || '',
    signatureLength: 32768,
    rect: [sx, sy, sx + sw, sy + sh],
    pageIndex: placeholderPageIndex,
  });
  hideSignatureWidgetBorder(pdfDocForSign, placeholderPageIndex);

  const pdfWithPlaceholder = Buffer.from(await pdfDocForSign.save({ useObjectStreams: false }));

  // ── Sign ──────────────────────────────────────────────────────────
  const signer       = new P12Signer(p12Buffer, { passphrase: p12Password || '' });
  const signInstance = new SignPdf();
  const signedBuf    = await signInstance.sign(pdfWithPlaceholder, signer);

  // ── Save ──────────────────────────────────────────────────────────
  const destDir      = outputDir || await getSignedDocumentPath();
  const ext          = path.extname(pdfPath);
  const base         = outputBaseName || path.basename(pdfPath, ext).replace(/^\d+-/, '');
  const nowForFilename = new Date();
  const year = String(nowForFilename.getFullYear());
  const month = String(nowForFilename.getMonth() + 1).padStart(2, '0');
  const day = String(nowForFilename.getDate()).padStart(2, '0');
  const hours = String(nowForFilename.getHours()).padStart(2, '0');
  const minutes = String(nowForFilename.getMinutes()).padStart(2, '0');
  const dateSuffix = `${year}${month}${day}${hours}${minutes}`;
  const signedFilename = outputBaseName ? `${base}${ext}` : `${base}_${dateSuffix}${ext}`;
  const signedPath   = path.join(destDir, signedFilename);
  await fs.writeFile(signedPath, signedBuf);

  return { signedFilename, signedPath };
};

module.exports = { signPdf };