import { parseHtmlSafely, sanitizeSignatureHtml } from '@/lib/email-sanitization';
import { htmlToPlainText } from '@/lib/html-to-text';
import { wantsSignatureSeparator } from '@/lib/signature-delimiter';

type SignatureSource = {
  textSignature?: string;
  htmlSignature?: string;
};

function normalizeSignatureLineBreaks(value: string): string {
  return value
    .replace(/\r\n?/g, '\n')
    .replace(/\u00a0/g, ' ')
    // Trims trailing spaces, but keeps the one that makes "-- " the RFC 3676
    // signature delimiter.
    .split('\n')
    .map((line) => (/^--[ \t]*$/.test(line) ? '-- ' : line.replace(/[ \t]+$/, '')))
    .join('\n')
    .replace(/\n{3,}/g, '\n\n')
    .trim();
}

export function getPlainTextSignature(signature?: SignatureSource | null): string {
  if (signature?.textSignature?.trim()) {
    return normalizeSignatureLineBreaks(signature.textSignature);
  }

  if (signature?.htmlSignature?.trim()) {
    return htmlToPlainText(sanitizeSignatureHtml(signature.htmlSignature));
  }

  return '';
}

export function appendPlainTextSignature(
  body: string,
  signature?: SignatureSource | null,
  options: { separator?: boolean } = {},
): string {
  const plainTextSignature = getPlainTextSignature(signature);
  if (!plainTextSignature) {
    return body;
  }

  const sep = wantsSignatureSeparator(options.separator, signature) ? '\n\n-- \n' : '\n\n';
  return `${body}${sep}${plainTextSignature}`;
}

/**
 * Whether a plain-text body already ends with the identity's signature.
 *
 * The HTML path detects an embedded signature by its markers
 * (`containsEmbeddedSignature`); plain text has none, so the body is matched
 * against the signature itself. Both sides go through the same line-break
 * normalization so a body that round-tripped through a draft (CRLF, trailing
 * spaces) still matches.
 */
export function plainTextBodyHasSignature(
  body: string,
  signature?: SignatureSource | null,
): boolean {
  const plainTextSignature = getPlainTextSignature(signature);
  if (!plainTextSignature) {
    return false;
  }
  return normalizeSignatureLineBreaks(body).endsWith(plainTextSignature);
}

/**
 * The plain-text body with a trailing signature - and the `-- ` separator
 * line in front of it - removed. Returns the body unchanged when it does not
 * end with the identity's signature. Used to tell an untouched compose body
 * (signature only) from one the user has already written into (#540).
 */
export function plainTextBodyWithoutSignature(
  body: string,
  signature?: SignatureSource | null,
): string {
  const plainTextSignature = getPlainTextSignature(signature);
  if (!plainTextSignature) {
    return body;
  }
  const normalized = normalizeSignatureLineBreaks(body);
  if (!normalized.endsWith(plainTextSignature)) {
    return body;
  }
  return normalized
    .slice(0, normalized.length - plainTextSignature.length)
    .replace(/\n*(?:-- ?)?\n*$/, '');
}

/**
 * Append a signature to an HTML body, preserving rich formatting. Used by the
 * quick-reply path so an HTML signature keeps its markup instead of being
 * flattened to plain text. Mirrors the composer's send-time signature block
 * (`buildSignatureHtml` in email-composer.tsx).
 */
export function appendHtmlSignature(
  htmlBody: string,
  signature?: SignatureSource | null,
  options: { separator?: boolean } = {},
): string {
  const sep = wantsSignatureSeparator(options.separator, signature) ? '<br><br>-- <br>' : '<br><br>';

  if (signature?.htmlSignature?.trim()) {
    return `${htmlBody}${sep}${sanitizeSignatureHtml(signature.htmlSignature)}`;
  }

  if (signature?.textSignature?.trim()) {
    const escaped = signature.textSignature
      .replace(/&/g, '&amp;')
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
      .replace(/\n/g, '<br>');
    return `${htmlBody}${sep}${escaped}`;
  }

  return htmlBody;
}

export function hasMeaningfulHtmlBody(html: string): boolean {
  if (!html.trim()) return false;

  const document = parseHtmlSafely(html);
  const richSelector = [
    'table',
    'img',
    'style',
    'b',
    'strong',
    'i',
    'em',
    'u',
    'font',
    'a[href]',
    'div[style]',
    'span[style]',
    'p[style]',
    'h1',
    'h2',
    'h3',
    'h4',
    'h5',
    'h6',
    'ul',
    'ol',
    'blockquote',
    'br',
  ].join(', ');

  if (document.querySelector(richSelector)) {
    return true;
  }

  const blockElements = document.body.querySelectorAll('p, div, blockquote, li');
  return blockElements.length > 1;
}