'use strict';

const { cleanBody } = require('./bodyParser');

const { formatDateTime } = require('../utils/time-formatter');

/**
 * threadBuilder.js
 * Reconstructs a clean, deduplicated email thread from a set of Graph API
 * message objects. Each message is stripped down to only its unique new
 * content — quoted prior messages are removed.
 */

// ---------------------------------------------------------------------------
// Quote-stripping patterns
// Ordered from most specific to most general.
// ---------------------------------------------------------------------------

const QUOTE_BOUNDARIES = [
  // Outlook-style attribution: "From: Name <email>\nSent: ..."
  /^From\s*:\s*.+\n(?:Sent|Date)\s*:/im,
  // Outlook-style with leading whitespace/non-breaking spaces
  /^\s*From\s*:\s*.+\n\s*(?:Sent|Date)\s*:/im,
  // Gmail/web client: "On Mon, Mar 13, 2026 at 8:32 AM, Name <email> wrote:"
  /^On\s+.{5,80}wrote\s*:\s*$/im,
  // Simple "wrote:" attribution line
  /^.{0,100}<.+@.+>\s+wrote\s*:/im,
  // Forwarded message header block
  /^-{3,}\s*(?:Forwarded|Original)\s+[Mm]essage\s*-{3,}/im,
  // Lines starting with > (standard quote marker)
  /^>+\s/m,
];

// ---------------------------------------------------------------------------
// Core functions
// ---------------------------------------------------------------------------

/**
 * Extract only the new/unique content from a single message body,
 * stripping all quoted prior messages.
 * @param {string} body - Cleaned body text
 * @returns {string} Unique message content only
 */
function extractUniqueContent(body) {
  if (!body) return '';

  let earliestBoundary = body.length;

  for (const pattern of QUOTE_BOUNDARIES) {
    const match = body.search(pattern);
    if (match !== -1 && match < earliestBoundary) {
      earliestBoundary = match;
    }
  }

  const unique = body.slice(0, earliestBoundary).trim();
  return unique;
}

/**
 * Format a single message as a clean thread entry.
 * @param {object} msg - Graph API message object (already body-cleaned)
 * @param {number} index - 1-based position in thread
 * @returns {string}
 */
function formatThreadEntry(msg, index) {
  const from = msg.from?.emailAddress
    ? `${msg.from.emailAddress.name || ''} <${msg.from.emailAddress.address}>`.trim()
    : 'Unknown';

  const to = (msg.toRecipients || [])
    .map(r => r.emailAddress?.name || r.emailAddress?.address || '')
    .filter(Boolean)
    .join(', ') || 'Unknown';

  const cc = (msg.ccRecipients || [])
    .map(r => r.emailAddress?.name || r.emailAddress?.address || '')
    .filter(Boolean)
    .join(', ');

  const date = msg.receivedDateTime
    ? formatDateTime(msg.receivedDateTime)
    : 'Unknown date';

  const bodyText = msg.body?.content || msg.bodyPreview || '';
  const unique = extractUniqueContent(bodyText);

  const lines = [
    `[${index}] ${date}`,
    `From: ${from}`,
    `To: ${to}`,
  ];
  if (cc) lines.push(`CC: ${cc}`);
  if (msg.hasAttachments) lines.push('Attachments: Yes');
  lines.push('');
  lines.push(unique || '(no unique content)');

  return lines.join('\n');
}

/**
 * Build a clean deduplicated thread from an array of Graph API message objects.
 * Messages are sorted chronologically and each is stripped to unique content only.
 *
 * @param {object[]} messages - Array of Graph API message objects with body.content populated
 * @param {string} [subject] - Thread subject (inferred from first message if omitted)
 * @returns {string} Formatted thread as a single string
 */
function buildThread(messages, subject) {
  if (!Array.isArray(messages) || messages.length === 0) {
    return '(no messages)';
  }

  // Sort chronologically
  const sorted = [...messages].sort((a, b) => {
    const ta = a.receivedDateTime ? new Date(a.receivedDateTime).getTime() : 0;
    const tb = b.receivedDateTime ? new Date(b.receivedDateTime).getTime() : 0;
    return ta - tb;
  });

  // Infer subject if not provided
  const threadSubject = subject
    || sorted[0]?.subject
    || '(no subject)';

  // Strip Re:/Fw: prefix for display
  const displaySubject = threadSubject.replace(/^(Re|Fwd?)\s*:\s*/i, '').trim();

  const header = [
    `Thread: ${displaySubject}`,
    `Messages: ${sorted.length}`,
    '='.repeat(60),
    '',
  ].join('\n');

  // Track which senders have already had their signature included.
  // First message from each sender keeps the signature; repeats get it stripped.
  const seenSenders = new Set();
  const entries = sorted
    .map((msg, i) => {
      const senderEmail = msg.from?.emailAddress?.address?.toLowerCase() || '';
      const isRepeat = seenSenders.has(senderEmail);
      if (senderEmail) seenSenders.add(senderEmail);

      const cleanedMsg = { ...msg };
      if (cleanedMsg.body?.content) {
        cleanedMsg.body = {
          ...cleanedMsg.body,
          content: cleanBody(cleanedMsg.body.content, { stripSignature: isRepeat }),
        };
      }
      return formatThreadEntry(cleanedMsg, i + 1);
    })
    .join('\n\n' + '-'.repeat(40) + '\n\n');

  return header + entries;
}

module.exports = { buildThread, extractUniqueContent };