const { ConfidentialClientApplication } = require('@azure/msal-node');
const { Client } = require('@microsoft/microsoft-graph-client');
const { readFileSync } = require('node:fs');
const { resolve } = require('node:path');

function loadEnv() {
  const envPath = resolve(__dirname, '..', '.env');
  const content = readFileSync(envPath, 'utf-8');
  const vars = {};
  for (const line of content.split('\n')) {
    const trimmed = line.trim();
    if (!trimmed || trimmed.startsWith('#')) continue;
    const [key, ...rest] = trimmed.split('=');
    vars[key.trim()] = rest.join('=').trim();
  }
  return vars;
}

async function buildGraphClient(env = loadEnv()) {
  const cca = new ConfidentialClientApplication({
    auth: {
      clientId: env.AZURE_CLIENT_ID,
      clientSecret: env.AZURE_CLIENT_SECRET,
      authority: `https://login.microsoftonline.com/${env.AZURE_TENANT_ID}`
    }
  });
  const tokenResponse = await cca.acquireTokenByClientCredential({
    scopes: ['https://graph.microsoft.com/.default']
  });
  return Client.init({
    authProvider: (done) => done(null, tokenResponse.accessToken),
    defaultVersion: 'v1.0'
  });
}

async function safeGet(client, path, options = {}) {
  try {
    let req = client.api(path);
    if (options.version && typeof req.version === 'function') req = req.version(options.version);
    if (options.query && typeof req.query === 'function') req = req.query(options.query);
    return await req.get();
  } catch (err) {
    if (err.statusCode === 404 || err.statusCode === 403) return null;
    throw err;
  }
}

async function resolveOnlineMeeting(client, userId, joinWebUrl) {
  const path = `/users/${userId}/onlineMeetings`;
  const resp = await safeGet(client, path, {
    query: { $filter: `JoinWebUrl eq '${joinWebUrl}'` }
  });
  const list = resp?.value || [];
  return list[0] || null;
}

async function fetchTranscriptVtt(client, userId, meetingId) {
  const list = await safeGet(client, `/users/${userId}/onlineMeetings/${meetingId}/transcripts`);
  const items = list?.value || [];
  if (items.length === 0) return null;
  const latest = [...items].sort((a, b) =>
    new Date(b.createdDateTime) - new Date(a.createdDateTime)
  )[0];
  const contentPath = `/users/${userId}/onlineMeetings/${meetingId}/transcripts/${latest.id}/content`;
  return await safeGet(client, contentPath);
}

async function fetchAiInsights(client, userId, meetingId) {
  const path = `/users/${userId}/onlineMeetings/${meetingId}/aiInsights`;
  const resp = await safeGet(client, path, { version: 'beta' });
  const items = resp?.value || [];
  return items[0] || null;
}

async function fetchRecordingUrl(client, userId, meetingId) {
  const list = await safeGet(client, `/users/${userId}/onlineMeetings/${meetingId}/recordings`);
  const items = list?.value || [];
  if (items.length === 0) return null;
  const latest = [...items].sort((a, b) =>
    new Date(b.createdDateTime) - new Date(a.createdDateTime)
  )[0];
  return latest.recordingContentUrl || latest.contentCorrelationId || null;
}

module.exports = {
  loadEnv,
  buildGraphClient,
  resolveOnlineMeeting,
  fetchTranscriptVtt,
  fetchAiInsights,
  fetchRecordingUrl
};