async function fetchJson(url, options) {
  const res = await fetch(url, options);
  if (!res.ok) throw new Error(`Fetch failed: ${url}`);
  return await res.json();
}

function option(value, label) {
  const el = document.createElement('option');
  el.value = value;
  el.textContent = label;
  return el;
}

function renderList(targetId, items, formatter) {
  const target = document.getElementById(targetId);
  if (!target) return;
  if (!items.length) {
    target.textContent = 'Nothing here yet.';
    target.classList.add('muted');
    return;
  }
  target.classList.remove('muted');
  target.innerHTML = '';
  for (const item of items) {
    const wrapper = document.createElement('div');
    wrapper.className = 'list-item';
    wrapper.innerHTML = formatter(item);
    target.appendChild(wrapper);
  }
}

async function populateCourses() {
  const data = await fetchJson('/api/d2l/courses');
  const courseSelect = document.getElementById('class-select');
  const courseNameInput = document.getElementById('class-name-input');
  const recordingSelect = document.getElementById('recording-class-select');
  const recordingNameInput = document.getElementById('recording-class-name-input');
  const courses = data.items || [];
  const byId = new Map(courses.map((course) => [String(course.d2l_course_id || course.id), course]));

  if (courseSelect) {
    courseSelect.innerHTML = '';
    courseSelect.appendChild(option('', 'Choose a class'));
    for (const course of courses) {
      courseSelect.appendChild(option(course.d2l_course_id || course.id, `${course.name}${course.finalSummary ? ' — ' + course.finalSummary : ''}`));
    }
    courseSelect.addEventListener('change', async (event) => {
      const courseId = event.target.value;
      const course = byId.get(String(courseId));
      if (courseNameInput) courseNameInput.value = course?.name || '';
      const assignmentSelect = document.getElementById('assignment-select');
      assignmentSelect.innerHTML = '';
      if (!courseId) {
        assignmentSelect.appendChild(option('', 'Pick a class first'));
        return;
      }
      assignmentSelect.appendChild(option('', 'Loading assignments…'));
      const assignmentData = await fetchJson(`/api/d2l/assignments?course_id=${encodeURIComponent(courseId)}`);
      assignmentSelect.innerHTML = '';
      assignmentSelect.appendChild(option('', 'Choose an assignment'));
      for (const assignment of assignmentData.items || []) {
        assignmentSelect.appendChild(option(assignment.title, assignment.title));
      }
    });
  }

  if (recordingSelect) {
    recordingSelect.innerHTML = '';
    recordingSelect.appendChild(option('', 'Choose a class'));
    for (const course of courses) {
      recordingSelect.appendChild(option(course.d2l_course_id || course.id, course.name));
    }
    recordingSelect.addEventListener('change', (event) => {
      const course = byId.get(String(event.target.value));
      if (recordingNameInput) recordingNameInput.value = course?.name || '';
    });
  }
}

async function loadDashboard() {
  const data = await fetchJson('/api/dashboard/summary');
  const counts = data.counts || {};
  const setText = (id, value) => {
    const el = document.getElementById(id);
    if (el) el.textContent = value;
  };
  setText('stat-courses', counts.courses ?? '0');
  setText('stat-assignments', counts.assignments ?? '0');
  setText('stat-submissions', counts.submissions ?? '0');
  setText('stat-recordings', counts.recordings ?? '0');
  setText('backend-note', `Storage backend: ${data.backend}`);
  if (data.latest_sync) {
    setText('sync-status', `Last sync: ${data.latest_sync.completed_at || 'unknown'} · ${data.latest_sync.assignment_count || 0} assignment rows`);
  }
  renderList('recent-assignments', data.recent_assignments || [], (item) => `<strong>${item.title || 'Untitled'}</strong><small>${item.course_name || ''}</small><small>Status: ${item.status || 'assigned'} · Grade: ${item.grade || '—'}</small>`);
  renderList('recent-submissions', data.recent_submissions || [], (item) => `<strong>${item.assignment_name || item.original_filename || 'Submission'}</strong><small>${item.class_name || ''}</small><small>Status: ${item.status || 'unknown'} · File: ${item.original_filename || '—'}</small>`);
  renderList('recent-recordings', data.recent_recordings || [], (item) => `<strong>${item.original_filename || 'Recording'}</strong><small>${item.session_date || ''}</small><small>Transcription: ${item.transcription_status || '—'} · Summary: ${item.summary_status || '—'}</small>`);
}

async function wireSyncButton() {
  const button = document.getElementById('sync-button');
  if (!button) return;
  button.addEventListener('click', async () => {
    button.disabled = true;
    button.textContent = 'Refreshing…';
    try {
      const result = await fetchJson('/api/d2l/sync', { method: 'POST' });
      const el = document.getElementById('sync-status');
      if (el) el.textContent = `Last sync: just now · ${result.assignment_count} assignment rows · backend ${result.backend}`;
      await loadDashboard();
    } catch (error) {
      const el = document.getElementById('sync-status');
      if (el) el.textContent = `Sync failed: ${error}`;
    } finally {
      button.disabled = false;
      button.textContent = 'Refresh from D2L';
    }
  });
}

populateCourses().catch((error) => {
  console.error('Failed to populate D2L selectors', error);
});
loadDashboard().catch((error) => {
  console.error('Failed to load dashboard summary', error);
});
wireSyncButton();