// Minimal row editor for timetable groups.

(function () {
  var form = document.getElementById('timetable-group-form');
  var timezoneInput = document.getElementById('timetable-group-timezone');
  var body = document.querySelector('[data-timetable-entries-body]');
  var addButton = document.querySelector('[data-add-timetable-entry]');
  var template = document.getElementById('timetable-entry-row-template');

  if (!form || !timezoneInput || !body || !addButton || !template) {
    return;
  }

  var DEFAULT_TIME_ZONE = 'Europe/London';

  function markDirty() {
    form.dataset.dirty = 'true';
  }

  function pad(value) {
    return String(value).padStart(2, '0');
  }

  function getDefaultTimeZone() {
    try {
      return Intl.DateTimeFormat().resolvedOptions().timeZone || DEFAULT_TIME_ZONE;
    } catch (_error) {
      return DEFAULT_TIME_ZONE;
    }
  }

  function resolveTimeZone(value) {
    var raw = String(value || '').trim();
    if (!raw) {
      return getDefaultTimeZone();
    }

    try {
      new Intl.DateTimeFormat('en-GB', { timeZone: raw }).format(new Date());
      return raw;
    } catch (_error) {
      return getDefaultTimeZone();
    }
  }

  function parseDateTimeLocalParts(value) {
    var raw = String(value || '').trim();
    var match = raw.match(/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?::(\d{2}))?$/);
    if (!match) {
      return null;
    }

    return {
      year: Number(match[1]),
      month: Number(match[2]),
      day: Number(match[3]),
      hour: Number(match[4]),
      minute: Number(match[5]),
      second: Number(match[6] || '0')
    };
  }

  function getDateTimeParts(date, timeZone) {
    if (!(date instanceof Date) || Number.isNaN(date.getTime())) {
      return null;
    }

    var resolvedTimeZone = resolveTimeZone(timeZone);
    var parts = new Intl.DateTimeFormat('en-GB', {
      timeZone: resolvedTimeZone,
      hour12: false,
      year: 'numeric',
      month: '2-digit',
      day: '2-digit',
      hour: '2-digit',
      minute: '2-digit',
      second: '2-digit'
    }).formatToParts(date);
    var mapped = Object.create(null);

    parts.forEach(function (part) {
      if (part && part.type && part.type !== 'literal') {
        mapped[part.type] = part.value;
      }
    });

    return mapped;
  }

  function formatDateTimeLocalValue(date, timeZone) {
    var parts = getDateTimeParts(date, timeZone);
    if (!parts) {
      return '';
    }

    return [
      String(parts.year || '').padStart(4, '0'),
      '-',
      pad(parts.month),
      '-',
      pad(parts.day),
      'T',
      pad(parts.hour),
      ':',
      pad(parts.minute)
    ].join('');
  }

  function getTimeZoneOffsetMillis(date, timeZone) {
    var parts = getDateTimeParts(date, timeZone);
    if (!parts) {
      return 0;
    }

    var localAsUtc = Date.UTC(
      Number(parts.year) || 0,
      (Number(parts.month) || 1) - 1,
      Number(parts.day) || 1,
      Number(parts.hour) || 0,
      Number(parts.minute) || 0,
      Number(parts.second) || 0,
      0
    );

    return localAsUtc - date.getTime();
  }

  function parseDateTimeLocalAsUtc(value, timeZone) {
    var raw = String(value || '').trim();
    var isoDate;
    var parts = parseDateTimeLocalParts(value);
    if (!parts) {
      isoDate = /(?:[zZ]|[+-]\d\d(?::?\d\d)?)$/.test(raw) ? new Date(raw) : null;
      return isoDate && !Number.isNaN(isoDate.getTime()) ? isoDate : null;
    }

    var resolvedTimeZone = resolveTimeZone(timeZone);
    var utcMillis = Date.UTC(parts.year, parts.month - 1, parts.day, parts.hour, parts.minute, parts.second, 0);
    var date = new Date(utcMillis);
    var offset = getTimeZoneOffsetMillis(date, resolvedTimeZone);
    var adjusted = new Date(utcMillis - offset);
    var adjustedOffset = getTimeZoneOffsetMillis(adjusted, resolvedTimeZone);

    if (adjustedOffset !== offset) {
      adjusted = new Date(utcMillis - adjustedOffset);
    }

    return Number.isNaN(adjusted.getTime()) ? null : adjusted;
  }

  function convertDateTimeLocalValue(value, sourceTimeZone, targetTimeZone) {
    var raw = String(value || '').trim();
    if (!raw) {
      return '';
    }

    var utcDate = parseDateTimeLocalAsUtc(raw, sourceTimeZone);
    if (!utcDate) {
      return '';
    }

    var resolvedTargetTimeZone = resolveTimeZone(targetTimeZone);
    if (resolvedTargetTimeZone === 'UTC') {
      return utcDate.toISOString();
    }

    return formatDateTimeLocalValue(utcDate, resolvedTargetTimeZone);
  }

  function clearFieldValidity(input) {
    if (!input) {
      return;
    }

    input.setCustomValidity('');
    input.classList.remove('is-invalid');
    if (input.removeAttribute) {
      input.removeAttribute('aria-invalid');
    }
  }

  function setFieldValidity(input, message) {
    if (!input) {
      return;
    }

    input.setCustomValidity(message);
    input.classList.add('is-invalid');
    if (input.setAttribute) {
      input.setAttribute('aria-invalid', 'true');
    }
  }

  function validateEntryRow(row) {
    var timezone = resolveTimeZone(timezoneInput.value);
    var startInput;
    var endInput;
    var startValue;
    var endValue;
    var startDate;
    var endDate;

    if (!row) {
      return;
    }

    startInput = row.querySelector('[name="entry_start_datetime[]"]');
    endInput = row.querySelector('[name="entry_end_datetime[]"]');

    clearFieldValidity(endInput);

    if (!startInput || !endInput) {
      return;
    }

    startValue = String(startInput.value || '').trim();
    endValue = String(endInput.value || '').trim();

    if (!startValue || !endValue) {
      return;
    }

    startDate = parseDateTimeLocalAsUtc(startValue, timezone);
    endDate = parseDateTimeLocalAsUtc(endValue, timezone);

    if (!startDate || !endDate) {
      return;
    }

    if (endDate.getTime() < startDate.getTime() + 60000) {
      setFieldValidity(endInput, 'End time must be at least 1 minute after the start time.');
    }
  }

  function bindRowValidation(row) {
    var startInput;
    var endInput;

    if (!row) {
      return;
    }

    startInput = row.querySelector('[name="entry_start_datetime[]"]');
    endInput = row.querySelector('[name="entry_end_datetime[]"]');

    if (!startInput || !endInput) {
      return;
    }

    function handleValidation() {
      validateEntryRow(row);
    }

    startInput.addEventListener('input', handleValidation);
    startInput.addEventListener('change', handleValidation);
    endInput.addEventListener('input', handleValidation);
    endInput.addEventListener('change', handleValidation);

    validateEntryRow(row);
  }

  function syncRowValuesToTimeZone(row, sourceTimeZone, targetTimeZone) {
    if (!row) {
      return;
    }

    ['entry_start_datetime[]', 'entry_end_datetime[]'].forEach(function (name) {
      var input = row.querySelector('[name="' + name + '"]');
      var convertedValue;

      if (!input) {
        return;
      }

      convertedValue = convertDateTimeLocalValue(input.value, sourceTimeZone, targetTimeZone);
      if (convertedValue) {
        input.value = convertedValue;
      }
    });
  }

  function syncAllRowsToTimeZone(sourceTimeZone, targetTimeZone) {
    body.querySelectorAll('[data-timetable-entry-row]').forEach(function (row) {
      syncRowValuesToTimeZone(row, sourceTimeZone, targetTimeZone);
      validateEntryRow(row);
    });
  }

  function syncFormDataToUtc(formData) {
    var rows = body.querySelectorAll('[data-timetable-entry-row]');
    var currentTimeZone = resolveTimeZone(timezoneInput.value);

    ['entry_id[]', 'entry_title[]', 'entry_short_description[]', 'entry_start_datetime[]', 'entry_end_datetime[]'].forEach(function (name) {
      formData.delete(name);
    });

    rows.forEach(function (row) {
      var idInput = row.querySelector('[name="entry_id[]"]');
      var titleInput = row.querySelector('[name="entry_title[]"]');
      var descriptionInput = row.querySelector('[name="entry_short_description[]"]');
      var startInput = row.querySelector('[name="entry_start_datetime[]"]');
      var endInput = row.querySelector('[name="entry_end_datetime[]"]');

      formData.append('entry_id[]', idInput ? idInput.value : '');
      formData.append('entry_title[]', titleInput ? titleInput.value : '');
      formData.append('entry_short_description[]', descriptionInput ? descriptionInput.value : '');
      formData.append('entry_start_datetime[]', startInput ? convertDateTimeLocalValue(startInput.value, currentTimeZone, 'UTC') : '');
      formData.append('entry_end_datetime[]', endInput ? convertDateTimeLocalValue(endInput.value, currentTimeZone, 'UTC') : '');
    });
  }

  function bindRemove(row) {
    var button = row.querySelector('[data-remove-timetable-entry]');
    if (!button) {
      return;
    }
    button.addEventListener('click', function () {
      row.remove();
      markDirty();
    });
  }

  function addRow() {
    var fragment = template.content.cloneNode(true);
    var row = fragment.querySelector('[data-timetable-entry-row]');
    if (!row) {
      return;
    }
    bindRemove(row);
    bindRowValidation(row);
    body.appendChild(fragment);
    markDirty();
  }

  function handleTimezoneChange() {
    var nextTimeZone = resolveTimeZone(timezoneInput.value || DEFAULT_TIME_ZONE);
    form.dataset.timetableTimezone = nextTimeZone;
    markDirty();
  }

  form.dataset.timetableTimezone = resolveTimeZone(timezoneInput.value || DEFAULT_TIME_ZONE);

  body.querySelectorAll('[data-timetable-entry-row]').forEach(function (row) {
    bindRemove(row);
    bindRowValidation(row);
  });

  form.addEventListener('formdata', function (event) {
    syncFormDataToUtc(event.formData);
  });

  timezoneInput.addEventListener('change', handleTimezoneChange);
  timezoneInput.addEventListener('input', handleTimezoneChange);

  addButton.addEventListener('click', addRow);
}());