/**
 * ModelListDisplay - Displays the list of available ONNX models
 * Requirements: 2.1, 2.2, 2.3, 2.4, 2.5, 2.6
 */

class ModelListDisplay {
  /**
   * @param {string} containerId - ID of the container element
   */
  constructor(containerId) {
    this._containerId = containerId;
    this._container = document.getElementById(containerId);
    this._selectedModelId = null;
    this._unsubscribe = null;

    if (!this._container) {
      console.warn(`[ModelListDisplay] Container #${containerId} not found`);
      return;
    }

    this._bindStateSubscriptions();
  }

  // ─── Private ──────────────────────────────────────────────────────────────

  _bindStateSubscriptions() {
    // Restore persisted selection
    const persistedId = window.StateManager
      ? window.StateManager.getPersistedSelectedModelId()
      : null;
    if (persistedId) {
      this._selectedModelId = persistedId;
    }

    // Subscribe to currentModel changes to keep selection in sync
    if (window.StateManager) {
      this._unsubscribe = window.StateManager.subscribe('currentModel', (model) => {
        const id = model && model.metadata ? model.metadata.fileName : null;
        if (id !== this._selectedModelId) {
          this._selectedModelId = id;
          this._updateSelectedState();
        }
      });
    }
  }

  /**
   * Format a file path to a human-readable name (show only the file name).
   * @param {string} filePath
   * @returns {string}
   */
  _formatFileName(filePath) {
    if (!filePath) return 'Unknown';
    // Use helper if available
    if (typeof formatFileName === 'function') {
      return formatFileName(filePath);
    }
    // Fallback: strip path separators
    const parts = filePath.replace(/\\/g, '/').split('/');
    return parts[parts.length - 1] || filePath;
  }

  /**
   * Build a single list item element for a model.
   * @param {ModelInfo} model
   * @returns {HTMLElement}
   */
  _buildItem(model) {
    const item = document.createElement('a');
    item.href = '#';
    item.className = 'list-group-item list-group-item-action model-list-item';
    item.dataset.modelId = model.id || model.path;
    item.setAttribute('role', 'button');
    item.setAttribute('aria-label', `Select model ${this._formatFileName(model.name || model.path)}`);

    const displayName = this._formatFileName(model.name || model.path);

    item.innerHTML = `
      <div class="d-flex align-items-center">
        <i class="fas fa-cube me-2 text-primary"></i>
        <div class="overflow-hidden">
          <div class="text-truncate fw-medium">${this._escapeHtml(displayName)}</div>
          ${model.description ? `<small class="text-muted text-truncate d-block">${this._escapeHtml(model.description)}</small>` : ''}
        </div>
      </div>
    `;

    // Mark as selected if this is the current model
    if (this._selectedModelId && (model.id === this._selectedModelId || model.path === this._selectedModelId)) {
      item.classList.add('active');
      item.setAttribute('aria-current', 'true');
    }

    item.addEventListener('click', (e) => {
      e.preventDefault();
      this._onModelClick(model, item);
    });

    return item;
  }

  /**
   * Handle model item click.
   * @param {ModelInfo} model
   * @param {HTMLElement} item
   */
  _onModelClick(model, item) {
    // Update visual selection
    this._selectedModelId = model.id || model.path;
    this._updateSelectedState();

    // Emit event via EventBus
    if (window.EventBus) {
      window.EventBus.emit(CONFIG.EVENTS.MODEL_SELECTED, model);
    }

    // Update StateManager if available (without triggering re-render loop)
    if (window.StateManager) {
      // Persist selection
      try {
        localStorage.setItem(CONFIG.STORAGE.SELECTED_MODEL, this._selectedModelId);
      } catch (_) { /* ignore */ }
    }
  }

  /**
   * Update the active/selected CSS class on all items.
   */
  _updateSelectedState() {
    if (!this._container) return;
    const items = this._container.querySelectorAll('.model-list-item');
    items.forEach((item) => {
      const isSelected = item.dataset.modelId === this._selectedModelId;
      item.classList.toggle('active', isSelected);
      if (isSelected) {
        item.setAttribute('aria-current', 'true');
      } else {
        item.removeAttribute('aria-current');
      }
    });
  }

  /**
   * Escape HTML special characters to prevent XSS.
   * @param {string} str
   * @returns {string}
   */
  _escapeHtml(str) {
    const div = document.createElement('div');
    div.appendChild(document.createTextNode(str));
    return div.innerHTML;
  }

  // ─── Public API ───────────────────────────────────────────────────────────

  /**
   * Render the model list.
   * @param {Array<ModelInfo>} models
   */
  render(models) {
    if (!this._container) return;

    this._container.innerHTML = '';

    if (!models || models.length === 0) {
      const empty = document.createElement('div');
      empty.className = 'list-group-item text-muted text-center py-3';
      empty.setAttribute('role', 'status');
      empty.innerHTML = `<i class="fas fa-inbox me-2"></i>${CONFIG.ERRORS.NO_MODELS_AVAILABLE}`;
      this._container.appendChild(empty);
      return;
    }

    const fragment = document.createDocumentFragment();
    models.forEach((model) => {
      fragment.appendChild(this._buildItem(model));
    });
    this._container.appendChild(fragment);
  }

  /**
   * Clear the model list display.
   */
  clear() {
    if (!this._container) return;
    this._container.innerHTML = '';
  }

  /**
   * Destroy the component and clean up subscriptions.
   */
  destroy() {
    if (this._unsubscribe) {
      this._unsubscribe();
      this._unsubscribe = null;
    }
  }
}

window.ModelListDisplay = ModelListDisplay;