/**
 * ExportHandler - Handles exporting model information as JSON
 * Requirements: 12.1, 12.2, 12.3, 12.4
 */

const ExportHandler = (function () {
  class ExportHandler {
    /**
     * @param {string} [exportBtnId='exportBtn'] - ID of the export button element
     */
    constructor(exportBtnId = 'exportBtn') {
      this._exportBtn = document.getElementById(exportBtnId);
      this._unsubscribe = null;

      this._init();
    }

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

    _init() {
      if (!this._exportBtn) {
        console.warn('[ExportHandler] Export button not found:', this._exportBtn);
        return;
      }

      // Bind click handler
      this._exportBtn.addEventListener('click', () => this._handleExport());

      // Subscribe to currentModel changes to enable/disable button
      this._unsubscribe = StateManager.subscribe('currentModel', (model) => {
        this._setButtonEnabled(!!model);
      });

      // Set initial state
      this._setButtonEnabled(!!StateManager.getCurrentModel());
    }

    /**
     * Enable or disable the export button.
     * @param {boolean} enabled
     */
    _setButtonEnabled(enabled) {
      if (!this._exportBtn) return;
      this._exportBtn.disabled = !enabled;
    }

    /**
     * Build the export payload from the current model.
     * @param {object} model - ParsedModel from StateManager
     * @returns {object}
     */
    _buildExportData(model) {
      const data = {};

      // Metadata
      data.metadata = model.metadata ? Object.assign({}, model.metadata) : {};

      // Inputs
      data.inputs = Array.isArray(model.inputs)
        ? model.inputs.map((i) => Object.assign({}, i))
        : [];

      // Outputs
      data.outputs = Array.isArray(model.outputs)
        ? model.outputs.map((o) => Object.assign({}, o))
        : [];

      // Graph (nodes + edges)
      if (model.graph) {
        data.graph = {
          name: model.graph.name || '',
          nodes: Array.isArray(model.graph.nodes)
            ? model.graph.nodes.map((n) => Object.assign({}, n))
            : [],
          edges: Array.isArray(model.graph.edges)
            ? model.graph.edges.map((e) => Object.assign({}, e))
            : [],
        };
      } else {
        data.graph = { name: '', nodes: [], edges: [] };
      }

      // Initializers
      data.initializers = Array.isArray(model.initializers)
        ? model.initializers.map((init) => Object.assign({}, init))
        : [];

      return data;
    }

    /**
     * Derive the download file name from the model's fileName metadata.
     * e.g. "model.onnx" → "model_info.json"
     * @param {object} metadata
     * @returns {string}
     */
    _buildFileName(metadata) {
      const fileName = (metadata && metadata.fileName) || 'model';
      // Strip directory path, keep base name
      const base = fileName.split('/').pop().split('\\').pop();
      // Remove extension
      const withoutExt = base.replace(/\.[^.]+$/, '');
      return `${withoutExt}_info.json`;
    }

    /**
     * Trigger a browser download of the given JSON string.
     * @param {string} jsonStr
     * @param {string} fileName
     */
    _triggerDownload(jsonStr, fileName) {
      const blob = new Blob([jsonStr], { type: 'application/json' });
      const url = URL.createObjectURL(blob);

      const anchor = document.createElement('a');
      anchor.href = url;
      anchor.download = fileName;
      anchor.style.display = 'none';
      document.body.appendChild(anchor);
      anchor.click();
      document.body.removeChild(anchor);

      // Release the object URL after a short delay
      setTimeout(() => URL.revokeObjectURL(url), 1000);
    }

    /**
     * Show a brief success or error notification.
     * Falls back to console if no ErrorDisplay is available.
     * @param {string} message
     * @param {'success'|'error'} type
     */
    _showNotification(message, type) {
      if (window.ErrorDisplay && typeof window.ErrorDisplay.show === 'function') {
        window.ErrorDisplay.show(message, type === 'error' ? 'error' : 'info');
      } else {
        if (type === 'error') {
          console.error('[ExportHandler]', message);
        } else {
          console.info('[ExportHandler]', message);
        }
      }
    }

    // ─── Export Handler ──────────────────────────────────────────────────────

    _handleExport() {
      try {
        const model = StateManager.getCurrentModel();

        if (!model) {
          this._showNotification(
            CONFIG.ERRORS.EXPORT_ERROR + ' No model is currently loaded.',
            'error'
          );
          return;
        }

        const exportData = this._buildExportData(model);
        const jsonStr = JSON.stringify(exportData, null, 2);
        const fileName = this._buildFileName(model.metadata);

        this._triggerDownload(jsonStr, fileName);
        this._showNotification(CONFIG.SUCCESS.MODEL_EXPORTED, 'success');
      } catch (err) {
        console.error('[ExportHandler] Export failed:', err);
        this._showNotification(CONFIG.ERRORS.EXPORT_ERROR, 'error');
      }
    }

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

    /**
     * Programmatically trigger an export (useful for testing).
     */
    export() {
      this._handleExport();
    }

    /**
     * Clean up subscriptions.
     */
    destroy() {
      if (typeof this._unsubscribe === 'function') {
        this._unsubscribe();
        this._unsubscribe = null;
      }
    }
  }

  return ExportHandler;
})();

// Export for global access in vanilla JS context
window.ExportHandler = ExportHandler;