/**
 * ModelComplexity - Displays model complexity metrics
 * Computes total parameters, memory footprint, and summary counts from parsed model data.
 * Requirements: 20.1, 20.2, 20.3, 20.4, 20.5
 */

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

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

    this._setupEventListeners();
  }

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

  /**
   * Listen for model:loaded events to auto-update metrics.
   */
  _setupEventListeners() {
    if (window.EventBus && typeof CONFIG !== 'undefined' && CONFIG.EVENTS) {
      window.EventBus.on(CONFIG.EVENTS.MODEL_LOADED, (data) => {
        if (data && data.model) {
          const metrics = this.compute(data.model);
          this.render(metrics);
        }
      });
    }
  }

  /**
   * Format a parameter count into a human-readable string.
   * Examples: 500 → "500", 1500 → "1.5K", 25600000 → "25.6M", 1200000000 → "1.2B"
   * @param {number} count
   * @returns {string}
   */
  _formatParameterCount(count) {
    if (count == null || isNaN(count) || count === 0) return '0';
    const abs = Math.abs(count);
    if (abs >= 1e9) {
      return (count / 1e9).toFixed(1).replace(/\.0$/, '') + 'B';
    }
    if (abs >= 1e6) {
      return (count / 1e6).toFixed(1).replace(/\.0$/, '') + 'M';
    }
    if (abs >= 1e3) {
      return (count / 1e3).toFixed(1).replace(/\.0$/, '') + 'K';
    }
    return String(count);
  }

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

  /**
   * Compute complexity metrics from a parsed model.
   * @param {object} parsedModel
   * @returns {{ totalParameters: number, memoryFootprint: number, totalNodes: number, totalEdges: number, totalInitializers: number }}
   */
  compute(parsedModel) {
    const nodes = (parsedModel && parsedModel.graph && parsedModel.graph.nodes) || [];
    const edges = (parsedModel && parsedModel.graph && parsedModel.graph.edges) || [];
    const initializers = (parsedModel && parsedModel.initializers) || [];

    let totalParameters = 0;
    let memoryFootprint = 0;

    for (const init of initializers) {
      totalParameters += (init.elementCount || 0);
      memoryFootprint += (init.size || 0);
    }

    this._metrics = {
      totalParameters,
      memoryFootprint,
      totalNodes: nodes.length,
      totalEdges: edges.length,
      totalInitializers: initializers.length,
    };

    return this._metrics;
  }

  /**
   * Render the complexity metrics into the container.
   * @param {{ totalParameters: number, memoryFootprint: number, totalNodes: number, totalEdges: number, totalInitializers: number }} metrics
   */
  render(metrics) {
    if (!this._container) return;

    if (!metrics) {
      this._container.innerHTML = '<p class="text-muted">No complexity metrics available.</p>';
      return;
    }

    const { totalParameters, memoryFootprint, totalNodes, totalEdges, totalInitializers } = metrics;

    const paramDisplay = this._formatParameterCount(totalParameters);
    const memoryDisplay = (typeof Formatters !== 'undefined' && Formatters.formatBytes)
      ? Formatters.formatBytes(memoryFootprint)
      : this._fallbackFormatBytes(memoryFootprint);

    let html = `
      <div class="mb-3">
        <div class="d-flex flex-wrap gap-3 small">
          <span><i class="fas fa-project-diagram me-1"></i><strong>${totalNodes}</strong> Nodes</span>
          <span><i class="fas fa-arrows-alt-h me-1"></i><strong>${totalEdges}</strong> Edges</span>
          <span><i class="fas fa-database me-1"></i><strong>${totalInitializers}</strong> Initializers</span>
        </div>
      </div>
      <div class="d-flex flex-wrap gap-3">
        <div class="card p-2 flex-fill text-center">
          <div class="small text-muted">Parameters</div>
          <div class="fw-bold">${paramDisplay === '0' ? '0 parameters' : paramDisplay}</div>
        </div>
        <div class="card p-2 flex-fill text-center">
          <div class="small text-muted">Memory Footprint</div>
          <div class="fw-bold">${memoryDisplay}</div>
        </div>
      </div>`;

    this._container.innerHTML = html;
  }

  /**
   * Fallback byte formatter when Formatters utility is not available.
   * @param {number} bytes
   * @returns {string}
   */
  _fallbackFormatBytes(bytes) {
    if (bytes == null || isNaN(bytes) || bytes === 0) return '0 B';
    const k = 1024;
    const sizes = ['B', 'KB', 'MB', 'GB', 'TB'];
    const i = Math.min(Math.floor(Math.log(Math.abs(bytes)) / Math.log(k)), sizes.length - 1);
    return (bytes / Math.pow(k, i)).toFixed(2) + ' ' + sizes[i];
  }

  /**
   * Clear the display.
   */
  clear() {
    this._metrics = null;
    if (!this._container) return;
    this._container.innerHTML = '<p class="text-muted">Select a model to view complexity metrics</p>';
  }

  /**
   * Get the last computed metrics.
   * @returns {object|null}
   */
  getMetrics() {
    return this._metrics;
  }

  /**
   * Get the formatted parameter count string (useful for testing).
   * @param {number} count
   * @returns {string}
   */
  formatParameterCount(count) {
    return this._formatParameterCount(count);
  }
}

window.ModelComplexity = ModelComplexity;