/**
 * Data Layer for Frozen Runs Visualization Tool
 * Handles API communication and data transformation.
 * © 2026 Donau2Space.de
 */

/**
 * Fetches metric data from the /metrics API endpoint.
 * @async
 * @param {string} [filter] - Optional filter parameter ('pinned' or 'unpinned').
 * @returns {Promise<Object[]>} Parsed metric data ready for visualization.
 */
export async function fetchMetrics(filter) {
  try {
    const queryParam = filter ? `?filter=${encodeURIComponent(filter)}` : '';
    const response = await fetch(`/metrics${queryParam}`, {
      method: 'GET',
      headers: {
        'Accept': 'application/json'
      }
    });

    if (!response.ok) {
      throw new Error(`API request failed with status ${response.status}`);
    }

    const rawData = await response.json();
    return parseMetricsData(rawData);
  } catch (error) {
    console.error('Error fetching metrics:', error);
    return [];
  }
}

/**
 * Parses and structures raw metric data from API.
 * @param {Array} data - Raw metric data from /metrics.
 * @returns {Array<Object>} Structured metric objects for visualization.
 */
export function parseMetricsData(data) {
  if (!Array.isArray(data)) return [];

  return data.map(entry => {
    const {
      metricName = 'unknown',
      runId = 'N/A',
      pinned_flag = false,
      effect_size = null,
      ci_lower = null,
      ci_upper = null
    } = entry ?? {};

    return {
      name: metricName,
      runId,
      pinned: Boolean(pinned_flag),
      effectSize: typeof effect_size === 'number' ? effect_size : null,
      confidenceInterval: {
        lower: typeof ci_lower === 'number' ? ci_lower : null,
        upper: typeof ci_upper === 'number' ? ci_upper : null
      }
    };
  });
}