/**
 * Validates a single feed object shape (pure function).
 * @param {unknown} item
 * @returns {boolean} True if item has id, name, lat, lng with correct types.
 */
export function isValidFeed(item) {
  if (!item || typeof item !== 'object') return false
  const o = /** @type {Record<string, unknown>} */ (item)
  return (
    typeof o.id === 'string'
    && typeof o.name === 'string'
    && typeof o.lat === 'number'
    && typeof o.lng === 'number'
  )
}

/**
 * Returns a safe stream URL (http/https only) or empty string. Prevents javascript:, data:, etc.
 * @param {unknown} url
 * @returns {string} Safe http(s) URL or empty string.
 */
export function sanitizeStreamUrl(url) {
  if (typeof url !== 'string' || !url.trim()) return ''
  const u = url.trim()
  if (u.startsWith('https://') || u.startsWith('http://')) return u
  return ''
}

/**
 * Sanitizes a validated feed for API response: safe streamUrl and sourceType only.
 * @param {{ id: string, name: string, lat: number, lng: number, [key: string]: unknown }} feed
 * @returns {{ id: string, name: string, lat: number, lng: number, streamUrl: string, sourceType: string, description?: string }} Sanitized feed for API.
 */
export function sanitizeFeedForResponse(feed) {
  return {
    id: feed.id,
    name: feed.name,
    lat: feed.lat,
    lng: feed.lng,
    streamUrl: sanitizeStreamUrl(feed.streamUrl),
    sourceType: feed.sourceType === 'hls' ? 'hls' : 'mjpeg',
    ...(typeof feed.description === 'string' ? { description: feed.description } : {}),
  }
}

/**
 * Filters and returns only valid feeds from an array (pure function).
 * @param {unknown[]} list
 * @returns {Array<{ id: string, name: string, lat: number, lng: number }>} Array of valid feed objects.
 */
export function getValidFeeds(list) {
  if (!Array.isArray(list)) return []
  return list.filter(isValidFeed)
}