const VOLATILE_SNAPSHOT_FIELDS = new Set([
  'requestHash', 'version', 'updatedAt', 'operatorId', 'operatorName', 'occurredAt',
])

function stableValue(value) {
  if (Array.isArray(value)) return value.map(stableValue)
  if (!value || typeof value !== 'object') return value
  return Object.fromEntries(Object.entries(value)
    .filter(([key]) => !VOLATILE_SNAPSHOT_FIELDS.has(key))
    .sort(([left], [right]) => left.localeCompare(right))
    .map(([key, nested]) => [key, stableValue(nested)]))
}

function snapshot(value) {
  if (value == null || value === '') return null
  try { return stableValue(typeof value === 'string' ? JSON.parse(value) : value) } catch { return value }
}

function sameSnapshot(left, right) {
  return JSON.stringify(snapshot(left)) === JSON.stringify(snapshot(right))
}

export function isPureStatusNoop(history) {
  if (history?.actionType !== 'STATUS_UPDATE') return false
  if ((history?.fromStatus ?? null) !== (history?.toStatus ?? null)) return false
  return sameSnapshot(history?.beforeSnapshot, history?.afterSnapshot)
}

function stableEventKey(history) {
  if (history?.operationId) return `operation:${history.operationId}`
  if (history?.eventId) return `event:${history.eventId}`
  if (history?.historyId) return `history:${history.historyId}`
  return null
}

export function visibleLoadingHistories(histories) {
  const seen = new Set()
  return (Array.isArray(histories) ? histories : []).filter((history) => {
    if (isPureStatusNoop(history)) return false
    const key = stableEventKey(history)
    if (!key) return true
    if (seen.has(key)) return false
    seen.add(key)
    return true
  })
}