/**
 * Ring-buffer stats history for per-container charts.
 */
const DEFAULT_MAX_POINTS = Number(process.env.PEARDOCK_STATS_HISTORY_POINTS) || 120

/** @type {Map<string, Array<{ t: number, cpu: number, memory: number }>>} */
const history = new Map()

/**
 * @param {string} containerId
 * @param {{ cpu: number, memory: number }} sample
 */
export function recordSample(containerId, sample) {
  if (!containerId) return
  let series = history.get(containerId)
  if (!series) {
    series = []
    history.set(containerId, series)
  }
  series.push({
    t: Date.now(),
    cpu: Number(sample.cpu) || 0,
    memory: Number(sample.memory) || 0,
  })
  while (series.length > DEFAULT_MAX_POINTS) series.shift()
}

/**
 * @param {string} containerId
 * @param {{ limit?: number }} [opts]
 */
export function getHistory(containerId, opts = {}) {
  const series = history.get(containerId) || []
  const limit = Math.min(Number(opts.limit) || DEFAULT_MAX_POINTS, DEFAULT_MAX_POINTS)
  return series.slice(-limit)
}

/**
 * @param {string[]} activeIds
 */
export function pruneMissing(activeIds) {
  const set = new Set(activeIds)
  for (const id of history.keys()) {
    if (!set.has(id)) history.delete(id)
  }
}

export function clearHistory() {
  history.clear()
}