/** @type {Map<string, number>} */
const delegateInflight = new Map()

/**
 * @param {string} kind
 * @param {Record<string, string | undefined> | null | undefined} env
 * @returns {number} max concurrent (0 = unlimited)
 */
function delegateMaxConcurrent(kind, env) {
  if (!env) return 0
  const spec =
    env[`BARE_OS_DELEGATE_${String(kind).toUpperCase()}_MAX_CONCURRENT`]
  if (spec != null && String(spec).trim() !== '') {
    const n = Number.parseInt(String(spec), 10)
    if (Number.isFinite(n) && n > 0) return Math.min(64, n)
  }
  const g = env.BARE_OS_DELEGATE_MAX_CONCURRENT
  if (g != null && String(g).trim() !== '') {
    const n = Number.parseInt(String(g), 10)
    if (Number.isFinite(n) && n > 0) return Math.min(64, n)
  }
  return 0
}

/**
 * @param {string} kind
 * @param {Record<string, string | undefined> | null | undefined} env
 * @returns {boolean}
 */
export function bareOsDelegateConcurrentTryEnter(kind, env) {
  const max = delegateMaxConcurrent(kind, env)
  if (!max) return true
  const cur = delegateInflight.get(kind) || 0
  if (cur >= max) return false
  delegateInflight.set(kind, cur + 1)
  return true
}

/** @param {string} kind */
export function bareOsDelegateConcurrentExit(kind) {
  const cur = (delegateInflight.get(kind) || 0) - 1
  if (cur <= 0) delegateInflight.delete(kind)
  else delegateInflight.set(kind, cur)
}

/** Snapshot for metrics / fairness introspection (not a security boundary). */
export function bareOsDelegateInflightSnapshot() {
  return Object.fromEntries(delegateInflight)
}