interface LeaseSnapshot {
  activeLeaseId: string | null
  activeTaskId: string | null
  activeTaskIds: string[]
  activeCount: number
  attemptId: string | null
  startedAt: number | null
  leaseExpiresAt: number | null
  lastExtendedAt: number | null
  lastReleasedAt: number | null
  lastOutcome: 'leased' | 'extended' | 'completed' | 'failed' | 'cleared' | null
}

interface ActiveLeaseState {
  taskId: string
  attemptId: string | null
  leaseExpiresAt: number | null
  startedAt: number
  lastExtendedAt: number | null
}

const activeLeases = new Map<string, ActiveLeaseState>()
const leaseState: LeaseSnapshot = {
  activeLeaseId: null,
  activeTaskId: null,
  activeTaskIds: [],
  activeCount: 0,
  attemptId: null,
  startedAt: null,
  leaseExpiresAt: null,
  lastExtendedAt: null,
  lastReleasedAt: null,
  lastOutcome: null,
}

function normalizeLeaseExpiresAt(value: number | string | null | undefined): number | null {
  if (typeof value === 'number') {
    return Number.isFinite(value) ? value : null
  }

  if (typeof value !== 'string' || !value.trim()) {
    return null
  }

  const timestamp = Date.parse(value)
  return Number.isNaN(timestamp) ? null : timestamp
}

export function setActiveLease(
  input: {
    taskId: string
    attemptId?: string | null
    leaseExpiresAt?: number | string | null
  } | null,
): void {
  if (!input) {
    activeLeases.clear()
    leaseState.activeLeaseId = null
    leaseState.activeTaskId = null
    leaseState.activeTaskIds = []
    leaseState.activeCount = 0
    leaseState.attemptId = null
    leaseState.startedAt = null
    leaseState.leaseExpiresAt = null
    leaseState.lastOutcome = 'cleared'
    leaseState.lastReleasedAt = Date.now()
    return
  }

  const normalized: ActiveLeaseState = {
    taskId: input.taskId,
    attemptId: input.attemptId ?? null,
    leaseExpiresAt: normalizeLeaseExpiresAt(input.leaseExpiresAt),
    startedAt: Date.now(),
    lastExtendedAt: null,
  }

  activeLeases.set(normalized.taskId, normalized)
  syncLeaseSnapshot()
  leaseState.lastOutcome = 'leased'
}

export function noteLeaseExtended(leaseExpiresAt?: number | string | null, taskId?: string): void {
  if (taskId) {
    const active = activeLeases.get(taskId)
    if (active) {
      active.leaseExpiresAt = normalizeLeaseExpiresAt(leaseExpiresAt) ?? active.leaseExpiresAt
      active.lastExtendedAt = Date.now()
      activeLeases.set(taskId, active)
    }
  } else {
    const first = activeLeases.values().next().value as ActiveLeaseState | undefined
    if (first) {
      first.leaseExpiresAt = normalizeLeaseExpiresAt(leaseExpiresAt) ?? first.leaseExpiresAt
      first.lastExtendedAt = Date.now()
      activeLeases.set(first.taskId, first)
    }
  }

  syncLeaseSnapshot()
  leaseState.lastExtendedAt = Date.now()
  leaseState.lastOutcome = 'extended'
}

export function noteLeaseReleased(
  reason: Exclude<LeaseSnapshot['lastOutcome'], 'leased' | 'extended' | null>,
  taskId?: string,
): void {
  if (taskId) {
    activeLeases.delete(taskId)
  } else {
    activeLeases.clear()
  }

  syncLeaseSnapshot()
  leaseState.lastReleasedAt = Date.now()
  leaseState.lastOutcome = reason
}

export function getLeaseManagerSnapshot(): LeaseSnapshot {
  return { ...leaseState }
}

function syncLeaseSnapshot(): void {
  const first = activeLeases.values().next().value as ActiveLeaseState | undefined

  leaseState.activeTaskIds = [...activeLeases.keys()]
  leaseState.activeCount = activeLeases.size
  leaseState.activeLeaseId = first?.taskId ?? null
  leaseState.activeTaskId = first?.taskId ?? null
  leaseState.attemptId = first?.attemptId ?? null
  leaseState.startedAt = first?.startedAt ?? null
  leaseState.leaseExpiresAt = first?.leaseExpiresAt ?? null
}