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;
}