interface LeaseSnapshot {
  activeLeaseId: string | null;
  activeTaskId: string | null;
  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;
}

const leaseState: LeaseSnapshot = {
  activeLeaseId: null,
  activeTaskId: null,
  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) {
    leaseState.activeLeaseId = null;
    leaseState.activeTaskId = null;
    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),
  };

  leaseState.activeLeaseId = normalized.taskId;
  leaseState.activeTaskId = normalized.taskId;
  leaseState.attemptId = normalized.attemptId;
  leaseState.startedAt = Date.now();
  leaseState.leaseExpiresAt = normalized.leaseExpiresAt;
  leaseState.lastOutcome = "leased";
}

export function noteLeaseExtended(leaseExpiresAt?: number | string | null): void {
  leaseState.lastExtendedAt = Date.now();
  leaseState.leaseExpiresAt = normalizeLeaseExpiresAt(leaseExpiresAt) ?? leaseState.leaseExpiresAt;
  leaseState.lastOutcome = "extended";
}

export function noteLeaseReleased(reason: Exclude<LeaseSnapshot["lastOutcome"], "leased" | "extended" | null>): void {
  leaseState.activeLeaseId = null;
  leaseState.activeTaskId = null;
  leaseState.attemptId = null;
  leaseState.startedAt = null;
  leaseState.leaseExpiresAt = null;
  leaseState.lastReleasedAt = Date.now();
  leaseState.lastOutcome = reason;
}

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