/**
 * Yonexus Server - Persistence Types
 * 
 * Defines the persistent record structures for client registry and state management.
 * Based on PLAN.md section 6 and 12.
 */

/**
 * Client pairing status
 */
export type PairingStatus = "unpaired" | "pending" | "paired" | "revoked";

/**
 * Client liveness status
 */
export type ClientLivenessStatus = "online" | "offline" | "unstable";

/**
 * Pairing notification delivery status
 */
export type PairingNotifyStatus = "pending" | "sent" | "failed";

/**
 * Security window entry for nonce tracking
 */
export interface NonceEntry {
  /** The nonce value */
  readonly nonce: string;
  /** UTC unix timestamp when the nonce was used */
  readonly timestamp: number;
}

/**
 * Security window entry for handshake attempt tracking
 */
export interface HandshakeAttemptEntry {
  /** UTC unix timestamp of the attempt */
  readonly timestamp: number;
}

/**
 * Persistent client record stored by Yonexus.Server
 * 
 * This structure represents the durable trust state for a client.
 * Rolling security windows (recentNonces, recentHandshakeAttempts) may be
 * cleared on server restart as per v1 semantics.
 */
export interface ClientRecord {
  /** Unique client identifier */
  readonly identifier: string;

  /** Client's public key (Ed25519 or other) - stored after pairing */
  publicKey?: string;

  /** Shared secret issued after successful pairing */
  secret?: string;

  /** Current pairing status */
  pairingStatus: PairingStatus;

  /** Pairing code (only valid when pairingStatus is "pending") */
  pairingCode?: string;

  /** Pairing expiration timestamp (UTC unix seconds) */
  pairingExpiresAt?: number;

  /** When the pairing notification was sent (UTC unix seconds) */
  pairingNotifiedAt?: number;

  /** Status of the pairing notification delivery */
  pairingNotifyStatus?: PairingNotifyStatus;

  /** Current liveness status (may be stale on restart) */
  status: ClientLivenessStatus;

  /** Last heartbeat received timestamp (UTC unix seconds) */
  lastHeartbeatAt?: number;

  /** Last successful authentication timestamp (UTC unix seconds) */
  lastAuthenticatedAt?: number;

  /**
   * Recent nonces used in authentication attempts.
   * This is a rolling window that may be cleared on restart.
   */
  recentNonces: NonceEntry[];

  /**
   * Recent handshake attempt timestamps.
   * This is a rolling window that may be cleared on restart.
   */
  recentHandshakeAttempts: number[];

  /** Record creation timestamp (UTC unix seconds) */
  readonly createdAt: number;

  /** Record last update timestamp (UTC unix seconds) */
  updatedAt: number;
}

/**
 * In-memory session state (not persisted)
 * 
 * Represents an active or pending WebSocket connection.
 */
export interface ClientSession {
  /** Client identifier */
  readonly identifier: string;

  /** WebSocket connection instance */
  readonly socket: unknown; // Will be typed as WebSocket when implementing transport

  /** Public key presented during hello, before pairing completes */
  publicKey?: string;

  /** Whether the client is currently authenticated */
  isAuthenticated: boolean;

  /** Session start timestamp (UTC unix seconds) */
  readonly connectedAt: number;

  /** Last activity timestamp (UTC unix seconds) */
  lastActivityAt: number;
}

/**
 * Server registry state
 * 
 * Contains both persistent and in-memory state for all clients.
 */
export interface ServerRegistry {
  /** Persistent client records keyed by identifier */
  clients: Map<string, ClientRecord>;

  /** Active WebSocket sessions keyed by identifier */
  sessions: Map<string, ClientSession>;
}

/**
 * Serialized form of ClientRecord for JSON persistence
 */
export interface SerializedClientRecord {
  identifier: string;
  publicKey?: string;
  secret?: string;
  pairingStatus: PairingStatus;
  pairingCode?: string;
  pairingExpiresAt?: number;
  pairingNotifiedAt?: number;
  pairingNotifyStatus?: PairingNotifyStatus;
  status: ClientLivenessStatus;
  lastHeartbeatAt?: number;
  lastAuthenticatedAt?: number;
  createdAt: number;
  updatedAt: number;
  // Note: recentNonces and recentHandshakeAttempts are intentionally
  // excluded from persistent serialization - they are cleared on restart
}

/**
 * Server persistence file format
 */
export interface ServerPersistenceData {
  /** Format version for migration support */
  version: number;

  /** Server-side client records */
  clients: SerializedClientRecord[];

  /** Persistence timestamp (UTC unix seconds) */
  persistedAt: number;
}

/**
 * Create a new empty client record
 */
export function createClientRecord(identifier: string): ClientRecord {
  const now = Math.floor(Date.now() / 1000);
  return {
    identifier,
    pairingStatus: "unpaired",
    status: "offline",
    recentNonces: [],
    recentHandshakeAttempts: [],
    createdAt: now,
    updatedAt: now
  };
}

/**
 * Convert a ClientRecord to its serialized form (for persistence)
 */
export function serializeClientRecord(record: ClientRecord): SerializedClientRecord {
  return {
    identifier: record.identifier,
    publicKey: record.publicKey,
    secret: record.secret,
    pairingStatus: record.pairingStatus,
    pairingCode: record.pairingCode,
    pairingExpiresAt: record.pairingExpiresAt,
    pairingNotifiedAt: record.pairingNotifiedAt,
    pairingNotifyStatus: record.pairingNotifyStatus,
    status: record.status,
    lastHeartbeatAt: record.lastHeartbeatAt,
    lastAuthenticatedAt: record.lastAuthenticatedAt,
    createdAt: record.createdAt,
    updatedAt: record.updatedAt
  };
}

/**
 * Deserialize a client record and initialize rolling windows
 */
export function deserializeClientRecord(
  serialized: SerializedClientRecord
): ClientRecord {
  return {
    ...serialized,
    recentNonces: [], // Rolling windows cleared on restart
    recentHandshakeAttempts: []
  };
}

/**
 * Check if a client record is in a pairable state
 */
export function isPairable(record: ClientRecord): boolean {
  return record.pairingStatus === "unpaired" || record.pairingStatus === "revoked";
}

/**
 * Check if a client record has a pending pairing that may have expired
 */
export function hasPendingPairing(record: ClientRecord): boolean {
  return record.pairingStatus === "pending" && record.pairingCode !== undefined;
}

/**
 * Check if a pending pairing has expired
 */
export function isPairingExpired(record: ClientRecord, now: number = Date.now() / 1000): boolean {
  if (!hasPendingPairing(record) || record.pairingExpiresAt === undefined) {
    return false;
  }
  return now > record.pairingExpiresAt;
}

/**
 * Check if a client is ready for authentication (has secret and is paired)
 */
export function canAuthenticate(record: ClientRecord): boolean {
  return record.pairingStatus === "paired" && record.secret !== undefined && record.publicKey !== undefined;
}