import type {
  OAuthClientInformation,
  OAuthClientInformationFull,
  OAuthClientMetadata,
  OAuthTokens,
} from '@modelcontextprotocol/sdk/shared/auth.js';

export type {
  OAuthClientInformation,
  OAuthClientInformationFull,
  OAuthClientMetadata,
  OAuthTokens,
};

/**
 * Storage adapter interface for persisting OAuth data
 */
export interface StorageAdapter {
  /**
   * Get a value by key
   */
  get(key: string): Promise<string | undefined> | string | undefined;

  /**
   * Set a value by key
   */
  set(key: string, value: string): Promise<void> | void;

  /**
   * Delete a value by key
   */
  delete(key: string): Promise<void> | void;
}

/**
 * Configuration for OAuth client provider
 */
export interface OAuthConfig {
  /**
   * OAuth client ID (can be provided or dynamically registered)
   */
  clientId?: string;

  /**
   * OAuth client secret (optional for public clients)
   */
  clientSecret?: string;

  /**
   * Redirect URI for OAuth callbacks
   */
  redirectUri?: string;

  /**
   * OAuth scope to request
   */
  scope?: string;

  /**
   * Session identifier for this OAuth client instance
   */
  sessionId?: string;

  /**
   * Storage adapter for persisting OAuth data
   */
  storage?: StorageAdapter;

  /**
   * OAuth client metadata for registration
   */
  clientMetadata?: Partial<OAuthClientMetadata>;

  /**
   * OAuth tokens (can be provided statically or loaded from storage)
   */
  tokens?: OAuthTokens & {
    expires_at?: number | undefined;
  };

  /**
   * Token refresh endpoint URL (optional, can be obtained from metadata)
   */
  tokenEndpoint?: string;

  /**
   * Token refresh configuration
   */
  tokenRefresh?: {
    /**
     * Maximum number of retry attempts for token refresh
     */
    maxRetries?: number;

    /**
     * Delay between retry attempts in milliseconds
     */
    retryDelay?: number;
  };
}

/**
 * Default OAuth client metadata
 */
export const DEFAULT_CLIENT_METADATA: OAuthClientMetadata = {
  redirect_uris: [],
  grant_types: ['authorization_code', 'refresh_token'],
  response_types: ['code'],
  token_endpoint_auth_method: 'client_secret_post',
  scope: 'openid profile email',
  client_name: 'MCP OAuth Client',
  client_uri: 'https://github.com/modelcontextprotocol/typescript-sdk',
};

/**
 * Generate a random session ID
 */
export function generateSessionId(): string {
  return crypto.randomUUID();
}

/**
 * Generate a random state parameter for CSRF protection
 */
export function generateState(): string {
  const array = new Uint8Array(32);

  crypto.getRandomValues(array);

  return Array.from(array, byte => byte.toString(16).padStart(2, '0')).join('');
}