/**
 * Log levels in order of severity
 */
export declare enum LogLevel {
    DEBUG = "debug",
    INFO = "info",
    WARN = "warn",
    ERROR = "error"
}
/**
 * Structured log entry
 */
export interface LogEntry {
    level: LogLevel;
    message: string;
    timestamp: Date;
    context?: Record<string, unknown>;
    correlationId?: string;
    error?: Error;
}
/**
 * Log transport interface for custom log handlers
 */
export interface LogTransport {
    log(entry: LogEntry): void | Promise<void>;
}
/**
 * Console transport with colored output
 */
export declare class ConsoleTransport implements LogTransport {
    private readonly colors;
    log(entry: LogEntry): void;
}
/**
 * JSON transport for structured logging
 */
export declare class JsonTransport implements LogTransport {
    log(entry: LogEntry): void;
}
/**
 * Logger configuration
 */
export interface LoggerConfig {
    /** Minimum log level to output */
    level: LogLevel;
    /** Log transports */
    transports: LogTransport[];
    /** Default context to include in all logs */
    defaultContext?: Record<string, unknown>;
    /** Whether to include timestamp */
    includeTimestamp?: boolean;
}
/**
 * Structured logger with context and correlation support
 *
 * @example
 * ```typescript
 * const logger = new Logger({
 *   level: LogLevel.INFO,
 *   transports: [new ConsoleTransport()],
 *   defaultContext: { service: 'elasticsearch-client' }
 * });
 *
 * logger.info('Connected to Elasticsearch', { node: 'localhost:9200' });
 *
 * const childLogger = logger.withContext({ operation: 'bulk-index' });
 * childLogger.debug('Processing batch', { size: 1000 });
 * ```
 */
export declare class Logger {
    private config;
    private context;
    private correlationId?;
    constructor(config?: Partial<LoggerConfig>);
    /**
     * Create a child logger with additional context
     */
    withContext(context: Record<string, unknown>): Logger;
    /**
     * Create a child logger with correlation ID
     */
    withCorrelation(correlationId: string): Logger;
    /**
     * Create a child logger for a specific namespace
     */
    child(namespace: string): Logger;
    /**
     * Log at DEBUG level
     */
    debug(message: string, meta?: Record<string, unknown>): void;
    /**
     * Log at INFO level
     */
    info(message: string, meta?: Record<string, unknown>): void;
    /**
     * Log at WARN level
     */
    warn(message: string, meta?: Record<string, unknown>): void;
    /**
     * Log at ERROR level
     *
     * Accepts either:
     * - error(message, Error, meta) - explicit error with optional metadata
     * - error(message, meta) - error context as metadata (error property extracted)
     */
    error(message: string, errorOrMeta?: Error | Record<string, unknown>, meta?: Record<string, unknown>): void;
    /**
     * Internal log method
     */
    private log;
    /**
     * Check if a log level should be output
     */
    private shouldLog;
    /**
     * Update logger configuration
     */
    setLevel(level: LogLevel): void;
    /**
     * Add a transport
     */
    addTransport(transport: LogTransport): void;
    /**
     * Get current log level
     */
    getLevel(): LogLevel;
}
/**
 * Default logger instance
 */
export declare const defaultLogger: Logger;