type Level = 'info' | 'debug' | 'error' | 'warn' | 'log'

export type TransportFunction = (level: Level, ...args: unknown[]) => void

type LoggerOptions = {
  transport: TransportFunction[]
}

/**
 * Concrete logger implementation produced by {@link createLogger}. Each log method writes to
 * the native `console` counterpart **and** fans out to every registered transport, so
 * third-party sinks (e.g. Sentry, Datadog) receive the same payload without extra wiring.
 *
 * `test` is intentionally a no-op — it exists as a scratch channel that leaves no output in
 * any environment.
 *
 * Transport functions are shared as a static property, meaning all `CustomLogger` instances
 * created in the same process share the same transport list. Only one call to
 * {@link createLogger} is expected per app.
 */
class CustomLogger {
  static transport: TransportFunction[]

  static applyTransport(level: Level, ...args: unknown[]) {
    CustomLogger.transport.map(fn => {
      fn(level, ...args)
    })
  }

  info(...args: unknown[]) {
    console.info(...args)
    CustomLogger.applyTransport('info', ...args)
  }

  error(...args: unknown[]) {
    console.error(...args)
    CustomLogger.applyTransport('error', ...args)
  }

  warn(...args: unknown[]) {
    console.warn(...args)
    CustomLogger.applyTransport('warn', ...args)
  }

  /** Intentional no-op. Use as a scratch channel for temporary logs that must not ship. */
  test(...args: unknown[]) {

  }

  log(...args: unknown[]) {
    console.log(...args)
    CustomLogger.applyTransport('log', ...args)
  }

  debug(...args: unknown[]) {
    console.debug(...args)
    CustomLogger.applyTransport('debug', ...args)
  }
}

/**
 * Wires up the transport list and returns a ready-to-use {@link CustomLogger} instance.
 *
 * The returned instance satisfies the logging method contract expected by {@link Logger},
 * so it should be used to replace the stub methods on the shared `logger` singleton after
 * calling `logger.initialize(config)`.
 *
 * Calling this more than once replaces the shared transport list for all existing instances.
 */
export const createLogger = (options: LoggerOptions) => {
  CustomLogger.transport = options.transport

  return new CustomLogger()
}