/**
 * Main entry point of Config2 library
 */
object Config {
  /**
   * Define location to read configuration files from. <p>
   * Supported protocols are classpath:, file: and no protocol (which mean file:)
   */
  def from(url: String): ConfigBuilder = ConfigImpl.builder(url)
}

trait ConfigBuilder {
  /**
   * Override previous location(s) with this one. Loaded properties will also be merged, taking this location with higher precedence.
   */
  def overrideWith(url: String): ConfigBuilder
  /**
   * Override previous location(s) with this set of properties. <p>
   * Typical values here are System.getProperties(), System.env() or Properties obtained from other sources
   */
  def overrideWith(props: java.util.Map[_, _]): ConfigBuilder
  /**
   * Override previous location(s) with this command-line arguments. <p>
   * Key names are prefixed with dashes, keys and values are separated by space.
   * I.e. "-app.port 8888" will set "app.port" property to "8888"
   */
  def overrideWith(cmdlineArgs: Array[String]): ConfigBuilder

  /**
   * Enable environment support. <p>
   * Environments are used to override configuration with environment specific values.
   * Default implementation looks for files in $(url)/$(envName)/ subfolder, where
   * envName is hostname or can be specified via config.environment system property.
   */
  def env(resolver: EnvironmentResolver = EnvironmentResolver()): ConfigBuilder

  /**
   * Declare configuration parameter. <p>
   * Used to validate collected configuration and print app usage information.
   */
  def params[Type](name: String, description: String)(implicit mf: Manifest[Type]): ConfigBuilder

  /**
   * Configure output and verbosity of Config2 logging. <p>
   * By default, information on all loaded files is printed to stdout. Verbose mode also prints information
   * on tried, but not loaded files. <p>
   * Generally this method cannot use Slf4j because Config2 can be used to configure logging itself!
   */
  def log(logger: String => Unit = println, verbose: Boolean = false): ConfigBuilder

  /**
   * Create instance of Config
   */
  def build(): Config
}

/**
 * Configured Config (pun intended) instance. <p>
 * Can be used to load Properties and files, using paths and settings provided by ConfigBuilder
 */
trait Config {
  /**
   * Read properties from standard Java Properties file. Multiple paths are tried as configured before.
   * Resulting Properties will be merged from all available sources
   * @file relative file name
   */
  def readProperties(file: String): ConfigPropeties

  /**
   * Read text file with specified encoding. Merge is not supported, so file with most precedence wins.
   * @file relative file name
   */
  def readText(file: String, encoding: Charset = StandardCharsets.UTF_8): String

  /**
   * Read text file with specified encoding. Merge is not supported, so file with most precedence wins.
   * Caller are responsible for closing the stream.
   * @file relative file name
   */
  def readFile(file: String): InputStream

  /**
   * Set of parameters declared in ConfigBuilder. Useful to log loaded parameters
   */
  val knownParams: Set[String]

  /**
   * Print usage information for declared parameters
   */
  def printUsage(w: PrintStream  = System.out)
}

/**
 * Useful wrapper around java.util.Properties
 */
trait ConfigPropeties {
  /**
   * Set of parameters declared in ConfigBuilder. Useful to log loaded parameters
   */
  val knownParams: Set[String]
  /**
   * Scala Map representation of Properties
   */
  val map: Map[String, String]

  /**
   * Copy of contents of this class. Modifications of resulting object will not be reflected in this class!
   */
  def props(): Properties

  /**
   * Typed getter for configuration values.
   * Supported types are String, Int, Long, Float, Double
   * This method throws runtime exceptions if value cannot be cast to required type
   */
  def get[Type](key: String)(implicit mf: Manifest[Type]): Option[Type]

  /**
   * Validate this Properties against declared parameters.
   * This method returns list of validation error messages.
   */
  def validate(): List[String]
}

object ConfigPropeties {
  implicit def toProperties(confProps: ConfigPropeties): Properties = confProps.props()
}

/**
 * Produce locations to look for environment-specific configuration files.
 * Returned list of urls should point to files in increasing precedence.
 * Generally this list starts with "url + file" entry.
 */
trait EnvironmentResolver {
  def resolve(url: String, file: String): List[String]
}

/**
 * Useful EnvironmentResolver-s
 */
object EnvironmentResolver {
  def apply(): EnvironmentResolver = {
    val name = System.getProperty("config.environment") match {
      case env if env != null && !env.trim().isEmpty() => env
      case _ => InetAddress.getLocalHost().getHostName()
    }

    apply(name)
  }

  def apply(name: String): EnvironmentResolver = {
    new EnvironmentResolverImpl(name)
  }

  def apply(cmdlineArgs: Array[String]): EnvironmentResolver = {
    cmdlineArgs.toList.dropWhile(_ != "-env") match {
      case "-env" :: env :: _ => apply(env)
      case _ => apply()
    }
  }
}