require "yaml" unless defined? YAML
require "erb" unless defined? ERB

require "hashie"
require "ambience/core_ext"

begin
  require "java"
rescue LoadError
end

module Ambience

  # = Ambience::Config
  #
  # App configuration feat. YAML and JVM properties. Lets you specify a default configuration
  # in a YAML file and overwrite details via local settings and JVM properties for production.
  class Config

    # Sets the path to a local ambience config file.
    def self.local_config=(local_config)
      @@local_config = local_config
    end

    # Returns the path to a local ambience config file for specifying user-specific
    # settings that don't belong into the application config file.
    def self.local_config
      @@local_config ||= File.join ENV["HOME"].to_s, ".ambience", "ambience.yml"
    end

    def initialize(config_file, env = nil)
      @config_file, @env = config_file, env
    end

    # Returns the Ambience config as a Hash.
    def to_hash
      config = load_config @config_file
      config = config.deep_merge local_config
      config.deep_merge jvm_config
    end

    # Returns the Ambience config as a Hashie::Mash.
    def to_mash
      Hashie::Mash.new to_hash
    end

  private

    def load_config(config_file)
      raise ArgumentError, "Missing config: #{config_file}" unless File.exist? config_file

      config = File.read config_file
      config = YAML.load ERB.new(config).result || {}
      config = config[@env.to_s] || config[@env.to_sym] if @env
      config
    end

    # Returns a Hash containing any local settings from the +@@local_config+.
    def local_config
      File.exist?(self.class.local_config) ? load_config(self.class.local_config) : {}
    end

    ## Returns a Hash containing any JVM properties.
    def jvm_config
      jvm_properties.inject({}) do |hash, (key, value)|
        hash.deep_merge hash_from_property(key, value)
      end
    end

    # Returns the JVM properties.
    def jvm_properties
      Ambience.jruby? ? java.lang.System.get_properties : {}
    end

    # Returns a Hash generated from a JVM +property+ and its +value+.
    #
    # ==== Example:
    #
    #   hash_from_property "webservice.auth.address", "http://auth.example.com"
    #   # => { "webservice" => { "auth" => { "address" => "http://auth.example.com" } } }
    def hash_from_property(property, value)
      property.split(".").reverse.inject(value) { |value, item| { item => value } }
    end

  end
end