module Configliere
  # Default locations where config files live
  DEFAULT_CONFIG_LOCATION = {
    machine: ->(scope){ Pathname('/etc').join(scope) },
    user:    ->(scope){ Pathname(ENV['HOME'] || '/').join(".#{scope}") },
    app:     ->(scope){ app_dir = '/' ; Pathname(Dir.pwd).ascend{ |path| app_dir = path.join('config') if path.join('config').exist? } ; app_dir }
  } unless defined?(DEFAULT_CONFIG_LOCATION)

  #
  # ConfigFile -- load configuration from a simple YAML file
  #
  module ConfigFile
    # Load params from a YAML file, as a hash of handle => param_hash pairs
    #
    # @param filename [String] the file to read. If it does not contain a '/',
    #   the filename is expanded relative to Configliere::DEFAULT_CONFIG_DIR
    # @param options [Hash]
    # @option options :env [String]
    #   If an :env option is given, only the indicated subhash is merged. This
    #   lets you for example specify production / environment / test settings
    #
    # @return [Configliere::Params] the Settings object
    #
    # @example
    #     # Read from ~/.configliere/foo.yaml
    #     Settings.read(foo.yaml)
    #
    # @example
    #     # Read from config/foo.yaml and use settings appropriate for development/staging/production
    #     Settings.read(App.root.join('config', 'environment.yaml'), :env => ENV['RACK_ENV'])
    #
    # The env option is *not* coerced to_sym, so make sure your key type matches the file's
    def read filename, options={}
      if filename.is_a?(Symbol) then raise Configliere::DeprecatedError, "Loading from a default config file is no longer provided" ; end
      filename = expand_filename(filename)
      begin
        case filetype(filename)
        when 'json' then read_json(File.open(filename), options)
        when 'yaml' then read_yaml(File.open(filename), options)
        else             read_yaml(File.open(filename), options)
        end
      rescue Errno::ENOENT
        warn "Loading empty configliere settings file #{filename}"
      end
      self
    end

    def read_yaml yaml_str, options={}
      require 'yaml'
      new_data = YAML.load(yaml_str) || {}
      # Extract the :env (production/development/etc)
      if options[:env]
        new_data = new_data[options[:env]] || {}
      end
      deep_merge! new_data
      self
    end

    #
    # we depend on you to require some sort of JSON
    #
    def read_json json_str, options={}
      require 'multi_json'
      new_data = MultiJson.load(json_str) || {}
      # Extract the :env (production/development/etc)
      if options[:env]
        new_data = new_data[options[:env]] || {}
      end
      deep_merge! new_data
      self
    end

    # save to disk.
    # * file is in YAML format, as a hash of handle => param_hash pairs
    # * filename defaults to Configliere::DEFAULT_CONFIG_FILE (~/.configliere, probably)
    def save! filename
      filename = expand_filename(filename)
      hsh = self.export.to_hash
      FileUtils.mkdir_p(File.dirname(filename))
      File.open(filename, 'w'){|f| f << YAML.dump(hsh) }
    end

    def determine_conf_location(level, scope)
      lookup_conf_dir(level, scope).join("#{scope}.yaml").to_s
    end
    
    def default_conf_dir
      lookup_conf_dir(:user, 'configliere')
    end
    
    def lookup_conf_dir(level, scope)
      Configliere::DEFAULT_CONFIG_LOCATION[level].call(scope)
    end

    def load_configuration_in_order!(scope = 'configliere')
      [ :machine, :user, :app ].each do |level| 
        conf = determine_conf_location(level, scope)
        read(conf) if Pathname(conf).exist? 
      end
      resolve!
    end
    
  protected

    def filetype filename
      filename =~ /\.([^\.]+)$/ ;
      $1
    end

    def expand_filename filename
      if filename.to_s.include?('/')
        File.expand_path(filename)
      else
        default_conf_dir.join(filename).to_s
      end
    end
  end

  # ConfigFile is included by default
  Param.class_eval do
    include ConfigFile
  end
end