module I18n
  # Handles exceptions raised in the backend. All exceptions except for
  # MissingTranslationData exceptions are re-thrown. When a MissingTranslationData
  # was caught the handler returns an error message string containing the key/scope.
  # Note that the exception handler is not called when the option :throw was given.
  class ExceptionHandler
    include Module.new {
      def call(exception, locale, key, options)
        if exception.is_a?(MissingTranslation)
          options[:rescue_format] == :html ? exception.html_message : exception.message
        elsif exception.is_a?(Exception)
          raise exception
        else
          throw :exception, exception
        end
      end
    }
  end

  class ArgumentError < ::ArgumentError; end

  class InvalidLocale < ArgumentError
    attr_reader :locale
    def initialize(locale)
      @locale = locale
      super "#{locale.inspect} is not a valid locale"
    end
  end

  class InvalidLocaleData < ArgumentError
    attr_reader :filename
    def initialize(filename)
      @filename = filename
      super "can not load translations from #{filename}, expected it to return a hash, but does not"
    end
  end

  class MissingTranslation
    module Base
      attr_reader :locale, :key, :options

      def initialize(locale, key, options = nil)
        @key, @locale, @options = key, locale, options.dup || {}
        options.each { |k, v| self.options[k] = v.inspect if v.is_a?(Proc) }
      end

      def html_message
        key = keys.last.to_s.gsub('_', ' ').gsub(/\b('?[a-z])/) { $1.capitalize }
        %(<span class="translation_missing" title="translation missing: #{keys.join('.')}">#{key}</span>)
      end

      def keys
        @keys ||= I18n.normalize_keys(locale, key, options[:scope]).tap do |keys|
          keys << 'no key' if keys.size < 2
        end
      end

      def message
        "translation missing: #{keys.join('.')}"
      end
      alias :to_s :message

      def to_exception
        MissingTranslationData.new(locale, key, options)
      end
    end

    include Base
  end

  class MissingTranslationData < ArgumentError
    include MissingTranslation::Base
  end

  class InvalidPluralizationData < ArgumentError
    attr_reader :entry, :count
    def initialize(entry, count)
      @entry, @count = entry, count
      super "translation data #{entry.inspect} can not be used with :count => #{count}"
    end
  end

  class MissingInterpolationArgument < ArgumentError
    attr_reader :values, :string
    def initialize(values, string)
      @values, @string = values, string
      super "missing interpolation argument in #{string.inspect} (#{values.inspect} given)"
    end
  end

  class ReservedInterpolationKey < ArgumentError
    attr_reader :key, :string
    def initialize(key, string)
      @key, @string = key, string
      super "reserved key #{key.inspect} used in #{string.inspect}"
    end
  end

  class UnknownFileType < ArgumentError
    attr_reader :type, :filename
    def initialize(type, filename)
      @type, @filename = type, filename
      super "can not load translations from #{filename}, the file type #{type} is not known"
    end
  end
end