module Virtus
  class Coercion

    # Coerce Object values
    class Object < Coercion
      primitive ::Object

      COERCION_METHOD_REGEXP = /\Ato_/.freeze

      # Create an Array from any Object
      #
      # @example with an object that does not respond to #to_a or #to_ary
      #   Virtus::Coercion::Object.to_array(value)         # => [ value ]
      #
      # @example with an object that responds to #to_a
      #   Virtus::Coercion::Object.to_array(Set[ value ])  # => [ value ]
      #
      # @example with n object that responds to #to_ary
      #   Virtus::Coercion::Object.to_array([ value ])     # => [ value ]
      #
      # @param [#to_a,#to_ary,Object] value
      # @param [#to_a,#to_ary,Object] value
      #
      # @return [Array]
      #
      # @api public
      def self.to_array(value)
        Array(value)
      end

      # Create a Hash from the Object if possible
      #
      # @example with a coercible object
      #   Virtus::Coercion::Object.to_hash(key => value)  # => { key => value }
      #
      # @example with an object that is not coercible
      #   Virtus::Coercion::Object.to_hash(value)  # => value
      #
      # @param [#to_hash, Object] value
      #
      # @return [Hash]
      #   returns a Hash when the object can be coerced
      # @return [Object]
      #   returns the value when the object cannot be coerced
      #
      # @api public
      def self.to_hash(value)
        coerce_with_method(value, :to_hash)
      end

      # Create a String from the Object if possible
      #
      # @example with a coercible object
      #   Virtus::Coercion::Object.to_string("string")  # => "string"
      #
      # @example with an object that is not coercible
      #   Virtus::Coercion::Object.to_string(value)  # => value
      #
      # @param [#to_str, Object] value
      #
      # @return [String]
      #   returns a String when the object can be coerced
      # @return [Object]
      #   returns the value when the object cannot be coerced
      #
      # @api public
      def self.to_string(value)
        coerce_with_method(value, :to_str)
      end

      # Create an Integer from the Object if possible
      #
      # @example with a coercible object
      #   Virtus::Coercion::Object.to_integer(1)  # => 1
      #
      # @example with an object that is not coercible
      #   Virtus::Coercion::Object.to_integer(value)  # => value
      #
      # @param [#to_int, Object] value
      #
      # @return [Integer]
      #   returns an Integer when the object can be coerced
      # @return [Object]
      #   returns the value when the object cannot be coerced
      #
      # @api public
      def self.to_integer(value)
        coerce_with_method(value, :to_int)
      end

      # Passthrough given value
      #
      # @param [Object] value
      #
      # @return [Object]
      #
      # @api private
      def self.method_missing(method, *args)
        if method.to_s =~ COERCION_METHOD_REGEXP and args.size == 1
          args.first
        else
          super
        end
      end

      private_class_method :method_missing

      # Try to use native coercion method on the given value
      #
      # @param [Object] value
      #
      # @param [Symbol] method
      #
      # @return [Object]
      #
      # @api private
      def self.coerce_with_method(value, method)
        value.respond_to?(method) ? value.public_send(method) : value
      end

      private_class_method :coerce_with_method

    end # class Object
  end # class Coercion
end # module Virtus