require 'hanami/utils/basic_object'
require 'hanami/utils/class_attribute'
require 'hanami/utils/hash'

module Hanami
  # Hanami Interactor
  #
  # @since 0.3.5
  module Interactor
    # Result of an operation
    #
    # @since 0.3.5
    class Result < Utils::BasicObject
      # Concrete methods
      #
      # @since 0.3.5
      # @api private
      #
      # @see Hanami::Interactor::Result#respond_to_missing?
      METHODS = ::Hash[initialize: true, success?: true, fail!: true, prepare!: true, errors: true, error: true].freeze

      # Initialize a new result
      #
      # @param payload [Hash] a payload to carry on
      #
      # @return [Hanami::Interactor::Result]
      #
      # @since 0.3.5
      # @api private
      def initialize(payload = {})
        @payload = _payload(payload)
        @errors  = []
        @success = true
      end

      # Check if the current status is successful
      #
      # @return [TrueClass,FalseClass] the result of the check
      #
      # @since 0.3.5
      def success?
        @success && errors.empty?
      end

      # Force the status to be a failure
      #
      # @since 0.3.5
      def fail!
        @success = false
      end

      # Returns all the errors collected during an operation
      #
      # @return [Array] the errors
      #
      # @since 0.3.5
      #
      # @see Hanami::Interactor::Result#error
      # @see Hanami::Interactor#call
      # @see Hanami::Interactor#error
      # @see Hanami::Interactor#error!
      def errors
        @errors.dup
      end

      # @since 0.5.0
      # @api private
      def add_error(*errors)
        @errors << errors
        @errors.flatten!
        nil
      end

      # Returns the first errors collected during an operation
      #
      # @return [nil,String] the error, if present
      #
      # @since 0.3.5
      #
      # @see Hanami::Interactor::Result#errors
      # @see Hanami::Interactor#call
      # @see Hanami::Interactor#error
      # @see Hanami::Interactor#error!
      def error
        errors.first
      end

      # Prepare the result before to be returned
      #
      # @param payload [Hash] an updated payload
      #
      # @since 0.3.5
      # @api private
      def prepare!(payload)
        @payload.merge!(_payload(payload))
        self
      end

      protected

      # @since 0.3.5
      # @api private
      def method_missing(m, *)
        @payload.fetch(m) { super }
      end

      # @since 0.3.5
      # @api private
      def respond_to_missing?(method_name, _include_all)
        method_name = method_name.to_sym
        METHODS[method_name] || @payload.key?(method_name)
      end

      # @since 0.3.5
      # @api private
      def _payload(payload)
        Utils::Hash.new(payload).symbolize!
      end

      # @since 0.3.5
      # @api private
      def __inspect
        " @success=#{@success} @payload=#{@payload.inspect}"
      end
    end

    # Override for <tt>Module#included</tt>.
    #
    # @since 0.3.5
    # @api private
    def self.included(base)
      super

      base.class_eval do
        prepend Interface
        extend  ClassMethods
      end
    end

    # Interactor interface
    #
    # @since 0.3.5
    module Interface
      # Initialize an interactor
      #
      # It accepts arbitrary number of arguments.
      # Developers can override it.
      #
      # @param args [Array<Object>] arbitrary number of arguments
      #
      # @return [Hanami::Interactor] the interactor
      #
      # @since 0.3.5
      #
      # @example Override #initialize
      #   require 'hanami/interactor'
      #
      #   class UpdateProfile
      #     include Hanami::Interactor
      #
      #     def initialize(user, params)
      #       @user   = user
      #       @params = params
      #     end
      #
      #     def call
      #       # ...
      #     end
      #   end
      def initialize(*args)
        super
      ensure
        @__result = ::Hanami::Interactor::Result.new
      end

      # Triggers the operation and return a result.
      #
      # All the instance variables will be available in the result.
      #
      # ATTENTION: This must be implemented by the including class.
      #
      # @return [Hanami::Interactor::Result] the result of the operation
      #
      # @raise [NoMethodError] if this isn't implemented by the including class.
      #
      # @example Expose instance variables in result payload
      #   require 'hanami/interactor'
      #
      #   class Signup
      #     include Hanami::Interactor
      #     expose :user, :params
      #
      #     def initialize(params)
      #       @params = params
      #       @user   = User.new(@params)
      #       @foo    = 'bar'
      #     end
      #
      #     def call
      #       @user = UserRepository.persist(@user)
      #     end
      #   end
      #
      #   result = Signup.new(name: 'Luca').call
      #   result.success? # => true
      #
      #   result.user   # => #<User:0x007fa311105778 @id=1 @name="Luca">
      #   result.params # => { :name=>"Luca" }
      #   result.foo    # => raises NoMethodError
      #
      # @example Failed precondition
      #   require 'hanami/interactor'
      #
      #   class Signup
      #     include Hanami::Interactor
      #     expose :user
      #
      #     def initialize(params)
      #       @params = params
      #       @user   = User.new(@params)
      #     end
      #
      #     # THIS WON'T BE INVOKED BECAUSE #valid? WILL RETURN false
      #     def call
      #       @user = UserRepository.persist(@user)
      #     end
      #
      #     private
      #     def valid?
      #       @params.valid?
      #     end
      #   end
      #
      #   result = Signup.new(name: nil).call
      #   result.success? # => false
      #
      #   result.user   # => #<User:0x007fa311105778 @id=nil @name="Luca">
      #
      # @example Bad usage
      #   require 'hanami/interactor'
      #
      #   class Signup
      #     include Hanami::Interactor
      #
      #     # Method #call is not defined
      #   end
      #
      #   Signup.new.call # => NoMethodError
      def call
        _call { super }
      end
    end

    private

    # Check if proceed with <tt>#call</tt> invokation.
    # By default it returns <tt>true</tt>.
    #
    # Developers can override it.
    #
    # @return [TrueClass,FalseClass] the result of the check
    #
    # @since 0.3.5
    def valid?
      true
    end

    # Fail and interrupt the current flow.
    #
    # @since 0.3.5
    #
    # @example
    #   require 'hanami/interactor'
    #
    #   class CreateEmailTest
    #     include Hanami::Interactor
    #
    #     def initialize(params)
    #       @params     = params
    #       @email_test = EmailTest.new(@params)
    #     end
    #
    #     def call
    #       persist_email_test!
    #       capture_screenshot!
    #     end
    #
    #     private
    #     def persist_email_test!
    #       @email_test = EmailTestRepository.persist(@email_test)
    #     end
    #
    #     # IF THIS RAISES AN EXCEPTION WE FORCE A FAILURE
    #     def capture_screenshot!
    #       Screenshot.new(@email_test).capture!
    #     rescue
    #       fail!
    #     end
    #   end
    #
    #   result = CreateEmailTest.new(account_id: 1).call
    #   result.success? # => false
    def fail!
      @__result.fail!
      throw :fail
    end

    # Log an error without interrupting the flow.
    #
    # When used, the returned result won't be successful.
    #
    # @param message [String] the error message
    #
    # @return false
    #
    # @since 0.3.5
    #
    # @see Hanami::Interactor#error!
    #
    # @example
    #   require 'hanami/interactor'
    #
    #   class CreateRecord
    #     include Hanami::Interactor
    #     expose :logger
    #
    #     def initialize
    #       @logger = []
    #     end
    #
    #     def call
    #       prepare_data!
    #       persist!
    #       sync!
    #     end
    #
    #     private
    #     def prepare_data!
    #       @logger << __method__
    #       error "Prepare data error"
    #     end
    #
    #     def persist!
    #       @logger << __method__
    #       error "Persist error"
    #     end
    #
    #     def sync!
    #       @logger << __method__
    #     end
    #   end
    #
    #   result = CreateRecord.new.call
    #   result.success? # => false
    #
    #   result.errors # => ["Prepare data error", "Persist error"]
    #   result.logger # => [:prepare_data!, :persist!, :sync!]
    def error(message)
      @__result.add_error message
      false
    end

    # Log an error AND interrupting the flow.
    #
    # When used, the returned result won't be successful.
    #
    # @param message [String] the error message
    #
    # @since 0.3.5
    #
    # @see Hanami::Interactor#error
    #
    # @example
    #   require 'hanami/interactor'
    #
    #   class CreateRecord
    #     include Hanami::Interactor
    #     expose :logger
    #
    #     def initialize
    #       @logger = []
    #     end
    #
    #     def call
    #       prepare_data!
    #       persist!
    #       sync!
    #     end
    #
    #     private
    #     def prepare_data!
    #       @logger << __method__
    #       error "Prepare data error"
    #     end
    #
    #     def persist!
    #       @logger << __method__
    #       error! "Persist error"
    #     end
    #
    #     # THIS WILL NEVER BE INVOKED BECAUSE WE USE #error! IN #persist!
    #     def sync!
    #       @logger << __method__
    #     end
    #   end
    #
    #   result = CreateRecord.new.call
    #   result.success? # => false
    #
    #   result.errors # => ["Prepare data error", "Persist error"]
    #   result.logger # => [:prepare_data!, :persist!]
    def error!(message)
      error(message)
      fail!
    end

    # @since 0.3.5
    # @api private
    def _call
      catch :fail do
        validate!
        yield
      end

      _prepare!
    end

    # @since 0.3.5
    def validate!
      fail! unless valid?
    end

    # @since 0.3.5
    # @api private
    def _prepare!
      @__result.prepare!(_exposures)
    end

    # @since 0.5.0
    # @api private
    def _exposures
      Hash[].tap do |result|
        self.class.exposures.each do |name, ivar|
          result[name] = instance_variable_get(ivar)
        end
      end
    end
  end

  # @since 0.5.0
  # @api private
  module ClassMethods
    # @since 0.5.0
    # @api private
    def self.extended(interactor)
      interactor.class_eval do
        include Utils::ClassAttribute

        class_attribute :exposures
        self.exposures = Utils::Hash.new
      end
    end

    # Expose local instance variables into the returning value of <tt>#call</tt>
    #
    # @param instance_variable_names [Symbol,Array<Symbol>] one or more instance
    #   variable names
    #
    # @since 0.5.0
    #
    # @see Hanami::Interactor::Result
    #
    # @example Expose instance variable
    #
    #   class Signup
    #     include Hanami::Interactor
    #     expose :user
    #
    #     def initialize(params)
    #       @params = params
    #       @user   = User.new(@params[:user])
    #     end
    #
    #     def call
    #       # ...
    #     end
    #   end
    #
    #   result = Signup.new(user: { name: "Luca" }).call
    #
    #   result.user   # => #<User:0x007fa85c58ccd8 @name="Luca">
    #   result.params # => NoMethodError
    def expose(*instance_variable_names)
      instance_variable_names.each do |name|
        exposures[name] = "@#{name}"
      end
    end
  end
end