require 'hanami/action/base_params'
require 'hanami/validations/form'

module Hanami
  module Action
    # A set of params requested by the client
    #
    # It's able to extract the relevant params from a Rack env of from an Hash.
    #
    # There are three scenarios:
    #   * When used with Hanami::Router: it contains only the params from the request
    #   * When used standalone: it contains all the Rack env
    #   * Default: it returns the given hash as it is. It's useful for testing purposes.
    #
    # @since 0.1.0
    class Params < BaseParams
      include Hanami::Validations::Form

      # Params errors
      #
      # @since 1.1.0
      class Errors < SimpleDelegator
        # @since 1.1.0
        # @api private
        def initialize(errors = {})
          super(errors)
        end

        # Add an error to the param validations
        #
        # This has a semantic similar to `Hash#dig` where you use a set of keys
        # to get a nested value, here you use a set of keys to set a nested
        # value.
        #
        # @param args [Array<Symbol, String>] an array of arguments: the last
        #   one is the message to add (String), while the beginning of the array
        #   is made of keys to reach the attribute.
        #
        # @raise [ArgumentError] when try to add a message for a key that is
        #   already filled with incompatible message type.
        #   This usually happens with nested attributes: if you have a `:book`
        #   schema and the input doesn't include data for `:book`, the messages
        #   will be `["is missing"]`. In that case you can't add an error for a
        #   key nested under `:book`.
        #
        # @since 1.1.0
        #
        # @example Basic usage
        #   require "hanami/controller"
        #
        #   class MyAction
        #     include Hanami::Action
        #
        #     params do
        #       required(:book).schema do
        #         required(:isbn).filled(:str?)
        #       end
        #     end
        #
        #     def call(params)
        #       # 1. Don't try to save the record if the params aren't valid
        #       return unless params.valid?
        #
        #       BookRepository.new.create(params[:book])
        #     rescue Hanami::Model::UniqueConstraintViolationError
        #       # 2. Add an error in case the record wasn't unique
        #       params.errors.add(:book, :isbn, "is not unique")
        #     end
        #   end
        #
        # @example Invalid argument
        #   require "hanami/controller"
        #
        #   class MyAction
        #     include Hanami::Action
        #
        #     params do
        #       required(:book).schema do
        #         required(:title).filled(:str?)
        #       end
        #     end
        #
        #     def call(params)
        #       puts params.to_h   # => {}
        #       puts params.valid? # => false
        #       puts params.error_messages # => ["Book is missing"]
        #       puts params.errors         # => {:book=>["is missing"]}
        #
        #       params.errors.add(:book, :isbn, "is not unique") # => ArgumentError
        #     end
        #   end
        def add(*args)
          *keys, key, error = args
          _nested_attribute(keys, key) << error
        rescue TypeError
          raise ArgumentError.new("Can't add #{args.map(&:inspect).join(', ')} to #{inspect}")
        end

        private

        # @since 1.1.0
        # @api private
        def _nested_attribute(keys, key)
          if keys.empty?
            self
          else
            keys.inject(self) { |result, k| result[k] ||= {} }
            dig(*keys)
          end[key] ||= []
        end
      end

      # This is a Hanami::Validations extension point
      #
      # @since 0.7.0
      # @api private
      def self._base_rules
        lambda do
          optional(:_csrf_token).filled(:str?)
        end
      end

      # Define params validations
      #
      # @param blk [Proc] the validations definitions
      #
      # @since 0.7.0
      #
      # @see http://hanamirb.org/guides/validations/overview/
      #
      # @example
      #   class Signup
      #     MEGABYTE = 1024 ** 2
      #     include Hanami::Action
      #
      #     params do
      #       required(:first_name).filled(:str?)
      #       required(:last_name).filled(:str?)
      #       required(:email).filled?(:str?, format?: /\A.+@.+\z/)
      #       required(:password).filled(:str?).confirmation
      #       required(:terms_of_service).filled(:bool?)
      #       required(:age).filled(:int?, included_in?: 18..99)
      #       optional(:avatar).filled(size?: 1..(MEGABYTE * 3))
      #     end
      #
      #     def call(params)
      #       halt 400 unless params.valid?
      #       # ...
      #     end
      #   end
      def self.params(&blk)
        validations(&blk || ->() {})
      end

      # Initialize the params and freeze them.
      #
      # @param env [Hash] a Rack env or an hash of params.
      #
      # @return [Params]
      #
      # @since 0.1.0
      # @api private
      def initialize(env)
        @env = env
        super(_extract_params)
        @result = validate
        @params = _params
        @errors = Errors.new(@result.messages)
        freeze
      end

      # Returns raw params from Rack env
      #
      # @return [Hash]
      #
      # @since 0.3.2
      def raw
        @input
      end

      # Returns structured error messages
      #
      # @return [Hash]
      #
      # @since 0.7.0
      #
      # @example
      #   params.errors
      #     # => {:email=>["is missing", "is in invalid format"], :name=>["is missing"], :tos=>["is missing"], :age=>["is missing"], :address=>["is missing"]}
      attr_reader :errors

      # Returns flat collection of full error messages
      #
      # @return [Array]
      #
      # @since 0.7.0
      #
      # @example
      #   params.error_messages
      #     # => ["Email is missing", "Email is in invalid format", "Name is missing", "Tos is missing", "Age is missing", "Address is missing"]
      def error_messages(error_set = errors)
        error_set.each_with_object([]) do |(key, messages), result|
          k = Utils::String.titleize(key)

          _messages = if messages.is_a?(Hash)
            error_messages(messages)
          else
            messages.map { |message| "#{k} #{message}" }
          end

          result.concat(_messages)
        end
      end

      # Returns true if no validation errors are found,
      # false otherwise.
      #
      # @return [TrueClass, FalseClass]
      #
      # @since 0.7.0
      #
      # @example
      #   params.valid? # => true
      def valid?
        errors.empty?
      end

      # Serialize params to Hash
      #
      # @return [::Hash]
      #
      # @since 0.3.0
      def to_h
        @params
      end
      alias_method :to_hash, :to_h

      private

      # @api private
      def _params
        _router_params.merge(@result.output)
      end
    end
  end
end