# frozen_string_literal: true

module Tesseract
  module Transaction
    module Steps
      # Adds a "merge" step that expects the input to the step to be a hash,
      # and then merges the successful result of the step into the input hash.
      # If the step results in a Failure then that Failure is returned instead.
      #
      # If the return value of the step is not a hash, then the return value is
      # merged into the input hash using the step name as the key.
      #
      # Usage:
      #
      # merge :user
      # merge :lookup_metadata
      #
      # # input: { user_id: 42, name: "Chuck" }
      # def user(user_id:, **)
      #   User.find(user_id)
      # end
      # # output: { user_id: 42, name: "Chuck", user: #<User id:42> }
      #
      # def lookup_metadata(user:,.**)
      #   resp = APIClient.get_email(user.client_id)
      #   { email: resp["user_email"], fists: resp["fists"]["items"].size }
      # end
      #
      # # output: { user_id: 42, name: "Chuck", user: #<User id:42>, email: "chuck@example", fists: 2 }
      #
      module Merge
        class MergeStepAdapter < Dry::Transaction::StepAdapters
          include Dry::Monads::Result::Mixin

          def call(operation, _options, input)
            result = operation.call(input[0])
            return result if result.try(:failure?)

            value = result.try(:value!) || result || {}
            value = { operation.operation.name => value } unless value.is_a?(Hash)

            Success(input[0].merge(value))
          end
        end
        Dry::Transaction::StepAdapters.register(:merge, MergeStepAdapter.new) unless Dry::Transaction::StepAdapters.key?(:merge)
      end
    end
  end
end