# frozen_string_literal: true
require "active_support/core_ext/module/attribute_accessors"
require "active_record/attribute_mutation_tracker"

module ActiveRecord
  module AttributeMethods
    module Dirty
      extend ActiveSupport::Concern

      include ActiveModel::Dirty

      included do
        if self < ::ActiveRecord::Timestamp
          raise "You cannot include Dirty after Timestamp"
        end

        class_attribute :partial_writes, instance_writer: false
        self.partial_writes = true

        after_create { changes_internally_applied }
        after_update { changes_internally_applied }

        # Attribute methods for "changed in last call to save?"
        attribute_method_affix(prefix: "saved_change_to_", suffix: "?")
        attribute_method_prefix("saved_change_to_")
        attribute_method_suffix("_before_last_save")

        # Attribute methods for "will change if I call save?"
        attribute_method_affix(prefix: "will_save_change_to_", suffix: "?")
        attribute_method_suffix("_change_to_be_saved", "_in_database")
      end

      # Attempts to +save+ the record and clears changed attributes if successful.
      def save(*)
        if status = super
          changes_applied
        end
        status
      end

      # Attempts to <tt>save!</tt> the record and clears changed attributes if successful.
      def save!(*)
        super.tap do
          changes_applied
        end
      end

      # <tt>reload</tt> the record and clears changed attributes.
      def reload(*)
        super.tap do
          @previous_mutation_tracker = nil
          clear_mutation_trackers
          @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
        end
      end

      def initialize_dup(other) # :nodoc:
        super
        @attributes = self.class._default_attributes.map do |attr|
          attr.with_value_from_user(@attributes.fetch_value(attr.name))
        end
        clear_mutation_trackers
      end

      def changes_internally_applied # :nodoc:
        @mutations_before_last_save = mutations_from_database
        forget_attribute_assignments
        @mutations_from_database = AttributeMutationTracker.new(@attributes)
      end

      def changes_applied # :nodoc:
        @previous_mutation_tracker = mutation_tracker
        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
        @mutation_tracker = nil
        @mutations_from_database = nil
      end

      def clear_changes_information # :nodoc:
        @previous_mutation_tracker = nil
        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
        forget_attribute_assignments
        clear_mutation_trackers
      end

      def raw_write_attribute(attr_name, *) # :nodoc:
        result = super
        clear_attribute_change(attr_name)
        result
      end

      def clear_attribute_changes(attr_names) # :nodoc:
        super
        attr_names.each do |attr_name|
          clear_attribute_change(attr_name)
        end
      end

      def changed_attributes # :nodoc:
        # This should only be set by methods which will call changed_attributes
        # multiple times when it is known that the computed value cannot change.
        if defined?(@cached_changed_attributes)
          @cached_changed_attributes
        else
          emit_warning_if_needed("changed_attributes", "saved_changes.transform_values(&:first)")
          super.reverse_merge(mutation_tracker.changed_values).freeze
        end
      end

      def changes # :nodoc:
        cache_changed_attributes do
          emit_warning_if_needed("changes", "saved_changes")
          super
        end
      end

      def previous_changes # :nodoc:
        unless previous_mutation_tracker.equal?(mutations_before_last_save)
          ActiveSupport::Deprecation.warn(<<-EOW.strip_heredoc)
            The behavior of `previous_changes` inside of after callbacks is
            deprecated without replacement. In the next release of Rails,
            this method inside of `after_save` will return the changes that
            were just saved.
          EOW
        end
        previous_mutation_tracker.changes
      end

      def attribute_changed_in_place?(attr_name) # :nodoc:
        mutation_tracker.changed_in_place?(attr_name)
      end

      # Did this attribute change when we last saved? This method can be invoked
      # as `saved_change_to_name?` instead of `saved_change_to_attribute?("name")`.
      # Behaves similarly to +attribute_changed?+. This method is useful in
      # after callbacks to determine if the call to save changed a certain
      # attribute.
      #
      # ==== Options
      #
      # +from+ When passed, this method will return false unless the original
      # value is equal to the given option
      #
      # +to+ When passed, this method will return false unless the value was
      # changed to the given value
      def saved_change_to_attribute?(attr_name, **options)
        mutations_before_last_save.changed?(attr_name, **options)
      end

      # Returns the change to an attribute during the last save. If the
      # attribute was changed, the result will be an array containing the
      # original value and the saved value.
      #
      # Behaves similarly to +attribute_change+. This method is useful in after
      # callbacks, to see the change in an attribute that just occurred
      #
      # This method can be invoked as `saved_change_to_name` in instead of
      # `saved_change_to_attribute("name")`
      def saved_change_to_attribute(attr_name)
        mutations_before_last_save.change_to_attribute(attr_name)
      end

      # Returns the original value of an attribute before the last save.
      # Behaves similarly to +attribute_was+. This method is useful in after
      # callbacks to get the original value of an attribute before the save that
      # just occurred
      def attribute_before_last_save(attr_name)
        mutations_before_last_save.original_value(attr_name)
      end

      # Did the last call to `save` have any changes to change?
      def saved_changes?
        mutations_before_last_save.any_changes?
      end

      # Returns a hash containing all the changes that were just saved.
      def saved_changes
        mutations_before_last_save.changes
      end

      # Alias for `attribute_changed?`
      def will_save_change_to_attribute?(attr_name, **options)
        mutations_from_database.changed?(attr_name, **options)
      end

      # Alias for `attribute_change`
      def attribute_change_to_be_saved(attr_name)
        mutations_from_database.change_to_attribute(attr_name)
      end

      # Alias for `attribute_was`
      def attribute_in_database(attr_name)
        mutations_from_database.original_value(attr_name)
      end

      # Alias for `changed?`
      def has_changes_to_save?
        mutations_from_database.any_changes?
      end

      # Alias for `changes`
      def changes_to_save
        mutations_from_database.changes
      end

      # Alias for `changed`
      def changed_attribute_names_to_save
        changes_to_save.keys
      end

      # Alias for `changed_attributes`
      def attributes_in_database
        changes_to_save.transform_values(&:first)
      end

      def attribute_was(*)
        emit_warning_if_needed("attribute_was", "attribute_before_last_save")
        super
      end

      def attribute_change(*)
        emit_warning_if_needed("attribute_change", "saved_change_to_attribute")
        super
      end

      def attribute_changed?(*)
        emit_warning_if_needed("attribute_changed?", "saved_change_to_attribute?")
        super
      end

      def changed?(*)
        emit_warning_if_needed("changed?", "saved_changes?")
        super
      end

      def changed(*)
        emit_warning_if_needed("changed", "saved_changes.keys")
        super
      end

      private

        def mutation_tracker
          unless defined?(@mutation_tracker)
            @mutation_tracker = nil
          end
          @mutation_tracker ||= AttributeMutationTracker.new(@attributes)
        end

        def emit_warning_if_needed(method_name, new_method_name)
          unless mutation_tracker.equal?(mutations_from_database)
            ActiveSupport::Deprecation.warn(<<-EOW.squish)
              The behavior of `#{method_name}` inside of after callbacks will
              be changing in the next version of Rails. The new return value will reflect the
              behavior of calling the method after `save` returned (e.g. the opposite of what
              it returns now). To maintain the current behavior, use `#{new_method_name}`
              instead.
            EOW
          end
        end

        def mutations_from_database
          unless defined?(@mutations_from_database)
            @mutations_from_database = nil
          end
          @mutations_from_database ||= mutation_tracker
        end

        def changes_include?(attr_name)
          super || mutation_tracker.changed?(attr_name)
        end

        def clear_attribute_change(attr_name)
          mutation_tracker.forget_change(attr_name)
          mutations_from_database.forget_change(attr_name)
        end

        def attribute_will_change!(attr_name)
          super
          if self.class.has_attribute?(attr_name)
            mutations_from_database.force_change(attr_name)
          else
            ActiveSupport::Deprecation.warn(<<-EOW.squish)
              #{attr_name} is not an attribute known to Active Record.
              This behavior is deprecated and will be removed in the next
              version of Rails. If you'd like #{attr_name} to be managed
              by Active Record, add `attribute :#{attr_name} to your class.
            EOW
            mutations_from_database.deprecated_force_change(attr_name)
          end
        end

        def _update_record(*)
          partial_writes? ? super(keys_for_partial_write) : super
        end

        def _create_record(*)
          partial_writes? ? super(keys_for_partial_write) : super
        end

        def keys_for_partial_write
          changed_attribute_names_to_save & self.class.column_names
        end

        def forget_attribute_assignments
          @attributes = @attributes.map(&:forgetting_assignment)
        end

        def clear_mutation_trackers
          @mutation_tracker = nil
          @mutations_from_database = nil
          @mutations_before_last_save = nil
        end

        def previous_mutation_tracker
          @previous_mutation_tracker ||= NullMutationTracker.instance
        end

        def mutations_before_last_save
          @mutations_before_last_save ||= previous_mutation_tracker
        end

        def cache_changed_attributes
          @cached_changed_attributes = changed_attributes
          yield
        ensure
          clear_changed_attributes_cache
        end

        def clear_changed_attributes_cache
          remove_instance_variable(:@cached_changed_attributes) if defined?(@cached_changed_attributes)
        end
    end
  end
end