# frozen_string_literal: true

module GraphQL
  module Execution
    class Interpreter
      class Runtime
        module GraphQLResult
          def initialize(result_name, parent_result, is_non_null_in_parent)
            @graphql_parent = parent_result
            if parent_result && parent_result.graphql_dead
              @graphql_dead = true
            end
            @graphql_result_name = result_name
            @graphql_is_non_null_in_parent = is_non_null_in_parent
            # Jump through some hoops to avoid creating this duplicate storage if at all possible.
            @graphql_metadata = nil
          end

          def path
            @path ||= build_path([])
          end

          def build_path(path_array)
            graphql_result_name && path_array.unshift(graphql_result_name)
            @graphql_parent ? @graphql_parent.build_path(path_array) : path_array
          end

          attr_accessor :graphql_dead
          attr_reader :graphql_parent, :graphql_result_name, :graphql_is_non_null_in_parent

          # @return [Hash] Plain-Ruby result data (`@graphql_metadata` contains Result wrapper objects)
          attr_accessor :graphql_result_data
        end

        class GraphQLResultHash
          def initialize(_result_name, _parent_result, _is_non_null_in_parent)
            super
            @graphql_result_data = {}
          end

          include GraphQLResult

          attr_accessor :graphql_merged_into

          def set_leaf(key, value)
            # This is a hack.
            # Basically, this object is merged into the root-level result at some point.
            # But the problem is, some lazies are created whose closures retain reference to _this_
            # object. When those lazies are resolved, they cause an update to this object.
            #
            # In order to return a proper top-level result, we have to update that top-level result object.
            # In order to return a proper partial result (eg, for a directive), we have to update this object, too.
            # Yowza.
            if (t = @graphql_merged_into)
              t.set_leaf(key, value)
            end

            @graphql_result_data[key] = value
            # keep this up-to-date if it's been initialized
            @graphql_metadata && @graphql_metadata[key] = value

            value
          end

          def set_child_result(key, value)
            if (t = @graphql_merged_into)
              t.set_child_result(key, value)
            end
            @graphql_result_data[key] = value.graphql_result_data
            # If we encounter some part of this response that requires metadata tracking,
            # then create the metadata hash if necessary. It will be kept up-to-date after this.
            (@graphql_metadata ||= @graphql_result_data.dup)[key] = value
            value
          end

          def delete(key)
            @graphql_metadata && @graphql_metadata.delete(key)
            @graphql_result_data.delete(key)
          end

          def each
            (@graphql_metadata || @graphql_result_data).each { |k, v| yield(k, v) }
          end

          def values
            (@graphql_metadata || @graphql_result_data).values
          end

          def key?(k)
            @graphql_result_data.key?(k)
          end

          def [](k)
            (@graphql_metadata || @graphql_result_data)[k]
          end

          def merge_into(into_result)
            self.each do |key, value|
              case value
              when GraphQLResultHash
                next_into = into_result[key]
                if next_into
                  value.merge_into(next_into)
                else
                  into_result.set_child_result(key, value)
                end
              when GraphQLResultArray
                # There's no special handling of arrays because currently, there's no way to split the execution
                # of a list over several concurrent flows.
                into_result.set_child_result(key, value)
              else
                # We have to assume that, since this passed the `fields_will_merge` selection,
                # that the old and new values are the same.
                into_result.set_leaf(key, value)
              end
            end
            @graphql_merged_into = into_result
          end
        end

        class GraphQLResultArray
          include GraphQLResult

          def initialize(_result_name, _parent_result, _is_non_null_in_parent)
            super
            @graphql_result_data = []
          end

          def graphql_skip_at(index)
            # Mark this index as dead. It's tricky because some indices may already be storing
            # `Lazy`s. So the runtime is still holding indexes _before_ skipping,
            # this object has to coordinate incoming writes to account for any already-skipped indices.
            @skip_indices ||= []
            @skip_indices << index
            offset_by = @skip_indices.count { |skipped_idx| skipped_idx < index}
            delete_at_index = index - offset_by
            @graphql_metadata && @graphql_metadata.delete_at(delete_at_index)
            @graphql_result_data.delete_at(delete_at_index)
          end

          def set_leaf(idx, value)
            if @skip_indices
              offset_by = @skip_indices.count { |skipped_idx| skipped_idx < idx }
              idx -= offset_by
            end
            @graphql_result_data[idx] = value
            @graphql_metadata && @graphql_metadata[idx] = value
            value
          end

          def set_child_result(idx, value)
            if @skip_indices
              offset_by = @skip_indices.count { |skipped_idx| skipped_idx < idx }
              idx -= offset_by
            end
            @graphql_result_data[idx] = value.graphql_result_data
            # If we encounter some part of this response that requires metadata tracking,
            # then create the metadata hash if necessary. It will be kept up-to-date after this.
            (@graphql_metadata ||= @graphql_result_data.dup)[idx] = value
            value
          end

          def values
            (@graphql_metadata || @graphql_result_data)
          end
        end
      end
    end
  end
end