require_relative 'base_command_builder'

module Gitlab
  module Triage
    module CommandBuilders
      class CommentBodyBuilder < BaseCommandBuilder
        SUPPORTED_PLACEHOLDERS = {
          created_at: "{{created_at}}".freeze,
          updated_at: "{{updated_at}}".freeze,
          closed_at: "{{closed_at}}".freeze,
          merged_at: "{{merged_at}}".freeze,
          state: "{{state}}".freeze,
          author: "@{{author.username}}".freeze,
          assignee: "@{{assignee.username}}".freeze,
          assignees: "@{{assignees.username}}".freeze,
          closed_by: "@{{closed_by.username}}".freeze,
          merged_by: "@{{merged_by.username}}".freeze,
          milestone: %(%"{{milestone.title}}").freeze,
          labels: %(~"{{labels}}").freeze,
          upvotes: "{{upvotes}}".freeze,
          downvotes: "{{downvotes}}".freeze
        }.freeze
        PLACEHOLDER_REGEX = /{{([\w\.]+)}}/

        attr_reader :resource

        def initialize(items, resource: nil)
          super(items)
          @resource = resource
        end

        private

        def separator
          "\n\n"
        end

        def format_item(item)
          return item unless resource

          SUPPORTED_PLACEHOLDERS.inject(item) do |comment, (placeholder, formatted_text)|
            next comment unless comment.include?("{{#{placeholder}}}")

            methods = formatted_text.match(/.*#{PLACEHOLDER_REGEX}.*/)[1].split('.')
            fields = resource_fields(resource, methods)

            final_fields = fields.map { |field| formatted_text.sub(PLACEHOLDER_REGEX, field.to_s) }

            if final_fields.any?
              comment.gsub("{{#{placeholder}}}", final_fields.join(', '))
            else
              comment
            end
          end
        end

        def resource_fields(resource, methods)
          method = methods.shift

          return Array(resource) unless method && resource
          return [] unless resource.key?(method)

          sub_resources = resource[method]
          Array.wrap(sub_resources).flat_map { |res| resource_fields(res, methods.dup) }
        end
      end
    end
  end
end