module OpenProject
  module Logging
    class LogDelegator
      class << self
        ##
        # Consume a message and let it be handled
        # by all handlers
        def log(exception, context = {})
          # in case we're getting ActionController::Parameters
          if context.respond_to?(:to_unsafe_h)
            context = context.to_unsafe_h
          else
            context = context.to_h.dup.with_indifferent_access
          end

          message =
            if exception.is_a? Exception
              context[:exception] = exception
              "#{exception}: #{exception.message}"
            else
              exception.to_s
            end

          # Mark backtrace
          if context[:exception]
            context[:backtrace] = clean_backtrace(context[:exception])
          end

          # Set current contexts
          context[:level] ||= context[:exception] ? :error : :info
          context[:current_user] ||= User.current

          registered_handlers.values.each do |handler|
            handler.call message, context
          rescue StandardError => e
            Rails.logger.error "Failed to delegate log to #{handler.inspect}: #{e.inspect}\nMessage: #{message.inspect}"
          end

          nil
        rescue StandardError => e
          Rails.logger.error "Failed to process log message #{exception.inspect}: #{e.inspect}"
        end

        %i(debug info warn error fatal unknown).each do |level|
          define_method(level) do |*args|
            message = args.shift
            context = args.shift || {}

            log(message, context.merge(level: level))
          end
        end

        ##
        # Get a clean backtrace
        def clean_backtrace(exception)
          return nil unless exception&.backtrace

          Rails.backtrace_cleaner.clean exception.backtrace
        end

        ##
        # The active set of error handlers
        def registered_handlers
          @handlers ||= default_handlers
        end

        ##
        # Register a new handler
        def register(key, handler)
          raise "#{key} already registered" if registered_handlers.key?(key)
          raise "handler must respond_to #call" unless handler.respond_to?(:call)

          @handlers[key] = handler
        end

        private

        def default_handlers
          { rails_logger: method(:rails_logger_handler) }
        end

        ##
        # A lambda handler for logging the error
        # to rails.
        def rails_logger_handler(message, context = {})
          Rails.logger.public_send(context[:level]) do
            "#{context_string(context)} #{message}"
          end

          if context.key?(:exception)
            Rails.logger.debug do
              exception = context[:exception]
              trace = context[:backtrace]&.join('; ')
              "[#{exception.class}] #{exception.message}: #{trace}"
            end
          end
        end

        ##
        # Create a context string
        def context_string(context)
          payload = context.slice(%i[current_user project reference]).compact
          extended = OpenProject::Logging.extend_payload!(payload, context)
          OpenProject::Logging.formatter.call extended
        end
      end
    end
  end
end