using Convention.RScript.Parser;
using System.Diagnostics.CodeAnalysis;

namespace Convention.RScript.Runner
{
    public class GoToRunner : JumpRuntimePointerRunner
    {
        [return: MaybeNull]
        public override object Run(ExpressionParser parser, RScriptSentence sentence, RScriptContext context)
        {
            // 检查并跳转到指定标签
            if (parser.Evaluate<bool>(sentence.info[0]))
            {
                if (context.Labels.TryGetValue(sentence.content, out var labelPointer))
                {
                    context.GotoPointerStack.Push(context.CurrentRuntimePointer);
                    DoJumpRuntimePointer(parser, labelPointer, context);
                }
                else if (context.NamespaceLabels.TryGetValue(sentence.content, out labelPointer))
                {
                    int current = context.CurrentRuntimePointer;
                    //DoEnterNamespace(parser);
                    context.SentenceRunners[RScriptSentence.Mode.EnterNamespace].Run(parser, context.CurrentSentence, context);
                    context.CurrentRuntimePointer = labelPointer;
                    for (int e = context.NamespaceLayer[context.NamespaceLabels[sentence.content]]; ;)
                    {
                        context.RunNextStep(parser);
                        if (context.CurrentRuntimePointer >= context.Sentences.Length)
                            break;
                        else if (context.CurrentRuntimePointer == e)
                            break;
                        else
                            context.CurrentRuntimePointer++;
                    }
                    //context.DoExitNamespace(parser);
                    context.SentenceRunners[RScriptSentence.Mode.ExitNamespace].Run(parser, context.CurrentSentence, context);
                    context.CurrentRuntimePointer = current;
                }
                else
                {
                    throw new RScriptRuntimeException($"Label '{sentence.content}' not found.", context.CurrentRuntimePointer);
                }
            }
            return null;
        }
    }
}