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

namespace Convention.RScript.Runner
{
    public abstract class JumpRuntimePointerRunner : IRSentenceRunner
    {
        protected static void DoJumpRuntimePointer(ExpressionParser parser, int target, RScriptContext context)
        {
            bool isForwardMove = target > context.CurrentRuntimePointer;
            int step = isForwardMove ? 1 : -1;
            int insLayer = 0;
            for (; context.CurrentRuntimePointer != target; context.CurrentRuntimePointer += step)
            {
                if (context.CurrentSentence.mode == RScriptSentence.Mode.ExitNamespace)
                {
                    if (isForwardMove)
                    {
                        if (insLayer > 0)
                            insLayer--;
                        else
                        {
                            for (int disLayer = -insLayer; disLayer > 0; disLayer--)
                                context.SentenceRunners[RScriptSentence.Mode.ExitNamespace].Run(parser, context.CurrentSentence, context);
                        }
                    }
                    else
                        insLayer++;
                }
                else if (context.CurrentSentence.mode == RScriptSentence.Mode.EnterNamespace)
                {
                    if (isForwardMove)
                        insLayer++;
                    else
                    {
                        if (insLayer > 0)
                            insLayer--;
                        else
                        {
                            for (int disLayer = -insLayer; disLayer > 0; disLayer--)
                                context.SentenceRunners[RScriptSentence.Mode.ExitNamespace].Run(parser, context.CurrentSentence, context);
                        }
                    }
                }
                if (insLayer > 0)
                {
                    for (; insLayer > 0; insLayer--)
                    {
                        context.SentenceRunners[RScriptSentence.Mode.EnterNamespace].Run(parser, context.CurrentSentence, context);
                    }
                }
                else if (insLayer < 0)
                {
                    for (; insLayer < 0; insLayer++)
                    {
                        context.SentenceRunners[RScriptSentence.Mode.ExitNamespace].Run(parser, context.CurrentSentence, context);
                    }
                }
            }
        }

        public abstract void Compile(ExpressionParser parser, RScriptSentence sentence, RScriptContext context);
        [return: MaybeNull]
        public abstract object Run(ExpressionParser parser, RScriptSentence sentence, RScriptContext context);
    }
}