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

namespace Convention.RScript.Runner
{
    public abstract class JumpRuntimePointerRunner : IRSentenceRunner
    {
        protected static void DoJumpRuntimePointer(ExpressionParser parser, int target, RScriptContext context)
        {
            int currentPointer = context.CurrentRuntimePointer;
            bool isForwardMove = target > context.CurrentRuntimePointer;
            int step = isForwardMove ? 1 : -1;
            int depth = 0;
            int lastLayer = 0;
            for (; context.CurrentRuntimePointer != target; context.CurrentRuntimePointer += step)
            {
                if (context.CurrentSentence.mode == RScriptSentence.Mode.ExitNamespace)
                {
                    if (isForwardMove)
                        lastLayer--;
                    else
                        lastLayer++;
                }
                else if (context.CurrentSentence.mode == RScriptSentence.Mode.EnterNamespace)
                {
                    if (isForwardMove)
                        lastLayer++;
                    else
                        lastLayer--;
                }
                depth = lastLayer < depth ? lastLayer : depth;
            }
            // 对上层的最深影响
            for (; depth < 0; depth++)
            {
                try
                {
                    context.SentenceRunners[RScriptSentence.Mode.ExitNamespace].Run(parser, context.CurrentSentence, context);
                }
                catch (Exception ex)
                {
                    throw new RScriptRuntimeException($"Jump pointer with error", currentPointer, ex);
                }
            }
            // 恢复正确的层数
            for (int i = depth, e = lastLayer; i < e; i++)
            {
                try
                {
                    context.SentenceRunners[RScriptSentence.Mode.EnterNamespace].Run(parser, context.CurrentSentence, context);
                }
                catch (Exception ex)
                {
                    throw new RScriptRuntimeException($"Jump pointer with error", currentPointer, ex);
                }
            }
        }

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