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

namespace Convention.RScript.Runner
{
    public class DefineVariableRunner : IRSentenceRunner
    {
        [return: MaybeNull]
        public object Run(ExpressionParser parser, RScriptSentence sentence, RScriptContext context)
        {
            // 定义变量
            var varTypeName = sentence.info[0];
            var varName = sentence.info[1];
            var varInitExpression = sentence.info[2];
            Type varType;
            object varDefaultValue;
            {
                if (varTypeName == "string")
                {
                    varType = typeof(string);
                    varDefaultValue = varInitExpression == null ? string.Empty : varInitExpression;
                }
                else if (varTypeName == "int")
                {
                    varType = typeof(int);
                    varDefaultValue = varInitExpression == null ? 0 : parser.Evaluate<int>(varInitExpression);
                }
                else if (varTypeName == "double")
                {
                    varType = typeof(double);
                    varDefaultValue = varInitExpression == null ? 0.0 : parser.Evaluate<double>(varInitExpression);
                }
                else if (varTypeName == "float")
                {
                    varType = typeof(float);
                    varDefaultValue = varInitExpression == null ? 0.0f : parser.Evaluate<float>(varInitExpression);
                }
                else if (varTypeName == "bool")
                {
                    varType = typeof(bool);
                    varDefaultValue = varInitExpression == null ? false : parser.Evaluate<bool>(varInitExpression);
                }
                else if (varTypeName == "var")
                {
                    varType = typeof(object);
                    varDefaultValue = varInitExpression == null ? new object() : parser.Evaluate(varInitExpression);
                }
                else
                {
                    throw new RScriptRuntimeException($"Unsupported variable type '{varTypeName}'.", context.CurrentRuntimePointer);
                }
            }
            if (context.CurrentLocalSpaceVariableNames.Peek().Contains(varName) == false)
            {
                context.Variables.Add(varName, new(varType, varDefaultValue));
                parser.context.Variables[varName] = varDefaultValue;
                context.CurrentLocalSpaceVariableNames.Peek().Add(varName);
            }
            else
            {
                throw new RScriptRuntimeException($"Variable '{varName}' already defined on this namespace.", context.CurrentRuntimePointer);
            }
            return null;
        }
    }
}