using System;
using System.Collections.Generic;
using Upsilon.BaseTypes;
using Upsilon.Binder;
using Upsilon.Binder.VariableSymbols;

namespace Upsilon.Evaluator
{
    public class EvaluationScope : IDisposable
    {
        public EvaluationScope ParentScope { get; private set; }
        private EvaluationScope _getOnlyParentScope;

        public readonly Dictionary<string, ScriptType> Variables;


        internal EvaluationScope(EvaluationScope parentScope)
        {
            ParentScope = parentScope;
            Variables = new Dictionary<string, ScriptType>();
        }

        internal EvaluationScope(Dictionary<string, ScriptType> vars)
        {
            Variables  = vars;
        }

        internal static EvaluationScope CreateWithGetOnlyParent(EvaluationScope parent)
        {
            var scope = new EvaluationScope(new Dictionary<string, ScriptType>()) {_getOnlyParentScope = parent};
            return scope;
        }

        public void Dispose()
        {
            ParentScope?.Dispose();
            ParentScope = null;
            Variables.Clear();
        }

        public void AssignToNearest(VariableSymbol symbol, ScriptType value)
        {
            lock (Variables)
            {
                if (Variables.ContainsKey(symbol.Name))
                {
                    Variables[symbol.Name] = value;
                }
                else if (ParentScope != null)
                {
                    ParentScope.AssignToNearest(symbol, value);
                }
                else
                {
                    Variables.Add(symbol.Name, value);
                }
            }
        }

        public void CreateLocal(VariableSymbol symbol, ScriptType value)
        {
            Variables[symbol.Name] = value;
        }

        public void Delete(VariableSymbol symbol)
        {
            Variables.Remove(symbol.Name);
        }

        public void Delete(string name)
        {
            Variables.Remove(name);
        }


        public bool TryGet(VariableSymbol symbol, out ScriptType obj)
        {
            if (Variables.TryGetValue(symbol.Name, out obj))
                return true;
            if (ParentScope != null)
                if (ParentScope.TryGet(symbol, out obj))
                    return true;
            if (_getOnlyParentScope != null)
                if (_getOnlyParentScope.TryGet(symbol, out obj))
                    return true;
            return false;
        }

        public bool TryGet(string variable, out ScriptType obj)
        {
            if (Variables.TryGetValue(variable, out obj))
                return true;
            if (ParentScope != null)
                if (ParentScope.TryGet(variable, out obj))
                    return true;
            if (_getOnlyParentScope != null)
                if (_getOnlyParentScope.TryGet(variable, out obj))
                    return true;
            return false;
        }
    }
}