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

namespace Upsilon.Evaluator
{
    public class EvaluationScope
    {
        private readonly EvaluationScope _parentScope;
        private EvaluationScope _getOnlyParentScope;

        public readonly Dictionary<string, ScriptType> Variables;
        private readonly Dictionary<string, ScriptType> _localVariables;


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

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

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

        public void Set(VariableSymbol symbol, ScriptType obj, bool createNew)
        {
            if (symbol.Local && createNew)
            {
                if (_localVariables.ContainsKey(symbol.Name))
                {
                    _localVariables[symbol.Name] = obj;
                }
                else
                {
                    _localVariables.Add(symbol.Name, obj);
                }
            }
            else
            {
                if (Variables.ContainsKey(symbol.Name))
                {
                    Variables[symbol.Name] = obj;
                }
                else if (_localVariables.ContainsKey(symbol.Name))
                {
                    _localVariables[symbol.Name] = obj;
                }
                else if (_parentScope != null && _parentScope.TryGet(symbol.Name, out _))
                {
                    _parentScope.Set(symbol, obj, false);
                }
                else
                {
                    Variables.Add(symbol.Name, obj);
                }

            }
        }

        public void SetGlobal(VariableSymbol symbol, ScriptType obj)
        {
            if (_parentScope != null)
                _parentScope.SetGlobal(symbol, obj);
            else
            {
                Set(symbol, obj, true);
            }
        }

        public bool TryGet(VariableSymbol symbol, out ScriptType obj)
        {
            if (_localVariables.TryGetValue(symbol.Name, out obj))
                return true;
            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 (_localVariables.TryGetValue(variable, out obj))
                return true;
            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;
        }
    }
}