using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;

namespace tlang
{
    public interface IScopeEnvironment : IEnumerable<KeyValuePair<string,TObject>>
    {
        bool VariableExists(string name);
        void SetVariable(string name,TObject obj);
        TObject GetVariable(string names);

        IScopeEnvironment SubEnv {get;}

        IScopeEnvironment RootEnv {get;}

        TObject this[string variable] {get;set;}
    }
    public class SubEnvironment : IScopeEnvironment
    {
         Dictionary<string,TObject> items = new Dictionary<string, TObject>();

        IScopeEnvironment root;
        IScopeEnvironment parent;

        public SubEnvironment(IScopeEnvironment root,IScopeEnvironment parent)
        {
            this.root=root;
            this.parent = parent;
        }

        public TObject this[string variable] { get => GetVariable(variable); set => SetVariable(variable,value); }

        public IScopeEnvironment SubEnv => new SubEnvironment(root,this);

        public IScopeEnvironment RootEnv => root;

        public IEnumerator<KeyValuePair<string, TObject>> GetEnumerator()
        {
            return getVars().GetEnumerator();
        }

        private IEnumerable<KeyValuePair<string,TObject>> getVars()
        {
            foreach(var v in parent)
            {
                yield return v;
            }
            foreach(var item in items)
            {
                yield return item;
            }
        }

        public TObject GetVariable(string name)
        {
            if(name == "last_ittr" && items.ContainsKey("last_ittr"))
            {
                return items["last_ittr"];
            }
            if(parent.VariableExists(name))
            {
                return parent[name];
            }
            if(items.ContainsKey(name))
            {
                return items[name];
            }
            return TObject.Uninit;
        }

        public void SetVariable(string name, TObject obj)
        {
            if(parent.VariableExists(name) && name != "last_ittr")
            {
                
                parent.SetVariable(name,obj);
            }else if(items.ContainsKey(name))
            {
                items[name] = obj;
            }else{
                items.Add(name,obj);
            }
        }

        public bool VariableExists(string name)
        {
            if(parent.VariableExists(name)) return true;
            return items.ContainsKey(name);
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return getVars().GetEnumerator();
        }
    }
    public class RootEnvironment : IScopeEnvironment
    {
        Dictionary<string,TObject> items = new Dictionary<string, TObject>();

        public IScopeEnvironment SubEnv => new SubEnvironment(this,this);

        public IScopeEnvironment RootEnv => this;

        public IEnumerator<KeyValuePair<string, TObject>> GetEnumerator()
        {
            return items.GetEnumerator();
        }

        public TObject GetVariable(string name)
        {
            if(items.ContainsKey(name))
            {
                return items[name];
            }else{
                return TObject.Uninit;
            }
        }

        public void SetVariable(string name, TObject obj)
        {
            if(items.ContainsKey(name))
            {
                items[name] = obj;
            }
            else
            {
                items.Add(name,obj);
            }
        }

        public bool VariableExists(string name)
        {
            return items.ContainsKey(name);
        }

        IEnumerator IEnumerable.GetEnumerator()
        {
            return items.GetEnumerator();
        }
        public TObject this[string variable] { get => GetVariable(variable); set => SetVariable(variable,value); }

    }

}