using System;
using System.Collections.Generic;
using System.Text;

namespace StgSharp.Script.Express
{
    public class ExpSwitchToken : ExpToken
    {
        private ExpToken _target;
        private List<ExpToken> _default;
        private Dictionary<ExpToken, List<ExpToken>> _cases;

        public List<ExpToken> this[ExpToken index]
        {
            get
            {
                if (_cases.TryGetValue(index, out var ret))
                {
                    return ret;
                }
                return _default;
            }
        }

        public ExpSwitchToken(string name, ExpSchema context,
            ExpToken target, IEnumerable<ExpToken> @default ,
            params (ExpToken label, IEnumerable<ExpToken> op)[] cases
            ) : base(name, context)
        {
            _target = target;
            if (@default == null)
            {
                _default = new List<ExpToken>();
            }
            else
            {
                _default = new List<ExpToken>(@default);
            }
            _cases = new Dictionary<ExpToken, List<ExpToken>>();
            foreach (var item in cases)
            {
                if (item.op == null)
                {
                    _cases.Add(item.label, new List<ExpToken>());
                }
                else
                {
                    _cases.Add(item.label, new List<ExpToken>(item.op));
                }
            }
        }

        public bool ContainsCase(ExpToken token)
        {
            return _cases.ContainsKey(token);
        }

        /// <summary>
        /// Adds an expression to certain <see langword="case"/>.
        /// The added expression will be run at last.
        /// </summary>
        /// <param name="label">Label of case to add operation</param>
        /// <param name="expressionRoot">Root token of the expression to be added.</param>
        /// <exception cref="ExpCaseNotFoundException">Cannot fine the case label in current witch expression.</exception>
        public void AddOperationToCase(ExpToken label, ExpToken expressionRoot)
        {
            AssertSchemaInclude(expressionRoot);
            if (_cases.TryGetValue(label,out var op))
            {
                op.Add(expressionRoot);
            }
            else
            {
                throw new ExpCaseNotFoundException(this, label);
            }
        }

        public void AddOperationToDefault(ExpToken expressionRoot)
        {
            if (expressionRoot != null)
            {
                _default.Add(expressionRoot);
            }
        }
    }
}