using Implab;
using System;
using System.Linq;

namespace Implab.Automaton.RegularExpressions {
    public abstract class Token<TTag> {
        public abstract void Accept(IVisitor<TTag> visitor);

        public Token<TTag> Extend() {
            return Cat(new EndToken<TTag>());
        }

        public Token<TTag> Tag<T>(T tag) where T : IConvertible {
            return Cat(new EndToken<TTag>(tag));
        }

        public Token<TTag> Cat(Token<TTag> right) {
            return new CatToken<TTag>(this, right);
        }

        public Token<TTag> Or(Token<TTag> right) {
            return new AltToken<TTag>(this, right);
        }

        public Token<TTag> Optional() {
            return Or(new EmptyToken<TTag>());
        }

        public Token<TTag> EClosure() {
            return new StarToken<TTag>(this);
        }

        public Token<TTag> Closure() {
            return Cat(new StarToken<TTag>(this));
        }

        public Token<TTag> Repeat(int count) {
            Token<TTag> token = null;

            for (int i = 0; i < count; i++)
                token = token != null ? token.Cat(this) : this;
            return token ?? new EmptyToken<TTag>();
        }

        public Token<TTag> Repeat(int min, int max) {
            if (min > max || min < 1)
                throw new ArgumentOutOfRangeException();
            var token = Repeat(min);

            for (int i = min; i < max; i++)
                token = token.Cat( this.Optional() );
            return token;
        }

        public static Token<TTag> New<T>(params T[] set) where T : struct, IConvertible {
            Safe.ArgumentNotNull(set, "set");
            Token<TTag> token = null;
            foreach(var c in set.Distinct())
                token = token == null ? new SymbolToken<TTag>(c) : token.Or(new SymbolToken<TTag>(c));
            return token;
        }
    }
}