using Implab;
using System;
using System.Linq;

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

        public Token End() {
            return Cat(new EndToken());
        }

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

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

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

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

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

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

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

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

        public Token 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( Optional() );
            return token;
        }

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