using System;
using System.Collections.Generic;
using System.Linq;
using Implab.Automaton;
using Implab.Automaton.RegularExpressions;

namespace Implab.Formats {
    /// <summary>
    /// Базовый абстрактный класс. Грамматика, позволяет формулировать выражения над алфавитом типа <c>char</c>.
    /// </summary>
    public abstract class Grammar<TSymbol> {
        
        protected abstract IAlphabetBuilder<TSymbol> AlphabetBuilder {
            get;
        }

        protected SymbolToken UnclassifiedToken() {
            return new SymbolToken(AutomatonConst.UnclassifiedInput);
        }

        protected void DefineAlphabet(IEnumerable<TSymbol> alphabet) {
            Safe.ArgumentNotNull(alphabet, "alphabet");

            foreach (var ch in alphabet)
                AlphabetBuilder.DefineSymbol(ch);
        }

        protected Token SymbolToken(TSymbol symbol) {
            return Token.New(TranslateOrAdd(symbol));
        }

        protected Token SymbolToken(IEnumerable<TSymbol> symbols) {
            Safe.ArgumentNotNull(symbols, "symbols");

            return Token.New(TranslateOrAdd(symbols).ToArray());
        }

        protected Token SymbolSetToken(params TSymbol[] set) {
            return SymbolToken(set);
        }

        int TranslateOrAdd(TSymbol ch) {
            var t = AlphabetBuilder.Translate(ch);
            if (t == AutomatonConst.UnclassifiedInput)
                t = AlphabetBuilder.DefineSymbol(ch);
            return t;
        }

        IEnumerable<int> TranslateOrAdd(IEnumerable<TSymbol> symbols) {
            return symbols.Distinct().Select(TranslateOrAdd);
        }

        int TranslateOrDie(TSymbol ch) {
            var t = AlphabetBuilder.Translate(ch);
            if (t == AutomatonConst.UnclassifiedInput)
                    throw new ApplicationException(String.Format("Symbol '{0}' is UNCLASSIFIED", ch));
            return t;
        }

        IEnumerable<int> TranslateOrDie(IEnumerable<TSymbol> symbols) {
            return symbols.Distinct().Select(TranslateOrDie);
        }

        protected Token SymbolTokenExcept(IEnumerable<TSymbol> symbols) {
            Safe.ArgumentNotNull(symbols, "symbols");

            return Token.New( Enumerable.Range(0, AlphabetBuilder.Count).Except(TranslateOrDie(symbols)).ToArray() );
        }
    }


}