using System;
using System.Collections.Generic;
using System.IO;
using Vellum;

namespace Clave.Vellum
{
    /// <summary>
    /// Saves a Chord as its formula.
    /// </summary>
    public sealed class ChordConverter : SaveConverter<Chord>
    {
        public override SaveNode Write(Chord value, SaveSession session)
        {
            return KeyFormulaConverter.ToTermsNode(value.Formula);
        }

        public override Chord Read(SaveNode node, SaveSession session)
        {
            var formula = KeyFormulaConverter.FromTermsNode(node);
            try
            {
                return Chord.FromFormula(formula);
            }
            catch (ArgumentException exception)
            {
                throw new InvalidDataException("A saved chord matches nothing a keyboard could produce.", exception);
            }
        }

        public override bool TryListChildren(SaveNode node, ChildList children)
        {
            // Everything it reads is built-in, and so left out.
            IReadOnlyList<SaveNode> items;
            return node.TryGetItems(out items);
        }
    }
}