BakaMusicPlayer/Bmp.Core/FFMpeg/CsCorePorts/TimeConverterFactory.cs

namespace Bmp.Core.FFMpeg.CsCorePorts;

/// <summary>
/// Provides <see cref="TimeConverter"/>s for converting raw time values (e.g. bytes, samples,...) to a <see cref="TimeSpan"/> and back.
/// </summary>
public sealed class TimeConverterFactory
{
    // ReSharper disable once InconsistentNaming
    private readonly static TimeConverterFactory _instance = new TimeConverterFactory();

    /// <summary>
    /// Gets the default instance of the factory.
    /// </summary>
    public static TimeConverterFactory Instance
    {
        get { return _instance; }
    }

    private readonly Dictionary<Type, TimeConverter> _timeConverters;
    private readonly Dictionary<Type, CacheItem> _cache;

    private TimeConverterFactory()
    {
        _timeConverters = new Dictionary<Type, TimeConverter>();
        _cache = new Dictionary<Type, CacheItem>();

        RegisterTimeConverterForSourceType<IWaveSource>(TimeConverter.WaveSourceTimeConverter);
        RegisterTimeConverterForSourceType<ISampleSource>(TimeConverter.SampleSourceTimeConverter);
    }

    /// <summary>
    /// Registers a new <see cref="TimeConverter"/> for a specific source type.
    /// </summary>
    /// <param name="timeConverter">The <see cref="TimeConverter"/> to register.</param>
    /// <typeparam name="TSource">The source type.</typeparam>
    /// <exception cref="ArgumentNullException">timeConverter is null.</exception>
    /// <exception cref="ArgumentException">There is already a <see cref="TimeConverter"/> registered for the specified <typeparamref name="TSource"/>.</exception>
    /// <remarks>The <see cref="TimeConverterFactory"/> class uses the source type to find choose the best <see cref="TimeConverter"/> for an <see cref="IAudioSource"/>. For more information, see <see cref="GetTimeConverterForSourceType"/>.</remarks>
    public void RegisterTimeConverterForSourceType<TSource>(TimeConverter timeConverter)
        where TSource : IAudioSource
    {
        if (timeConverter == null)
            throw new ArgumentNullException("timeConverter");

        var type = typeof(TSource);
        if (_timeConverters.ContainsKey(type))
            throw new ArgumentException("A timeconverter for the same source type got already registered.");

        _timeConverters.Add(type, timeConverter);
    }

    /// <summary>
    /// Unregisters a previously registered <see cref="TimeConverter"/>.
    /// </summary>
    /// <typeparam name="TSource">The source type, that got passed to the <see cref="RegisterTimeConverterForSourceType{TSource}"/> method previously.</typeparam>
    /// <exception cref="ArgumentException">The specified source type could not be found.</exception>
    public void UnregisterTimeConverter<TSource>()
        where TSource : IAudioSource
    {
        var type = typeof(TSource);
        if (!_timeConverters.ContainsKey(type))
            throw new ArgumentException("There is no timeconverter registered for the specified source type.");

        _timeConverters.Remove(type);
    }

    /// <summary>
    /// Gets the <see cref="TimeConverter"/> for the specified <paramref name="source"/>.
    /// </summary>
    /// <param name="source">The <see cref="IAudioSource"/> object to get the <see cref="TimeConverter"/> for.</param>
    /// <typeparam name="TSource">The type of the <paramref name="source"/>.</typeparam>
    /// <returns>The best <see cref="TimeConverter"/> for the specified <paramref name="source"/>.</returns>
    /// <exception cref="ArgumentNullException">The specified <paramref name="source"/> is null.</exception>
    /// <exception cref="ArgumentException">
    /// Specified type is no AudioSource.;type
    /// or
    /// No registered time converter for the specified source type was found.
    /// or
    /// Multiple possible time converters, for the specified source type, were found. Specify which time converter to use, through the <see cref="TimeConverterAttribute"/>.
    /// </exception>
    /// <remarks>
    /// The <see cref="GetTimeConverterForSource{TSource}(TSource)"/> chooses the best <see cref="TimeConverter"/> for the specified <paramref name="source"/>.
    /// If there is no <see cref="TimeConverterAttribute"/> applied to the <see cref="IAudioSource"/> object (the <paramref name="source"/>), it looks up the inheritance hierarchy (interfaces included) of the <see cref="IAudioSource"/> object
    /// and searches for all registered source types. If there is a match it returns the associated <see cref="TimeConverter"/>. If there are more or less than one match BUT no <see cref="TimeConverterAttribute"/>
    /// it throws an exception.</remarks>
    public TimeConverter GetTimeConverterForSource<TSource>(TSource source) where TSource : class, IAudioSource
    {
        if (source == null)
            throw new ArgumentNullException("source");

        return GetTimeConverterForSourceType(source.GetType());
    }

    /// <summary>
    /// Gets the <see cref="TimeConverter"/> for the specified source type.
    /// </summary>
    /// <typeparam name="TSource">The type of the source.</typeparam>
    /// <returns>The best <see cref="TimeConverter"/> for the specified source type.</returns>
    /// <exception cref="ArgumentException">
    /// Specified type is no AudioSource.;type
    /// or
    /// No registered time converter for the specified source type was found.
    /// or
    /// Multiple possible time converters, for the specified source type, were found. Specify which time converter to use, through the <see cref="TimeConverterAttribute"/>.
    /// </exception>
    /// <remarks>
    /// The <see cref="GetTimeConverterForSource{TSource}()"/> chooses the best <see cref="TimeConverter"/> for the specified source type.
    /// If there is no <see cref="TimeConverterAttribute"/> applied to the <see cref="IAudioSource"/> object, it looks up the inheritance hierarchy (interfaces included) of the <see cref="IAudioSource"/> object
    /// and searches for all registered source types. If there is a match it returns the associated <see cref="TimeConverter"/>. If there are more or less than one match BUT no <see cref="TimeConverterAttribute"/>
    /// it throws an exception.</remarks>
    public TimeConverter GetTimeConverterForSource<TSource>()
        where TSource : IAudioSource
    {
        return GetTimeConverterForSourceType(typeof(TSource));
    }

    /// <summary>
    /// Gets the <see cref="TimeConverter"/> for the specified <paramref name="sourceType"/>.
    /// </summary>
    /// <param name="sourceType">The <see cref="Type"/> to get the associated <see cref="TimeConverter"/> for.</param>
    /// <returns>The best <see cref="TimeConverter"/> for the specified <paramref name="sourceType"/>.</returns>
    /// <exception cref="ArgumentException">
    /// Specified type is no AudioSource.;type
    /// or
    /// No registered time converter for the specified source type was found.
    /// or
    /// Multiple possible time converters, for the specified source type, were found. Specify which time converter to use, through the <see cref="TimeConverterAttribute"/>.
    /// </exception>
    /// <remarks>
    /// The <see cref="GetTimeConverterForSourceType(Type)"/> chooses the best <see cref="TimeConverter"/> for the specified <paramref name="sourceType"/>.
    /// If there is no <see cref="TimeConverterAttribute"/> applied to the <see cref="IAudioSource"/> object (the <paramref name="sourceType"/>), it looks up the inheritance hierarchy (interfaces included) of the <see cref="IAudioSource"/> object
    /// and searches for all registered source types. If there is a match it returns the associated <see cref="TimeConverter"/>. If there are more or less than one match BUT no <see cref="TimeConverterAttribute"/>
    /// it throws an exception.</remarks>
    public TimeConverter GetTimeConverterForSourceType(Type sourceType)
    {
        if (sourceType == null)
            throw new ArgumentNullException("sourceType");

        if (!typeof(IAudioSource).IsAssignableFrom(sourceType))
            throw new ArgumentException("Specified type is no AudioSource.", "sourceType");

        //we may got it already in the cache
        if (_cache.ContainsKey(sourceType))
            return _cache[sourceType].GetTimeConverter();

        //nope, there is nothing in the cache

        //search for a TimeConverterAttribute
        var attribute =
            sourceType.GetCustomAttributes(typeof(TimeConverterAttribute), false).FirstOrDefault() as
                TimeConverterAttribute;

        TimeConverter timeConverter = null;
        try
        {
            if (attribute == null)
            {
                //there is no attribute
                //search for base types
                var baseTypes = GetTypes(sourceType).Where(x => _timeConverters.ContainsKey(x)).ToArray();
                //we've got a match
                if (baseTypes.Length == 1)
                {
                    timeConverter = _timeConverters[baseTypes.First()];
                    return timeConverter;
                }
                //we've got no match
                if (baseTypes.Length == 0)
                    throw new ArgumentException(
                        "No registered time converter for the specified source type was found.");
                //else baseTypes.Length > 1    
                throw new ArgumentException(
                    "Multiple possible time converters, for the specified source type, were found. Specify which time converter to use, through the TimeConverterAttribute.");
            }

            var timeConverterType = attribute.TimeConverterType;
            timeConverter = (TimeConverter)Activator.CreateInstance(timeConverterType, attribute.Args);

            return timeConverter;
        }
        finally
        {
            //add the result to the cache
            if (timeConverter != null)
            {
                CacheItem cacheItem;
                if (attribute == null)
                    cacheItem = new CacheItem { CreateNewInstance = false, TimeConverter = timeConverter };
                else
                    cacheItem = new CacheItem
                    {
                        CreateNewInstance = attribute.ForceNewInstance,
                        TimeConverterAttribute = attribute,
                        TimeConverter = attribute.ForceNewInstance ? null : timeConverter
                    };

                _cache[sourceType] = cacheItem;
            }
        }
    }

    /// <summary>
    /// Clears the internal cache.
    /// </summary>
    public void ClearCache()
    {
        _cache.Clear();
    }

    private IEnumerable<Type> GetTypes(Type type)
    {
        //copied from dadhi see http://stackoverflow.com/questions/1823655/given-a-c-sharp-type-get-its-base-classes-and-implemented-interfaces
        return type.BaseType == typeof(object)
            ? type.GetInterfaces()
            : Enumerable
                .Repeat(type.BaseType, 1)
                .Concat(type.GetInterfaces())
                .Concat(GetTypes(type.BaseType))
                .Distinct();
    }

    private class CacheItem
    {
        public TimeConverter TimeConverter { get; set; }

        public TimeConverterAttribute TimeConverterAttribute { get; set; }

        public bool CreateNewInstance { get; set; }

        public TimeConverter GetTimeConverter()
        {
            if (CreateNewInstance)
                return (TimeConverter)Activator.CreateInstance(TimeConverterAttribute.TimeConverterType, TimeConverterAttribute.Args);
            return TimeConverter;
        }
    }
}