using System.Runtime.InteropServices;

namespace Susurrus.XAudio2
{
    /// <summary>
    /// The WAVEFORMATEX that tells XAudio2 what a source voice's samples look like.
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct WaveFormatEx
    {
        public const ushort PcmTag = 1;
        public const ushort FloatTag = 3;

        public ushort FormatTag;
        public ushort Channels;
        public uint SamplesPerSecond;
        public uint AverageBytesPerSecond;
        public ushort BlockAlign;
        public ushort BitsPerSample;
        public ushort ExtraSize;

        /// <summary>
        /// Returns the format of interleaved samples of <paramref name="format"/>.
        /// </summary>
        public static WaveFormatEx Of(SampleFormat format, int channelCount, int sampleRate)
        {
            int bytesPerSample = DecodedSound.GetBytesPerSample(format);
            WaveFormatEx returnMe = new WaveFormatEx();
            returnMe.FormatTag = format == SampleFormat.Float32 ? FloatTag : PcmTag;
            returnMe.Channels = (ushort)channelCount;
            returnMe.SamplesPerSecond = (uint)sampleRate;
            returnMe.BlockAlign = (ushort)(bytesPerSample * channelCount);
            returnMe.AverageBytesPerSecond = (uint)(returnMe.BlockAlign * sampleRate);
            returnMe.BitsPerSample = (ushort)(bytesPerSample * 8);
            returnMe.ExtraSize = 0;
            return returnMe;
        }
    }
}