using System;
using System.Runtime.InteropServices.JavaScript;
using System.Threading.Tasks;

namespace Susurrus.WebAudio
{
    /// <summary>
    /// The thin layer between C# and the browser's Web Audio API, mirroring Susurrus.WebAudio.js.
    /// </summary>
    public static partial class WebAudioInterop
    {
        private static Task loadTask;

        /// <summary>
        /// Must be awaited once, from the browser host's own startup code, before any other member of this class or of
        /// <see cref="WebAudioModule"/> is used.  JSHost.ImportAsync can't be awaited synchronously, since nothing can
        /// pump the browser's microtask queue while the single WASM thread is blocked on it.
        /// </summary>
        public static Task EnsureLoadedAsync()
        {
            return loadTask ??= JSHost.ImportAsync("susurrus-webaudio", "../Susurrus.WebAudio.js");
        }

        [JSImport("isAvailable", "susurrus-webaudio")]
        public static partial bool IsAvailable();

        [JSImport("newAudioContext", "susurrus-webaudio")]
        public static partial JSObject NewAudioContext();

        [JSImport("create", "susurrus-webaudio")]
        public static partial JSObject Create(JSObject context, int voiceCount, bool limit);

        [JSImport("setLimiterEnabled", "susurrus-webaudio")]
        public static partial void SetLimiterEnabled(JSObject engine, bool enabled);

        [JSImport("isRunning", "susurrus-webaudio")]
        public static partial bool IsRunning(JSObject engine);

        [JSImport("destroy", "susurrus-webaudio")]
        public static partial void Destroy(JSObject engine, bool closeContext);

        [JSImport("decode", "susurrus-webaudio")]
        [return: JSMarshalAs<JSType.Promise<JSType.Object>>]
        public static partial Task<JSObject> Decode(JSObject engine, byte[] encoded);

        [JSImport("makeBuffer", "susurrus-webaudio")]
        public static partial JSObject MakeBuffer(
            JSObject engine, byte[] samples, int sampleRate, int channelCount, bool isFloat);

        [JSImport("getDuration", "susurrus-webaudio")]
        public static partial double GetDuration(JSObject buffer);

        [JSImport("getChannelCount", "susurrus-webaudio")]
        public static partial int GetChannelCount(JSObject buffer);

        [JSImport("play", "susurrus-webaudio")]
        public static partial void Play(JSObject engine, int slot, JSObject buffer, double volume, double pitch,
            double pan, bool loop, double loopStart, double loopEnd);

        [JSImport("streamStart", "susurrus-webaudio")]
        public static partial void StreamStart(JSObject engine, int slot, double volume, double pitch, double pan);

        [JSImport("streamQueue", "susurrus-webaudio")]
        public static partial void StreamQueue(JSObject engine, int slot, byte[] samples, int byteCount,
            int sampleRate, int channelCount, bool isFloat);

        [JSImport("streamQueued", "susurrus-webaudio")]
        public static partial int StreamQueued(JSObject engine, int slot);

        [JSImport("streamEnd", "susurrus-webaudio")]
        public static partial void StreamEnd(JSObject engine, int slot);

        [JSImport("stop", "susurrus-webaudio")]
        public static partial void Stop(JSObject engine, int slot);

        [JSImport("setVolume", "susurrus-webaudio")]
        public static partial void SetVolume(JSObject engine, int slot, double volume);

        [JSImport("setPitch", "susurrus-webaudio")]
        public static partial void SetPitch(JSObject engine, int slot, double pitch);

        [JSImport("setPan", "susurrus-webaudio")]
        public static partial void SetPan(JSObject engine, int slot, double pan);

        [JSImport("setPaused", "susurrus-webaudio")]
        public static partial void SetPaused(JSObject engine, int slot, bool paused);

        [JSImport("takeEnded", "susurrus-webaudio")]
        public static partial int TakeEnded(JSObject engine, int word);
    }
}