From e24192fb26a41cdb8c712a12ef2ae41dcfd246d3 Mon Sep 17 00:00:00 2001
From: Alessandro Proto <me@alexdevs.me>
Date: Mon, 13 Feb 2023 22:36:30 +0100
Subject: [PATCH] Add support for other audio waveforms

---
 Capy64/Assets/bios.lua            |  2 +-
 Capy64/Core/Audio.cs              | 54 +++++++++++++++++++++++++++++++
 Capy64/Runtime/Libraries/Audio.cs | 26 ++++++++++++---
 3 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/Capy64/Assets/bios.lua b/Capy64/Assets/bios.lua
index 14b57e3..198e4d9 100644
--- a/Capy64/Assets/bios.lua
+++ b/Capy64/Assets/bios.lua
@@ -241,7 +241,7 @@ local function bootScreen()
 	end
 end
 
-audio.beep(1000, 0.4, 0.2)
+audio.beep(1000, 0.4, 0.2, "square")
 
 if shouldInstallOS() then
 	installOS()
diff --git a/Capy64/Core/Audio.cs b/Capy64/Core/Audio.cs
index a097d62..3a2eb19 100644
--- a/Capy64/Core/Audio.cs
+++ b/Capy64/Core/Audio.cs
@@ -4,6 +4,7 @@ using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
+using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
 
@@ -14,8 +15,11 @@ public class Audio : IDisposable
     public const int SampleRate = 48000;
     public const AudioChannels Channels = AudioChannels.Mono;
     public readonly DynamicSoundEffectInstance Sound;
+
+    private static readonly Random rng = new();
     public Audio()
     {
+        GenerateSawtoothWave(440, 1);
         Sound = new DynamicSoundEffectInstance(SampleRate, Channels);
     }
 
@@ -59,6 +63,56 @@ public class Audio : IDisposable
         return buffer;
     }
 
+    public static byte[] GenerateTriangleWave(double frequency, double time, double volume = 1d)
+    {
+        var amplitude = 128 * volume;
+        var timeStep = 1d / SampleRate;
+        frequency /= 2;
+
+        var buffer = new byte[(int)(SampleRate * time)];
+        var ctime = 0d;
+        for (int i = 0; i < buffer.Length; i++)
+        {
+            var st = ctime * frequency - Math.Floor(ctime * frequency + 0.5);
+            var x = Math.Abs(st) * 2.0f - 1.0f;
+            buffer[i] = (byte)(amplitude * x);
+            ctime += timeStep;
+        }
+        return buffer;
+    }
+
+    public static byte[] GenerateSawtoothWave(double frequency, double time, double volume = 1d)
+    {
+        var amplitude = 128 * volume;
+        var timeStep = 1d / SampleRate;
+        frequency /= 2;
+
+        var buffer = new byte[(int)(SampleRate * time)];
+        var ctime = 0d;
+        for (int i = 0; i < buffer.Length; i++)
+        {
+            var x = ctime * frequency - Math.Floor(ctime * frequency + 0.5);
+            buffer[i] = (byte)(amplitude * x);
+            ctime += timeStep;
+        }
+        return buffer;
+    }
+
+    public static byte[] GenerateNoiseWave(double time, double volume = 1d)
+    {
+        var amplitude = 128 * volume;
+        var timeStep = 1d / SampleRate;
+
+        var buffer = new byte[(int)(SampleRate * time)];
+        var ctime = 0d;
+        for (int i = 0; i < buffer.Length; i++)
+        {
+            buffer[i] = (byte)rng.Next(0, (int)amplitude);
+            ctime += timeStep;
+        }
+        return buffer;
+    }
+
     public void Dispose()
     {
         GC.SuppressFinalize(this);
diff --git a/Capy64/Runtime/Libraries/Audio.cs b/Capy64/Runtime/Libraries/Audio.cs
index d64d30e..f19cff0 100644
--- a/Capy64/Runtime/Libraries/Audio.cs
+++ b/Capy64/Runtime/Libraries/Audio.cs
@@ -139,15 +139,31 @@ public class Audio : IPlugin
     {
         var L = Lua.FromIntPtr(state);
 
-        var freq = L.CheckNumber(1);
+        var freq = L.OptNumber(1, 440);
         var time = L.OptNumber(2, 1);
         var volume = L.OptNumber(3, 1);
-
-
-
         volume = Math.Clamp(volume, 0, 1);
 
-        var buffer = Core.Audio.GenerateSquareWave(freq, time, volume);
+        var form = L.CheckOption(4, "sine", new string[]
+        {
+            "sine",
+            "square",
+            "triangle",
+            "sawtooth",
+            "noise",
+            null,
+        });
+
+
+        var buffer = form switch
+        {
+            0 => Core.Audio.GenerateSineWave(freq, time, volume),
+            1 => Core.Audio.GenerateSquareWave(freq, time, volume),
+            2 => Core.Audio.GenerateTriangleWave(freq, time, volume),
+            3 => Core.Audio.GenerateSawtoothWave(freq, time, volume),
+            4 => Core.Audio.GenerateNoiseWave(time, volume),
+            _ => throw new NotImplementedException()
+        };
 
         try
         {