[feature]: ADSR (#15)

closes #14

Reviewed-on: #15

src/ADSR.cpp

@@ -0,0 +1,97 @@
+#include "ADSR.h"
+#include "Logger.h"
+#include "Settings.h"
+
+ADSR::ADSR(/* args */) {
+    m_parameters.attack_time = 1.f;
+    m_parameters.decay_time = 0.4f;
+    m_parameters.sustain_level = 0.6f;
+    m_parameters.release_time = 0.8f;
+    m_ramp = new Ramp(0, SAMPLE_RATE);
+}
+
+ADSR::ADSR(ADSRParameters param) { m_parameters = param; }
+
+ADSR::~ADSR() { delete m_ramp; }
+
+bool ADSR::is_attack_elapsed() {
+    return m_state == Attack && m_ramp->IsCompleted();
+}
+
+bool ADSR::is_decay_elapsed() {
+    return m_state == Decay && m_ramp->IsCompleted();
+}
+
+bool ADSR::is_release_elapsed() {
+    return m_state == Release && m_ramp->IsCompleted();
+}
+
+void ADSR::recheck_state() {
+    switch (m_state) {
+        case Attack:
+            if (is_attack_elapsed()) {
+                m_state = Decay;
+                m_ramp->RampTo(m_parameters.sustain_level,
+                               m_parameters.decay_time);
+            }
+            break;
+        case Decay:
+            if (is_decay_elapsed()) {
+                m_state = Sustain;
+            }
+            break;
+        case Release:
+            if (is_release_elapsed()) {
+                m_state = Off;
+            }
+            break;
+        default:
+            break;
+    }
+}
+
+void ADSR::process_sample(float* sample) {
+    if (m_state == Off) {
+        (*sample) = 0;
+    } else if (m_state == Attack) {
+        (*sample) = (*sample) * m_ramp->Process();
+    } else if (m_state == Decay) {
+        (*sample) = (*sample) * m_ramp->Process();
+    } else if (m_state == Sustain) {
+        (*sample) = (*sample) * m_parameters.sustain_level;
+    } else if (m_state == Release) {
+        (*sample) = (*sample) * m_ramp->Process();
+    }
+}
+
+void ADSR::OnSetNote() {
+    write_log("Set ADSR\n");
+    if (m_state == Off) {
+        m_state = Attack;
+    } else if (m_state == Release) {
+        m_state = Attack;
+    };
+
+    m_ramp->RampTo(1, m_parameters.attack_time);
+}
+
+void ADSR::OnUnsetNote() {
+    write_log("Unset ADSR\n");
+    m_state = Release;
+    m_ramp->RampTo(0, m_parameters.release_time);
+}
+
+void ADSR::Process(std::vector<float>& samples) {
+    for (std::size_t i = 0; i < samples.size(); i++) {
+        recheck_state();
+        process_sample(&samples[i]);
+    }
+}
+
+void ADSR::SetParameters(float attack, float decay, float sustain,
+                         float release) {
+    m_parameters.attack_time = attack;
+    m_parameters.decay_time = decay;
+    m_parameters.sustain_level = sustain;
+    m_parameters.release_time = release;
+}