From af484658565920005a502553422530493a5d91de Mon Sep 17 00:00:00 2001
From: Jacob Lee <jacob@unabridgedsoftware.com>
Date: Wed, 24 Nov 2021 23:32:31 -0500
Subject: Refactor envelope to use line iterator

---
 klangfarbrs/src/envelope.rs | 88 +++++++++------------------------------------
 1 file changed, 16 insertions(+), 72 deletions(-)

(limited to 'klangfarbrs/src/envelope.rs')

diff --git a/klangfarbrs/src/envelope.rs b/klangfarbrs/src/envelope.rs
index 3da7977..ce3071d 100644
--- a/klangfarbrs/src/envelope.rs
+++ b/klangfarbrs/src/envelope.rs
@@ -1,25 +1,20 @@
-use super::{Millisecond, Amplitude, SamplesPerSecond};
+use super::{Millisecond, Amplitude, SamplesPerSecond, Line};
 
 pub struct Envelope {
-    pub attack: Vec<Amplitude>,
-    pub decay: Vec<Amplitude>,
-    pub release: Vec<Amplitude>,
-    pub index: usize,
+    pub attack: Line,
+    pub decay: Line,
+    pub release: Line,
 }
 
 impl Envelope {
     pub fn new(
         attack: Millisecond, decay: Millisecond, sustain: Amplitude, release: Millisecond, sample_rate: SamplesPerSecond
     ) -> Self {
-        let attack = interpolate(0.0, 1.0, ms_to_samples(attack, sample_rate));
-        let decay = interpolate(1.0, sustain, ms_to_samples(decay, sample_rate));
-        let release = interpolate(sustain, 0.0, ms_to_samples(release, sample_rate));
+        let attack = Line::new(0.0, 1.0, attack, sample_rate);
+        let decay = Line::new(1.0, sustain, decay, sample_rate);
+        let release = Line::new(sustain, 0.0, release, sample_rate);
 
-        Self { attack, decay, release, index: 0 }
-    }
-
-    pub fn len(&self) -> usize {
-        self.attack.len() + self.decay.len() + self.release.len()
+        Self { attack, decay, release }
     }
 }
 
@@ -27,67 +22,16 @@ impl Iterator for Envelope {
     type Item = Amplitude;
 
     fn next(&mut self) -> Option<Self::Item> {
-        let idx = self.index;
-        let atk = self.attack.len();
-        let atkdcy = atk + self.decay.len();
-
-        self.index += 1;
-
-        if idx < self.len() {
-            let val = if idx < atk {
-                self.attack[idx]
-            } else if idx >= atk && idx < atkdcy  {
-                self.decay[idx - atk]
+        let mut val = self.attack.next();
+        if val.is_none() {
+            val = self.decay.next();
+            if val.is_none() {
+                self.release.next()
             } else {
-                self.release[idx - atkdcy]
-            };
-
-            Some(val)
-        } else {
-            None
-        }
-    }
-}
-
-fn interpolate(start: Amplitude, end: Amplitude, milliseconds: Millisecond) -> Vec<Amplitude> {
-    let step_size = (end - start) / milliseconds as f32;
-    let mut amps = vec!();
-    let mut current_val = start + step_size;
-
-    for i in 0..=milliseconds {
-        if i == 0 {
-            amps.push(start)
-        } else if i == milliseconds {
-            amps.push(end)
+                val
+            }
         } else {
-            amps.push(current_val);
-            current_val += step_size;
+            val
         }
     }
-
-    amps
-}
-
-fn ms_to_samples(ms: Millisecond, sample_rate: SamplesPerSecond) -> u32 {
-    let multiplier = sample_rate as u32 / 1000;
-    multiplier * ms
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn it_has_expected_total_length() {
-        let expected = 3 + ms_to_samples(30, 48000.0) as usize;
-        let total = Envelope::new(10, 10, 1.0, 10, 48000.0).len();
-        assert_eq! (expected, total)
-    }
-
-    #[test]
-    fn interpolate_works() {
-        let expected = vec![0.0, 0.2, 0.4, 0.6, 0.8, 1.0];
-        let result = interpolate(0.0, 1.0, 5);
-        assert_eq!(expected, result)
-    }
 }
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