continue popgen; plays music, not yet saving files

code/popgen/Cargo.toml

@@ -11,4 +11,5 @@ path = "src/popgen.rs"
 clap = { version = "4.5.23", features = ["derive"] }
 rand = "0.8.5"
 regex = "1.11.1"
+rodio = "0.20.1"
 

code/popgen/README.md

@@ -28,6 +28,26 @@ cargo run -- -b 80 --root C[2]
 [popgen.rs](./src/popgen.rs)
 
 ## Access outputs
-
+TODO
 
 ## Reflections, Results, Analysis
+The effort involved for this portfolio objective was non trivial. I'll briefy discuss a some of the techniques and challenges involved specific to this implementation in rust. For a "how it works" perspective, I feel the comments copied over from python source and my few additions allow the code to be self documenting
+
+### External Crates:
+* [clap](https://crates.io/crates/clap): In order to not drop any functionality from the original source, I wanted to ensure my application could handle all of the command-line argument as is done in popgen.py. I noticed there, [argparse](https://docs.python.org/3/library/argparse.html) was doing some heaving lifting. I only briefy pondered rolling my own command line parsing, but then I remembered a past experience doing so with much simpler arguments. That made using `clap` a straightforward decision.
+* [rand](https://crates.io/crates/rand): Picking the sequence of notes requires some randomness
+* [regex](https://crates.io/crates/regex): The go-to for regex, validating and parsing the note from the command line arguments
+* [rodio](https://crates.io/crates/rodio): Back in a portfolio objective rodio, cpal, portaudio-rs. I did a little research, and it seemed that rodio was the most abstract/easy to use, but still allowed me to manually set the sample rate as is necessary
+
+### Typing hell
+The most tedious aspect of this objective was dealing with the typecasting needed for integer and float arithmetic. I won't discuss strong typing/rust arguments or any of that, but the crux of issues here came down to a few competing philosophies.
+* I want to use the smallest integer units possible to handle the basic parameters. For example, a `u8` should easily contain the `bpm`
+* Many parameters can be, and often are negative requiring the use of signed integers such as `melody_root`, `position`, etc. On one hand, I did not realize this in time, so some rework was required. On the other hand, there is a desire to capture initial values as unsigned if that seems appropriate, and cast them only as needed for signed arithmetic (Example: `chord_root` into `bass_note`).
+* I want to use the highest precision possible floating point representation for the wave data samples which go to the buffer, to ensure the most accurate audio. I initially chose `f64` for this before realizing that `rodio` seems to only work with `f32`. Aside from that, all sorts of casting was needed up from the base integer units.
+* Array indicies must be of type `usize`
+While the code here works it containers several occourences of risky `as` casting, and `.try_into().unwrap()` which are not properly handled. As I have time, I will fix some of this stuff up.
+
+### Testing:
+I brought in the provided unit tests for `note_to_key_offset` and `chord_to_note_offset`. These turned out to be rather useful for ensuring my functions of the same name worked correctly. I began adding some tests for `make_notes` and may do the same for other functional units. I could move the tests into another source file, but decided not to, as to better parallel the source material.
+
+### Results:

code/popgen/src/popgen.rs

@@ -1,6 +1,6 @@
 // "Pop Music Generator" - Rust Edition
 // David Westgate 2024
-// Initial python implementation (and most comments) from Bart Massey
+// Initial python implementation, tests and some comments from Bart Massey
 // https://github.com/pdx-cs-sound/popgen/blob/main/popgen.py
 
 use clap::Parser;
@@ -32,26 +32,85 @@ const CHORD_LOOP: [u8; 4] = [8, 5, 6, 4];
 // Given a MIDI key number and an optional number of beats of
 // note duration, return a sine wave for that note.
 fn make_note(key: i8, n: Option<u8>, beat_samples: u32, samplerate: u16) -> Vec<f32> {
-    todo!()
+    let num_beats: f32 = n.unwrap_or(1).try_into().unwrap();
+    let samplerate_f: f32 = samplerate.try_into().unwrap();
+    let beatsamples_f: f32 = beat_samples as f32;
+    let key_f: f32 = key.try_into().unwrap();
+    let f: f32 = 440f32 * (2f32).powf((key_f - 69f32) / 12f32);
+    let b: u32 = (beat_samples as u32) * (n.unwrap_or(1) as u32);
+    let b_f: f32 = beatsamples_f * num_beats;
+
+    let cycles: f32 = 2f32 * PI * f * b_f / samplerate_f;
+    (0..b)
+        .map(|v: u32| ((v as f32) / b_f * cycles).sin())
+        .collect::<Vec<f32>>()
 }
 
+// Floor division of possibly negative values (GPT generated)
+// Intended to match pythons // operator
+fn floor_div(a: i8, b: i8) -> i8 {
+    let div = a / b;
+    let rem = a % b;
 
+    if rem != 0 && (a < 0) != (b < 0) {
+        div - 1
+    } else {
+        div
+    }
+}
 
+// modulus of possibly negative value (GPT generated)
+fn safe_mod_index(value: i8, modulus: usize) -> usize {
+    assert!(modulus > 0, "Modulus must be positive");
+
+    // Compute the modulo
+    let remainder = value % modulus as i8;
+
+    // Adjust for negative remainders
+    let adjusted = if remainder < 0 {
+        remainder + modulus as i8
+    } else {
+        remainder
+    };
+
+    // Convert to usize
+    adjusted as usize
+}
 
 //  Given a scale note with root note 0, return a key offset
 //  from the corresponding root MIDI key.
 fn note_to_key_offset(note: i8) -> i8 {
-    todo!()
+    let scale_degree: usize = safe_mod_index(note, 7);
+    let major_scale = MAJOR_SCALE[scale_degree];
+    (floor_div(note, 7) * 12) + major_scale as i8
 }
 
 //  Given a position within a chord, return a scale note
 //  offset — zero-based.
 fn chord_to_note_offset(posn: i8) -> i8 {
-    todo!()
+    let chord_posn: usize = safe_mod_index(posn, 3);
+    let major_chord = MAJOR_CHORD[chord_posn];
+    floor_div(posn, 3) * 7 + (major_chord as i8) - 1
 }
 
 fn pick_notes(chord_root: u8, position: &mut i8, rng: &mut rand::prelude::ThreadRng) -> [i8; 4] {
-    todo!()
+    let mut notes: [i8; 4] = [0; 4]; //Vec would work too, but less memory efficient
+
+    let mut p: i8 = *position;
+
+    for note in &mut notes {
+        let chord_note_offset: i8 = chord_to_note_offset(p);
+        let chord_note: i8 = note_to_key_offset((chord_root as i8) + chord_note_offset);
+        *note = chord_note;
+        if rng.gen::<f32>() > 0.5 {
+            p = p + 1;
+        } else {
+            p = p - 1;
+        }
+    }
+
+    *position = p;
+    notes
 }
 
 //  Turn a note name into a corresponding MIDI key number.
@@ -59,7 +118,51 @@ fn pick_notes(chord_root: u8, position: &mut i8, rng: &mut rand::prelude::Thread
 //  "D" or "Eb[5]". Default is octave 4 if no octave is
 //  specified.
 fn parse_note(note_str: &str, regex: Regex) -> u32 {
-    todo!()
+    let mut octave: u32 = 4;
+    match regex.find(note_str) {
+        Some(_) => {}
+        None => {
+            eprintln!("Invalid Note: {}", note_str);
+            std::process::exit(1)
+        }
+    };
+    let chars: std::str::Chars<'_> = note_str.chars();
+    let mut it: std::str::Chars<'_> = chars.into_iter();
+    let base_note: char = it.next().unwrap();
+    let mut flat: bool = false;
+    match it.next() {
+        Some(c) => {
+            if c == 'b' {
+                flat = true;
+                match it.next() {
+                    Some(c) => {
+                        if c == '[' {
+                            octave = it.next().unwrap().to_digit(10).unwrap();
+                        } else {
+                            eprintln!("Invalid Notation: {}", note_str);
+                            std::process::exit(1)
+                        }
+                    }
+                    None => {}
+                }
+            } else if c == '[' {
+                octave = it.next().unwrap().to_digit(10).unwrap();
+            } else {
+                eprintln!("Invalid Notation: {}", note_str);
+                std::process::exit(1)
+            }
+        }
+        None => {}
+    }
+
+    let index: usize = match flat {
+        true => NAMES.iter().position(|&n| n == format!("{}b", base_note)),
+        false => NAMES.iter().position(|&n| n == base_note.to_string()),
+    }
+    .unwrap();
+    let index_32: u32 = index as u32;
+    let r: u32 = index_32 + (12 * octave);
+    return r;
 }
 
 #[derive(Parser, Debug)]
@@ -87,7 +190,20 @@ struct Args {
     output: String,
 }
 
+// Rodio example https://github.com/RustAudio/rodio/blob/master/examples/basic.rs
+fn play(samples: Vec<f32>) {
 
+    let (_stream, stream_handle) =  OutputStream::try_default().unwrap();
+    let source = SamplesBuffer::new(1,48_000, samples);
+
+    let sink = Sink::try_new(&stream_handle).unwrap();
+
+    sink.append(source);
+
+    sink.sleep_until_end();
+
+
+}
 
 fn main() {
     println!("Hello, pop!");
@@ -113,7 +229,139 @@ fn main() {
         .try_into()
         .unwrap();
 
+    // Samples per beat.
+    let beat_samples: u32 = ((samplerate as f32) / (f32::from(bpm) / 60f32)).round() as u32;
 
+    let mut sound: Vec<f32> = vec![];
 
+    for chord_root in CHORD_LOOP {
+        let notes = pick_notes(chord_root - 1, &mut position, &mut rng);
+
+        let mut melody: Vec<Vec<f32>> = vec![];
+        for note in notes {
+            let melody_note: Vec<f32> = make_note(note +melody_root_i8 , None, beat_samples, samplerate);
+            melody.push(melody_note);
         }
 
+        let bass_note: i8 = note_to_key_offset((chord_root - 1) as i8);
+        let bass: Vec<f32> = make_note(bass_note + bass_root, Some(4), beat_samples, samplerate);
+        let bass_gain = 1 - melody_gain;
+        
+        // Scale the waveforms
+        let flattened_melody: Vec<f32> = melody.into_iter().flatten().collect();
+        let scaled_melody: Vec<f32> = flattened_melody.iter().map(|&x| x * melody_gain as f32).collect();
+        let scaled_bass: Vec<f32> = bass.iter().map(|&x| x * bass_gain as f32).collect();
+
+        let paired_notes: Vec<(f32, f32)> = scaled_melody.iter().zip(scaled_bass.iter()).map(|(&m, &b)| (m, b)).collect();
+
+        let combined_waveform: Vec<f32> = paired_notes.iter().map(|(m, b)| m + b).collect();
+
+        sound.extend(combined_waveform);
+
+    }
+    if args.output.eq(NO_OUTPUT) {
+        play(sound);
+    }
+    else {
+        todo!()
+    }
+}
+
+#[test]
+fn test() {
+    let note_tests: [(i8, i8); 11] = [
+        (-9, -15),
+        (-8, -13),
+        (-7, -12),
+        (-6, -10),
+        (-2, -3),
+        (-1, -1),
+        (0, 0),
+        (6, 11),
+        (7, 12),
+        (8, 14),
+        (9, 16),
+    ];
+
+    for (n, k) in note_tests {
+        let k0 = note_to_key_offset(n);
+        assert!(
+            k0 == k,
+            "note_to_key_offset: for note {}, expected offet {}. Got offset {}",
+            n,
+            k,
+            k0
+        );
+    }
+
+    let chord_tests: [(i8, i8); 8] = [
+        (-3, -7),
+        (-2, -5),
+        (-1, -3),
+        (0, 0),
+        (1, 2),
+        (2, 4),
+        (3, 7),
+        (4, 9),
+    ];
+
+    for (n, c) in chord_tests {
+        let c0 = chord_to_note_offset(n);
+        assert!(
+            c0 == c,
+            "chord_to_note_offset: for chord posn {}, expected scale note {}. Got scale note {}",
+            n,
+            c,
+            c0
+        )
+    }
+
+    // Random selction of notes to test parse
+    let parsed_notes_tests = [
+        ("Db", 49),
+        ("Db[4]", 49),
+        ("C", 48),
+        ("C[5]", 60),
+        ("A[1]", 21),
+        ("F[7]", 89),
+        ("Gb[3]", 42),
+        ("Gb", 54),
+        ("G[1]", 19),
+    ];
+    let note_name_regexp: Regex = Regex::new(REGEX_BASE).unwrap();
+    for (n, v) in parsed_notes_tests {
+        let v0 = parse_note(n, note_name_regexp.clone());
+        assert!(v0 == v, "parse note: {}, expected {}. Got {}", n, v, v0)
+    }
+
+    // Random collection of some spot checks relative to make_note frequency generations
+    // make_note(key: i8, n: Option<u8>, beat_samples: u32 , samplerate: u16) -> Vec<f64>
+    // TODO:
+    //  1) More tests, with a variety of all parameters
+    //  2) Improve some sort of rounding/truncating with the long floats
+    let make_notes_tests: [(i8, Option<u8>, u32, u16, [f32; 4]); 1] = [(
+        48,
+        Some(1),
+        288000,
+        48_000,
+        [
+            0.0,
+            0.017122516431822686,
+            0.034240012506541136,
+            0.05134746933903016,
+        ],
+    )];
+    for (i, (key, n, beat_samples, samplerate, results)) in make_notes_tests.iter().enumerate() {
+        let wave = make_note(*key, *n, *beat_samples, *samplerate);
+        for (j, expected_sample) in results.iter().enumerate() {
+            let result_sample = wave.get(j).unwrap();
+            assert!(
+                *expected_sample == *result_sample,
+                "Make note: {:?}, expected {}. Got {}",
+                make_notes_tests[i],
+                *expected_sample,
+                *result_sample
+            )
+        }
+    }
+}