moving average and base-quality

src/bin/commands/trimmer.rs

@@ -19,6 +19,14 @@ pub(crate) struct TrimmerOpts {
     #[clap(long, short = 't', default_value = "5")]
     threads: usize,
 
+    /// Minimum base-quality to keep a base when trimming tails.
+    #[clap(long, short = 'q', default_value = "20")]
+    trim_tail_quality: u8,
+
+    /// Window size for moving average when trimming tails.
+    #[clap(long, short = 'w', default_value = "20")]
+    trim_tail_window: u8,
+
     /// Level of compression to use to compress outputs.
     #[clap(long, short = 'c', default_value = "5")]
     compression_level: usize,

src/bin/main.rs

@@ -5,7 +5,7 @@ pub mod commands;
 use anyhow::Result;
 use clap::Parser;
 use commands::command::Command;
-use commands::{demux::Demux, trimmer::Trimmer};
+use commands::{demux::Demux, trimmer::TrimmerOpts};
 use enum_dispatch::enum_dispatch;
 use env_logger::Env;
 
@@ -23,7 +23,7 @@ struct Args {
 #[command(version)]
 enum Subcommand {
     Demux(Demux),
-    Trimmer(Trimmer),
+    Trimmer(TrimmerOpts),
 }
 
 fn main() -> Result<()> {

src/lib/base_quality.rs

@@ -0,0 +1,73 @@
+use super::moving_average::MovingAverage;
+
+use std::ops::Range;
+
+pub(crate) fn find_oscillating_quals(bqs: &[u8]) -> Range<usize> {
+    return 0..0;
+}
+
+pub(crate) enum Tail {
+    Left,
+    Right,
+    Both,
+}
+
+/// Uses a moving average to return a range of high quality bases.
+/// If all bases are high-quality, the range is the full read.
+pub(crate) fn find_high_quality_bases(
+    bqs: &[u8],
+    min_quality: u8,
+    window: u8,
+    tail: Tail,
+) -> Range<usize> {
+    let mut left = 0;
+    let mut right = bqs.len();
+    if matches!(tail, Tail::Left | Tail::Both) {
+        let mut ma = MovingAverage::<u8>::new(window as usize);
+        for &bq in bqs {
+            let mean = ma.push(bq);
+            if mean >= min_quality as f64 {
+                break;
+            }
+            left += 1;
+        }
+    }
+    if matches!(tail, Tail::Right | Tail::Both) {
+        let mut ma = MovingAverage::<u8>::new(window as usize);
+        for &bq in bqs.iter().rev() {
+            let mean = ma.push(bq);
+            if mean >= min_quality as f64 {
+                break;
+            }
+            right -= 1;
+        }
+    }
+    left..right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_find_hq_all() {
+        let bqs = b"IIIIIIII";
+        let range = find_high_quality_bases(bqs, 'I' as u8, 3, Tail::Both);
+        assert_eq!(range, 0..bqs.len());
+    }
+
+    #[test]
+    fn test_find_hq_ends() {
+        let bqs = b"EIIIIIIE";
+        let range = find_high_quality_bases(bqs, 'I' as u8, 1, Tail::Both);
+        assert_eq!(range, 1..bqs.len() - 1);
+
+        let bqs = b"EIIIIIIE";
+        let range = find_high_quality_bases(bqs, 'I' as u8, 1, Tail::Left);
+        assert_eq!(range, 1..bqs.len());
+
+        let bqs = b"EIIIIIIE";
+        let range = find_high_quality_bases(bqs, 'I' as u8, 1, Tail::Right);
+        assert_eq!(range, 0..bqs.len() - 1);
+    }
+}

src/lib/mod.rs

@@ -1,4 +1,6 @@
 pub mod barcode_matching;
+pub mod base_quality;
+pub mod moving_average;
 pub mod pair_overlap;
 pub mod samples;
 

src/lib/moving_average.rs

@@ -0,0 +1,53 @@
+/// A simple moving average calculator.
+/// Only requires that T is convertable to f64.
+/// Uses space of window * size_of(T) bytes.
+pub(crate) struct MovingAverage<T> {
+    window: usize,
+    values: Vec<T>,
+    sum: f64,
+    idx: usize,
+    count: usize,
+}
+
+impl<T: Copy + Default + std::convert::Into<f64>> MovingAverage<T> {
+    /// create a new moving average calculator with a window of `window` values.
+    pub fn new(window: usize) -> Self {
+        Self { window, values: vec![T::default(); window], sum: 0.0, idx: 0, count: 0 }
+    }
+
+    /// push a new value into the moving average calculator and get the new mean.
+    pub fn push(&mut self, value: T) -> f64 {
+        let old_value = self.values[self.idx];
+        self.values[self.idx] = value;
+        self.sum = self.sum + value.into() - old_value.into();
+        self.idx = (self.idx + 1) % self.window;
+        self.count += 1;
+        self.mean()
+    }
+
+    /// get the current mean.
+    #[inline]
+    pub fn mean(&self) -> f64 {
+        self.sum / (self.count.min(self.window) as f64)
+    }
+}
+
+// write some tests for the calculator
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_moving_average() {
+        let window_size = 3;
+        let mut ma = MovingAverage::new(window_size);
+        // NOTE the first value is always the mean
+        // we use min of values added and window size to calculate the mean
+        assert_eq!(ma.push(1), 1 as f64 / 1 as f64);
+        assert_eq!(ma.push(2), (1 + 2) as f64 / 2 as f64);
+        assert_eq!(ma.push(3), (1 + 2 + 3) as f64 / window_size as f64);
+        assert_eq!(ma.push(4), (2 + 3 + 4) as f64 / window_size as f64);
+        assert_eq!(ma.push(5), (3 + 4 + 5) as f64 / window_size as f64);
+        assert_eq!(ma.push(6), (4 + 5 + 6) as f64 / window_size as f64);
+    }
+}