feat(core): add shift left/right operators to Signal

argus-core/src/signals/shift_ops.rs

@@ -0,0 +1,61 @@
+use core::iter::zip;
+use core::time::Duration;
+
+use itertools::{enumerate, Itertools};
+
+use super::traits::LinearInterpolatable;
+use super::{InterpolationMethod, Signal};
+
+impl<T> Signal<T>
+where
+    T: Copy + LinearInterpolatable,
+{
+    /// Shift all samples in the signal by `delta` amount to the left.
+    ///
+    /// This essentially filters out all samples with time points greater than `delta`,
+    /// and subtracts `delta` from the rest of the time points.
+    pub fn shift_left(&self, delta: Duration) -> Self {
+        match self {
+            Signal::Sampled { values, time_points } => {
+                // We want to skip any time points < delta, and subtract the rest.
+                // Moreover, if the signal doesn't start at 0 after the shift, we may
+                // want to interpolate from the previous value.
+
+                // Find the first index that satisfies `t >= delta` while also checking
+                // if we need to interpolate
+                let Some((idx, first_t)) = time_points.into_iter().find_position(|&t| t >= &delta)
+                else {
+                    // Return an empty signal (we exhauseted all samples).
+                    return Signal::Empty;
+                };
+
+                let mut new_samples: Vec<(Duration, T)> = Vec::with_capacity(time_points.len() - idx);
+                // Let's see if we need to find a new sample
+                if idx > 0 && first_t != &delta {
+                    // The shifted signal will not start at 0, and we have a previous
+                    // index to interpolate from.
+                    let v = self.interpolate_at(delta, InterpolationMethod::Linear).unwrap();
+                    new_samples.push((Duration::ZERO, v));
+                }
+                // Shift the rest of the samples
+                new_samples.extend(zip(&time_points[idx..], &values[idx..]).map(|(&t, &v)| (t - delta, v)));
+                new_samples.into_iter().collect()
+            }
+            // Empty and constant signals can't really be changed
+            sig => sig.clone(),
+        }
+    }
+
+    /// Shift all samples in the signal by `delta` amount to the right.
+    ///
+    /// This essentially adds `delta` to all time points.
+    pub fn shift_right(&self, delta: Duration) -> Self {
+        match self {
+            Signal::Sampled { values, time_points } => {
+                zip(time_points, values).map(|(&t, &v)| (t + delta, v)).collect()
+            }
+            // Empty and constant signals can't really be changed
+            sig => sig.clone(),
+        }
+    }
+}