Implemented delta-ing methods w/ unit tests.

gamelog/src/period.rs

@@ -23,6 +23,24 @@ impl PlayHandle for Period {
     }
 }
 
+impl Period {
+    pub fn deltas(&self) -> Vec<i8> {
+        let len = self.events.len() - 1;
+        let mut idx: usize = 0;
+        let mut deltas: Vec<i8> = vec![];
+
+        while idx < len {
+            if let Some(value) = self.events[idx].delta(&self.events[idx + 1]) {
+                deltas.push(value);
+            }
+
+            idx += 1
+        }
+
+        deltas
+    }
+}
+
 #[derive(Debug, Deserialize, Clone, PartialEq)]
 pub enum Quarter {
     First,
@@ -31,3 +49,50 @@ pub enum Quarter {
     Fourth,
     Overtime(u8),
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::{Action, Down, Team, TerrainState};
+
+    #[test]
+    fn deltas() {
+        let period = Period {
+            start: Quarter::First,
+            end: None,
+            events: vec![
+                Event::Kickoff(Team::Nebraska),
+                Event::Play(Play {
+                    action: Action::Unknown,
+                    down: Some(Down::First),
+                    terrain: Some(TerrainState::Yards(10)),
+                }),
+                Event::Play(Play {
+                    action: Action::Unknown,
+                    down: Some(Down::Second),
+                    terrain: Some(TerrainState::Yards(13)),
+                }),
+                Event::Play(Play {
+                    action: Action::Unknown,
+                    down: Some(Down::Third),
+                    terrain: Some(TerrainState::Yards(8)),
+                }),
+                Event::Turnover(Team::Nebraska),
+                Event::Play(Play {
+                    action: Action::Unknown,
+                    down: Some(Down::First),
+                    terrain: Some(TerrainState::Yards(10)),
+                }),
+                Event::Play(Play {
+                    action: Action::Unknown,
+                    down: Some(Down::First),
+                    terrain: Some(TerrainState::Yards(10)),
+                }),
+            ],
+        };
+
+        let expected: Vec<i8> = vec![10, -3, 5, 10];
+
+        assert!(period.deltas() == expected)
+    }
+}