rust lib: add grid and ray

2 files changed, 58 insertions, 5 deletions

diff --git a/lib/rust/Cargo.lock b/lib/rust/Cargo.lock
new file mode 100644
index 0000000..eee204e
--- /dev/null
+++ b/lib/rust/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "aoc"
+version = "0.1.0"
diff --git a/lib/rust/src/lib.rs b/lib/rust/src/lib.rs
index b93cf3f..25c82db 100644
--- a/lib/rust/src/lib.rs
+++ b/lib/rust/src/lib.rs
@@ -1,5 +1,24 @@
-pub fn add(left: u64, right: u64) -> u64 {
-    left + right
+#[derive(Debug)]
+pub struct Grid<T> {
+    grid: Vec<Vec<T>>,
+}
+
+impl<T> Grid<T> {
+    pub fn new(grid: Vec<Vec<T>>) -> Grid<T> {
+        Grid { grid }
+    }
+
+    pub fn ray(&self, (x, y): (usize, usize), (dx, dy): (i64, i64)) -> impl Iterator<Item = &T> {
+        let (x, y) = (i64::try_from(x).unwrap(), i64::try_from(y).unwrap());
+        (0..)
+            .map(move |n| {
+                self.grid
+                    .get(usize::try_from(y + n * dy).unwrap())
+                    .and_then(|row| row.get(usize::try_from(x + n * dx).unwrap()))
+            })
+            .take_while(Option::is_some)
+            .flatten()
+    }
 }
 
 #[cfg(test)]
@@ -7,8 +26,35 @@ mod tests {
     use super::*;
 
     #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
+    fn create_grid() {
+        let _grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
+    }
+
+    #[test]
+    fn ray_empty() {
+        let grid = Grid::<u64>::new(vec![vec![]]);
+        assert!(grid.ray((1, 1), (1, 2)).eq(vec![].iter()))
+    }
+
+    #[test]
+    fn ray_single_element() {
+        let grid = Grid::<u64>::new(vec![vec![1]]);
+        assert!(grid.ray((0, 0), (1, 2)).eq(vec![1].iter()))
+    }
+
+    #[test]
+    fn ray_horizontal() {
+        let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
+        assert!(grid.ray((0, 0), (1, 0)).eq(vec![1, 2, 3].iter()))
+    }
+    #[test]
+    fn ray_vertical() {
+        let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
+        assert!(grid.ray((1, 0), (0, 1)).eq(vec![2, 5, 8].iter()))
+    }
+    #[test]
+    fn ray_diagonal() {
+        let grid = Grid::new(vec![vec![1, 2, 3], vec![4, 5, 6], vec![7, 8, 9]]);
+        assert!(grid.ray((0, 0), (1, 2)).eq(vec![1, 8].iter()))
     }
 }