1 files changed, 41 insertions, 0 deletions
diff --git a/aoc-2020-gleam/src/util/dir.gleam b/aoc-2020-gleam/src/util/dir.gleam
new file mode 100644
index 0000000..6f637d9
--- /dev/null
+++ b/aoc-2020-gleam/src/util/dir.gleam
@@ -0,0 +1,41 @@
+import gleam/int
+import gleam/iterator as iter
+import ext/resultx as resx
+import ext/iteratorx as iterx
+import util/pos.{Pos}
+
+pub type Dir {
+  North
+  East
+  South
+  West
+}
+
+pub fn offset(direction: Dir) -> Pos {
+  case direction {
+    North -> #(0, 1)
+    East -> #(1, 0)
+    South -> #(0, -1)
+    West -> #(-1, 0)
+  }
+}
+
+pub fn degree_to_turn(degree: Int) -> Int {
+  resx.assert_unwrap(int.modulo(degree / 90, by: 4))
+}
+
+fn rotate_clockwise_once(direction: Dir) -> Dir {
+  case direction {
+    North -> East
+    East -> South
+    South -> West
+    West -> North
+  }
+}
+
+pub fn rotate_clockwise(this direction: Dir, by times: Int) -> Dir {
+  direction
+  |> iterx.unfold_infinitely(with: rotate_clockwise_once)
+  |> iter.at(times)
+  |> resx.assert_unwrap
+}