From 19aa9b8d1afd3670eb2862be0516295df7318f06 Mon Sep 17 00:00:00 2001
From: Timothy Warren <twarren@nabancard.com>
Date: Wed, 30 Dec 2020 09:52:14 -0500
Subject: [PATCH] More snake-like movement

---
 src/main.rs | 83 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 69 insertions(+), 14 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 0430d6a..c53a652 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -25,12 +25,16 @@ impl Size {
     }
 }
 
-struct SnakeHead;
+struct SnakeHead {
+    direction: Direction,
+}
 struct Materials {
     head_material: Handle<ColorMaterial>,
     food_material: Handle<ColorMaterial>,
 }
 
+struct SnakeMoveTimer(Timer);
+
 struct Food;
 
 struct FoodSpawnTimer(Timer);
@@ -40,6 +44,24 @@ impl Default for FoodSpawnTimer {
     }
 }
 
+#[derive(PartialEq, Copy, Clone)]
+enum Direction {
+    Left,
+    Up,
+    Right,
+    Down,
+}
+impl Direction {
+    fn opposite(self) -> Self {
+        match self {
+            Self::Left => Self::Right,
+            Self::Right => Self::Left,
+            Self::Up => Self::Down,
+            Self::Down => Self::Up,
+        }
+    }
+}
+
 fn setup(commands: &mut Commands, mut materials: ResMut<Assets<ColorMaterial>>) {
     commands.spawn(Camera2dBundle::default());
     commands.insert_resource(Materials {
@@ -55,28 +77,52 @@ fn spawn_snake(commands: &mut Commands, materials: Res<Materials>) {
             sprite: Sprite::new(Vec2::new(10.0, 10.0)),
             ..Default::default()
         })
-        .with(SnakeHead)
+        .with(SnakeHead {
+            direction: Direction::Up,
+        })
         .with(Position { x: 3, y: 3 })
         .with(Size::square(0.8));
 }
 
 fn snake_movement(
     keyboard_input: Res<Input<KeyCode>>,
-    mut head_positions: Query<&mut Position, With<SnakeHead>>,
+    snake_timer: ResMut<SnakeMoveTimer>,
+    mut heads: Query<(Entity, &mut SnakeHead)>,
+    mut positions: Query<&mut Position>,
 ) {
-    for mut pos in head_positions.iter_mut() {
-        if keyboard_input.pressed(KeyCode::Left) {
-            pos.x -= 1;
+    if let Some((head_entity, mut head)) = heads.iter_mut().next() {
+        let mut head_pos = positions.get_mut(head_entity).unwrap();
+        let dir: Direction = if keyboard_input.pressed(KeyCode::Left) {
+            Direction::Left
+        } else if keyboard_input.pressed(KeyCode::Down) {
+            Direction::Down
+        } else if keyboard_input.pressed(KeyCode::Up) {
+            Direction::Up
+        } else if keyboard_input.pressed(KeyCode::Right) {
+            Direction::Right
+        } else {
+            head.direction
+        };
+        if dir != head.direction.opposite() {
+            head.direction = dir;
         }
-        if keyboard_input.pressed(KeyCode::Right) {
-            pos.x += 1;
-        }
-        if keyboard_input.pressed(KeyCode::Down) {
-            pos.y -= 1;
-        }
-        if keyboard_input.pressed(KeyCode::Up) {
-            pos.y += 1;
+        if !snake_timer.0.finished() {
+            return;
         }
+        match &head.direction {
+            Direction::Left => {
+                head_pos.x -= 1;
+            }
+            Direction::Right => {
+                head_pos.x += 1;
+            }
+            Direction::Up => {
+                head_pos.y += 1;
+            }
+            Direction::Down => {
+                head_pos.y -= 1;
+            }
+        };
     }
 }
 
@@ -127,6 +173,10 @@ fn food_spawner(
     }
 }
 
+fn snake_timer(time: Res<Time>, mut snake_timer: ResMut<SnakeMoveTimer>) {
+    snake_timer.0.tick(time.delta_seconds());
+}
+
 fn main() {
     App::build()
         .add_resource(ClearColor(Color::rgb(0.04, 0.04, 0.04)))
@@ -136,12 +186,17 @@ fn main() {
             height: 500.0,
             ..Default::default()
         })
+        .add_resource(SnakeMoveTimer(Timer::new(
+            Duration::from_millis(150),
+            true,
+        )))
         .add_startup_system(setup.system())
         .add_startup_stage("game_setup", SystemStage::single(spawn_snake.system()))
         .add_system(snake_movement.system())
         .add_system(position_translation.system())
         .add_system(size_scaling.system())
         .add_system(food_spawner.system())
+        .add_system(snake_timer.system())
         .add_plugins(DefaultPlugins)
         .run();
 }