1 files changed, 233 insertions, 0 deletions
diff --git a/2020/src/bin/day_12.rs b/2020/src/bin/day_12.rs
new file mode 100644
index 0000000..489cdca
--- /dev/null
+++ b/2020/src/bin/day_12.rs
@@ -0,0 +1,233 @@
+use bevy::prelude::*;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::ops::Deref;
+
+fn main() {
+    App::build()
+        .add_resource(WindowDescriptor {
+            title: "Advent of Code".to_string(),
+            width: 1920,
+            height: 1080,
+            ..Default::default()
+        })
+        .add_resource(ClearColor(Color::rgb(0., 0., 0.)))
+        .add_startup_system(setup_camera.system())
+        .add_startup_system(read_input_file.system())
+        .add_system(move_normal_ship.system())
+        .add_system(move_waypoint_ship.system())
+        .add_plugins(DefaultPlugins)
+        .run();
+}
+
+fn setup_camera(mut commands: Commands) {
+    commands.spawn(Camera2dComponents::default());
+}
+
+#[derive(PartialEq, Eq, Clone, Copy)]
+struct Position {
+    x: i64,
+    y: i64,
+}
+impl Position {
+    fn manhattan_distance(&self, other: &Position) -> i64 {
+        (self.x - other.x).abs() + (self.y - other.y).abs()
+    }
+}
+impl std::ops::Add<&Position> for &Position {
+    type Output = Position;
+    fn add(self, other: &Position) -> Self::Output {
+        Position {
+            x: self.x + other.x,
+            y: self.y + other.y,
+        }
+    }
+}
+impl std::ops::Mul<i64> for Position {
+    type Output = Position;
+    fn mul(self, other: i64) -> Self::Output {
+        Position {
+            x: self.x * other,
+            y: self.y * other,
+        }
+    }
+}
+
+enum Facing {
+    North,
+    South,
+    East,
+    West,
+}
+impl Facing {
+    fn right(&mut self) {
+        use Facing::*;
+        *self = match self {
+            North => East,
+            East => South,
+            South => West,
+            West => North,
+        }
+    }
+
+    fn reverse(&mut self) {
+        self.right();
+        self.right();
+    }
+
+    fn left(&mut self) {
+        self.reverse();
+        self.right();
+    }
+}
+
+struct Instructions(Vec<Instruction>);
+#[derive(Clone)]
+enum Instruction {
+    North(i64),
+    South(i64),
+    East(i64),
+    West(i64),
+    Left(i64),
+    Right(i64),
+    Forward(i64),
+}
+
+struct InstructionPointer(usize);
+
+struct Waypoint(Position);
+
+fn read_input_file(mut commands: Commands) {
+    let f = File::open("./inputs/day_12.txt").unwrap();
+
+    let instructions: Vec<Instruction> = BufReader::new(f)
+        .lines()
+        .map(|line| {
+            let line = line.unwrap();
+            let line = line.trim();
+
+            let val: i64 = line[1..].parse().unwrap();
+            let instruction = match line.chars().next().unwrap() {
+                'N' => Instruction::North(val),
+                'S' => Instruction::South(val),
+                'E' => Instruction::East(val),
+                'W' => Instruction::West(val),
+                'L' => Instruction::Left(val),
+                'R' => Instruction::Right(val),
+                'F' => Instruction::Forward(val),
+                other => panic!("Unknown instruction: {}", other),
+            };
+            instruction
+        })
+        .collect();
+
+    commands.spawn((
+        Instructions(instructions.clone()),
+        InstructionPointer(0),
+        Facing::East,
+        Position { x: 0, y: 0 },
+    ));
+
+    commands.spawn((
+        Waypoint(Position { x: 10, y: 1 }),
+        Instructions(instructions),
+        InstructionPointer(0),
+        Position { x: 0, y: 0 },
+    ));
+}
+
+fn move_normal_ship(
+    mut q: Query<
+        Without<
+            Waypoint,
+            (
+                &Instructions,
+                &mut InstructionPointer,
+                &mut Facing,
+                &mut Position,
+            ),
+        >,
+    >,
+) {
+    for (instructions, mut instruction_pointer, mut facing, mut position) in q.iter_mut() {
+        if let Some(instruction) = instructions.0.get(instruction_pointer.0) {
+            use Instruction::*;
+            match instruction {
+                North(val) => position.y += val,
+                South(val) => position.y -= val,
+                East(val) => position.x += val,
+                West(val) => position.x -= val,
+                Left(90) | Right(270) => facing.left(),
+                Left(180) | Right(180) => facing.reverse(),
+                Left(270) | Right(90) => facing.right(),
+                Left(val) | Right(val) => panic!("Unknown left/right val: {}", val),
+                Forward(val) => match facing.deref() {
+                    Facing::North => position.y += val,
+                    Facing::South => position.y -= val,
+                    Facing::East => position.x += val,
+                    Facing::West => position.x -= val,
+                },
+            };
+
+            instruction_pointer.0 += 1;
+        } else {
+            println!(
+                "Normal Ship at destination: {} x {}, Manhattan distance: {}",
+                position.x,
+                position.y,
+                position.manhattan_distance(&Position { x: 0, y: 0 })
+            );
+        }
+    }
+}
+
+fn move_waypoint_ship(
+    instructions: &Instructions,
+    mut waypoint: Mut<Waypoint>,
+    mut instruction_pointer: Mut<InstructionPointer>,
+    mut position: Mut<Position>,
+) {
+    if let Some(instruction) = instructions.0.get(instruction_pointer.0) {
+        use Instruction::*;
+        match instruction {
+            North(val) => waypoint.0.y += val,
+            South(val) => waypoint.0.y -= val,
+            East(val) => waypoint.0.x += val,
+            West(val) => waypoint.0.x -= val,
+            Left(90) | Right(270) => {
+                waypoint.0 = Position {
+                    x: -waypoint.0.y,
+                    y: waypoint.0.x,
+                }
+            }
+            Left(180) | Right(180) => {
+                waypoint.0 = Position {
+                    x: -waypoint.0.x,
+                    y: -waypoint.0.y,
+                }
+            }
+            Left(270) | Right(90) => {
+                waypoint.0 = Position {
+                    x: waypoint.0.y,
+                    y: -waypoint.0.x,
+                }
+            }
+            Left(val) | Right(val) => panic!("Unknown left/right val: {}", val),
+            Forward(val) => *position = position.deref() + &(waypoint.0 * *val),
+        };
+
+        // println!(
+        //     "Position: {} x {}. Waypoint: {} x {}",
+        //     position.x, position.y, waypoint.0.x, waypoint.0.y
+        // );
+
+        instruction_pointer.0 += 1;
+    } else {
+        println!(
+            "Waypoint Ship at destination: {} x {}, Manhattan distance: {}",
+            position.x,
+            position.y,
+            position.manhattan_distance(&Position { x: 0, y: 0 })
+        );
+    }
+}