1 files changed, 148 insertions, 0 deletions
diff --git a/src/game.rs b/src/game.rs
new file mode 100644
index 0000000..19940cd
--- /dev/null
+++ b/src/game.rs
@@ -0,0 +1,148 @@
+pub use glam::i32::IVec2 as Pos;
+use rand::seq::IteratorRandom;
+use std::cell::RefCell;
+
+trait Swap {
+    fn swap(self) -> Self;
+}
+
+impl Swap for Pos {
+    fn swap(self) -> Self {
+        Self::new(self.y, self.x)
+    }
+}
+
+pub struct Field(RefCell<u32>);
+
+enum MergeResult {
+    Merged,
+    Replaced,
+    Blocked,
+    Empty,
+}
+
+impl Field {
+    fn new() -> Self {
+        Self(RefCell::new(0))
+    }
+
+    pub fn value(&self) -> u32 {
+        *self.0.borrow()
+    }
+
+    fn merge(&self, other: &Self) -> MergeResult {
+        let mut s = self.0.borrow_mut();
+        let mut o = other.0.borrow_mut();
+
+        if *o == 0 {
+            return MergeResult::Empty;
+        }
+
+        if *s == 0 {
+            *s = *o;
+            *o = 0;
+
+            return MergeResult::Replaced;
+        }
+
+        if *s == *o {
+            *s += 1;
+            *o = 0;
+
+            return MergeResult::Merged;
+        }
+
+        MergeResult::Blocked
+    }
+}
+
+pub struct Board {
+    pub size: Pos,
+    fields: Vec<Vec<Field>>,
+}
+
+pub enum Dir {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
+impl Board {
+    pub fn new(size: Pos) -> Self {
+        Self {
+            size,
+            fields: (0..size.x)
+                .map(|_| (0..size.y).map(|_| Field::new()).collect())
+                .collect(),
+        }
+    }
+
+    pub fn step(&self, dir: Dir) -> bool {
+        let dir = match dir {
+            Dir::Up => -Pos::Y,
+            Dir::Down => Pos::Y,
+            Dir::Left => -Pos::X,
+            Dir::Right => Pos::X,
+        };
+
+        let step_row = dir.abs().swap();
+        let step_col = -dir;
+
+        let len_row = (step_row.abs() * self.size).max_element();
+        let len_col = (step_col.abs() * self.size).max_element();
+
+        let start = (dir + Pos::ONE) / 2 * (self.size - Pos::ONE);
+
+        let mut moved = false;
+
+        for row in 0..len_row {
+            let start_row = start + row * step_row;
+
+            for col1 in 0..len_col - 1 {
+                let field1 = self.get(start_row + col1 * step_col);
+
+                for col2 in col1 + 1..len_col {
+                    let field2 = self.get(start_row + col2 * step_col);
+
+                    match field1.merge(field2) {
+                        MergeResult::Merged => {
+                            moved = true;
+                            break;
+                        }
+                        MergeResult::Replaced => {
+                            moved = true;
+                        }
+                        MergeResult::Blocked => break,
+                        MergeResult::Empty => {}
+                    }
+                }
+            }
+        }
+
+        moved
+    }
+
+    pub fn get(&self, pos: Pos) -> &Field {
+        self.fields
+            .get(pos.x as usize)
+            .unwrap()
+            .get(pos.y as usize)
+            .unwrap()
+    }
+
+    pub fn spawn<R>(&self, rng: &mut R)
+    where
+        R: rand::Rng + ?core::marker::Sized,
+    {
+        if let Some(field) = self
+            .fields
+            .iter()
+            .flat_map(|v| v.iter())
+            .filter(|f| f.value() == 0)
+            .choose(rng)
+        {
+            *field.0.borrow_mut() = 1;
+        }
+    }
+}