1 files changed, 79 insertions, 0 deletions
diff --git a/src/sim/cell/materials/fire.rs b/src/sim/cell/materials/fire.rs
new file mode 100644
index 0000000..e0416b0
--- /dev/null
+++ b/src/sim/cell/materials/fire.rs
@@ -0,0 +1,79 @@
+use rand::RngExt;
+
+use crate::sim::{
+    cell::{cell::Cell, materials::MaterialId},
+    cell_sim::sim::UpdateCtx,
+};
+
+trait FireCellView {
+    fn get_ticks_lived(self) -> u16;
+    fn set_ticks_lived(&mut self, ticks: u16) -> ();
+    fn is_flammable(self) -> bool;
+}
+
+impl FireCellView for Cell {
+    fn get_ticks_lived(self) -> u16 {
+        self.data
+    }
+    fn set_ticks_lived(&mut self, ticks: u16) {
+        self.data = ticks;
+    }
+    // this could be a property of the material def, I think it's better here for now
+    fn is_flammable(self) -> bool {
+        [MaterialId::Wood].contains(&self.material)
+    }
+}
+
+// TODO optimize number of rng calls?
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    let ticks_lived = ctx.cell.get_ticks_lived();
+    // 2 seconds
+    if ticks_lived > 240 {
+        // we have a chance to live longer--roughly 50% chance of living an extra second
+        if ctx.rng.random_range(0.0..1.0) > 0.995 {
+            // kill ourselves, with a chance to turn into ash
+            if ctx.rng.random_range(0.0..1.0) > 0.8 {
+                // TODO ash material
+                ctx.set_cell(0, 0, Cell::from_material(MaterialId::Sand));
+            } else {
+                ctx.set_cell(0, 0, Cell::void());
+            }
+            return;
+        }
+    }
+
+    // at an average of 4 times per lifespan, try to spread
+    // 1/60 * 240 = 4
+    if ctx.rng.random_range(0.0..1.0) > (59.0 / 60.0) {
+        let (dx, dy) = (ctx.rng.random_range(-1..=1), ctx.rng.random_range(-1..=1));
+        if let Some(target) = ctx.get_cell(dx, dy)
+            && target.is_flammable()
+        {
+            ctx.set_cell(dx, dy, Cell::from_material(MaterialId::Fire));
+        }
+    }
+
+    // 8 times in our lifespan, emit smoke
+    if ticks_lived.is_multiple_of(30)
+        && let Some(target) = ctx.get_cell(0, -1)
+        && target.material == MaterialId::Void
+    {
+        for (dx, dy) in [
+            (0, -1),
+            (1 - ctx.seqno_parity as i32 * 2, 0),
+            (-1 + ctx.seqno_parity as i32 * 2, 0),
+            (0, 1),
+        ] {
+            if let Some(target) = ctx.get_cell(dx, dy)
+                && target.material == MaterialId::Void
+            {
+                ctx.set_cell(dx, dy, Cell::from_material(MaterialId::Smoke));
+                break;
+            }
+        }
+    }
+
+    ctx.cell.set_ticks_lived(ticks_lived + 1);
+    ctx.set_cell(0, 0, *ctx.cell);
+}