wip

8 files changed, 389 insertions, 0 deletions

diff --git a/src/sim/cell/cell.rs b/src/sim/cell/cell.rs
new file mode 100644
index 0000000..d35fa76
--- /dev/null
+++ b/src/sim/cell/cell.rs
@@ -0,0 +1,38 @@
+use crate::sim::cell::materials::MaterialId;
+
+#[derive(Clone, Copy)]
+pub struct Cell {
+    pub material: MaterialId,
+    pub flags: u8,
+    pub data: u16,
+}
+
+impl Cell {
+    const FLAG_PARITY: u8 = 0b0000_0001;
+
+    #[inline]
+    pub fn parity(self) -> u8 {
+        self.flags & Self::FLAG_PARITY
+    }
+    #[inline]
+    pub fn flip_parity(&mut self) {
+        self.flags ^= Self::FLAG_PARITY;
+    }
+}
+
+impl Cell {
+    pub fn void() -> Cell {
+        Cell {
+            material: MaterialId::Void,
+            flags: 0,
+            data: 0,
+        }
+    }
+    pub fn from_material(material: MaterialId) -> Cell {
+        Cell {
+            material,
+            flags: 0,
+            data: 0,
+        }
+    }
+}
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);
+}
diff --git a/src/sim/cell/materials/gas.rs b/src/sim/cell/materials/gas.rs
new file mode 100644
index 0000000..c0cd9f9
--- /dev/null
+++ b/src/sim/cell/materials/gas.rs
@@ -0,0 +1,76 @@
+use crate::sim::cell_sim::sim::UpdateCtx;
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    // if the water can fall, do so
+    if ctx.candidates_swap(&[
+        (0, -1),
+        (-1 + 2 * ctx.seqno_parity as i32, -1),
+        (1 - 2 * ctx.seqno_parity as i32, -1),
+    ]) {
+        return;
+    }
+
+    // if the water can't fall, check if we can move left or right
+    // these are inverted on parity so that we don't preference a direction
+    let left_target = ctx.get_cell(-1, 0);
+    let can_move_left =
+        left_target.is_some_and(|c| c.material.def().density < ctx.material.density);
+    let right_target = ctx.get_cell(1, 0);
+    let can_move_right =
+        right_target.is_some_and(|c| c.material.def().density < ctx.material.density);
+
+    // we can't move down or to other side, so we're stuck
+    if !can_move_left && !can_move_right {
+        return;
+    }
+
+    // if we can't move left, just move right
+    if !can_move_left {
+        ctx.candidates_swap(&[(1, 0)]);
+        return;
+    }
+    // and vice versa
+    if !can_move_right {
+        ctx.candidates_swap(&[(-1, 0)]);
+        return;
+    }
+
+    // find the closest hole within 20 pixels (TODO optimize)
+    // a hole is any space below us with a lesser density
+    // prevents equidistance stuck state
+    let starting_side = if ctx.seqno_parity == 0 { 1 } else { -1 };
+    for i in 0..20 {
+        let side = if i % 2 == 0 {
+            starting_side
+        } else {
+            -starting_side
+        };
+
+        let offset = side * (1 + i / 2);
+        let hole_target = ctx.get_cell(offset, -1);
+        if let Some(target) = hole_target
+            && target.material.def().density < ctx.material.density
+        {
+            // we identified a hole and we know that the space on this side is open
+            // move toward the hole
+            // new_target.flags = new_target.flags ^ 0b1;
+            ctx.candidates_swap(&[(side, 0)]);
+            return;
+        }
+    }
+
+    // we didn't find a hole, so just move "randomly" on the same surface
+    // TODO when to settle?
+    let target_x = if !can_move_left {
+        1
+    } else if !can_move_right {
+        -1
+    } else if ctx.seqno_parity % 2 == 1 {
+        1
+    } else {
+        -1
+    };
+
+    ctx.candidates_swap(&[(target_x, 0)]);
+}
diff --git a/src/sim/cell/materials/mod.rs b/src/sim/cell/materials/mod.rs
new file mode 100644
index 0000000..a55ed51
--- /dev/null
+++ b/src/sim/cell/materials/mod.rs
@@ -0,0 +1,88 @@
+use crate::sim::cell_sim::sim::UpdateCtx;
+
+mod fire;
+mod gas;
+mod sand;
+mod smoke;
+mod water;
+
+#[repr(u8)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum MaterialId {
+    Void = 0,
+    Sand,
+    Wood,
+    Water,
+    Gas,
+    Fire,
+    Smoke,
+}
+
+pub struct MaterialDef {
+    pub name: &'static str,
+    pub color: (u8, u8, u8, u8),
+    pub density: u8,
+    pub sim_update: Option<fn(ctx: &mut UpdateCtx) -> ()>,
+}
+
+static MATERIALS: [MaterialDef; 7] = [
+    MaterialDef {
+        name: "Void",
+        color: (0x00, 0x00, 0x00, 0x00),
+        density: 0,
+        sim_update: None,
+    },
+    MaterialDef {
+        name: "Sand",
+        color: (0xDE, 0xCB, 0x85, 0xFF),
+        density: 50,
+        sim_update: Some(sand::sim_update),
+    },
+    MaterialDef {
+        name: "Wood",
+        color: (0x85, 0x56, 0x1D, 0xFF),
+        density: 50,
+        sim_update: None,
+    },
+    MaterialDef {
+        name: "Water",
+        color: (0x38, 0xA9, 0xFF, 0xFF),
+        density: 40,
+        sim_update: Some(water::sim_update),
+    },
+    MaterialDef {
+        name: "Gas",
+        color: (0xBD, 0xFF, 0xE4, 0xAA),
+        density: 10,
+        sim_update: Some(gas::sim_update),
+    },
+    MaterialDef {
+        name: "Fire",
+        color: (0xFC, 0x66, 0x00, 0xAA),
+        // for now this matches wood
+        density: 50,
+        sim_update: Some(fire::sim_update),
+    },
+    MaterialDef {
+        name: "Smoke",
+        color: (0x32, 0x35, 0x36, 0xAA),
+        density: 15,
+        sim_update: Some(smoke::sim_update),
+    },
+];
+
+impl MaterialId {
+    pub const ALL: [MaterialId; 7] = [
+        MaterialId::Void,
+        MaterialId::Sand,
+        MaterialId::Wood,
+        MaterialId::Water,
+        MaterialId::Gas,
+        MaterialId::Fire,
+        MaterialId::Smoke,
+    ];
+    #[inline]
+    pub fn def(self) -> &'static MaterialDef {
+        &MATERIALS[self as usize]
+    }
+}
diff --git a/src/sim/cell/materials/sand.rs b/src/sim/cell/materials/sand.rs
new file mode 100644
index 0000000..d2d1265
--- /dev/null
+++ b/src/sim/cell/materials/sand.rs
@@ -0,0 +1,10 @@
+use crate::sim::cell_sim::sim::UpdateCtx;
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    ctx.candidates_swap(&[
+        (0, 1),
+        (-1 + 2 * ctx.seqno_parity as i32, 1),
+        (1 - 2 * ctx.seqno_parity as i32, 1),
+    ]);
+}
diff --git a/src/sim/cell/materials/smoke.rs b/src/sim/cell/materials/smoke.rs
new file mode 100644
index 0000000..2ee7c00
--- /dev/null
+++ b/src/sim/cell/materials/smoke.rs
@@ -0,0 +1,20 @@
+use rand::RngExt;
+
+use crate::sim::cell_sim::sim::UpdateCtx;
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    // only allow upward movement some of the time to limit movement speed
+    if ctx.rng.random_range(0.0..1.0) > 0.8 && ctx.candidates_swap(&[(0, -1)]) {
+        return;
+    }
+    // same for each horizontal direction
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.candidates_swap(&[(1 - ctx.seqno_parity as i32 * 2, 0)])
+    {
+        return;
+    }
+    if ctx.rng.random_range(0.0..1.0) > 0.8
+        && ctx.candidates_swap(&[(-1 + ctx.seqno_parity as i32 * 2, 0)])
+    {}
+}
diff --git a/src/sim/cell/materials/water.rs b/src/sim/cell/materials/water.rs
new file mode 100644
index 0000000..4b848fb
--- /dev/null
+++ b/src/sim/cell/materials/water.rs
@@ -0,0 +1,76 @@
+use crate::sim::cell_sim::sim::UpdateCtx;
+
+#[inline]
+pub fn sim_update(ctx: &mut UpdateCtx) {
+    // if the water can fall, do so
+    if ctx.candidates_swap(&[
+        (0, 1),
+        (-1 + 2 * ctx.seqno_parity as i32, 1),
+        (1 - 2 * ctx.seqno_parity as i32, 1),
+    ]) {
+        return;
+    }
+
+    // if the water can't fall, check if we can move left or right
+    // these are inverted on parity so that we don't preference a direction
+    let left_target = ctx.get_cell(-1, 0);
+    let can_move_left =
+        left_target.is_some_and(|c| c.material.def().density < ctx.material.density);
+    let right_target = ctx.get_cell(1, 0);
+    let can_move_right =
+        right_target.is_some_and(|c| c.material.def().density < ctx.material.density);
+
+    // we can't move down or to other side, so we're stuck
+    if !can_move_left && !can_move_right {
+        return;
+    }
+
+    // if we can't move left, just move right
+    if !can_move_left {
+        ctx.candidates_swap(&[(1, 0)]);
+        return;
+    }
+    // and vice versa
+    if !can_move_right {
+        ctx.candidates_swap(&[(-1, 0)]);
+        return;
+    }
+
+    // find the closest hole within 20 pixels (TODO optimize)
+    // a hole is any space below us with a lesser density
+    // prevents equidistance stuck state
+    let starting_side = if ctx.seqno_parity == 0 { 1 } else { -1 };
+    for i in 0..20 {
+        let side = if i % 2 == 0 {
+            starting_side
+        } else {
+            -starting_side
+        };
+
+        let offset = side * (1 + i / 2);
+        let hole_target = ctx.get_cell(offset, 1);
+        if let Some(target) = hole_target
+            && target.material.def().density < ctx.material.density
+        {
+            // we identified a hole and we know that the space on this side is open
+            // move toward the hole
+            // new_target.flags = new_target.flags ^ 0b1;
+            ctx.candidates_swap(&[(side, 0)]);
+            return;
+        }
+    }
+
+    // we didn't find a hole, so just move "randomly" on the same surface
+    // TODO when to settle?
+    // let target_x = if !can_move_left {
+    //     1
+    // } else if !can_move_right {
+    //     -1
+    // } else if ctx.seqno_parity % 2 == 1 {
+    //     1
+    // } else {
+    //     -1
+    // };
+
+    // ctx.candidates_swap(&[(target_x, 0)]);
+}
diff --git a/src/sim/cell/mod.rs b/src/sim/cell/mod.rs
new file mode 100644
index 0000000..2d2175c
--- /dev/null
+++ b/src/sim/cell/mod.rs
@@ -0,0 +1,2 @@
+pub mod cell;
+pub mod materials;