check for initial food placement

battlesnake/src/bin/seed-cracker.rs

@@ -240,7 +240,8 @@ struct PreparedGame {
     corners: [Option<u8>; 4],
     cardinals: [Option<u8>; 4],
     corner_first: bool,
-    food_spawns: Vec<FoodSpawn>,
+    initial_food: Box<[(u8, u8)]>,
+    food_spawns: Box<[FoodSpawn]>,
     food_chance: u8,
 }
 
@@ -258,42 +259,116 @@ enum FoodSpawn {
 
 impl PreparedGame {
     fn prepare(requests: &[Request]) -> Self {
-        debug!("Preparing initial board state");
         let request = &requests[0];
-        assert_eq!(request.turn, 0);
-        let mn = 1;
-        let md = (request.board.width - 1) / 2;
-        let mx = request.board.width - 2;
-        let corners = [
-            Coord { x: mn, y: mn },
-            Coord { x: mn, y: mx },
-            Coord { x: mx, y: mn },
-            Coord { x: mx, y: mx },
-        ];
-        let cardinals = [
-            Coord { x: mn, y: md },
-            Coord { x: md, y: mn },
-            Coord { x: md, y: mx },
-            Coord { x: mx, y: md },
-        ];
-        let corner_first = corners.contains(&request.board.snakes[0].head);
-        let corners = corners.map(|start| {
-            request
-                .board
-                .snakes
-                .iter()
-                .position(|snake| snake.head == start)
-                .map(|pos| (pos % 4).az())
-        });
-        let cardinals = cardinals.map(|start| {
-            request
-                .board
-                .snakes
-                .iter()
-                .position(|snake| snake.head == start)
-                .map(|pos| (pos % 4).az())
-        });
+        let (corner_first, corners, cardinals) = prepare_starts(request);
 
+        let initial_food = prepare_initial_food(request);
+
+        let (food_chance, food_spawns) = prepare_food_placement(requests, request);
+
+        Self {
+            corners,
+            cardinals,
+            corner_first,
+            initial_food,
+            food_spawns,
+            food_chance,
+        }
+    }
+
+    fn validate(&self, input_rand: &mut SeedRand, seed: i64, log: bool) -> bool {
+        if log {
+            debug!("Checking Start positions");
+        }
+        let mut corners = [None; 4];
+        for (a, b) in self.corners.iter().zip(corners.iter_mut()) {
+            *b = a.map(usize::from);
+        }
+        let mut cardinals = [None; 4];
+        for (a, b) in self.cardinals.iter().zip(cardinals.iter_mut()) {
+            *b = a.map(usize::from);
+        }
+        let rand = get_rand(input_rand, seed, 0);
+        if !rand.shuffle_check(&mut corners) {
+            if log {
+                error!("Corners are shuffled wrong");
+            }
+            return false;
+        }
+        if !rand.shuffle_check(&mut cardinals) {
+            if log {
+                error!("Cardinals are shuffled wrong");
+            }
+            return false;
+        }
+        if rand.int_n(2) == usize::from(self.corner_first) {
+            if log {
+                error!("Corners and cardinals are flipped: {}", self.corner_first);
+            }
+            return false;
+        }
+
+        if log {
+            debug!("Checking Starting food");
+        }
+        for &(selected, possibilities) in &self.initial_food {
+            if rand.int_n(usize::from(possibilities)).az::<u8>() != selected {
+                if log {
+                    error!("Initial food spawn is wrong: expected {selected}");
+                }
+                return false;
+            }
+        }
+
+        self.food_spawns.iter().enumerate().all(|(turn, spawn)| {
+            if log {
+                debug!("Checking turn {turn}");
+            }
+            let rand = get_rand(input_rand, seed, (turn).az());
+
+            match spawn {
+                spawn @ (FoodSpawn::Forced {
+                    selected,
+                    free_spots,
+                }
+                | FoodSpawn::Random {
+                    selected,
+                    free_spots,
+                }) => {
+                    if matches!(spawn, FoodSpawn::Random { .. })
+                        && 100 - rand.int_n(100) >= usize::from(self.food_chance)
+                    {
+                        if log {
+                            error!("Food not spawned, when some should have been spawned");
+                        }
+                        return false;
+                    }
+
+                    let mut foods = vec![None; usize::from(*free_spots)];
+                    foods[usize::from(*selected)] = Some(0);
+                    let correct = rand.shuffle_check(&mut foods);
+                    if log && !correct {
+                        error!("Wrong food selected: {foods:?}");
+                    }
+                    correct
+                }
+                FoodSpawn::None => {
+                    let correct = 100 - rand.int_n(100) >= usize::from(self.food_chance);
+                    if log && !correct {
+                        error!("Food spawned, when none should have been spawned");
+                    }
+                    correct
+                }
+                FoodSpawn::Blocked => {
+                    // We can't get any info if there isn't even a chance for food
+                    true
+                }
+            }
+        })
+    }
+}
+
+fn prepare_food_placement(requests: &[Request], request: &Request) -> (u8, Box<[FoodSpawn]>) {
     debug!("Preparing food placement");
     let food_chance = request.game.ruleset.settings.food_spawn_chance;
     let food_min = request.game.ruleset.settings.minimum_food;
@@ -354,94 +429,116 @@ impl PreparedGame {
             }
         })
         .collect();
-
-        Self {
-            corners,
-            cardinals,
-            corner_first,
-            food_spawns,
-            food_chance,
-        }
+    (food_chance, food_spawns)
 }
 
-    fn validate(&self, input_rand: &mut SeedRand, seed: i64, log: bool) -> bool {
-        if log {
-            debug!("Checking Start positions");
-        }
-        let mut corners = [None; 4];
-        for (a, b) in self.corners.iter().zip(corners.iter_mut()) {
-            *b = a.map(usize::from);
-        }
-        let mut cardinals = [None; 4];
-        for (a, b) in self.cardinals.iter().zip(cardinals.iter_mut()) {
-            *b = a.map(usize::from);
-        }
-        let rand = get_rand(input_rand, seed, 0);
-        if !rand.shuffle_check(&mut corners) {
-            if log {
-                error!("Corners are shuffled wrong");
-            }
-            return false;
-        }
-        if !rand.shuffle_check(&mut cardinals) {
-            if log {
-                error!("Cardinals are shuffled wrong");
-            }
-            return false;
-        }
-        if rand.int_n(2) == usize::from(self.corner_first) {
-            if log {
-                error!("Corners and cardinals are flipped: {}", self.corner_first);
-            }
+fn prepare_initial_food(request: &Request) -> Box<[(u8, u8)]> {
+    debug!("Preparing initial food spawn");
+    let center = Coord {
+        x: (request.board.width - 1) / 2,
+        y: (request.board.height) / 2,
+    };
+    let initial_food = request
+        .board
+        .snakes
+        .iter()
+        .enumerate()
+        .map(|(i, snake)| {
+            let head = snake.head;
+            let possible_food_locations = [
+                Coord {
+                    x: head.x - 1,
+                    y: head.y - 1,
+                },
+                Coord {
+                    x: head.x - 1,
+                    y: head.y + 1,
+                },
+                Coord {
+                    x: head.x + 1,
+                    y: head.y - 1,
+                },
+                Coord {
+                    x: head.x + 1,
+                    y: head.y + 1,
+                },
+            ];
+            let available_food_locations: Vec<_> = possible_food_locations
+                .into_iter()
+                .filter(|food| {
+                    // Don't place in the center
+                    if *food == center {
                         return false;
                     }
 
-        self.food_spawns.iter().enumerate().all(|(turn, spawn)| {
-            if log {
-                debug!("Checking turn {turn}");
-            }
-            let rand = get_rand(input_rand, seed, (turn).az());
-
-            match spawn {
-                spawn @ (FoodSpawn::Forced {
-                    selected,
-                    free_spots,
-                }
-                | FoodSpawn::Random {
-                    selected,
-                    free_spots,
-                }) => {
-                    if matches!(spawn, FoodSpawn::Random { .. })
-                        && 100 - rand.int_n(100) >= usize::from(self.food_chance)
+                    // Food must be further than snake from center on at least one axis
+                    if !((food.x < head.x && head.x < center.x)
+                        || (food.x > head.x && head.x > center.x)
+                        || (food.y < head.y && head.y < center.y)
+                        || (food.y > head.y && head.y > center.y))
                     {
-                        if log {
-                            error!("Food not spawned, when some should have been spawned");
-                        }
                         return false;
                     }
 
-                    let mut foods = vec![None; usize::from(*free_spots)];
-                    foods[usize::from(*selected)] = Some(0);
-                    let correct = rand.shuffle_check(&mut foods);
-                    if log && !correct {
-                        error!("Wrong food selected: {foods:?}");
+                    // Don't spawn food in corners
+                    if (food.x == 0 || food.x == (request.board.width - 1))
+                        && (food.y == 0 || food.y == (request.board.height - 1))
+                    {
+                        return false;
                     }
-                    correct
-                }
-                FoodSpawn::None => {
-                    let correct = 100 - rand.int_n(100) >= usize::from(self.food_chance);
-                    if log && !correct {
-                        error!("Food spawned, when none should have been spawned");
-                    }
-                    correct
-                }
-                FoodSpawn::Blocked => {
-                    // We can't get any info if there isn't even a chance for food
+
                     true
-                }
-            }
                 })
+                .collect();
+
+            let possibilities = available_food_locations.len().az();
+            let selected = available_food_locations
+                .iter()
+                .position(|food| *food == request.board.food[i])
+                .unwrap()
+                .az();
+            (selected, possibilities)
+        })
+        .collect();
+    initial_food
 }
+
+fn prepare_starts(request: &Request) -> (bool, [Option<u8>; 4], [Option<u8>; 4]) {
+    debug!("Preparing initial board state");
+    assert_eq!(request.turn, 0);
+    let mn = 1;
+    let md = (request.board.width - 1) / 2;
+    let mx = request.board.width - 2;
+    let corners = [
+        Coord { x: mn, y: mn },
+        Coord { x: mn, y: mx },
+        Coord { x: mx, y: mn },
+        Coord { x: mx, y: mx },
+    ];
+    let cardinals = [
+        Coord { x: mn, y: md },
+        Coord { x: md, y: mn },
+        Coord { x: md, y: mx },
+        Coord { x: mx, y: md },
+    ];
+    let corner_first = corners.contains(&request.board.snakes[0].head);
+    let corners = corners.map(|start| {
+        request
+            .board
+            .snakes
+            .iter()
+            .position(|snake| snake.head == start)
+            .map(|pos| (pos % 4).az())
+    });
+    let cardinals = cardinals.map(|start| {
+        request
+            .board
+            .snakes
+            .iter()
+            .position(|snake| snake.head == start)
+            .map(|pos| (pos % 4).az())
+    });
+    (corner_first, corners, cardinals)
 }
 
 #[must_use]