Basic Game logic

3 files changed, 113 insertions, 3 deletions

diff --git a/game.adb b/game.adb
index cd96177..2c1934d 100644
--- a/game.adb
+++ b/game.adb
@@ -1,5 +1,82 @@
-with Game;
+with Ada.Numerics.Discrete_Random;
+
 
 package body Game is
-	null
+
+	procedure Init(game: out T_Game;
+		           width: Positive;
+				   height: Positive) is
+	begin
+		game.width := width;
+		game.height := height;
+		game.direction := DIRECTION_RIGHT;
+		Enqueue(game.snake, (2, 2));
+		Enqueue(game.snake, (2, 3));
+		game.food := (1, 1);
+	end Init;
+
+	function Next(game: in out T_Game) return Boolean is
+		new_head: constant T_Position := Next_Head(game);
+	begin
+		if not In_Border(game, new_head) then
+			return false;
+		end if;
+		Enqueue(game.snake, new_head);
+		if new_head /= game.food then
+			Dequeue(game.snake);
+		end if;
+
+		return true;
+	end Next;
+
+	procedure Spawn_Food(game: in out T_Game) is
+		subtype T_Width_Random_Range is Positive range 1..game.width;
+		subtype T_Height_Random_Range is Positive range 1..game.height;
+		package P_Width_Random is new Ada.Numerics.Discrete_Random(T_Width_Random_Range);
+		package P_Height_Random is new Ada.Numerics.Discrete_Random(T_Height_Random_Range);
+		use P_Width_Random;
+		use P_Height_Random;
+
+		width_random_generator: P_Width_Random.Generator;
+		height_random_generator: P_Height_Random.Generator;
+
+		function Valid_Food(game: T_Game; food: T_Position) return Boolean is
+			cursor: T_List := game.snake.front;
+		begin
+			while cursor /= null loop
+				if food = cursor.data then
+					return false;
+				end if;
+				cursor := cursor.next;
+			end loop;
+			return true;
+		end Valid_Food;
+
+		food: T_Position;
+	begin
+		-- reset in main
+		loop
+			food := (random(height_random_generator), random(width_random_generator));
+			exit when Valid_Food(game, food);
+		end loop;
+		game.food := food;
+	end Spawn_Food;
+
+	function Next_Head(game: T_Game) return T_Position is
+		head: T_Position := game.snake.back.data;
+	begin
+		case game.direction is
+			when DIRECTION_UP    => head.y := head.y - 1;
+			when DIRECTION_DOWN  => head.y := head.y + 1;
+			when DIRECTION_LEFT  => head.x := head.x - 1;
+			when DIRECTION_RIGHT => head.x := head.x + 1;
+		end case;
+		return head;
+	end Next_Head;
+
+	function In_Border(game: T_Game; pos: T_Position) return Boolean is
+	begin
+		return pos.y >= 1 and pos.y <= game.height and pos.x >= 1 and pos.x <= game.width;
+	end In_Border;
+
 end Game;
diff --git a/game.ads b/game.ads
index a58a59f..67247c8 100644
--- a/game.ads
+++ b/game.ads
@@ -1,8 +1,39 @@
+with Queue;
+
 package Game is
 
+	type T_Position is record
+		x: Natural;
+		y: Natural;
+	end record;
+
+	package P_Position_Queue is new Queue(T_Position);
+	use P_Position_Queue;
+
+	type T_Direction is (
+		DIRECTION_UP,
+		DIRECTION_DOWN,
+		DIRECTION_LEFT,
+		DIRECTION_RIGHT
+	);
+
 	type T_Game is record
-		null;
+		height:    Positive;
+		width:     Positive;
+		snake:     T_Queue;
+		direction: T_Direction;
+		food:      T_Position;
 	end record;
 
+	procedure Init(game: out T_Game;
+		           width: Positive;
+				   height: Positive);
+	function Next(game: in out T_Game) return Boolean;
+
+private
+
+	procedure Spawn_Food(game: in out T_Game);
+	function Next_Head(game: T_Game) return T_Position;
+	function In_Border(game: T_Game; pos: T_Position) return Boolean;
 
 end Game;
diff --git a/main.adb b/main.adb
index 59d6fe7..51a29a2 100644
--- a/main.adb
+++ b/main.adb
@@ -6,6 +6,8 @@ use  Graphics;
 
 with Queue;
 
+with Game;
+
 procedure Main is
 	state: T_State;
 begin