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with Ada.Numerics.Discrete_Random;
package body Game is
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);
Reset(game.width_generator);
Reset(game.height_generator);
Spawn_Food(game);
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) or else In_Body(game, new_head) then
return false;
end if;
Enqueue(game.snake, new_head);
if new_head /= game.food then
Dequeue(game.snake);
else
Spawn_Food(game);
end if;
return true;
end Next;
procedure Change_Direction(game: in out T_Game;
direction: T_Direction) is
begin
case direction is
when DIRECTION_UP =>
if game.direction /= DIRECTION_DOWN then
game.direction := direction;
end if;
when DIRECTION_DOWN =>
if game.direction /= DIRECTION_UP then
game.direction := direction;
end if;
when DIRECTION_LEFT =>
if game.direction /= DIRECTION_RIGHT then
game.direction := direction;
end if;
when DIRECTION_RIGHT =>
if game.direction /= DIRECTION_LEFT then
game.direction := direction;
end if;
end case;
end Change_Direction;
procedure Spawn_Food(game: in out T_Game) is
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
loop
food := (random(game.height_generator), random(game.width_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;
function In_Body(game: T_Game; pos: T_Position) return Boolean is
cursor: T_List := game.snake.front;
begin
while cursor /= null loop
if pos = cursor.data then
return true;
end if;
cursor := cursor.next;
end loop;
return false;
end In_Body;
end Game;
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