1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements.  See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License.  You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 package websocket.snake;
18 
19 import java.io.IOException;
20 import java.util.ArrayDeque;
21 import java.util.Collection;
22 import java.util.Deque;
23 
24 import jakarta.websocket.CloseReason;
25 import jakarta.websocket.CloseReason.CloseCodes;
26 import jakarta.websocket.Session;
27 
28 public class Snake {
29 
30     private static final int DEFAULT_LENGTH = 5;
31 
32     private final int id;
33     private final Session session;
34 
35     private Direction direction;
36     private int length = DEFAULT_LENGTH;
37     private Location head;
38     private final Deque<Location> tail = new ArrayDeque<>();
39     private final String hexColor;
40 
Snake(int id, Session session)41     public Snake(int id, Session session) {
42         this.id = id;
43         this.session = session;
44         this.hexColor = SnakeAnnotation.getRandomHexColor();
45         resetState();
46     }
47 
resetState()48     private void resetState() {
49         this.direction = Direction.NONE;
50         this.head = SnakeAnnotation.getRandomLocation();
51         this.tail.clear();
52         this.length = DEFAULT_LENGTH;
53     }
54 
kill()55     private synchronized void kill() {
56         resetState();
57         sendMessage("{\"type\": \"dead\"}");
58     }
59 
reward()60     private synchronized void reward() {
61         length++;
62         sendMessage("{\"type\": \"kill\"}");
63     }
64 
65 
sendMessage(String msg)66     protected void sendMessage(String msg) {
67         try {
68             session.getBasicRemote().sendText(msg);
69         } catch (IOException ioe) {
70             CloseReason cr =
71                     new CloseReason(CloseCodes.CLOSED_ABNORMALLY, ioe.getMessage());
72             try {
73                 session.close(cr);
74             } catch (IOException ioe2) {
75                 // Ignore
76             }
77         }
78     }
79 
update(Collection<Snake> snakes)80     public synchronized void update(Collection<Snake> snakes) {
81         Location nextLocation = head.getAdjacentLocation(direction);
82         if (nextLocation.x >= SnakeAnnotation.PLAYFIELD_WIDTH) {
83             nextLocation.x = 0;
84         }
85         if (nextLocation.y >= SnakeAnnotation.PLAYFIELD_HEIGHT) {
86             nextLocation.y = 0;
87         }
88         if (nextLocation.x < 0) {
89             nextLocation.x = SnakeAnnotation.PLAYFIELD_WIDTH;
90         }
91         if (nextLocation.y < 0) {
92             nextLocation.y = SnakeAnnotation.PLAYFIELD_HEIGHT;
93         }
94         if (direction != Direction.NONE) {
95             tail.addFirst(head);
96             if (tail.size() > length) {
97                 tail.removeLast();
98             }
99             head = nextLocation;
100         }
101 
102         handleCollisions(snakes);
103     }
104 
handleCollisions(Collection<Snake> snakes)105     private void handleCollisions(Collection<Snake> snakes) {
106         for (Snake snake : snakes) {
107             boolean headCollision = id != snake.id && snake.getHead().equals(head);
108             boolean tailCollision = snake.getTail().contains(head);
109             if (headCollision || tailCollision) {
110                 kill();
111                 if (id != snake.id) {
112                     snake.reward();
113                 }
114             }
115         }
116     }
117 
getHead()118     public synchronized Location getHead() {
119         return head;
120     }
121 
getTail()122     public synchronized Collection<Location> getTail() {
123         return tail;
124     }
125 
setDirection(Direction direction)126     public synchronized void setDirection(Direction direction) {
127         this.direction = direction;
128     }
129 
getLocationsJson()130     public synchronized String getLocationsJson() {
131         StringBuilder sb = new StringBuilder();
132         sb.append(String.format("{\"x\": %d, \"y\": %d}",
133                 Integer.valueOf(head.x), Integer.valueOf(head.y)));
134         for (Location location : tail) {
135             sb.append(',');
136             sb.append(String.format("{\"x\": %d, \"y\": %d}",
137                     Integer.valueOf(location.x), Integer.valueOf(location.y)));
138         }
139         return String.format("{\"id\":%d,\"body\":[%s]}",
140                 Integer.valueOf(id), sb.toString());
141     }
142 
getId()143     public int getId() {
144         return id;
145     }
146 
getHexColor()147     public String getHexColor() {
148         return hexColor;
149     }
150 }
151