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1 'use strict';
2
3 /*
4 Serpentity is a simple entity framework inspired by Ash.
5
6 Usage:
7
8 const Serpentity = require('serpentity');
9
10 ## Instantiating an engine
11
12 const engine = new Serpentity();
13
14 Add entities or systems, systems are added with a priority (the smaller
15 the number, the earlier it will be called):
16
17 engine.addEntity(entityFactory());
18 engine.addSystem(new GameSystem(), priority);
19
20 Update all systems:
21
22 engine.update(dt);
23
24 Remove entities or systems:
25
26 engine.removeEntity(entityReference);
27 engine.removeSystem(systemReference);
28
29 ## Creating Entities
30
31 Entities are the basic object of Serpentity, and they do nothing.
32
33 const entity = new Serpentity.Entity();
34
35 All the behavior is added through components
36
37 ## Creating Components
38
39 Components define data that we can add to an entity. This data will
40 eventually be consumed by "Systems"
41
42 const PositionComponent = class PositionComponent extends Serpentity.Component {
43 constructor(config) {
44
45 this.x = 0;
46 this.y = 0;
47
48 super(config);
49 }
50 };
51
52 You can add components to entities by using the add method:
53
54 entity.addComponent(new PositionComponent());
55
56
57 Systems can refer to entities by requesting nodes.
58
59 ## Working with Nodes
60
61 Nodes are sets of components that you define, so your system can require
62 entities that always follow the API defined in the node.
63
64 const MovementNode = class MovementNode extends Serpentity.Node;
65 MovementNode.position = PositionComponent;
66 MovementNode.motion = MotionComponent;
67
68 You can then request an array of all the nodes representing entities
69 that comply with that API
70
71 engine.getNodes(MovementNode);
72
73 ## Creating Systems
74
75 Systems are called on every update, and they use components through nodes.
76
77 const TestSystem = class TestSystem extends Serpentity.System {
78 added(engine){
79
80 this.nodeList = engine.getNodes(MovementNode);
81 }
82
83 removed(engine){
84
85 this.nodeList = undefined;
86 }
87
88 update(dt){
89
90 for (const node of this.nodeList) {
91 console.log(`Current position is: ${node.position.x},${node.position.y}`);
92 }
93 }
94 };
95
96 ## That's it
97
98 Just run `engine.update(dt)` in your game loop :D
99
100 */
101 const Serpentity = class Serpentity {
102
103 constructor(config) {
104
105 this.systems = [];
106 this.entities = [];
107 this._nodeCollections = [];
108 this._nodeCollectionKeys = [];
109
110 Object.assign(this, config);
111 }
112
113 /*
114 * Adds a system to the engine, so its update method will be called
115 * with the others. Triggers added hook.
116 *
117 * returns true if added succesfully, false if already added
118 */
119 addSystem(system, priority) {
120
121 if (this.systems.indexOf(system) >= 0) {
122 return false;
123 }
124
125 system.priority = priority;
126
127 let lastIndex = 0;
128
129 const found = this.systems.some((existingSystem, i) => {
130
131 lastIndex = i;
132 if (existingSystem.priority >= system.priority) {
133 return true;
134 }
135 });
136
137 if (!found) {
138 lastIndex += 1;
139 }
140
141 this.systems.splice(lastIndex, 0, system);
142 system.added(this);
143 return true;
144 }
145
146 /*
147 * Removes a system from the engine, so its update method will no
148 * longer will be called. Triggers the removed hook.
149 *
150 * returns true if removed succesfully, false if already added
151 */
152 removeSystem(system) {
153
154 const position = this.systems.indexOf(system);
155 if (position >= 0) {
156 this.systems[position].removed(this);
157 this.systems.splice(position, 1);
158 return true;
159 }
160
161 return false;
162 }
163
164 /*
165 * Adds an entity to the engine, adds to existing node collections
166 *
167 * returns true if added, false if already there
168 */
169 addEntity(entity) {
170
171 if (this.entities.indexOf(entity) >= 0) {
172 return false;
173 }
174 this.entities.push(entity);
175
176 for (const collection of this._nodeCollections) {
177 collection.add(entity);
178 }
179
180 return true;
181 }
182
183 /*
184 * Removes entity from system, removing from all node collections
185 *
186 * returns true if removed, false if not present
187 */
188 removeEntity(entity) {
189
190 const position = this.entities.indexOf(entity);
191 if (position >= 0) {
192 for (const collection of this._nodeCollections) {
193 collection.remove(entity);
194 }
195
196 this.entities.splice(position, 1);
197 return true;
198 }
199
200 return false;
201 }
202
203 /*
204 * Given a Node Class, retrieves a list of all the nodes for each
205 * applicable entity.
206 */
207 getNodes(nodeType) {
208
209 const position = this._nodeCollectionKeys.indexOf(nodeType);
210
211 if (position >= 0) {
212 return this._nodeCollections[position].nodes;
213 }
214
215 const nodeCollection = new Serpentity.NodeCollection({
216 type : nodeType
217 });
218
219 this._nodeCollectionKeys.push(nodeType);
220 this._nodeCollections.push(nodeCollection);
221
222 for (const entity of this.entities) {
223 nodeCollection.add(entity);
224 }
225
226 return nodeCollection;
227 }
228
229 /*
230 * Calls update for every loaded system.
231 */
232 update(dt) {
233
234 for (const system of this.systems) {
235 system.update(dt);
236 }
237 }
238 };
239
240 // Add namespaced objects.
241 Serpentity.Component = require('./serpentity/component.js');
242 Serpentity.Entity = require('./serpentity/entity.js');
243 Serpentity.Node = require('./serpentity/node.js');
244 Serpentity.NodeCollection = require('./serpentity/node_collection.js');
245 Serpentity.System = require('./serpentity/system.js');
246
247 module.exports = Serpentity;