Move particle stuff to a system to simplify spawning particles

1 files changed, 57 insertions, 0 deletions

diff --git a/src/systems/particle.js b/src/systems/particle.js
new file mode 100644
index 0000000..e58c0a0
--- /dev/null
+++ b/src/systems/particle.js
@@ -0,0 +1,57 @@
+game.system.Particle = () => {
+  "use strict"; 
+  const particleSpawners = {};
+  
+  const particleSpawner = ({colors, maxAmount, minAmount, minLife, maxLife, minRadius, maxRadius, maxSpeed, spawnFunction}) => {
+    return Array(randomInRange(minAmount, maxAmount)).fill(0).map(() => {
+      let particleSpec = {
+        x: Math.random(),
+        y: Math.random(),
+        dx: Math.random() * maxSpeed - maxSpeed / 2,
+        dy: Math.random() * maxSpeed - maxSpeed / 2,
+        radius: randomInRange(minRadius, maxRadius),
+        color: colors[randomInRange(0, colors.length-1)],
+        lifetime: randomInRange(minLife, maxLife),
+        elapsed: 0,
+      };
+      if (spawnFunction) {
+        particleSpec = {...particleSpec, ...spawnFunction(particleSpec)};
+      }
+      return particleSpec;
+    });
+  }
+
+  const update = (elapsedTime, entities, _changedIds) => {
+    for (let id in entities) {
+      const entity = entities[id];
+      if (entity.hasComponent("particles")) {
+        if (!particleSpawners[entity.id]) {
+          particleSpawners[entity.id] = particleSpawner(entity.components.particles.spec.spec);
+          entities[id].particleSprite = game.graphics.Sprite({
+            drawFunction: (elapsedTime, {x, y, width, height}, context) => {
+              let particleSpawner = particleSpawners[entity.id];
+              particleSpawner.map((particleSpec) => particleSpec.elapsed += elapsedTime);
+              particleSpawners[id] = particleSpawner.filter((particleSpec) => particleSpec.lifetime > particleSpec.elapsed);
+              particleSpawner = particleSpawners[id];
+              if (particleSpawner.length === 0) {
+                entities[id].removeComponent("alive");
+              }
+              particleSpawner.map((particleSpec) => {
+                const position = {x: (particleSpec.x * width) + x + particleSpec.dx * particleSpec.elapsed, y: (particleSpec.y * height) + y + particleSpec.dy * particleSpec.elapsed};
+                const fill = context.fillStyle;
+                context.fillStyle = particleSpec.color;
+                context.beginPath();
+                context.arc(position.x, position.y, particleSpec.radius, 0, 2 * Math.PI);
+                context.fill();
+                context.fillStyle = fill;
+              });
+            }
+          });
+        }
+      }
+    }
+    return new Set();
+  };
+
+  return { update };
+};