From b5a612cd0fb0a50ecf6f831cffc0a8e0678d03ce Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Tue, 18 May 2021 10:29:00 +0100
Subject: [PATCH] Add space invaders chat effect

---
 src/effects/index.ts               |  11 +++
 src/effects/spaceinvaders/index.ts | 119 +++++++++++++++++++++++++++++
 src/i18n/strings/en_EN.json        |   2 +
 3 files changed, 132 insertions(+)
 create mode 100644 src/effects/spaceinvaders/index.ts

diff --git a/src/effects/index.ts b/src/effects/index.ts
index 1a6858be08..8ecb80020d 100644
--- a/src/effects/index.ts
+++ b/src/effects/index.ts
@@ -62,6 +62,17 @@ export const CHAT_EFFECTS: Array<Effect<{ [key: string]: any }>> = [
             maxDrift: 5,
         },
     } as Effect<SnowfallOptions>,
+    {
+        emojis: ["👾", "🌌"],
+        msgType: "io.element.effects.space_invaders",
+        command: "spaceinvaders",
+        description: () => _td("Sends the given message with a space themed effect"),
+        fallbackMessage: () => _t("sends space invaders") + " 👾",
+        options: {
+            maxCount: 50,
+            gravity: 0.01,
+        },
+    } as Effect<SpaceInvadersOptions>,
 ];
 
 
diff --git a/src/effects/spaceinvaders/index.ts b/src/effects/spaceinvaders/index.ts
new file mode 100644
index 0000000000..55eb6dc29f
--- /dev/null
+++ b/src/effects/spaceinvaders/index.ts
@@ -0,0 +1,119 @@
+/*
+ Copyright 2021 The Matrix.org Foundation C.I.C.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ */
+import ICanvasEffect from '../ICanvasEffect';
+import { arrayFastClone } from "../../utils/arrays";
+
+export type SpaceInvadersOptions = {
+    /**
+     * The maximum number of invaders to render at a given time
+     */
+    maxCount: number;
+    /**
+     * The amount of gravity to apply to the invaders
+     */
+    gravity: number;
+}
+
+type Invader = {
+    x: number;
+    y: number;
+    xCol: number;
+    gravity: number;
+}
+
+export const DefaultOptions: SpaceInvadersOptions = {
+    maxCount: 50,
+    gravity: 0.005,
+};
+
+const KEY_FRAME_INTERVAL = 15; // 15ms, roughly
+const GLYPH = "👾";
+
+export default class SpaceInvaders implements ICanvasEffect {
+    private readonly options: SpaceInvadersOptions;
+
+    constructor(options: { [key: string]: any }) {
+        this.options = {...DefaultOptions, ...options};
+    }
+
+    private context: CanvasRenderingContext2D | null = null;
+    private particles: Array<Invader> = [];
+    private lastAnimationTime: number;
+
+    public isRunning: boolean;
+
+    public start = async (canvas: HTMLCanvasElement, timeout = 3000) => {
+        if (!canvas) {
+            return;
+        }
+        this.context = canvas.getContext('2d');
+        this.particles = [];
+        const count = this.options.maxCount;
+        while (this.particles.length < count) {
+            this.particles.push(this.resetParticle({} as Invader, canvas.width, canvas.height));
+        }
+        this.isRunning = true;
+        requestAnimationFrame(this.renderLoop);
+        if (timeout) {
+            window.setTimeout(this.stop, timeout);
+        }
+    }
+
+    public stop = async () => {
+        this.isRunning = false;
+    }
+
+    private resetParticle = (particle: Invader, width: number, height: number): Invader => {
+        particle.x = Math.random() * width;
+        particle.y = Math.random() * -height;
+        particle.xCol = particle.x;
+        particle.gravity = this.options.gravity + (Math.random() * 6) + 4;
+        return particle;
+    }
+
+    private renderLoop = (): void => {
+        if (!this.context || !this.context.canvas) {
+            return;
+        }
+        if (this.particles.length === 0) {
+            this.context.clearRect(0, 0, this.context.canvas.width, this.context.canvas.height);
+        } else {
+            const timeDelta = Date.now() - this.lastAnimationTime;
+            if (timeDelta >= KEY_FRAME_INTERVAL || !this.lastAnimationTime) {
+                // Clear the screen first
+                this.context.clearRect(0, 0, this.context.canvas.width, this.context.canvas.height);
+
+                this.lastAnimationTime = Date.now();
+                this.animateAndRenderSnowflakes();
+            }
+            requestAnimationFrame(this.renderLoop);
+        }
+    };
+
+    private animateAndRenderSnowflakes() {
+        if (!this.context || !this.context.canvas) {
+            return;
+        }
+        this.context.font = "50px Twemoji";
+        for (const particle of arrayFastClone(this.particles)) {
+            particle.y += particle.gravity;
+
+            this.context.save();
+            this.context.fillText(GLYPH, particle.x, particle.y);
+            this.context.restore();
+        }
+    }
+}
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 9d5e17ba2d..5e0cd4c47c 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -884,6 +884,8 @@
     "sends fireworks": "sends fireworks",
     "Sends the given message with snowfall": "Sends the given message with snowfall",
     "sends snowfall": "sends snowfall",
+    "Sends the given message with a space themed effect": "Sends the given message with a space themed effect",
+    "sends space invaders": "sends space invaders",
     "unknown person": "unknown person",
     "Consulting with %(transferTarget)s. <a>Transfer to %(transferee)s</a>": "Consulting with %(transferTarget)s. <a>Transfer to %(transferee)s</a>",
     "You held the call <a>Switch</a>": "You held the call <a>Switch</a>",