feat(🧮): Coordinate transformations (#141)

.circleci/config.yml

@@ -34,6 +34,8 @@ jobs:
           key: v1-dependencies-{{ checksum "package.json" }}
 
       # run tests!
+      - run: yarn lint
+      - run: yarn tsc
       - run: yarn test
 
       - deploy:

.eslintrc

@@ -10,5 +10,8 @@
         ]
       }
     ]
+  },
+  "env": {
+    "jest": true
   }
 }

README.md

@@ -205,6 +205,38 @@ Returns the coordinate of a cubic bezier curve.
 `p0` and `p3` are respectively the starting and ending point of the curve.
 `p1` and `p2` are the control points.
 
+## Coordinates
+
+In order to easily build certain types of animations, it can be extremely useful to switch from one coordinate system to another.
+
+For instance, to convert a `x` and `y` coordinate from the React Native canvas to a polar coordinate system centered at `100, 100`:
+
+```jsx
+const x = 0;
+const y = 100;
+const center = { x: 100, y: 100 };
+const {alpha, radius} = cartesian2Polart(
+  canvas2Cartesian({ x, y }, center)
+);
+// alpha is π, radius: 100
+```
+
+```
+cartesian2Canvas({ x, y }, center)
+```
+
+```
+canvas2Cartesian({ x, y }, center)
+```
+
+```
+cartesianToPolar({ x, y })
+```
+
+```
+polarToCartesian({ x, y })
+```
+
 ## String
 
 ### `string`

babel.config.js

@@ -0,0 +1,9 @@
+// babel.config.js
+module.exports = {
+  presets: ["@babel/preset-env", "@babel/preset-react", "@babel/preset-flow"],
+  plugins: [
+    "@babel/plugin-proposal-class-properties",
+    "@babel/plugin-proposal-nullish-coalescing-operator",
+    "@babel/plugin-proposal-optional-chaining"
+  ]
+};

jest.config.js

@@ -0,0 +1,186 @@
+// For a detailed explanation regarding each configuration property, visit:
+// https://jestjs.io/docs/en/configuration.html
+
+module.exports = {
+  // All imported modules in your tests should be mocked automatically
+  // automock: false,
+
+  // Stop running tests after `n` failures
+  // bail: 0,
+
+  // Respect "browser" field in package.json when resolving modules
+  // browser: false,
+
+  // The directory where Jest should store its cached dependency information
+  // cacheDirectory: "/private/var/folders/xf/hkqnmwhs2894qycxl5cx3hf40000gn/T/jest_dx",
+
+  // Automatically clear mock calls and instances between every test
+  // clearMocks: false,
+
+  // Indicates whether the coverage information should be collected while executing the test
+  // collectCoverage: false,
+
+  // An array of glob patterns indicating a set of files for which coverage information should be collected
+  // collectCoverageFrom: null,
+
+  // The directory where Jest should output its coverage files
+  // coverageDirectory: null,
+
+  // An array of regexp pattern strings used to skip coverage collection
+  // coveragePathIgnorePatterns: [
+  //   "/node_modules/"
+  // ],
+
+  // A list of reporter names that Jest uses when writing coverage reports
+  // coverageReporters: [
+  //   "json",
+  //   "text",
+  //   "lcov",
+  //   "clover"
+  // ],
+
+  // An object that configures minimum threshold enforcement for coverage results
+  // coverageThreshold: null,
+
+  // A path to a custom dependency extractor
+  // dependencyExtractor: null,
+
+  // Make calling deprecated APIs throw helpful error messages
+  // errorOnDeprecated: false,
+
+  // Force coverage collection from ignored files using an array of glob patterns
+  // forceCoverageMatch: [],
+
+  // A path to a module which exports an async function that is triggered once before all test suites
+  // globalSetup: null,
+
+  // A path to a module which exports an async function that is triggered once after all test suites
+  // globalTeardown: null,
+
+  // A set of global variables that need to be available in all test environments
+  // globals: {},
+
+  // The maximum amount of workers used to run your tests. Can be specified as % or a number. E.g. maxWorkers: 10% will use 10% of your CPU amount + 1 as the maximum worker number. maxWorkers: 2 will use a maximum of 2 workers.
+  // maxWorkers: "50%",
+
+  // An array of directory names to be searched recursively up from the requiring module's location
+  // moduleDirectories: [
+  //   "node_modules"
+  // ],
+
+  // An array of file extensions your modules use
+  // moduleFileExtensions: [
+  //   "js",
+  //   "json",
+  //   "jsx",
+  //   "ts",
+  //   "tsx",
+  //   "node"
+  // ],
+
+  // A map from regular expressions to module names that allow to stub out resources with a single module
+  // moduleNameMapper: {},
+
+  // An array of regexp pattern strings, matched against all module paths before considered 'visible' to the module loader
+  // modulePathIgnorePatterns: [],
+
+  // Activates notifications for test results
+  // notify: false,
+
+  // An enum that specifies notification mode. Requires { notify: true }
+  // notifyMode: "failure-change",
+
+  // A preset that is used as a base for Jest's configuration
+  preset: "react-native",
+
+  // Run tests from one or more projects
+  // projects: null,
+
+  // Use this configuration option to add custom reporters to Jest
+  // reporters: undefined,
+
+  // Automatically reset mock state between every test
+  // resetMocks: false,
+
+  // Reset the module registry before running each individual test
+  // resetModules: false,
+
+  // A path to a custom resolver
+  // resolver: null,
+
+  // Automatically restore mock state between every test
+  // restoreMocks: false,
+
+  // The root directory that Jest should scan for tests and modules within
+  // rootDir: null,
+
+  // A list of paths to directories that Jest should use to search for files in
+  roots: ["src"],
+
+  // Allows you to use a custom runner instead of Jest's default test runner
+  // runner: "jest-runner",
+
+  // The paths to modules that run some code to configure or set up the testing environment before each test
+  // setupFiles: [],
+
+  // A list of paths to modules that run some code to configure or set up the testing framework before each test
+  // setupFilesAfterEnv: [],
+
+  // A list of paths to snapshot serializer modules Jest should use for snapshot testing
+  // snapshotSerializers: [],
+
+  // The test environment that will be used for testing
+  testEnvironment: "node"
+
+  // Options that will be passed to the testEnvironment
+  // testEnvironmentOptions: {},
+
+  // Adds a location field to test results
+  // testLocationInResults: false,
+
+  // The glob patterns Jest uses to detect test files
+  // testMatch: [
+  //   "**/__tests__/**/*.[jt]s?(x)",
+  //   "**/?(*.)+(spec|test).[tj]s?(x)"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all test paths, matched tests are skipped
+  // testPathIgnorePatterns: [
+  //   "/node_modules/"
+  // ],
+
+  // The regexp pattern or array of patterns that Jest uses to detect test files
+  // testRegex: [],
+
+  // This option allows the use of a custom results processor
+  // testResultsProcessor: null,
+
+  // This option allows use of a custom test runner
+  // testRunner: "jasmine2",
+
+  // This option sets the URL for the jsdom environment. It is reflected in properties such as location.href
+  // testURL: "http://localhost",
+
+  // Setting this value to "fake" allows the use of fake timers for functions such as "setTimeout"
+  // timers: "real",
+
+  // A map from regular expressions to paths to transformers
+  // transform: null,
+
+  // An array of regexp pattern strings that are matched against all source file paths, matched files will skip transformation
+  // transformIgnorePatterns: [
+  //   "/node_modules/"
+  // ],
+
+  // An array of regexp pattern strings that are matched against all modules before the module loader will automatically return a mock for them
+  // unmockedModulePathPatterns: undefined,
+
+  // Indicates whether each individual test should be reported during the run
+  // verbose: null,
+
+  // An array of regexp patterns that are matched against all source file paths before re-running tests in watch mode
+  // watchPathIgnorePatterns: [],
+
+  // Whether to use watchman for file crawling
+  // watchman: true,
+};

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "lint": "eslint --ext .ts,.tsx src",
     "tsc": "tsc --noEmit",
-    "test": "yarn lint && yarn tsc",
+    "test": "jest",
     "prepare": "bob build",
     "semantic-release": "semantic-release"
   },
@@ -27,12 +27,23 @@
     "react-native-reanimated": "*"
   },
   "devDependencies": {
+    "@babel/core": "^7.7.7",
+    "@babel/plugin-proposal-class-properties": "^7.7.4",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.7.4",
+    "@babel/plugin-proposal-optional-chaining": "^7.7.5",
+    "@babel/preset-env": "^7.7.7",
+    "@babel/preset-flow": "^7.7.4",
+    "@babel/preset-react": "^7.7.4",
+    "@babel/preset-typescript": "^7.7.7",
     "@react-native-community/bob": "^0.4.1",
     "@types/color": "^3.0.0",
+    "@types/jest": "^24.0.24",
     "@types/react": "*",
     "@types/react-native": "^0.60.25",
+    "babel-jest": "^24.9.0",
     "eslint": "^6.7.2",
     "eslint-config-react-native-wcandillon": "2.3.1",
+    "jest": "^24.9.0",
     "react": "^16.8.6",
     "react-native": "^0.61.0",
     "react-native-gesture-handler": "~1.5.0",

src/Coordinates.test.ts

@@ -0,0 +1,65 @@
+import {
+  canvas2Cartesian,
+  cartesian2Canvas,
+  cartesian2Polar,
+  polar2Cartesian
+} from "./Coordinates";
+
+jest.mock("react-native-reanimated");
+
+test("canvas2Cartesian 1", () => {
+  const point = canvas2Cartesian({ x: 500, y: 200 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(0);
+  expect(point.y[" __value"]).toBe(-0);
+});
+
+test("canvas2Cartesian 2", () => {
+  const point = canvas2Cartesian({ x: 0, y: 0 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(-500);
+  expect(point.y[" __value"]).toBe(200);
+});
+
+test("canvas2Cartesian 3", () => {
+  const point = canvas2Cartesian({ x: 600, y: 300 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(100);
+  expect(point.y[" __value"]).toBe(-100);
+});
+
+test("cartesian2Canvas 1", () => {
+  const point = cartesian2Canvas({ x: 0, y: 0 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(500);
+  expect(point.y[" __value"]).toBe(200);
+});
+
+test("cartesian2Canvas 2", () => {
+  const point = cartesian2Canvas({ x: -500, y: 200 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(0);
+  expect(point.y[" __value"]).toBe(0);
+});
+
+test("canvas2Cartesian 3", () => {
+  const point = cartesian2Canvas({ x: 100, y: -100 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(600);
+  expect(point.y[" __value"]).toBe(300);
+});
+
+test("canvas2Cartesian 3", () => {
+  const point = cartesian2Canvas({ x: 100, y: -100 }, { x: 500, y: 200 });
+  expect(point.x[" __value"]).toBe(600);
+  expect(point.y[" __value"]).toBe(300);
+});
+
+test("cartesian2Polar", () => {
+  const x = 0;
+  const y = 100;
+  const center = { x: 100, y: 100 };
+  const { alpha, radius } = cartesian2Polar(canvas2Cartesian({ x, y }, center));
+  expect(alpha[" __value"]).toBe(Math.PI);
+  expect(radius[" __value"]).toBe(100);
+  const { x: x1, y: y1 } = cartesian2Canvas(
+    polar2Cartesian({ alpha, radius }),
+    center
+  );
+  expect(x1[" __value"]).toBe(0);
+  expect(Math.round(y1[" __value"])).toBe(100);
+});

src/Coordinates.ts

@@ -0,0 +1,39 @@
+import Animated from "react-native-reanimated";
+
+import { atan2 } from "./Math";
+
+const { sub, multiply, add, cos, sin, pow, sqrt } = Animated;
+
+export interface Point {
+  x: Animated.Adaptable<number>;
+  y: Animated.Adaptable<number>;
+}
+
+export interface PolarPoint {
+  alpha: Animated.Adaptable<number>;
+  radius: Animated.Adaptable<number>;
+}
+
+export const canvas2Cartesian = ({ x, y }: Point, center: Point): Point => {
+  return {
+    x: sub(x, center.x),
+    y: multiply(sub(y, center.y), -1)
+  };
+};
+
+export const cartesian2Canvas = ({ x, y }: Point, center: Point): Point => ({
+  x: add(x, center.x),
+  y: add(multiply(y, -1), center.y)
+});
+
+export const cartesian2Polar = ({ x, y }: Point): PolarPoint => {
+  return {
+    alpha: atan2(y, x),
+    radius: sqrt(add(pow(x, 2), pow(y, 2)))
+  };
+};
+
+export const polar2Cartesian = ({ alpha, radius }: PolarPoint): Point => ({
+  x: multiply(radius, cos(alpha)),
+  y: multiply(radius, sin(alpha))
+});