add Hexagon

lib/components/hexagon.js

@@ -0,0 +1,67 @@
+import { vec2 } from '../vector2.js'
+import { Polygon } from './polygon.js'
+
+/** @typedef {import('../vector2.js').Vector2} Vector2 */
+
+/**
+ * @typedef {object} HexagonAttributes
+ * @property {Vector2} center
+ * @property {number} [circumradius] the radius of the circumscribed circle. Either the apothem or the circumradius must be defined.
+ * @property {number} [apothem] the radius of the inscribed circle. Either the apothem or the circumradius must be defined.
+ * @property {Radians} [rotation=0]
+ */
+
+export class Hexagon extends Polygon {
+  /** @type {number} */
+  #rotation = 0
+  /** @type {number} */
+  #circumradius
+  /** @type {number} */
+  #apothem
+  /** @type {Vector2} */
+  #center
+
+  /**
+   * @param {HexagonAttributes} attributes
+   */
+  constructor({ center, circumradius, apothem, rotation = 0, ...attributes }) {
+    if (typeof circumradius !== 'number' && typeof apothem !== 'number') {
+      throw new Error('Must provide either circumradius or apothem')
+    }
+
+    // @ts-expect-error either circumradius or apothem is defined at this point
+    const cr = circumradius ?? (apothem * 2) / Math.sqrt(3)
+    const points = new Array(6)
+    for (let i = 0; i < 6; i++) {
+      const angle = (Math.PI / 3) * i + rotation
+      points[i] = center.add(
+        vec2(Math.cos(angle), Math.sin(angle)).multiply(cr),
+      )
+    }
+
+    super({ ...attributes, points })
+    this.#center = center
+    this.#circumradius = cr
+    this.#apothem = apothem ?? (cr * Math.sqrt(3)) / 2
+  }
+
+  /**
+   * @returns {Hexagon[]} the list of neighboring hexagons, assuming a hexagonal grid
+   */
+  neighbors() {
+    const hexagons = new Array(6)
+    for (let i = 0; i < 6; i++) {
+      const angle = (Math.PI / 3) * i + this.#rotation + Math.PI / 6
+      const center = this.#center.add(
+        vec2(Math.cos(angle), Math.sin(angle)).multiply(this.#apothem * 2),
+      )
+      hexagons[i] = new Hexagon({
+        center,
+        circumradius: this.#circumradius,
+        rotation: this.#rotation,
+        ...this.attributes,
+      })
+    }
+    return hexagons
+  }
+}

lib/components/hexagon.test.js

@@ -0,0 +1,33 @@
+import assert from 'node:assert'
+import { describe, it } from 'node:test'
+import { Hexagon } from './hexagon.js'
+import { vec2 } from '../vector2.js'
+
+describe('Hexagon', () => {
+  it('renders a hexagonal polygon', () => {
+    const hex = new Hexagon({
+      center: vec2(10, 10),
+      circumradius: 1,
+      rotation: Math.PI / 6,
+    })
+    hex.numericPrecision = 2
+    assert.strictEqual(
+      hex.render(),
+      '<polygon points="10.87,10.5 10,11 9.13,10.5 9.13,9.5 10,9 10.87,9.5"></polygon>',
+    )
+  })
+
+  describe('.neighbors', () => {
+    it('returns the correct number of neighbors', () => {
+      const hex = new Hexagon({
+        center: vec2(10, 10),
+        circumradius: 1,
+        rotation: Math.PI / 6,
+      })
+      const neighbors = hex.neighbors()
+      assert.strictEqual(neighbors.length, 6)
+    })
+
+    it.todo('returns the correct neighbors')
+  })
+})

lib/components/index.js

@@ -1,8 +1,9 @@
-export * from './tag.js'
-export * from './svg.js'
 export * from './circle.js'
-export * from './path.js'
 export * from './defs.js'
-export * from './rectangle.js'
+export * from './hexagon.js'
+export * from './path.js'
 export * from './polygon.js'
 export * from './polyline.js'
+export * from './rectangle.js'
+export * from './svg.js'
+export * from './tag.js'

lib/index.js

@@ -1,14 +1,14 @@
-export * from './random.js'
-export * from './math.js'
-export * from './util.js'
-export * from './vector2.js'
-export * from './color/rgb.js'
 export { ColorHsl, hsl } from './color/hsl.js'
 export * from './color/color-sequence.js'
-export * from './constants.js'
+export * from './color/rgb.js'
 export * from './components/index.js'
-export * from './data-structures/grid.js'
+export * from './constants.js'
 export * from './data-structures/fractalized-line.js'
-export * from './noise/oscillator.js'
+export * from './data-structures/grid.js'
+export * from './math.js'
 export * from './noise/oscillator-noise.js'
+export * from './noise/oscillator.js'
+export * from './random.js'
 export * from './render.js'
+export * from './util.js'
+export { Vector2, vec2 } from './vector2.js'