feat: add geometry triangle

Geometry/Test/Triangle.test.js

@@ -0,0 +1,95 @@
+import Triangle from '../Triangle'
+
+describe('Triangle', () => {
+  describe('Constructor', () => {
+    test('creates a triangle with base and height', () => {
+      const triangle = new Triangle(5, 10)
+      expect(triangle).toBeInstanceOf(Triangle)
+      expect(triangle.base).toBe(5)
+      expect(triangle.height).toBe(10)
+      expect(triangle.sides).toEqual([5, null, null])
+    })
+
+    test('creates a triangle with three sides', () => {
+      const triangle = new Triangle(3, 4, 5)
+      expect(triangle).toBeInstanceOf(Triangle)
+      expect(triangle.sides).toEqual([3, 4, 5])
+      expect(triangle.base).toBe(3) // Assuming base is one of the sides
+      expect(triangle.height).toBe(null)
+    })
+
+    test('throws an error if invalid number of arguments', () => {
+      expect(() => new Triangle()).toThrow(
+        'Invalid number of arguments. Use either (base, height) or (sideA, sideB, sideC).'
+      )
+      expect(() => new Triangle(1)).toThrow(
+        'Invalid number of arguments. Use either (base, height) or (sideA, sideB, sideC).'
+      )
+    })
+
+    test('throws an error if the triangle is invalid', () => {
+      expect(() => new Triangle(1, 2, 3)).toThrow(
+        'Invalid triangle: The sum of any two sides must be greater than the third side.'
+      )
+    })
+  })
+
+  describe('Area Calculation', () => {
+    test('calculates area correctly using base and height', () => {
+      const triangle = new Triangle(5, 10)
+      expect(triangle.area()).toBe(25)
+    })
+
+    test("calculates area correctly using Heron's formula", () => {
+      const triangle = new Triangle(3, 4, 5)
+      expect(triangle.area()).toBe(6) // Area of a 3-4-5 triangle
+    })
+  })
+
+  describe('Perimeter Calculation', () => {
+    test('calculates perimeter correctly for three sides', () => {
+      const triangle = new Triangle(3, 4, 5)
+      expect(triangle.perimeter()).toBe(12) // 3 + 4 + 5
+    })
+
+    test('throws an error if not all sides are known', () => {
+      const triangle = new Triangle(5, 10)
+      expect(() => triangle.perimeter()).toThrow(
+        'Cannot calculate perimeter: not all sides are known.'
+      )
+    })
+  })
+
+  describe('Getters', () => {
+    test('base getter returns correct value', () => {
+      const triangle = new Triangle(5, 10)
+      expect(triangle.base).toBe(5)
+    })
+
+    test('height getter returns correct value', () => {
+      const triangle = new Triangle(5, 10)
+      expect(triangle.height).toBe(10)
+    })
+
+    test('sides getter returns correct values', () => {
+      const triangle = new Triangle(3, 4, 5)
+      expect(triangle.sides).toEqual([3, 4, 5])
+    })
+  })
+
+  describe('String Representation', () => {
+    test('returns correct string representation for base and height', () => {
+      const triangle = new Triangle(5, 10)
+      expect(triangle.toString()).toBe(
+        'Triangle: base = 5, height = 10, sides = 5, unknown, unknown, area = 25, perimeter = unknown'
+      )
+    })
+
+    test('returns correct string representation for three sides', () => {
+      const triangle = new Triangle(3, 4, 5)
+      expect(triangle.toString()).toBe(
+        'Triangle: base = 3, height = unknown, sides = 3, 4, 5, area = 6, perimeter = 12'
+      )
+    })
+  })
+})

Geometry/Triangle.js

@@ -0,0 +1,157 @@
+/**
+ * This class represents a Triangle and provides methods to calculate its area and perimeter
+ * based on either all three sides or the base and height.
+ * @see {@link https://en.wikipedia.org/wiki/Triangle}
+ * @class
+ */
+export default class Triangle {
+  /** @private */
+  #base
+
+  /** @private */
+  #height
+
+  /** @private */
+  #sides
+
+  /**
+   * Creates a triangle instance.
+   * @constructor
+   * @param {...number} args - The dimensions of the triangle.
+   * @throws {Error} Will throw an error if the number of arguments is invalid or if the triangle is invalid.
+   */
+  constructor(...args) {
+    if (args.length === 2) {
+      this.#initializeFromBaseAndHeight(...args)
+    } else if (args.length === 3) {
+      this.#initializeFromSides(...args)
+    } else {
+      throw new Error(
+        'Invalid number of arguments. Use either (base, height) or (sideA, sideB, sideC).'
+      )
+    }
+  }
+
+  /**
+   * Initializes the triangle from base and height.
+   * @private
+   * @param {number} base - The base of the triangle.
+   * @param {number} height - The height of the triangle.
+   */
+  #initializeFromBaseAndHeight(base, height) {
+    this.#base = base
+    this.#height = height
+    this.#sides = [base, null, null]
+  }
+
+  /**
+   * Initializes the triangle from three sides.
+   * @private
+   * @param {number} sideA - The length of side A.
+   * @param {number} sideB - The length of side B.
+   * @param {number} sideC - The length of side C.
+   * @throws {Error} Will throw an error if the triangle is invalid.
+   */
+  #initializeFromSides(sideA, sideB, sideC) {
+    if (!this.#isValidTriangle(sideA, sideB, sideC)) {
+      throw new Error(
+        'Invalid triangle: The sum of any two sides must be greater than the third side.'
+      )
+    }
+    this.#sides = [sideA, sideB, sideC]
+    this.#base = sideA // Assuming base is one of the sides for consistency
+    this.#height = null
+  }
+
+  /**
+   * Checks if three sides can form a valid triangle.
+   * @private
+   * @param {number} a - The length of side A.
+   * @param {number} b - The length of side B.
+   * @param {number} c - The length of side C.
+   * @returns {boolean} True if the triangle is valid; false otherwise.
+   */
+  #isValidTriangle(a, b, c) {
+    return a + b > c && b + c > a && c + a > b
+  }
+
+  /**
+   * Calculates the area of the triangle.
+   * @public
+   * @returns {number} The area of the triangle.
+   */
+  area() {
+    if (this.#height !== null) {
+      return 0.5 * this.#base * this.#height
+    }
+    // Using Heron's formula
+    const [a, b, c] = this.#sides
+    const s = (a + b + c) / 2
+    return Math.sqrt(s * (s - a) * (s - b) * (s - c))
+  }
+
+  /**
+   * Calculates the perimeter of the triangle.
+   * @public
+   * @returns {number} The perimeter of the triangle.
+   * @throws {Error} Will throw an error if not all sides are known.
+   */
+  perimeter() {
+    if (this.#sides.some((side) => side === null)) {
+      throw new Error('Cannot calculate perimeter: not all sides are known.')
+    }
+    return this.#sides.reduce((sum, side) => sum + side, 0)
+  }
+
+  /**
+   * Returns a string representation of the triangle.
+   * @public
+   * @returns {string} A string describing the triangle's dimensions and area/perimeter.
+   */
+  toString() {
+    const areaValue = this.area()
+    let perimeterValue
+
+    // Check if all sides are known for perimeter calculation
+    if (this.#sides.some((side) => side === null)) {
+      perimeterValue = 'unknown'
+    } else {
+      perimeterValue = this.perimeter()
+    }
+
+    return (
+      `Triangle: base = ${this.#base}, height = ${
+        this.#height ?? 'unknown'
+      }, ` +
+      `sides = ${this.#sides.map((side) => side ?? 'unknown').join(', ')}, ` +
+      `area = ${areaValue}, perimeter = ${perimeterValue}`
+    )
+  }
+
+  /**
+   * Gets the base of the triangle.
+   * @public
+   * @returns {number} The base of the triangle.
+   */
+  get base() {
+    return this.#base
+  }
+
+  /**
+   * Gets the height of the triangle.
+   * @public
+   * @returns {number|null} The height of the triangle or null if not defined.
+   */
+  get height() {
+    return this.#height
+  }
+
+  /**
+   * Gets the lengths of all sides of the triangle.
+   * @public
+   * @returns {Array<number|null>} An array containing lengths of all three sides or null for unknown sides.
+   */
+  get sides() {
+    return this.#sides
+  }
+}