From dd243a4e235b29a70a61e49069b811928ecc5d33 Mon Sep 17 00:00:00 2001
From: Richard King <richrdkng@gmail.com>
Date: Wed, 23 Aug 2023 12:08:12 +0200
Subject: [PATCH] feat(weighted): initial release

---
 packages/weighted/src/RandomWeighted/index.ts | 69 +++++++++++++++++++
 packages/weighted/src/index.ts                |  7 ++
 .../test/RandomWeighted/index.test.ts         | 69 +++++++++++++++++++
 3 files changed, 145 insertions(+)
 create mode 100644 packages/weighted/src/RandomWeighted/index.ts
 create mode 100644 packages/weighted/src/index.ts
 create mode 100644 packages/weighted/test/RandomWeighted/index.test.ts

diff --git a/packages/weighted/src/RandomWeighted/index.ts b/packages/weighted/src/RandomWeighted/index.ts
new file mode 100644
index 0000000..c7ceab2
--- /dev/null
+++ b/packages/weighted/src/RandomWeighted/index.ts
@@ -0,0 +1,69 @@
+import { RandomGenerator } from '@grandom/core'
+
+export default class RandomWeighted extends RandomGenerator {
+  /**
+   * Returns a value according the weights.
+   *
+   * @param weightsWithValues An array of weight-value pairs.
+   */
+  weighted <T extends Array<[number, any]>> (weightsWithValues: T): T[number][1]
+
+  /**
+   * Returns a value according the weights.
+   *
+   * @param values An array of values.
+   * @param weights An array of weights.
+   */
+  weighted <T> (values: T[], weights: number[]): T
+
+  weighted (arg1: any, arg2?: any): any {
+    if (typeof arg1 !== 'undefined') {
+      const weights: number[] = []
+      const elements: any[] = []
+
+      // process weightsWithValues -----------------------------------------------------------------
+      if (typeof arg2 === 'undefined') {
+        if (!Array.isArray(arg1)) {
+          // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
+          throw new Error(`weightsWithValues must be an array, got: ${arg1} (typeof === '${typeof arg1}').`)
+        }
+
+        if (arg1.length < 1) {
+          return
+        }
+
+        for (const weightWithValue of arg1) {
+          const weight = weightWithValue[0]
+
+          if (!(1 in weightWithValue)) {
+            // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
+            throw new Error(`value doesn't exist in ${weightWithValue}`)
+          }
+
+          const value = weightWithValue[1]
+
+          weights.push(weight)
+          elements.push(value)
+        }
+
+        return this._engine.nextWeighted(elements, weights)
+
+      // process values, and weights ---------------------------------------------------------------
+      } else {
+        if (arg1.length < 1) {
+          return
+        }
+
+        for (let i = 0; i < arg1.length; i++) {
+          const value = arg1[i]
+          const weight = arg2[i]
+
+          weights.push(weight)
+          elements.push(value)
+        }
+
+        return this._engine.nextWeighted(elements, weights)
+      }
+    }
+  }
+}
diff --git a/packages/weighted/src/index.ts b/packages/weighted/src/index.ts
new file mode 100644
index 0000000..bacb7cb
--- /dev/null
+++ b/packages/weighted/src/index.ts
@@ -0,0 +1,7 @@
+import BasicEngine from '@grandom/engines/basic'
+import RandomWeighted from './RandomWeighted'
+
+const random = new RandomWeighted(new BasicEngine())
+const weighted = random.weighted.bind(random)
+
+export default weighted
diff --git a/packages/weighted/test/RandomWeighted/index.test.ts b/packages/weighted/test/RandomWeighted/index.test.ts
new file mode 100644
index 0000000..8b269ef
--- /dev/null
+++ b/packages/weighted/test/RandomWeighted/index.test.ts
@@ -0,0 +1,69 @@
+import { BasicEngine } from '@grandom/engines'
+import RandomWeighted from '../../src/RandomWeighted'
+
+const random = new RandomWeighted(new BasicEngine())
+
+describe('RandomWeighted', () => {
+  describe('.weighted()', () => {
+    describe('weight-value pair array', () => {
+      test('empty weight-value array', () => {
+        expect(random.weighted([])).toBeUndefined()
+      })
+
+      test('weight-value array of length === 1', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted([[1, 'a']])).toBe('a')
+        }
+      })
+
+      test('weight-value array of length === 2', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted([
+            [1, 'a'],
+            [2, 3]
+          ])).toBeOneOf(['a', 3])
+        }
+      })
+
+      test('weight-value array of length === 3', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted([
+            [1, 'a'],
+            [2, 3],
+            [3, false]
+          ])).toBeOneOf(['a', 3, false])
+        }
+      })
+    })
+
+    describe('values array, weights array', () => {
+      test('empty values, empty weights', () => {
+        expect(random.weighted([], [])).toBeUndefined()
+      })
+
+      test('1 pair of value-weight', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted(['a'], [1])).toBe('a')
+        }
+      })
+
+      test('2 pairs of value-weight', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted(
+            ['a', 3],
+            [1, 2]
+          )).toBeOneOf(['a', 3])
+        }
+      })
+
+      test('3 pairs of value-weight', () => {
+        for (let i = 0; i < 10_000; i++) {
+          expect(random.weighted(
+            ['a', 3, false],
+            [1, 2, 3]
+          )).toBeOneOf(['a', 3, false])
+        }
+      })
+    })
+  })
+})