feat: add geohash functionality

Author: kevinand11

README.md

@@ -9,27 +9,14 @@ If this is a brand new project, make sure to create a `package.json` first with
 Installation is done using the [`npm install` command](https://docs.npmjs.com/getting-started/installing-npm-packages-locally):
 
 ### Using npm:
-
     npm install valleyed
 
 ### Using yarn:
-
     yarn add valleyed
 
 ### Using CDN:
-
 [Valleyed jsDelivr CDN](https://www.jsdelivr.com/package/npm/valleyed)
 
-### Using Skypack:
-
-[Valleyed Skypack CDN](https://www.skypack.dev/view/valleyed)
-
-## Contributing
-
-[Contributing Guide](Contributing.md)
-
-[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/kevinand11/valleyed) 
-
 
 ## Basic Usage
 

src/index.ts

@@ -1,7 +1,7 @@
 export * from './api'
-
-export { Validator } from './validators'
-export * from './utils/rules'
-export * from './utils/differ'
 export * from './rules'
-export * from './utils/functions'
+export * from './utils/differ'
+export * from './utils/functions'
+export * from './utils/geohash'
+export * from './utils/rules'
+export { Validator } from './validators'

src/utils/geohash.ts

@@ -0,0 +1,152 @@
+import { v } from '../api'
+
+const Base32Chars = '0123456789bcdefghjkmnpqrstuvwxyz'
+const Base2Chars = '01'
+
+const base10ToBaseX = (num: number, base: number, chars: string) => {
+	const charsObj = Object.fromEntries(
+		chars.toLowerCase().split('')
+			.map((value, index) => [index, value])
+	)
+	const bits: string[] = []
+	if (num === 0) return '0'
+	while (num > 0) {
+		bits.push(charsObj[num % base] ?? '')
+		num = Math.floor(num / base)
+	}
+	return bits.reverse().join('')
+}
+
+const baseXToBase10 = (num: string, base: number, chars: string) => {
+	const charsObj = Object.fromEntries(
+		chars.toLowerCase().split('')
+			.map((value, index) => [value, index])
+	)
+
+	return num
+		.toLowerCase()
+		.split('')
+		.reduce((acc, cur, index, arr) => {
+			const pos = charsObj[cur] ?? 0
+			return acc + pos * Math.pow(base, arr.length - index - 1)
+		}, 0)
+}
+
+const dichotomy = (min: number, max: number, bits: string) => {
+	const res = bits
+		.split('')
+		.concat('')
+		.reduce((acc, cur) => {
+			const mid = (min + max) / 2
+			const error = (max - min) / 2
+			acc.mid = mid
+			acc.error = error
+			if (cur === '1') min = mid
+			else max = mid
+			return acc
+		}, { mid: 0, error: 0 })
+	const value = res.mid - res.error
+	return { value, interval: res.error * 2 }
+}
+
+export class Geohash {
+	static #coords (hash: string) {
+		const base10 = baseXToBase10(hash, 32, Base32Chars)
+		const base2 = base10ToBaseX(base10, 2, Base2Chars)
+			.padStart(hash.length * 5, '0')
+
+		const coords = base2
+			.split('')
+			.reduce((acc, cur, index) => {
+				if (index % 2 === 0) {
+					acc.long += cur
+				} else {
+					acc.lat += cur
+				}
+				return acc
+			}, { lat: '', long: '' })
+
+		return coords
+	}
+
+	static decode (hash: string): [number, number] {
+		const valid = v.string().min(1).parse(hash)
+		if (!valid.valid) throw new Error(valid.errors[0])
+
+		const coords = this.#coords(hash)
+		const lat = dichotomy(-90, 90, coords.lat).value
+		const long = dichotomy(-180, 180, coords.long).value
+		return [lat, long]
+	}
+
+	static encode (coords: [number, number]): string {
+		const valid = v.tuple([v.number(), v.number()]).parse(coords)
+		if (!valid.valid) throw new Error(valid.errors[0])
+
+		let idx = 0, bit = 0,
+			evenBit = true, geohash = ''
+		const mins = [-90, -180], maxs = [90, 180]
+
+		while (geohash.length < 18) {
+			const key = evenBit ? 1 : 0
+			const mid = (mins[key] + maxs[key]) / 2
+			if (coords[key] >= mid) {
+				idx = idx * 2 + 1
+				mins[key] = mid
+			} else {
+				idx = idx * 2
+				maxs[key] = mid
+			}
+			evenBit = !evenBit
+
+			bit += 1
+			if (bit === 5) {
+				geohash += base10ToBaseX(idx, 32, Base32Chars)
+				bit = idx = 0
+			}
+		}
+		return geohash.replace(/0+$/, '')
+	}
+
+	static neighbors (hash: string) {
+		const valid = v.string().min(1).parse(hash)
+		if (!valid.valid) throw new Error(valid.errors[0])
+
+		const coords = this.#coords(hash)
+		const lat = dichotomy(-90, 90, coords.lat)
+		const long = dichotomy(-180, 180, coords.long)
+		const neighbors = [
+			[lat.value - lat.interval, long.value - long.interval],
+			[lat.value - lat.interval, long.value],
+			[lat.value - lat.interval, long.value + long.interval],
+
+			[lat.value, long.value - long.interval],
+			[lat.value, long.value + long.interval],
+
+			[lat.value + lat.interval, long.value - long.interval],
+			[lat.value + lat.interval, long.value],
+			[lat.value + lat.interval, long.value + long.interval],
+		].map(([lat, long]) => {
+			return Geohash.encode([
+				this.#wrap(lat, 90),
+				this.#wrap(long, 180)
+			])
+		})
+		return {
+			bl: neighbors[0],
+			bc: neighbors[1],
+			br: neighbors[2],
+			cl: neighbors[3],
+			cr: neighbors[4],
+			tl: neighbors[5],
+			tc: neighbors[6],
+			tr: neighbors[7],
+		}
+	}
+
+	static #wrap (num: number, base: number) {
+		if (num < -base) num = num + base * 2
+		if (num > +base) num = num - base * 2
+		return num
+	}
+}