From 47ea7a90ad539c2aa37598b6f8c8322c05c5c44d Mon Sep 17 00:00:00 2001
From: Felicio Mununga <felicio@users.noreply.github.com>
Date: Fri, 10 Jun 2022 19:30:23 +0200
Subject: [PATCH] Add color hash function (#264)

---
 .../utils/public-key-to-color-hash.test.ts    | 63 ++++++++++++++
 .../src/utils/public-key-to-color-hash.ts     | 85 +++++++++++++++++++
 2 files changed, 148 insertions(+)
 create mode 100644 packages/status-js/src/utils/public-key-to-color-hash.test.ts
 create mode 100644 packages/status-js/src/utils/public-key-to-color-hash.ts

diff --git a/packages/status-js/src/utils/public-key-to-color-hash.test.ts b/packages/status-js/src/utils/public-key-to-color-hash.test.ts
new file mode 100644
index 0000000..7544fd0
--- /dev/null
+++ b/packages/status-js/src/utils/public-key-to-color-hash.test.ts
@@ -0,0 +1,63 @@
+import {
+  hexToColorHash,
+  publicKeyToColorHash,
+} from './public-key-to-color-hash'
+
+test('returns color hash from public key', () => {
+  expect(
+    publicKeyToColorHash(
+      '0x04e25da6994ea2dc4ac70727e07eca153ae92bf7609db7befb7ebdceaad348f4fc55bbe90abf9501176301db5aa103fc0eb3bc3750272a26c424a10887db2a7ea8'
+    )
+  ).toEqual([
+    [3, 30],
+    [2, 10],
+    [5, 5],
+    [3, 14],
+    [5, 4],
+    [4, 19],
+    [3, 16],
+    [4, 0],
+    [5, 28],
+    [4, 13],
+    [4, 15],
+  ])
+})
+
+test('returns undefined for invalid public keys', () => {
+  expect(publicKeyToColorHash('abc')).toBeUndefined()
+  expect(publicKeyToColorHash('0x01')).toBeUndefined()
+  expect(
+    publicKeyToColorHash(
+      '0x01e25da6994ea2dc4ac70727e07eca153ae92bf7609db7befb7ebdceaad348f4fc55bbe90abf9501176301db5aa103fc0eb3bc3750272a26c424a10887db2a7ea8'
+    )
+  ).toBeUndefined()
+  expect(
+    publicKeyToColorHash(
+      '0x04425da6994ea2dc4ac70727e07eca153ae92bf7609db7befb7ebdceaad348f4fc55bbe90abf9501176301db5aa103fc0eb3bc3750272a26c424a10887db2a7ea8'
+    )
+  ).toBeUndefined()
+})
+
+test('returns color hash from hex', () => {
+  expect(hexToColorHash('0', 4, 4)).toEqual([[1, 0]])
+  expect(hexToColorHash('1', 4, 4)).toEqual([[1, 1]])
+  expect(hexToColorHash('4', 4, 4)).toEqual([[2, 0]])
+  expect(hexToColorHash('F', 4, 4)).toEqual([[4, 3]])
+})
+
+test('returns color hash from hex with redecued collision resistance', () => {
+  expect(hexToColorHash('FF', 4, 4)).toEqual([
+    [4, 3],
+    [4, 0],
+  ])
+  expect(hexToColorHash('FC', 4, 4)).toEqual([
+    [4, 3],
+    [4, 0],
+  ])
+  expect(hexToColorHash('FFFF', 4, 4)).toEqual([
+    [4, 3],
+    [4, 0],
+    [4, 3],
+    [4, 0],
+  ])
+})
diff --git a/packages/status-js/src/utils/public-key-to-color-hash.ts b/packages/status-js/src/utils/public-key-to-color-hash.ts
new file mode 100644
index 0000000..3aac05c
--- /dev/null
+++ b/packages/status-js/src/utils/public-key-to-color-hash.ts
@@ -0,0 +1,85 @@
+import * as secp256k1 from 'ethereum-cryptography/secp256k1'
+
+type ColorHash = number[][]
+
+const COLOR_HASH_COLORS_COUNT = 32
+const COLOR_HASH_SEGMENT_MAX_LENGTH = 5
+
+export function publicKeyToColorHash(publicKey: string): ColorHash | undefined {
+  const publicKeyHex = publicKey.replace(/^0[xX]/, '') // ensures hexadecimal digits without "base prefix"
+
+  let compressedPublicKeyDigits: string
+  try {
+    compressedPublicKeyDigits =
+      secp256k1.Point.fromHex(publicKeyHex).toHex(true) // validates and adds "sign prefix" too
+  } catch (error) {
+    return undefined
+  }
+
+  const colorHashHex = compressedPublicKeyDigits.slice(43, 63)
+  const colorHash = hexToColorHash(
+    colorHashHex,
+    COLOR_HASH_COLORS_COUNT,
+    COLOR_HASH_SEGMENT_MAX_LENGTH
+  )
+
+  return colorHash
+}
+
+export function hexToColorHash(
+  hex: string,
+  colorsCount: number,
+  segmentLength: number
+): ColorHash {
+  const colorIndices = numberToIndices(
+    BigInt(`0x${hex}`),
+    BigInt(colorsCount * segmentLength)
+  )
+  const colorHash = colorIndicesToColorHash(colorIndices, colorsCount)
+
+  return colorHash
+}
+
+function numberToIndices(number: bigint, base: bigint): bigint[] {
+  const indices: bigint[] = []
+  let nextNumber = number
+
+  if (nextNumber === 0n) {
+    return [0n]
+  }
+
+  while (nextNumber > 0n) {
+    const modulo = secp256k1.utils.mod(nextNumber, base)
+    nextNumber = nextNumber / base // truncates fractional results
+
+    indices.push(modulo)
+  }
+
+  return indices.reverse()
+}
+
+function colorIndicesToColorHash(
+  colorIndices: bigint[],
+  colorsCount: number
+): ColorHash {
+  const colorHash: ColorHash = []
+  let previousColorIndex: number | undefined = undefined
+
+  for (const currentColorIndex of colorIndices) {
+    const colorLength = Math.ceil((Number(currentColorIndex) + 1) / colorsCount)
+    const nextColorIndex = Number(currentColorIndex % BigInt(colorsCount))
+
+    let colorIndex: number
+    if (nextColorIndex !== previousColorIndex) {
+      colorIndex = nextColorIndex
+    } else {
+      colorIndex = Number((currentColorIndex + 1n) % BigInt(colorsCount))
+    }
+
+    previousColorIndex = colorIndex
+
+    colorHash.push([colorLength, colorIndex])
+  }
+
+  return colorHash
+}