VisualHash.swift (Value -> Emoji / Pastel / Neon)

VisualHash.swift

import CryptoKit
import SwiftUI

#if canImport(UIKit)
  import UIKit
#elseif canImport(AppKit)
  import AppKit
#endif

public enum VisualHash {

  public static func pastel(from item: some Codable) -> Color {
    let raw = try! JSONEncoder().encode(item)
    let hash = SHA256.hash(data: raw)
           let data = Array(hash)
           let r = Double(data[0]) / 255.0
           let g = Double(data[1]) / 255.0
           let b = Double(data[2]) / 255.0

           let reader = Color(
               red: r,
               green: g,
               blue: b
           )

           let pastelHue = reader.hsba.hue
           let pastelSaturation = 0.05 + (reader.hsba.saturation * 0.35)
           let pastelBrightness = 0.6 + (reader.hsba.brightness * 0.4)

           return Color(
               hue: pastelHue,
               saturation: pastelSaturation,
               brightness: pastelBrightness
           )
  }

  public static func neon(from item: some Codable) -> Color {
    let raw = try! JSONEncoder().encode(item)
    let hash = SHA256.hash(data: raw)
    let data = Array(hash)
    let r = Double(data[0]) / 255.0
    let g = Double(data[1]) / 255.0
    let b = Double(data[2]) / 255.0

    let reader = Color(
        red: r,
        green: g,
        blue: b
    )

    let neonHue = reader.hsba.hue
    let neonSaturation = 0.7 + (reader.hsba.saturation * 0.3)
    let neonBrightness = 0.5 + (reader.hsba.brightness * 0.5)

    return Color(
      hue: neonHue,
      saturation: neonSaturation,
      brightness: neonBrightness
    )
  }

  public static func emoji(from item: some Codable) -> String {
    let raw = try! JSONEncoder().encode(item)
    let hash = SHA256.hash(data: raw).intValue
    let index = abs(hash) % contiguousEmoji.count
    return String(contiguousEmoji[index])
  }

}

extension Digest {
  var bytes: [UInt8] { Array(makeIterator()) }
  var data: Data { Data(bytes) }

  var intValue: Int {
    Int(bytes.map { String(format: "%02X", $0) }.joined(), radix: 10) ?? -1
  }
}

extension Color {
  var hsba: (hue: CGFloat, saturation: CGFloat, brightness: CGFloat, alpha: CGFloat) {
    #if canImport(UIKit)
      typealias NativeColor = UIColor
    #elseif canImport(AppKit)
      typealias NativeColor = NSColor
    #endif

    var h: CGFloat = 0
    var s: CGFloat = 0
    var b: CGFloat = 0
    var a: CGFloat = 0

    NativeColor(self)
      .getHue(&h, saturation: &s, brightness: &b, alpha: &a)

    return (h, s, b, a)
  }
}

fileprivate let contiguousEmoji: [UnicodeScalar] = {
    let ranges: [ClosedRange<Int>] = [
        0x1f600...0x1f64f,
        0x1f680...0x1f6c5,
        0x1f6cb...0x1f6d2,
        0x1f6e0...0x1f6e5,
        0x1f6f3...0x1f6fa,
        0x1f7e0...0x1f7eb,
        0x1f90d...0x1f93a,
        0x1f93c...0x1f945,
        0x1f947...0x1f971,
        0x1f973...0x1f976,
        0x1f97a...0x1f9a2,
        0x1f9a5...0x1f9aa,
        0x1f9ae...0x1f9ca,
        0x1f9cd...0x1f9ff,
        0x1fa70...0x1fa73,
        0x1fa78...0x1fa7a,
        0x1fa80...0x1fa82,
        0x1fa90...0x1fa95,
    ]

    return ranges.reduce([], +).map { return UnicodeScalar($0)! }
}()