#!/usr/bin/env swift
// A script to set the accent colour of your Mac.
//
// This mimics the accent colour picker in the General pane of
// System Preferences, and should cause all apps to pick up the change.
//
// Usage: pass the colour you want to use as a single command-line argument,
// e.g.
//
//      $ set_accent_colour red
//      $ set_accent_colour green
//
// Tested on macOS Monterey.
//
// You may need to run `chmod +x set_accent_colour` first and install the Xcode
// command-line tools.
//
// == How it works ==
//
// You can set the accent colour using a `defaults write` command,
// e.g. to change your accent colour to pink:
//
//      $ defaults write -globalDomain AppleAccentColor -int 6
//
// But this doesn't take effect immediately -- we have to send notifications
// AppleColorPreferencesChangedNotification and
// AppleAquaColorVariantChanged to tell apps they should update their UIs.
//
// == Attribution ==
//
// Based on code/ideas by Henrik Helmers, Garth Mortensen, and Robert Sesek.
//
// See https://alexwlchan.net/2022/11/changing-the-macos-accent-colour/

import Foundation

// A map of colour names to the int values in AppleAccentColor.
//
// I created this map by selected all the accent colours in System Preferences,
// then running `defaults read -globalDomain AppleAccentColor` and recording
// the result.
let colourMap = [
  ("red",       0),
  ("orange",    1),
  ("yellow",    2),
  ("green",     3),
  ("blue",      4),
  ("purple",    5),
  ("pink",      6),
  ("graphite", -1),
]

// Read the selected colour from the command-line arguments.
func getSelectedColour() -> String {
  let arguments = CommandLine.arguments

  let colourNames = colourMap.map { $0.0 }

  // If the user hasn't supplied a colour, of they've selected an invalid
  // colour, print a helpful help message. e.g.
  //
  //    $ set_accent_colour blurple
  //    Usage: set_accent_colour <red|orange|yellow|green|blue|purple|pink|graphite>
  //
  if arguments.count != 2 || !colourNames.contains(arguments[1]) {
    let colours = colourNames.joined(separator:"|")
    fputs("Usage: \(arguments[0]) <\(colours)>\n", stderr)
    exit(1)
  }

  return arguments[1]
}

func setAccentColour(colour: String) -> () {
  let colourDict = Dictionary(uniqueKeysWithValues: colourMap)
  let accentValue: Int = colourDict[colour]!

  // This is the equivalent of
  //
  //    $ defaults write -globalDomain AppleAccentColor -int <prefValue>
  //
  UserDefaults.standard.setPersistentDomain(
    ["AppleAccentColor": Optional(accentValue) as Any],
    forName: UserDefaults.globalDomain
  )

  let notifications = [
    "AppleColorPreferencesChangedNotification",
    "AppleAquaColorVariantChanged"
  ]

  for name in notifications {
    let notifyEvent = Notification.Name(name)
    DistributedNotificationCenter.default().post(name: notifyEvent, object: nil)
  }
}

let colour = getSelectedColour()
setAccentColour(colour: colour)