#!/usr/bin/env swift
// Draws the 1024x1024 Share app icon. Run from apps/ios:
//   swift Branding/make-icon.swift Share/Assets.xcassets/AppIcon.appiconset/AppIcon.png
import AppKit
import CoreGraphics
import ImageIO

let size = 1024
let output = CommandLine.arguments.count > 1
  ? CommandLine.arguments[1]
  : "Share/Assets.xcassets/AppIcon.appiconset/AppIcon.png"

func color(_ hex: UInt32, _ alpha: CGFloat = 1) -> NSColor {
  NSColor(
    calibratedRed: CGFloat((hex >> 16) & 0xFF) / 255,
    green: CGFloat((hex >> 8) & 0xFF) / 255,
    blue: CGFloat(hex & 0xFF) / 255,
    alpha: alpha
  )
}

guard let rep = NSBitmapImageRep(
  bitmapDataPlanes: nil,
  pixelsWide: size,
  pixelsHigh: size,
  bitsPerSample: 8,
  samplesPerPixel: 4,
  hasAlpha: true,
  isPlanar: false,
  colorSpaceName: .deviceRGB,
  bytesPerRow: 0,
  bitsPerPixel: 0
) else {
  fatalError("Could not create bitmap")
}

NSGraphicsContext.saveGraphicsState()
NSGraphicsContext.current = NSGraphicsContext(bitmapImageRep: rep)
NSGraphicsContext.current?.imageInterpolation = .high
NSGraphicsContext.current?.shouldAntialias = true

let canvas = NSRect(x: 0, y: 0, width: size, height: size)
let background = NSGradient(colors: [color(0x07111F), color(0x0B3B36)])!
background.draw(in: canvas, angle: -55)

// Soft teal glow in the upper-left and blue glow in the lower-right.
let tealGlow = NSGradient(colors: [color(0x5EEAD4, 0.35), color(0x5EEAD4, 0)])!
tealGlow.draw(
  in: NSBezierPath(ovalIn: NSRect(x: -260, y: 430, width: 1020, height: 1020)),
  relativeCenterPosition: NSPoint(x: 0, y: 0)
)
let blueGlow = NSGradient(colors: [color(0x60A5FA, 0.28), color(0x60A5FA, 0)])!
blueGlow.draw(
  in: NSBezierPath(ovalIn: NSRect(x: 300, y: -300, width: 980, height: 980)),
  relativeCenterPosition: NSPoint(x: 0, y: 0)
)

// A barely-there inset panel gives the flat icon some depth.
let panel = NSBezierPath(
  roundedRect: NSRect(x: 116, y: 116, width: 792, height: 792),
  xRadius: 180,
  yRadius: 180
)
color(0xFFFFFF, 0.035).setFill()
panel.fill()
color(0xFFFFFF, 0.07).setStroke()
panel.lineWidth = 2
panel.stroke()

func strokeArrow(shaftFrom: NSPoint, shaftTo: NSPoint,
                 headLeft: NSPoint, headTip: NSPoint, headRight: NSPoint,
                 tint: NSColor) {
  let shadow = NSShadow()
  shadow.shadowColor = color(0x000000, 0.3)
  shadow.shadowBlurRadius = 34
  shadow.shadowOffset = NSSize(width: 0, height: -16)
  shadow.set()

  tint.setStroke()
  let shaft = NSBezierPath()
  shaft.move(to: shaftFrom)
  shaft.line(to: shaftTo)
  shaft.lineWidth = 74
  shaft.lineCapStyle = .round
  shaft.stroke()

  let head = NSBezierPath()
  head.move(to: headLeft)
  head.line(to: headTip)
  head.line(to: headRight)
  head.lineWidth = 78
  head.lineCapStyle = .round
  head.lineJoinStyle = .round
  head.stroke()
}

// Up arrow on the left.
strokeArrow(
  shaftFrom: NSPoint(x: 350, y: 288),
  shaftTo: NSPoint(x: 350, y: 610),
  headLeft: NSPoint(x: 238, y: 490),
  headTip: NSPoint(x: 350, y: 640),
  headRight: NSPoint(x: 462, y: 490),
  tint: color(0xF4FFFC)
)

// Down arrow on the right.
strokeArrow(
  shaftFrom: NSPoint(x: 674, y: 736),
  shaftTo: NSPoint(x: 674, y: 414),
  headLeft: NSPoint(x: 562, y: 534),
  headTip: NSPoint(x: 674, y: 384),
  headRight: NSPoint(x: 786, y: 534),
  tint: color(0x5EEAD4)
)

// Three small dots suggest a swarm: peers nearby, not a central server.
for (point, alpha) in [
  (NSPoint(x: 250, y: 790), CGFloat(0.55)),
  (NSPoint(x: 512, y: 840), CGFloat(0.35)),
  (NSPoint(x: 790, y: 260), CGFloat(0.45)),
] {
  let dot = NSBezierPath(ovalIn: NSRect(x: point.x - 7, y: point.y - 7, width: 14, height: 14))
  color(0xFFFFFF, alpha).setFill()
  dot.fill()
}

NSGraphicsContext.restoreGraphicsState()

guard let cgImage = rep.cgImage else {
  fatalError("Could not make a CGImage")
}

// App Store icons must not contain an alpha channel. Drawing the rendered
// image into an opaque context and then encoding that image gives us an
// RGB PNG without changing a single visible pixel.
let width = cgImage.width
let height = cgImage.height
let colorSpace = CGColorSpaceCreateDeviceRGB()
guard let context = CGContext(
  data: nil,
  width: width,
  height: height,
  bitsPerComponent: 8,
  bytesPerRow: 0,
  space: colorSpace,
  bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue
) else {
  fatalError("Could not create an opaque context")
}
context.draw(cgImage, in: CGRect(x: 0, y: 0, width: width, height: height))
guard let opaque = context.makeImage() else {
  fatalError("Could not render the opaque icon")
}

let url = URL(fileURLWithPath: output)
try FileManager.default.createDirectory(
  at: url.deletingLastPathComponent(),
  withIntermediateDirectories: true
)
guard let destination = CGImageDestinationCreateWithURL(
  url as CFURL,
  "public.png" as CFString,
  1,
  nil
) else {
  fatalError("Could not create a PNG destination")
}
CGImageDestinationAddImage(destination, opaque, nil)
guard CGImageDestinationFinalize(destination) else {
  fatalError("Could not write the PNG")
}
print("Wrote \(url.path)")