// Generates docs/hero.png — the banner at the top of the README.
//
// Composes the already-generated app icon with the wordmark and tagline rather
// than redrawing the coats, so the banner can never drift out of step with the
// icon itself. Run generate-icon.swift first.
//
// Usage:
//   swift icon/generate-icon.swift icon/AppIcon.iconset
//   cp icon/AppIcon.iconset/icon_512x512.png icon/shannoncoat.png
//   iconutil -c icns icon/AppIcon.iconset -o icon/AppIcon.icns
//   rm -rf icon/AppIcon.iconset
//   swift icon/generate-hero.swift icon/shannoncoat.png docs/hero.png
import Cocoa

private func rgb(_ hex: UInt32) -> NSColor {
    NSColor(srgbRed: CGFloat((hex >> 16) & 255) / 255, green: CGFloat((hex >> 8) & 255) / 255,
            blue: CGFloat(hex & 255) / 255, alpha: 1)
}

// Slate ground rather than cloud: GitHub renders READMEs on both a light and a
// dark page, and a dark banner sits comfortably on either, where a near-white
// one glares against a dark page. It also lets the coral icon carry the colour.
private let ground = rgb(0x26_26_25)
private let wordmark = rgb(0xF0_EE_E6)
private let subtitle = rgb(0xA8_A2_98)

private let width = 1200
private let height = 360

let args = CommandLine.arguments
let iconPath = args.count > 1 ? args[1] : "icon/shannoncoat.png"
let outPath = args.count > 2 ? args[2] : "docs/hero.png"

guard let icon = NSImage(contentsOfFile: iconPath) else {
    fatalError("couldn't read \(iconPath) — run generate-icon.swift first")
}

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

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

ground.setFill()
NSBezierPath(rect: NSRect(x: 0, y: 0, width: width, height: height)).fill()

let iconSide: CGFloat = 184
icon.draw(in: NSRect(x: 96, y: (CGFloat(height) - iconSide) / 2, width: iconSide, height: iconSide))

let textX: CGFloat = 96 + iconSide + 56
let name = NSAttributedString(string: "shannoncoat", attributes: [
    .font: NSFont.systemFont(ofSize: 76, weight: .semibold),
    .foregroundColor: wordmark,
])
let tagline = NSAttributedString(string: "which coat will Claude wear today?", attributes: [
    .font: NSFont.systemFont(ofSize: 30, weight: .regular),
    .foregroundColor: subtitle,
])

// Stacked around the vertical centre, using each string's own measured height
// so the pair sits optically centred against the icon rather than by guesswork.
let nameSize = name.size(), taglineSize = tagline.size()
let gap: CGFloat = 14
let blockHeight = nameSize.height + gap + taglineSize.height
let top = (CGFloat(height) + blockHeight) / 2
name.draw(at: NSPoint(x: textX, y: top - nameSize.height))
tagline.draw(at: NSPoint(x: textX + 3, y: top - nameSize.height - gap - taglineSize.height))

NSGraphicsContext.restoreGraphicsState()

let outURL = URL(fileURLWithPath: outPath)
try? FileManager.default.createDirectory(
    at: outURL.deletingLastPathComponent(), withIntermediateDirectories: true)
guard let png = rep.representation(using: .png, properties: [:]) else {
    fatalError("failed to encode hero PNG")
}
try! png.write(to: outURL)
print("wrote \(outPath)")