import AppKit
import CoreText

@MainActor
final class ShortcutIndicator: NSStackView {
    init(_ keys: String..., backgroundColor: NSColor? = nil, fontSize: CGFloat = 12, keySize: CGFloat = 18) {
        super.init(frame: .zero)
        orientation = .horizontal
        alignment = .centerY
        spacing = 2
        setHuggingPriority(.required, for: .horizontal)
        setHuggingPriority(.required, for: .vertical)
        translatesAutoresizingMaskIntoConstraints = false
        setAccessibilityElement(false)
        for key in keys {
            let badge = ShortcutKeyBadge(labelWithString: key)
            badge.font = .systemFont(ofSize: fontSize, weight: .medium)
            badge.textColor = ThemePalette.secondaryText
            badge.alignment = .center
            badge.wantsLayer = true
            badge.layer?.cornerRadius = 5
            badge.layer?.borderWidth = 1
            badge.layer?.borderColor = ThemePalette.secondaryText.withAlphaComponent(0.35).cgColor
            badge.layer?.backgroundColor = backgroundColor?.cgColor
            badge.setAccessibilityElement(false)
            badge.translatesAutoresizingMaskIntoConstraints = false
            NSLayoutConstraint.activate([
                badge.widthAnchor.constraint(equalToConstant: keySize),
                badge.heightAnchor.constraint(equalToConstant: keySize)
            ])
            addArrangedSubview(badge)
        }
    }

    func setSingleKey(_ key: String) {
        precondition(arrangedSubviews.count == 1)
        (arrangedSubviews[0] as? NSTextField)?.stringValue = key
    }

    required init?(coder: NSCoder) { fatalError("Conjure creates shortcut indicators programmatically") }
}

@MainActor
private final class ShortcutKeyBadge: NSTextField {
    // NSTextField's horizontal alignment insets otherwise make an 18-point badge 22 points wide.
    override var alignmentRectInsets: NSEdgeInsets { NSEdgeInsets(top: 0, left: 0, bottom: 0, right: 0) }

    override func draw(_ dirtyRect: NSRect) {
        guard let context = NSGraphicsContext.current?.cgContext else { return }
        let line = CTLineCreateWithAttributedString(attributedStringValue)
        let ink = CTLineGetBoundsWithOptions(line, .useGlyphPathBounds)
        context.saveGState()
        context.textMatrix = .identity
        // Center visible ink, not the font's asymmetric ascender/descender line box.
        context.translateBy(x: bounds.midX - ink.midX, y: bounds.midY + ink.midY)
        context.scaleBy(x: 1, y: -1)
        context.textPosition = .zero
        CTLineDraw(line, context)
        context.restoreGState()
    }
}