Add QRCodeGenerator utility and make iOS-only

Sources/Bedrock/Utilities/QRCodeGenerator.swift

@@ -0,0 +1,122 @@
+//
+//  QRCodeGenerator.swift
+//  Bedrock
+//
+//  Generates QR codes from string payloads.
+//
+
+import SwiftUI
+import CoreImage
+import CoreImage.CIFilterBuiltins
+
+/// Generates QR codes from string data.
+///
+/// Use this to create QR codes for URLs, vCards, or any text payload.
+///
+/// ## Example
+///
+/// ```swift
+/// if let qrImage = QRCodeGenerator.generate(from: "https://example.com") {
+///     Image(decorative: qrImage, scale: 1.0)
+/// }
+/// ```
+public enum QRCodeGenerator {
+    
+    /// The CIContext used for rendering.
+    private static let context = CIContext()
+    
+    /// Error correction levels for QR codes.
+    public enum CorrectionLevel: String, Sendable {
+        /// Low (7% recovery)
+        case low = "L"
+        /// Medium (15% recovery)
+        case medium = "M"
+        /// Quartile (25% recovery)
+        case quartile = "Q"
+        /// High (30% recovery)
+        case high = "H"
+    }
+    
+    /// Generates a QR code image from a string payload.
+    /// - Parameters:
+    ///   - payload: The string to encode.
+    ///   - correctionLevel: Error correction level (default: medium).
+    ///   - scale: Scale factor for the output image (default: 10).
+    /// - Returns: A CGImage of the QR code, or nil if generation fails.
+    public static func generate(
+        from payload: String,
+        correctionLevel: CorrectionLevel = .medium,
+        scale: CGFloat = 10
+    ) -> CGImage? {
+        let data = Data(payload.utf8)
+        let filter = CIFilter.qrCodeGenerator()
+        filter.setValue(data, forKey: "inputMessage")
+        filter.correctionLevel = correctionLevel.rawValue
+        
+        guard let outputImage = filter.outputImage else { return nil }
+        
+        let scaledImage = outputImage.transformed(
+            by: CGAffineTransform(scaleX: scale, y: scale)
+        )
+        
+        return context.createCGImage(scaledImage, from: scaledImage.extent)
+    }
+}
+
+// MARK: - SwiftUI View
+
+/// A SwiftUI view that displays a QR code.
+///
+/// ## Example
+///
+/// ```swift
+/// QRCodeImageView(payload: card.vCardPayload)
+///     .frame(width: 200, height: 200)
+/// ```
+public struct QRCodeImageView: View {
+    /// The string to encode as a QR code.
+    public let payload: String
+    
+    /// Error correction level.
+    public let correctionLevel: QRCodeGenerator.CorrectionLevel
+    
+    /// Creates a QR code view.
+    /// - Parameters:
+    ///   - payload: The string to encode.
+    ///   - correctionLevel: Error correction level (default: medium).
+    public init(
+        payload: String,
+        correctionLevel: QRCodeGenerator.CorrectionLevel = .medium
+    ) {
+        self.payload = payload
+        self.correctionLevel = correctionLevel
+    }
+    
+    public var body: some View {
+        if let cgImage = QRCodeGenerator.generate(
+            from: payload,
+            correctionLevel: correctionLevel
+        ) {
+            Image(decorative: cgImage, scale: 1.0)
+                .interpolation(.none)
+                .resizable()
+                .scaledToFit()
+                .accessibilityLabel("QR code")
+        } else {
+            Image(systemName: "qrcode")
+                .font(.largeTitle)
+                .foregroundStyle(.secondary)
+        }
+    }
+}
+
+#Preview {
+    VStack(spacing: Design.Spacing.large) {
+        QRCodeImageView(payload: "https://example.com")
+            .frame(width: 150, height: 150)
+        
+        QRCodeImageView(payload: "BEGIN:VCARD\nFN:John Doe\nEND:VCARD")
+            .frame(width: 150, height: 150)
+    }
+    .padding()
+}