Added proper Base64 URL coding support

Sources/WebPush/Helpers/DataProtocol+Base64URLCoding.swift

@@ -0,0 +1,33 @@
+//
+//  DataProtocol+Base64URLCoding.swift
+//  swift-webpush
+//
+//  Created by Dimitri Bouniol on 2024-12-06.
+//  Copyright © 2024 Mochi Development, Inc. All rights reserved.
+//
+
+import Foundation
+
+extension DataProtocol {
+    func base64URLEncodedString() -> String {
+        Data(self)
+            .base64EncodedString()
+            .replacingOccurrences(of: "+", with: "-")
+            .replacingOccurrences(of: "/", with: "_")
+            .replacingOccurrences(of: "=", with: "")
+    }
+}
+
+extension DataProtocol where Self: RangeReplaceableCollection {
+    init?(base64URLEncoded string: String) {
+        var base64String = string.replacingOccurrences(of: "-", with: "+").replacingOccurrences(of: "_", with: "/")
+        while base64String.count % 4 != 0 {
+            base64String = base64String.appending("=")
+        }
+
+        guard let decodedData = Data(base64Encoded: base64String)
+        else { return nil }
+
+        self = Self(decodedData)
+    }
+}

Sources/WebPush/VAPID/VAPIDKey.swift

@@ -69,6 +69,6 @@ extension VAPID.Key: Identifiable {
     }
 
     public var id: ID {
-        ID(privateKey.publicKey.x963Representation.base64EncodedString()) // TODO: make url-safe
+        ID(privateKey.publicKey.x963Representation.base64URLEncodedString())
     }
 }

Tests/WebPushTests/Base64URLCodingTests.swift

@@ -0,0 +1,25 @@
+//
+//  Base64URLCodingTests.swift
+//  swift-webpush
+//
+//  Created by Dimitri Bouniol on 2024-12-06.
+//  Copyright © 2024 Mochi Development, Inc. All rights reserved.
+//
+
+import Foundation
+import Testing
+@testable import WebPush
+
+@Test func base64URLDecoding() async throws {
+    let string              = ">>> Hello, swift-webpush world??? 🎉"
+    let base64Encoded       = "Pj4+IEhlbGxvLCBzd2lmdC13ZWJwdXNoIHdvcmxkPz8/IPCfjok="
+    let base64URLEncoded    = "Pj4-IEhlbGxvLCBzd2lmdC13ZWJwdXNoIHdvcmxkPz8_IPCfjok"
+    #expect(String(decoding: Data(base64URLEncoded: base64Encoded)!, as: UTF8.self) == string)
+    #expect(String(decoding: Data(base64URLEncoded: base64URLEncoded)!, as: UTF8.self) == string)
+}
+
+@Test func base64URLEncoding() async throws {
+    let string              = ">>> Hello, swift-webpush world??? 🎉"
+    let base64URLEncoded    = "Pj4-IEhlbGxvLCBzd2lmdC13ZWJwdXNoIHdvcmxkPz8_IPCfjok"
+    #expect(Array(string.utf8).base64URLEncodedString() == base64URLEncoded)
+}