Implement auto-update system with Sparkle framework

Package.swift

@@ -15,12 +15,14 @@ let package = Package(
         )
     ],
     dependencies: [
-        // No external dependencies required for now
+        .package(url: "https://github.com/sparkle-project/Sparkle", from: "2.5.2")
     ],
     targets: [
         .executableTarget(
             name: "ClickIt",
-            dependencies: [],
+            dependencies: [
+                .product(name: "Sparkle", package: "Sparkle")
+            ],
             resources: [.process("Resources")]
         ),
         .testTarget(

Sources/ClickIt/Core/Update/AppcastGenerator.swift

@@ -0,0 +1,302 @@
+import Foundation
+
+/// Generates Sparkle-compatible appcast XML from GitHub Releases API data
+struct AppcastGenerator {
+
+    // MARK: - Data Models
+
+    struct GitHubRelease: Codable {
+        let id: Int
+        let tagName: String
+        let name: String?
+        let body: String?
+        let prerelease: Bool
+        let draft: Bool
+        let publishedAt: String?
+        let assets: [GitHubAsset]
+        let htmlUrl: String
+
+        private enum CodingKeys: String, CodingKey {
+            case id, name, body, prerelease, draft, assets
+            case tagName = "tag_name"
+            case publishedAt = "published_at"
+            case htmlUrl = "html_url"
+        }
+    }
+
+    struct GitHubAsset: Codable {
+        let id: Int
+        let name: String
+        let size: Int
+        let downloadCount: Int
+        let browserDownloadUrl: String
+
+        private enum CodingKeys: String, CodingKey {
+            case id, name, size
+            case downloadCount = "download_count"
+            case browserDownloadUrl = "browser_download_url"
+        }
+    }
+
+    // MARK: - Configuration
+
+    struct AppcastConfig {
+        let appName: String
+        let bundleId: String
+        let repository: String
+        let minimumSystemVersion: String
+        let includeBetaReleases: Bool
+
+        static let `default` = AppcastConfig(
+            appName: "ClickIt",
+            bundleId: AppConstants.appcastURL.contains("clickit") ? "com.jsonify.clickit" : "com.example.clickit",
+            repository: AppConstants.githubRepository,
+            minimumSystemVersion: AppConstants.minimumOSVersion,
+            includeBetaReleases: false
+        )
+    }
+
+    // MARK: - Public Methods
+
+    /// Fetches GitHub releases and generates appcast XML
+    static func generateAppcast(config: AppcastConfig = .default) async throws -> String {
+        let releases = try await fetchGitHubReleases(repository: config.repository)
+        let filteredReleases = filterReleases(releases, includeBeta: config.includeBetaReleases)
+        return generateAppcastXML(releases: filteredReleases, config: config)
+    }
+
+    /// Generates appcast XML from provided releases data
+    static func generateAppcastXML(releases: [GitHubRelease], config: AppcastConfig) -> String {
+        let items = releases.compactMap { release -> String? in
+            generateAppcastItem(release: release, config: config)
+        }
+
+        return generateFullAppcast(items: items, config: config)
+    }
+
+    // MARK: - Private Methods
+
+    /// Fetches releases from GitHub API
+    private static func fetchGitHubReleases(repository: String) async throws -> [GitHubRelease] {
+        guard let url = URL(string: "https://api.github.com/repos/\(repository)/releases") else {
+            throw AppcastError.invalidURL
+        }
+
+        let (data, response) = try await URLSession.shared.data(from: url)
+
+        guard let httpResponse = response as? HTTPURLResponse,
+              200...299 ~= httpResponse.statusCode else {
+            throw AppcastError.networkError
+        }
+
+        do {
+            return try JSONDecoder().decode([GitHubRelease].self, from: data)
+        } catch {
+            throw AppcastError.decodingError(error)
+        }
+    }
+
+    /// Filters releases based on configuration
+    private static func filterReleases(_ releases: [GitHubRelease], includeBeta: Bool) -> [GitHubRelease] {
+        return releases.filter { release in
+            // Skip drafts
+            guard !release.draft else { return false }
+
+            // Include/exclude prerelease based on configuration
+            if release.prerelease && !includeBeta {
+                return false
+            }
+
+            // Must have at least one asset
+            return !release.assets.isEmpty
+        }
+        .sorted { lhs, rhs in
+            // Sort by published date, newest first
+            guard let lhsDate = parseDate(lhs.publishedAt),
+                  let rhsDate = parseDate(rhs.publishedAt) else {
+                return false
+            }
+            return lhsDate > rhsDate
+        }
+    }
+
+    /// Generates individual appcast item XML
+    private static func generateAppcastItem(release: GitHubRelease, config: AppcastConfig) -> String? {
+        // Find the main app asset (typically .zip or .dmg)
+        guard let mainAsset = findMainAsset(in: release.assets) else {
+            return nil
+        }
+
+        let version = extractVersion(from: release.tagName)
+        let title = release.name ?? "\(config.appName) \(version)"
+        let description = formatReleaseNotes(release.body)
+        let pubDate = formatPubDate(release.publishedAt)
+
+        return """
+        <item>
+            <title><![CDATA[\(title)]]></title>
+            <description><![CDATA[\(description)]]></description>
+            <link>\(release.htmlUrl)</link>
+            <sparkle:version>\(version)</sparkle:version>
+            <sparkle:shortVersionString>\(version)</sparkle:shortVersionString>
+            <sparkle:minimumSystemVersion>\(config.minimumSystemVersion)</sparkle:minimumSystemVersion>
+            <pubDate>\(pubDate)</pubDate>
+            <enclosure url="\(mainAsset.browserDownloadUrl)" 
+                       length="\(mainAsset.size)" 
+                       type="application/octet-stream" 
+                       sparkle:version="\(version)" 
+                       sparkle:shortVersionString="\(version)" />
+        </item>
+        """
+    }
+
+    /// Finds the main downloadable asset (ZIP or DMG)
+    private static func findMainAsset(in assets: [GitHubAsset]) -> GitHubAsset? {
+        // Prefer ZIP files for auto-updates, then DMG
+        return assets.first { asset in
+            asset.name.lowercased().hasSuffix(".zip")
+        } ?? assets.first { asset in
+            asset.name.lowercased().hasSuffix(".dmg")
+        }
+    }
+
+    /// Extracts version number from Git tag
+    private static func extractVersion(from tagName: String) -> String {
+        // Remove common prefixes like "v", "beta-v", etc.
+        let cleanTag = tagName.replacingOccurrences(of: "^(beta-)?v?", with: "", options: .regularExpression)
+        return cleanTag.isEmpty ? tagName : cleanTag
+    }
+
+    /// Formats release notes for XML
+    private static func formatReleaseNotes(_ body: String?) -> String {
+        guard let body = body, !body.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty else {
+            return "No release notes available."
+        }
+
+        // Basic HTML conversion for better display
+        let formatted = body
+            .replacingOccurrences(of: "### ", with: "<h3>")
+            .replacingOccurrences(of: "## ", with: "<h2>")
+            .replacingOccurrences(of: "# ", with: "<h1>")
+            .replacingOccurrences(of: "\n", with: "<br>")
+
+        return formatted
+    }
+
+    /// Formats publication date for RSS
+    private static func formatPubDate(_ publishedAt: String?) -> String {
+        guard let publishedAt = publishedAt,
+              let date = parseDate(publishedAt) else {
+            return RFC822DateFormatter.string(from: Date())
+        }
+
+        return RFC822DateFormatter.string(from: date)
+    }
+
+    /// Parses ISO 8601 date string
+    private static func parseDate(_ dateString: String?) -> Date? {
+        guard let dateString = dateString else { return nil }
+
+        let formatter = ISO8601DateFormatter()
+        formatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+
+        return formatter.date(from: dateString) ?? ISO8601DateFormatter().date(from: dateString)
+    }
+
+    /// Generates complete appcast XML structure
+    private static func generateFullAppcast(items: [String], config: AppcastConfig) -> String {
+        let itemsXML = items.joined(separator: "\n        ")
+        let lastBuildDate = RFC822DateFormatter.string(from: Date())
+
+        return """
+        <?xml version="1.0" encoding="UTF-8"?>
+        <rss version="2.0" xmlns:sparkle="http://www.andymatuschak.org/xml-namespaces/sparkle" xmlns:dc="http://purl.org/dc/elements/1.1/">
+            <channel>
+                <title>\(config.appName) Updates</title>
+                <link>https://github.com/\(config.repository)</link>
+                <description>Software updates for \(config.appName)</description>
+                <language>en</language>
+                <lastBuildDate>\(lastBuildDate)</lastBuildDate>
+
+        \(itemsXML)
+
+            </channel>
+        </rss>
+        """
+    }
+
+    // MARK: - Date Formatter
+
+    private static let RFC822DateFormatter: DateFormatter = {
+        let formatter = DateFormatter()
+        formatter.dateFormat = "EEE, dd MMM yyyy HH:mm:ss Z"
+        formatter.locale = Locale(identifier: "en_US_POSIX")
+        formatter.timeZone = TimeZone(abbreviation: "GMT")
+        return formatter
+    }()
+}
+
+// MARK: - Error Types
+
+enum AppcastError: Error, LocalizedError {
+    case invalidURL
+    case networkError
+    case decodingError(Error)
+    case noValidReleases
+
+    var errorDescription: String? {
+        switch self {
+        case .invalidURL:
+            return "Invalid GitHub API URL"
+        case .networkError:
+            return "Network request failed"
+        case .decodingError(let error):
+            return "Failed to decode GitHub API response: \(error.localizedDescription)"
+        case .noValidReleases:
+            return "No valid releases found"
+        }
+    }
+}
+
+// MARK: - Convenience Extensions
+
+extension AppcastGenerator {
+
+    /// Generates appcast for beta releases
+    static func generateBetaAppcast() async throws -> String {
+        var config = AppcastConfig.default
+        config = AppcastConfig(
+            appName: config.appName,
+            bundleId: config.bundleId,
+            repository: config.repository,
+            minimumSystemVersion: config.minimumSystemVersion,
+            includeBetaReleases: true
+        )
+        return try await generateAppcast(config: config)
+    }
+
+    /// Validates that the generated XML is well-formed
+    static func validateAppcastXML(_ xml: String) -> Bool {
+        guard let data = xml.data(using: .utf8) else { return false }
+
+        let parser = XMLParser(data: data)
+        let delegate = XMLValidationDelegate()
+        parser.delegate = delegate
+
+        return parser.parse() && !delegate.hasError
+    }
+}
+
+// MARK: - XML Validation
+
+private class XMLValidationDelegate: NSObject, XMLParserDelegate {
+    var hasError = false
+
+    func parser(_ parser: XMLParser, parseErrorOccurred parseError: Error) {
+        hasError = true
+    }
+
+    func parser(_ parser: XMLParser, validationErrorOccurred validationError: Error) {
+        hasError = true
+    }
+}