refactor(scanner): migrate to Swift Regex and remove NSString bridges (#288)

Replace `NSRegularExpression` with Swift `Regex` literals and
`Regex(pattern)` across the scanner pipeline. Fall back to
`NSRegularExpression` in `BinaryStringScanner` for patterns using
lookbehind (unsupported by Swift Regex). Replace `(string as
NSString).lastPathComponent` casts with `URL(fileURLWithPath:)`
in `IPSWExtractor`.

Signed-off-by: Patrick Linnane <patrick@linnane.io>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: p-linnane

Sources/macOSdbKit/Scanner/BinaryStringScanner.swift

@@ -37,13 +37,18 @@ public enum BinaryStringScanner {
         matching pattern: String,
         minLength: Int = defaultMinLength
     ) -> String? {
-        guard let regex = try? NSRegularExpression(pattern: pattern) else { return nil }
-
-        let strings = extractStrings(from: data, minLength: minLength)
-        for string in strings {
-            let range = NSRange(string.startIndex..., in: string)
-            if let match = regex.firstMatch(in: string, range: range) {
-                if let matchRange = Range(match.range, in: string) {
+        // Swift Regex doesn't support lookbehind; fall back to NSRegularExpression
+        if let regex = try? Regex(pattern) {
+            for string in extractStrings(from: data, minLength: minLength) {
+                if let match = string.firstMatch(of: regex) {
+                    return String(string[match.range])
+                }
+            }
+        } else if let nsRegex = try? NSRegularExpression(pattern: pattern) {
+            for string in extractStrings(from: data, minLength: minLength) {
+                let range = NSRange(string.startIndex..., in: string)
+                if let match = nsRegex.firstMatch(in: string, range: range),
+                   let matchRange = Range(match.range, in: string) {
                     return String(string[matchRange])
                 }
             }
@@ -56,15 +61,20 @@ public enum BinaryStringScanner {
         matching pattern: String,
         minLength: Int = defaultMinLength
     ) -> [String] {
-        guard let regex = try? NSRegularExpression(pattern: pattern) else { return [] }
-
         var results: [String] = []
-        let strings = extractStrings(from: data, minLength: minLength)
-        for string in strings {
-            let range = NSRange(string.startIndex..., in: string)
-            regex.enumerateMatches(in: string, range: range) { match, _, _ in
-                if let match, let matchRange = Range(match.range, in: string) {
-                    results.append(String(string[matchRange]))
+        if let regex = try? Regex(pattern) {
+            for string in extractStrings(from: data, minLength: minLength) {
+                for match in string.matches(of: regex) {
+                    results.append(String(string[match.range]))
+                }
+            }
+        } else if let nsRegex = try? NSRegularExpression(pattern: pattern) {
+            for string in extractStrings(from: data, minLength: minLength) {
+                let range = NSRange(string.startIndex..., in: string)
+                nsRegex.enumerateMatches(in: string, range: range) { match, _, _ in
+                    if let match, let matchRange = Range(match.range, in: string) {
+                        results.append(String(string[matchRange]))
+                    }
                 }
             }
         }

Sources/macOSdbKit/Scanner/IPSWExtractor.swift

@@ -80,7 +80,7 @@ public actor IPSWExtractor {
         var result = ClassifiedEntries()
         for entry in archive {
             let name = entry.path
-            let basename = (name as NSString).lastPathComponent
+            let basename = URL(fileURLWithPath: name).lastPathComponent
             if basename.hasPrefix("kernelcache") {
                 result.kernelcaches.append(entry)
             } else if name.hasSuffix(".dmg") || name.hasSuffix(".dmg.aea") {
@@ -144,7 +144,7 @@ public actor IPSWExtractor {
 
         var paths: [URL] = []
         for entry in entries {
-            let basename = (entry.path as NSString).lastPathComponent
+            let basename = URL(fileURLWithPath: entry.path).lastPathComponent
             let destPath = kernelsDir.appendingPathComponent(basename)
             _ = try archive.extract(entry, to: destPath)
             paths.append(destPath)
@@ -164,7 +164,7 @@ public actor IPSWExtractor {
         }
 
         let entryByFilename = Dictionary(
-            dmgEntries.map { ((($0.path as NSString).lastPathComponent), $0) },
+            dmgEntries.map { ((URL(fileURLWithPath: $0.path).lastPathComponent), $0) },
             uniquingKeysWith: { first, _ in first }
         )
 
@@ -184,14 +184,14 @@ public actor IPSWExtractor {
             Self.logger.warning("No manifest DMG mapping; using largest DMG as system image")
         }
 
-        let systemBasename = (systemEntry.path as NSString).lastPathComponent
+        let systemBasename = URL(fileURLWithPath: systemEntry.path).lastPathComponent
         let systemPath = workDir.appendingPathComponent(systemBasename)
         Self.logger.info("Extracting system DMG: \(systemBasename) (\(systemEntry.uncompressedSize) bytes)")
         _ = try archive.extract(systemEntry, to: systemPath)
 
         var cryptexPath: URL?
         if let cryptexEntry {
-            let cryptexBasename = (cryptexEntry.path as NSString).lastPathComponent
+            let cryptexBasename = URL(fileURLWithPath: cryptexEntry.path).lastPathComponent
             let path = workDir.appendingPathComponent(cryptexBasename)
             Self.logger.info("Extracting cryptex DMG: \(cryptexBasename) (\(cryptexEntry.uncompressedSize) bytes)")
             _ = try archive.extract(cryptexEntry, to: path)
@@ -249,7 +249,7 @@ public actor IPSWExtractor {
                            let info = roleDict["Info"] as? [String: Any],
                            let filePath = info["Path"] as? String,
                            filePath.hasSuffix(".dmg") || filePath.hasSuffix(".dmg.aea") {
-                            let filename = (filePath as NSString).lastPathComponent
+                            let filename = URL(fileURLWithPath: filePath).lastPathComponent
                             dmgRoles[roleName] = filename
                         }
                     }
@@ -265,7 +265,7 @@ public actor IPSWExtractor {
                       let kernelPath = kernelInfo["Path"] as? String else {
                     continue
                 }
-                let kernelFilename = (kernelPath as NSString).lastPathComponent
+                let kernelFilename = URL(fileURLWithPath: kernelPath).lastPathComponent
                 kernelDeviceMap[kernelFilename, default: []].insert(productType)
             }
         }
@@ -304,15 +304,10 @@ public actor IPSWExtractor {
     /// Parse OS version and build from IPSW filename as a last resort.
     /// Example: "UniversalMac_15.6.1_24G90_Restore.ipsw" → ("15.6.1", "24G90")
     private func parseFromFilename(_ filename: String) -> (osVersion: String, buildNumber: String) {
-        let pattern = #"UniversalMac_([0-9]+\.[0-9]+(?:\.[0-9]+)?)_([A-Za-z0-9]+)_Restore"#
-        guard let regex = try? NSRegularExpression(pattern: pattern),
-              let match = regex.firstMatch(
-                  in: filename, range: NSRange(filename.startIndex..., in: filename)
-              ),
-              let versionRange = Range(match.range(at: 1), in: filename),
-              let buildRange = Range(match.range(at: 2), in: filename) else {
+        let regex = /UniversalMac_(\d+\.\d+(?:\.\d+)?)_([A-Za-z0-9]+)_Restore/
+        guard let match = filename.firstMatch(of: regex) else {
             return ("", "")
         }
-        return (String(filename[versionRange]), String(filename[buildRange]))
+        return (String(match.1), String(match.2))
     }
 }

Sources/macOSdbKit/Scanner/KernelParser.swift

@@ -66,42 +66,30 @@ public enum KernelParser {
     // MARK: - Version extraction
 
     private static func findDarwinVersion(in strings: [String]) -> String {
-        let pattern = #"Darwin Kernel Version ([0-9]+\.[0-9]+\.[0-9]+)"#
-        guard let regex = try? NSRegularExpression(pattern: pattern) else { return "" }
-
+        let regex = /Darwin Kernel Version (\d+\.\d+\.\d+)/
         for string in strings {
-            let range = NSRange(string.startIndex..., in: string)
-            if let match = regex.firstMatch(in: string, range: range),
-               let captureRange = Range(match.range(at: 1), in: string) {
-                return String(string[captureRange])
+            if let match = string.firstMatch(of: regex) {
+                return String(match.1)
             }
         }
         return ""
     }
 
     private static func findXNUVersion(in strings: [String]) -> String? {
-        let pattern = #"xnu-([0-9]+\.[0-9]+\.[0-9]+(?:\.[0-9]+)*)"#
-        guard let regex = try? NSRegularExpression(pattern: pattern) else { return nil }
-
+        let regex = /xnu-(\d+\.\d+\.\d+(?:\.\d+)*)/
         for string in strings {
-            let range = NSRange(string.startIndex..., in: string)
-            if let match = regex.firstMatch(in: string, range: range),
-               let captureRange = Range(match.range(at: 1), in: string) {
-                return String(string[captureRange])
+            if let match = string.firstMatch(of: regex) {
+                return String(match.1)
             }
         }
         return nil
     }
 
     private static func findArchSuffix(in strings: [String]) -> String {
-        let pattern = #"RELEASE_ARM64_([A-Za-z0-9]+)"#
-        guard let regex = try? NSRegularExpression(pattern: pattern) else { return "" }
-
+        let regex = /RELEASE_ARM64_([A-Za-z0-9]+)/
         for string in strings {
-            let range = NSRange(string.startIndex..., in: string)
-            if let match = regex.firstMatch(in: string, range: range),
-               let captureRange = Range(match.range(at: 1), in: string) {
-                return String(string[captureRange])
+            if let match = string.firstMatch(of: regex) {
+                return String(match.1)
             }
         }
         return ""

Sources/macOSdbKit/Scanner/SDKMetadataParser.swift

@@ -57,16 +57,12 @@ enum SDKMetadataParser {
             return extractMultiDefineVersion(from: content, defines: definition.pattern)
         }
 
-        guard let regex = try? NSRegularExpression(pattern: definition.pattern),
-              let match = regex.firstMatch(
-                in: content,
-                range: NSRange(content.startIndex..., in: content)
-              ),
-              let matchRange = Range(match.range, in: content) else {
+        guard let regex = try? Regex(definition.pattern),
+              let match = content.firstMatch(of: regex) else {
             return nil
         }
 
-        return definition.normalize(String(content[matchRange]))
+        return definition.normalize(String(content[match.range]))
     }
 
     /// Extract version from multiple `#define NAME value` lines and join as "major.minor.patch".
@@ -76,16 +72,16 @@ enum SDKMetadataParser {
 
         for name in names {
             let pattern = #"#\s*define\s+"# + name + #"\s+(\S+)"#
-            guard let regex = try? NSRegularExpression(pattern: pattern),
-                  let match = regex.firstMatch(
-                    in: content,
-                    range: NSRange(content.startIndex..., in: content)
-                  ),
-                  match.numberOfRanges > 1,
-                  let valueRange = Range(match.range(at: 1), in: content) else {
+            guard let regex = try? Regex(pattern),
+                  let match = content.firstMatch(of: regex),
+                  match.count > 1 else {
+                return nil
+            }
+            if let value = match[1].substring {
+                parts.append(String(value))
+            } else {
                 return nil
             }
-            parts.append(String(content[valueRange]))
         }
 
         return parts.joined(separator: ".")

Tests/macOSdbKitTests/ScannerTests.swift

@@ -323,8 +323,12 @@ struct ScannerConfigTests {
     func allPatternsCompile() {
         for def in filesystemComponents + dyldCacheComponents + toolchainComponents
                     + developerComponents + frameworkComponents {
-            let regex = try? NSRegularExpression(pattern: def.pattern)
-            #expect(regex != nil, "Pattern failed to compile for \(def.name): \(def.pattern)")
+            let swiftRegex = try? Regex(def.pattern)
+            let nsRegex = try? NSRegularExpression(pattern: def.pattern)
+            #expect(
+                swiftRegex != nil || nsRegex != nil,
+                "Pattern failed to compile for \(def.name): \(def.pattern)"
+            )
         }
     }
 
@@ -380,13 +384,12 @@ struct ScannerConfigTests {
                 continue
             }
 
-            let regex = try NSRegularExpression(pattern: def.pattern)
-            let range = NSRange(input.startIndex..., in: input)
-            let match = regex.firstMatch(in: input, range: range)
+            let regex = try Regex(def.pattern)
+            let match = input.firstMatch(of: regex)
             #expect(match != nil, "Pattern for \(name) did not match '\(input)'")
 
-            if let match, let matchRange = Range(match.range, in: input) {
-                #expect(String(input[matchRange]) == expected)
+            if let match {
+                #expect(String(input[match.range]) == expected)
             }
         }
     }