added string utils to obtain the external address of a path

Author: albertopeam

Sources/Web3Core/KeystoreManager/BIP44.swift

@@ -25,10 +25,48 @@ public enum BIP44Error: Equatable {
 extension HDNode: BIP44 {
     public func derive(path: String, warns: Bool = true) async throws -> HDNode? {
         if warns {
-            // https://github.com/bitcoin/bips/blob/master/bip-0044.mediawiki#account-discovery
+            if let externalPath = path.externalChangePath {
+                
+            }
             return nil
         } else {
             return derive(path: path, derivePrivateKey: true)
         }
     }
 }
+
+extension String {
+    /// Returns a new BIP32 path that uses an external change, if the path is invalid returns nil
+    var externalChangePath: String? {
+        do {
+            guard isBip44Path else {
+                return nil
+            }
+            let changePathPattern = "'/[0-1]/"
+            let regex = try NSRegularExpression(pattern: changePathPattern, options: [.caseInsensitive])
+            let range = NSRange(location: 0, length: utf16.count)
+            let matches = regex.numberOfMatches(in: self, range: range)
+            if matches == 1 {
+                let result = regex.stringByReplacingMatches(in: self, options: [], range: range, withTemplate: "'/0/")
+                return result
+            } else {
+                return nil
+            }
+        } catch {
+            return nil
+        }
+    }
+    
+    /// Verifies if matches BIP44 path standard
+    var isBip44Path: Bool {
+        do {
+            let pattern = "^m/44'/\\d+'/\\d+'/[0-1]/\\d+$"
+            let regex = try NSRegularExpression(pattern: pattern, options: [.caseInsensitive])
+            let matches = regex.numberOfMatches(in: self, range: NSRange(location: 0, length: utf16.count))
+            return matches == 1
+        } catch {
+            return false
+        }
+    }
+}
+

Tests/web3swiftTests/localTests/BIP44Tests.swift

@@ -7,7 +7,7 @@ import XCTest
 import Web3Core
 @testable import web3swift
 
-final class BIP44Tests: XCTestCase {
+final class BIP44Tests: LocalTestCase {
 
     private let mnemonic = "fruit wave dwarf banana earth journey tattoo true farm silk olive fence"
 

Tests/web3swiftTests/localTests/StringBIP44Tests.swift

@@ -0,0 +1,70 @@
+//
+//  StringBIP44Tests.swift
+//  Created by Alberto Penas Amor on 18/12/22.
+//
+
+import XCTest
+@testable import Web3Core
+
+final class StringBIP44Tests: XCTestCase {
+    
+    //MARK: - externalChangePath
+    
+    func testInvalidChangesReturnNil() throws {
+        let invalidPaths = ["m/44'/60'/0'/-1/0",
+                            "m/44'/60'/0'/2/0"]
+        invalidPaths.forEach { invalidPath in
+            XCTAssertNil(invalidPath.externalChangePath)
+        }
+    }
+    
+    func testInternalChangeReturnsExternalChangePath() throws {
+        let path = "m/44'/60'/0'/1/0"
+        let result = path.externalChangePath
+        XCTAssertEqual(result, "m/44'/60'/0'/0/0")
+    }
+    
+    func testExternalChangeReturnsExternalChangePath() throws {
+        let path = "m/44'/60'/0'/0/0"
+        let result = path.externalChangePath
+        XCTAssertEqual(result, path)
+    }
+    
+    //MARK: - isBip44Path
+    
+    func testVerifyBip44Paths() {
+        let validPaths = ["m/44'/0'/0'/0/0",
+                          "m/44'/1'/0'/0/0",
+                          "m/44'/0'/1'/0/0",
+                          "m/44'/0'/0'/1/0",
+                          "m/44'/0'/0'/0/1"]
+        validPaths.forEach { validPath in
+            let result = validPath.isBip44Path
+            XCTAssertTrue(result)
+        }
+    }
+    
+    func testVerifyNotBip44Paths() {
+        let invalidPaths = ["",
+                            "/44'/60'/0'/0/0",
+                            "m44'/60'/0'/0/0",
+                            "m0'/60'/0'/0/0",
+                            "m/'/60'/0'/0/0",
+                            "m/60'/0'/0/0",
+                            "m/44'/60/0'/0/0",
+                            "m/44'/'/0'/0/0",
+                            "m/44'/60'/0/0/0",
+                            "m/44'/60'/'/0/0",
+                            "m/44'/60'/0'/0",
+                            "m/44'/60'/0'/0/",
+                            "m/44'/60'/0'/-1/0",
+                            "m/44'/60'/0'/2/0",
+                            "m/44'/60.0'/0'/0/0",
+                            "m/44'/60'/0.0'/0/0",
+                            "m/44'/60'/0'/0/0.0"]
+        invalidPaths.forEach { invalidPath in
+            let result = invalidPath.isBip44Path
+            XCTAssertFalse(result)
+        }
+    }
+}