added string utils to extract the account from a bip44 path

Author: albertopeam

Sources/Web3Core/KeystoreManager/BIP44.swift

@@ -25,9 +25,11 @@ public enum BIP44Error: Equatable {
 extension HDNode: BIP44 {
     public func derive(path: String, warns: Bool = true) async throws -> HDNode? {
         if warns {
-            if let externalPath = path.externalChangePath {
-                
+            var accountIndex = 0
+            guard let account = path.accountFromPath else {
+                return nil
             }
+            
             return nil
         } else {
             return derive(path: path, derivePrivateKey: true)
@@ -36,6 +38,20 @@ extension HDNode: BIP44 {
 }
 
 extension String {
+    /// Returns the account from the path if the string contains a well formed BIP44 path
+    var accountFromPath: Int? {
+        guard isBip44Path else {
+            return nil
+        }
+        let components = components(separatedBy: "/")
+        let accountIndex = 3
+        let rawAccount = components[accountIndex].trimmingCharacters(in: CharacterSet(charactersIn: "'"))
+        guard let account = Int(rawAccount) else {
+            return nil
+        }
+        return account
+    }
+    
     /// Returns a new BIP32 path that uses an external change, if the path is invalid returns nil
     var externalChangePath: String? {
         do {

Tests/web3swiftTests/localTests/StringBIP44Tests.swift

@@ -7,8 +7,68 @@ import XCTest
 @testable import Web3Core
 
 final class StringBIP44Tests: XCTestCase {
+    private var invalidPaths: [String]!
 
-    //MARK: - externalChangePath
+    override func setUpWithError() throws {
+        try super.setUpWithError()
+        invalidPaths = ["",
+                        "m",
+                        "m/",
+                        "m/44",
+                        "m/44'",
+                        "m/44'/",
+                        "m/44'/60",
+                        "m/44'/60'",
+                        "m/44'/60'/",
+                        "m/44'/60'/0",
+                        "m/44'/60'/0'",
+                        "m/44'/60'/0'/",
+                        "m/44'/60'/0'/0",
+                        "m/44'/60'/0'/0/",
+                        "/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"]
+    }
+    
+    override func tearDownWithError() throws {
+        try super.tearDownWithError()
+        invalidPaths = nil
+    }
+    
+    // MARK: - accountFromPath
+    
+    func testInvalidPathReturnNilAccount() throws {
+        invalidPaths.forEach { invalidPath in
+            XCTAssertNil(invalidPath.accountFromPath)
+        }
+    }
+    
+    func testValidPathReturnAccount() {
+        let scenarios: [TestScenario<String, Int>] = [
+            .init(input: "m/44'/60'/0'/1/4", expected: 0),
+            .init(input: "m/44'/60'/1'/0/3", expected: 1),
+            .init(input: "m/44'/60'/2'/0/2", expected: 2),
+            .init(input: "m/44'/60'/3'/0/1", expected: 3),
+            .init(input: "m/44'/60'/4'/0/0", expected: 4)]
+        scenarios.forEach { scenario in
+            XCTAssertEqual(scenario.input.accountFromPath, scenario.expected)
+        }
+    }
+    
+    // MARK: - externalChangePath
 
     func testInvalidChangesReturnNil() throws {
         let invalidPaths = ["m/44'/60'/0'/-1/0",
@@ -30,7 +90,7 @@ final class StringBIP44Tests: XCTestCase {
         XCTAssertEqual(result, path)
     }
 
-    //MARK: - isBip44Path
+    // MARK: - isBip44Path
 
     func testVerifyBip44Paths() {
         let validPaths = ["m/44'/0'/0'/0/0",
@@ -39,32 +99,18 @@ final class StringBIP44Tests: XCTestCase {
                           "m/44'/0'/0'/1/0",
                           "m/44'/0'/0'/0/1"]
         validPaths.forEach { validPath in
-            let result = validPath.isBip44Path
-            XCTAssertTrue(result)
+            XCTAssertTrue(validPath.isBip44Path)
         }
     }
 
     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)
+            XCTAssertFalse(invalidPath.isBip44Path)
         }
     }
 }
+
+struct TestScenario<I, E> {
+    let input: I
+    let expected: E
+}