Polish and simplify PasswordStore model class

pass/Controllers/CommitLogsTableViewController.swift

@@ -16,7 +16,7 @@ class CommitLogsTableViewController: UITableViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         NotificationCenter.default.addObserver(self, selector: #selector(updateCommitLogs), name: .passwordStoreUpdated, object: nil)
-        commits = passwordStore.getRecentCommits(count: 20)
+        commits = getCommitLogs()
         self.tableView.estimatedRowHeight = 50
         self.tableView.rowHeight = UITableViewAutomaticDimension
     }
@@ -41,8 +41,17 @@ class CommitLogsTableViewController: UITableViewController {
         return cell
     }
     
-    func updateCommitLogs () {
-        commits = passwordStore.getRecentCommits(count: 20)
+    func updateCommitLogs() {
+        commits = getCommitLogs()
         tableView.reloadData()
     }
+    
+    private func getCommitLogs() -> [GTCommit] {
+        do {
+            return try passwordStore.getRecentCommits(count: 20)
+        } catch {
+            Utils.alert(title: "Error", message: error.localizedDescription, controller: self, completion: nil)
+            return []
+        }
+    }
 }

pass/Controllers/GitCredential.swift

@@ -0,0 +1,107 @@
+//
+//  GitCredential.swift
+//  pass
+//
+//  Created by Mingshen Sun on 30/4/2017.
+//  Copyright © 2017 Bob Sun. All rights reserved.
+//
+
+import Foundation
+import UIKit
+import SwiftyUserDefaults
+import ObjectiveGit
+import SVProgressHUD
+
+struct GitCredential {
+    var credential: Credential
+    
+    enum Credential {
+        case http(userName: String, controller: UIViewController)
+        case ssh(userName: String, publicKeyFile: URL, privateKeyFile: URL, controller: UIViewController)
+    }
+    
+    init(credential: Credential) {
+        self.credential = credential
+    }
+    
+    func credentialProvider() throws -> GTCredentialProvider {
+        var attempts = 0
+        var lastPassword: String? = nil
+        return GTCredentialProvider { (_, _, _) -> (GTCredential?) in
+            var credential: GTCredential? = nil
+            
+            switch self.credential {
+            case let .http(userName, controller):
+                var newPassword = Utils.getPasswordFromKeychain(name: "gitPassword")
+                if newPassword == nil || attempts != 0 {
+                    if let requestedPassword = self.requestGitPassword(controller, lastPassword) {
+                        newPassword	= requestedPassword
+                        Utils.addPasswordToKeychain(name: "gitPassword", password: newPassword)
+                    } else {
+                        return nil
+                    }
+                }
+                attempts += 1
+                lastPassword = newPassword
+                credential = try? GTCredential(userName: userName, password: newPassword!)
+            case let .ssh(userName, publicKeyFile, privateKeyFile, controller):
+                var newPassword = Utils.getPasswordFromKeychain(name: "gitSSHKeyPassphrase")
+                if newPassword == nil || attempts != 0  {
+                    if let requestedPassword = self.requestGitPassword(controller, lastPassword) {
+                        newPassword	= requestedPassword
+                        Utils.addPasswordToKeychain(name: "gitSSHKeyPassphrase", password: newPassword)
+                    } else {
+                        return nil
+                    }
+                }
+                attempts += 1
+                lastPassword = newPassword
+                credential = try? GTCredential(userName: userName, publicKeyURL: publicKeyFile, privateKeyURL: privateKeyFile, passphrase: newPassword!)
+            }
+            return credential
+        }
+    }
+    
+    func delete() {
+        switch credential {
+        case .http:
+            Utils.removeKeychain(name: "gitPassword")
+        case .ssh:
+            Utils.removeKeychain(name: "gitSSHKeyPassphrase")
+        }
+    }
+    
+    private func requestGitPassword(_ controller: UIViewController, _ lastPassword: String?) -> String? {
+        let sem = DispatchSemaphore(value: 0)
+        var password: String?
+        var message = ""
+        switch credential {
+        case .http:
+            message = "Please fill in the password of your Git account."
+        case .ssh:
+            message = "Please fill in the password of your SSH key."
+        }
+        
+        DispatchQueue.main.async {
+            SVProgressHUD.dismiss()
+            let alert = UIAlertController(title: "Password", message: message, preferredStyle: UIAlertControllerStyle.alert)
+            alert.addTextField(configurationHandler: {(textField: UITextField!) in
+                textField.text = lastPassword ?? ""
+                textField.isSecureTextEntry = true
+            })
+            alert.addAction(UIAlertAction(title: "OK", style: UIAlertActionStyle.default, handler: {_ in
+                password = alert.textFields!.first!.text
+                sem.signal()
+            }))
+            alert.addAction(UIAlertAction(title: "Cancel", style: .cancel) { _ in
+                password = nil
+                sem.signal()
+            })
+            controller.present(alert, animated: true, completion: nil)
+        }
+        
+        let _ = sem.wait(timeout: .distantFuture)
+        return password
+    }
+}
+