Project public key files for use in configs (#264)

Sources/Packages/Sources/SecretKit/PublicKeyStandinFileController.swift

@@ -0,0 +1,41 @@
+import Foundation
+import OSLog
+
+/// Controller responsible for writing public keys to disk, so that they're easily accessible by scripts.
+public class PublicKeyFileStoreController {
+
+    private let logger = Logger()
+    private let directory: String
+
+    /// Initializes a PublicKeyFileStoreController.
+    public init(homeDirectory: String) {
+        directory = homeDirectory.appending("/PublicKeys")
+    }
+
+    /// Writes out the keys specified to disk.
+    /// - Parameter secrets: The Secrets to generate keys for.
+    /// - Parameter clear: Whether or not the directory should be erased before writing keys.
+    public func generatePublicKeys(for secrets: [AnySecret], clear: Bool = false) throws {
+        logger.log("Writing public keys to disk")
+        if clear {
+            try? FileManager.default.removeItem(at: URL(fileURLWithPath: directory))
+        }
+        try? FileManager.default.createDirectory(at: URL(fileURLWithPath: directory), withIntermediateDirectories: false, attributes: nil)
+        let keyWriter = OpenSSHKeyWriter()
+        for secret in secrets {
+            let path = path(for: secret)
+            guard let data = keyWriter.openSSHString(secret: secret).data(using: .utf8) else { continue }
+            FileManager.default.createFile(atPath: path, contents: data, attributes: nil)
+        }
+        logger.log("Finished writing public keys")
+    }
+
+    /// The path for a Secret's public key.
+    /// - Parameter secret: The Secret to return the path for.
+    /// - Returns: The path to the Secret's public key.
+    /// - Warning: This method returning a path does not imply that a key has been written to disk already. This method only describes where it will be written to.
+    public func path<SecretType: Secret>(for secret: SecretType) -> String {
+        directory.appending("/").appending("\(secret.name.replacingOccurrences(of: " ", with: "-")).pub")
+    }
+
+}