Add provider configuration generation.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

WireGuard/Models/Tunnel+Extension.swift

@@ -10,7 +10,90 @@ import Foundation
 
 extension Tunnel {
     public func generateProviderConfiguration() -> [String: Any] {
-        //TODO: generate ProviderConfiguration from tunnel with WireGuard config.
-        return [:]
+        var providerConfiguration = [String: Any]()
+
+        providerConfiguration["title"] = self.title
+        var settingsString = "replace_peers=true\n"
+        if let interface = interface {
+            settingsString += generateInterfaceProviderConfiguration(interface)
+        }
+
+        if let peers = peers?.array as? [Peer] {
+            peers.forEach {
+                settingsString += generatePeerProviderConfiguration($0)
+            }
+
+        }
+
+        providerConfiguration["settings"] = settingsString
+
+        return providerConfiguration
+    }
+
+    private func  generateInterfaceProviderConfiguration(_ interface: Interface) -> String {
+        var settingsString = "replace_peers=true\n"
+
+        if let hexPrivateKey = base64KeyToHex(interface.privateKey) {
+            settingsString += "private_key=\(hexPrivateKey)\n"
+        }
+        if interface.listenPort > 0 {
+            settingsString += "listen_port=\(interface.listenPort)\n"
+        }
+        if let dns = interface.dns {
+            settingsString += "dns=\(dns)\n"
+        }
+        if interface.mtu > 0 {
+            settingsString += "mtu=\(interface.mtu)\n"
+        }
+
+        return settingsString
+    }
+
+    private func  generatePeerProviderConfiguration(_ peer: Peer) -> String {
+        var settingsString = ""
+
+        if let hexPublicKey = base64KeyToHex(peer.publicKey) {
+            settingsString += "public_key=\(hexPublicKey)"
+        }
+        if let presharedKey = peer.presharedKey {
+            settingsString += "preshared_key=\(presharedKey)"
+        }
+        if let endpoint = peer.endpoint {
+            settingsString += "endpoint=\(endpoint)"
+        }
+        if peer.persistentKeepalive > 0 {
+            settingsString += "persistent_keepalive_interval=\(peer.persistentKeepalive)"
+        }
+        if let allowedIPs = peer.allowedIPs {
+            settingsString += "allowed_ip=\(allowedIPs)" // TODO: split on ,
+        }
+
+        return settingsString
     }
 }
+
+private func base64KeyToHex(_ base64: String?) -> String? {
+    guard let base64 = base64 else {
+        return nil
+    }
+
+    guard base64.count == 44 else {
+        return nil
+    }
+
+    guard base64.last == "=" else {
+        return nil
+    }
+
+    guard let keyData = Data(base64Encoded: base64) else {
+        return nil
+    }
+
+    guard keyData.count == 32 else {
+        return nil
+    }
+
+    let hexKey = keyData.reduce("") {$0 + String(format: "%02x", $1)}
+
+    return hexKey
+}