feat: Allow setting custom headers

Closes #74

Author: kylef

CHANGELOG.md

@@ -1,5 +1,12 @@
 # JSON Web Token Changelog
 
+## Master
+
+### Enhancements
+
+- Allow passing additional headers when encoding a JWT.
+
+
 ## 2.1.0
 
 ### Enhancements

Sources/Encode.swift

@@ -5,7 +5,7 @@ import Foundation
  - parameter algorithm: The algorithm to sign the payload with
  - returns: The JSON web token as a String
  */
-public func encode(claims: ClaimSet, algorithm: Algorithm) -> String {
+public func encode(claims: ClaimSet, algorithm: Algorithm, headers: [String: String]? = nil) -> String {
   func encodeJSON(_ payload: [String: Any]) -> String? {
     if let data = try? JSONSerialization.data(withJSONObject: payload) {
       return base64encode(data)
@@ -14,7 +14,13 @@ public func encode(claims: ClaimSet, algorithm: Algorithm) -> String {
     return nil
   }
 
-  let header = encodeJSON(["typ": "JWT", "alg": algorithm.description])!
+  var headers = headers ?? [:]
+  if !headers.keys.contains("typ") {
+    headers["typ"] = "JWT"
+  }
+  headers["alg"] = algorithm.description
+
+  let header = encodeJSON(headers)!
   let payload = encodeJSON(claims.claims)!
   let signingInput = "\(header).\(payload)"
   let signature = algorithm.sign(signingInput)
@@ -26,8 +32,8 @@ public func encode(claims: ClaimSet, algorithm: Algorithm) -> String {
  - parameter algorithm: The algorithm to sign the payload with
  - returns: The JSON web token as a String
  */
-public func encode(claims: [String: Any], algorithm: Algorithm) -> String {
-  return encode(claims: ClaimSet(claims: claims), algorithm: algorithm)
+public func encode(claims: [String: Any], algorithm: Algorithm, headers: [String: String]? = nil) -> String {
+  return encode(claims: ClaimSet(claims: claims), algorithm: algorithm, headers: headers)
 }
 
 

Tests/JWTTests/JWTTests.swift

@@ -28,6 +28,13 @@ class EncodeTests: XCTestCase {
       XCTAssertEqual(payload as! [String: String], ["iss": "fuller.li"])
     }
   }
+
+  func testEncodingClaimsWithHeaders() {
+    let algorithm = Algorithm.hs256("secret".data(using: .utf8)!)
+    let jwt = JWT.encode(claims: ClaimSet(), algorithm: algorithm, headers: ["kid": "x"])
+
+    XCTAssertEqual(jwt, "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6IngifQ.e30.ddEotxYYMMdat5HPgYFQnkHRdPXsxPG71ooyhIUoqGA")
+  }
 }
 
 class PayloadTests: XCTestCase {