refactor: Use guard where possible

Author: siemensikkema

Sources/Claims.swift

@@ -1,30 +1,32 @@
 import Foundation
 
-func validateClaims(_ payload:Payload, audience:String?, issuer:String?) throws {
+func validateClaims(_ payload: Payload, audience: String?, issuer: String?) throws {
   try validateIssuer(payload, issuer: issuer)
   try validateAudience(payload, audience: audience)
   try validateDate(payload, key: "exp", comparison: .orderedAscending, failure: .expiredSignature, decodeError: "Expiration time claim (exp) must be an integer")
   try validateDate(payload, key: "nbf", comparison: .orderedDescending, failure: .immatureSignature, decodeError: "Not before claim (nbf) must be an integer")
   try validateDate(payload, key: "iat", comparison: .orderedDescending, failure: .invalidIssuedAt, decodeError: "Issued at claim (iat) must be an integer")
 }
 
-func validateAudience(_ payload:Payload, audience:String?) throws {
-  if let audience = audience {
-    if let aud = payload["aud"] as? [String] {
-      if !aud.contains(audience) {
-        throw InvalidToken.invalidAudience
-      }
-    } else if let aud = payload["aud"] as? String {
-      if aud != audience {
-        throw InvalidToken.invalidAudience
-      }
-    } else {
-      throw InvalidToken.decodeError("Invalid audience claim, must be a string or an array of strings")
+func validateAudience(_ payload: Payload, audience: String?) throws {
+  guard let audience = audience else {
+    return
+  }
+
+  if let aud = payload["aud"] as? [String] {
+    if !aud.contains(audience) {
+      throw InvalidToken.invalidAudience
+    }
+  } else if let aud = payload["aud"] as? String {
+    if aud != audience {
+      throw InvalidToken.invalidAudience
     }
+  } else {
+    throw InvalidToken.decodeError("Invalid audience claim, must be a string or an array of strings")
   }
 }
 
-func validateIssuer(_ payload:Payload, issuer:String?) throws {
+func validateIssuer(_ payload: Payload, issuer: String?) throws {
   if let issuer = issuer {
     if let iss = payload["iss"] as? String {
       if iss != issuer {

Sources/Decode.swift

@@ -75,12 +75,11 @@ func load(_ jwt:String) throws -> (header: Payload, payload: Payload, signature:
   let signatureSegment = segments[2]
   let signatureInput = "\(headerSegment).\(payloadSegment)"
 
-  let headerData = base64decode(headerSegment)
-  if headerData == nil {
+  guard let headerData = base64decode(headerSegment) else {
     throw InvalidToken.decodeError("Header is not correctly encoded as base64")
   }
 
-  let header = (try? JSONSerialization.jsonObject(with: headerData!, options: JSONSerialization.ReadingOptions(rawValue: 0))) as? Payload
+  let header = (try? JSONSerialization.jsonObject(with: headerData, options: JSONSerialization.ReadingOptions(rawValue: 0))) as? Payload
   if header == nil {
     throw InvalidToken.decodeError("Invalid header")
   }
@@ -95,12 +94,11 @@ func load(_ jwt:String) throws -> (header: Payload, payload: Payload, signature:
     throw InvalidToken.decodeError("Invalid payload")
   }
 
-  let signature = base64decode(signatureSegment)
-  if signature == nil {
+  guard let signature = base64decode(signatureSegment) else {
     throw InvalidToken.decodeError("Signature is not correctly encoded as base64")
   }
 
-  return (header: header!, payload: payload!, signature: signature!, signatureInput: signatureInput)
+  return (header: header!, payload: payload!, signature: signature, signatureInput: signatureInput)
 }
 
 // MARK: Signature Verification