Add support for additional headers

include/jwt/impl/jwt.ipp

@@ -322,7 +322,10 @@ template <typename Map, typename... Rest>
 void jwt_object::set_parameters(
     params::detail::headers_param<Map>&& header, Rest&&... rargs)
 {
-  //TODO: add kid support
+  for (const auto& elem : header.get()) {
+    header_.add_header(std::move(elem.first), std::move(elem.second));
+  }
+
   set_parameters(std::forward<Rest>(rargs)...);
 }
 

include/jwt/jwt.hpp

@@ -125,6 +125,48 @@ jwt::string_view reg_claims_to_str(enum registered_claims claim) noexcept
   assert (0 && "Code not reached");
 }
 
+/**
+ * A helper class that enables reuse of the 
+ * std::set container with custom comparator.
+ */
+struct jwt_set
+{
+  /**
+   * Transparent comparator.
+   * @note: C++14 only.
+   */
+  struct case_compare
+  {
+    using is_transparent = std::true_type;
+
+    bool operator()(const std::string& lhs, const std::string& rhs) const
+    {
+      int ret = strcmp(lhs.c_str(), rhs.c_str());
+      return (ret < 0);
+    }
+
+    bool operator()(const jwt::string_view lhs, const jwt::string_view rhs) const
+    {
+      int ret = strcmp(lhs.data(), rhs.data());
+      return (ret < 0);
+    }
+
+    bool operator()(const std::string& lhs, const jwt::string_view rhs) const
+    {
+      int ret = strcmp(lhs.data(), rhs.data());
+      return (ret < 0);
+    }
+
+    bool operator()(const jwt::string_view lhs, const std::string& rhs) const
+    {
+      int ret = strcmp(lhs.data(), rhs.data());
+      return (ret < 0);
+    }
+  };
+
+  using header_claim_set_t = std::set<std::string, case_compare>;
+};
+
 // Fwd declaration for friend functions to specify the 
 // default arguments
 // See: https://stackoverflow.com/a/23336823/434233
@@ -235,7 +277,11 @@ public: // 'tors
   /*
    * Default constructor.
    */
-  jwt_header() = default;
+  jwt_header()
+  {
+    payload_["alg"] = "none";
+    payload_["typ"] = "JWT";
+  }
 
   /**
    * Constructor taking specified algorithm type
@@ -245,6 +291,8 @@ public: // 'tors
     : alg_(alg)
     , typ_(typ)
   {
+    payload_["typ"] = type_to_str(typ_).to_string();
+    payload_["alg"] = alg_to_str(alg_).to_string();
   }
 
   /**
@@ -269,9 +317,10 @@ public: // Exposed APIs
   /**
    * Set the algorithm.
    */
-  void algo(enum algorithm alg) noexcept
+  void algo(enum algorithm alg)
   {
     alg_ = alg;
+    payload_["alg"] = alg_to_str(alg_).to_string();
   }
 
   /**
@@ -280,6 +329,7 @@ public: // Exposed APIs
   void algo(const jwt::string_view sv)
   {
     alg_ = str_to_alg(sv.data());
+    payload_["alg"] = alg_to_str(alg_).to_string();
   }
 
   /**
@@ -295,11 +345,21 @@ public: // Exposed APIs
    * header would not be valid after modifying the type.
    */
   /**
-   * Set the JWS type.
+   * Set the JWT type.
    */
   void typ(enum type typ) noexcept
   {
     typ_ = typ;
+    payload_["typ"] = type_to_str(typ_).to_string();
+  }
+
+  /**
+   * Set the JWT type header. String overload.
+   */
+  void typ(const jwt::string_view sv)
+  {
+    typ_ = str_to_type(sv.data());
+    payload_["typ"] = type_to_str(typ_).to_string();
   }
 
   /**
@@ -310,6 +370,38 @@ public: // Exposed APIs
     return typ_;
   }
 
+  /**
+   * Add a header to the JWT header.
+   */
+  template <typename T,
+            typename=std::enable_if_t<
+                      !std::is_same<jwt::string_view, std::decay_t<T>>::value
+                     >
+           >
+  bool add_header(const jwt::string_view hname, T&& hvalue, bool overwrite=false)
+  {
+    auto itr = headers_.find(hname);
+    if (itr != std::end(headers_) && !overwrite) {
+      return false;
+    }
+
+    headers_.emplace(hname.data(), hname.length());
+    payload_[hname.data()] = std::forward<T>(hvalue);
+
+    return true;
+  }
+
+  /**
+   * Add a header to the JWT header.
+   * Overload which takes the header value as `jwt::string_view`
+   */
+  bool add_header(const jwt::string_view cname, const jwt::string_view cvalue, bool overwrite=false)
+  {
+    return add_header(cname,
+                      std::string{cvalue.data(), cvalue.length()},
+                      overwrite);
+  }
+
   /**
    * Get the URL safe base64 encoded string
    * of the header.
@@ -347,14 +439,9 @@ public: // Exposed APIs
    * @note: Presence of this member function is a requirement
    * for some interfaces (Eg: `write_interface`).
    */
-  json_t create_json_obj() const
+  const json_t& create_json_obj() const
   {
-    json_t obj = json_t::object();
-    //TODO: should be able to do with string_view
-    obj["typ"] = type_to_str(typ_).to_string();
-    obj["alg"] = alg_to_str(alg_).to_string();
-
-    return obj;
+    return payload_;
   }
 
 private: // Data members
@@ -363,6 +450,12 @@ private: // Data members
 
   /// The type of header
   enum type      typ_ = type::JWT;
+
+  // The JSON payload object
+  json_t payload_;
+
+  //Extra headers for JWS
+  jwt_set::header_claim_set_t headers_; 
 };
 
 
@@ -424,10 +517,6 @@ public: // Exposed APIs
       return false;
     }
 
-    if (itr != claim_names_.end() && overwrite) {
-      claim_names_.erase(itr);
-    }
-
     // Add it to the known set of claims
     claim_names_.emplace(cname.data(), cname.length());
 
@@ -650,43 +739,11 @@ public: // Exposed APIs
   }
 
 private:
-  /**
-   * Transparent comparator.
-   * @note: C++14 only.
-   */
-  struct case_compare 
-  {
-    using is_transparent = std::true_type;
-
-    bool operator()(const std::string& lhs, const std::string& rhs) const
-    {
-      int ret = strcmp(lhs.c_str(), rhs.c_str());
-      return (ret < 0);
-    }
-
-    bool operator()(const jwt::string_view lhs, const jwt::string_view rhs) const
-    {
-      int ret = strcmp(lhs.data(), rhs.data());
-      return (ret < 0);
-    }
-
-    bool operator()(const std::string& lhs, const jwt::string_view rhs) const
-    {
-      int ret = strcmp(lhs.data(), rhs.data());
-      return (ret < 0);
-    }
-
-    bool operator()(const jwt::string_view lhs, const std::string& rhs) const
-    {
-      int ret = strcmp(lhs.data(), rhs.data());
-      return (ret < 0);
-    }
-  };
 
   /// JSON object containing payload
   json_t payload_;
   /// The set of claim names in the payload
-  std::set<std::string, case_compare> claim_names_;
+  jwt_set::header_claim_set_t claim_names_;
 };
 
 /**