Add-ons: add UrlType enum class, QualifiedUrl class and Addon::getUrls() method

QualifiedUrl is essentially a pair containing an enum value
(addons::UrlType::homePage, addons::UrlType::download, etc.) and an
std::string for the URL per se, with adequate getters and setters.

Addon::getUrls() is for people who wish to process all non-empty URLs
occurring as part of the add-on metadata in batch.

Mailing-list discussion:

  https://sourceforge.net/p/flightgear/mailman/message/36159711/

src/Add-ons/Addon.cxx

@@ -25,12 +25,15 @@
 #include <utility>
 #include <vector>
 
+#include <cassert>
+
 #include <simgear/misc/sg_path.hxx>
 #include <simgear/nasal/cppbind/Ghost.hxx>
 #include <simgear/nasal/cppbind/NasalHash.hxx>
 #include <simgear/nasal/naref.h>
 #include <simgear/props/props.hxx>
 #include <simgear/props/props_io.hxx>
+#include <simgear/sg_inlines.h>
 
 #include <Main/globals.hxx>
 #include <Scripting/NasalSys.hxx>
@@ -51,6 +54,31 @@ namespace flightgear
 namespace addons
 {
 
+// ***************************************************************************
+// *                              QualifiedUrl                               *
+// ***************************************************************************
+
+QualifiedUrl::QualifiedUrl(UrlType type, std::string url)
+  : _type(type),
+    _url(std::move(url))
+{ }
+
+UrlType QualifiedUrl::getType() const
+{ return _type; }
+
+void QualifiedUrl::setType(UrlType type)
+{ _type = type; }
+
+std::string QualifiedUrl::getUrl() const
+{ return _url; }
+
+void QualifiedUrl::setUrl(const std::string& url)
+{ _url = url; }
+
+// ***************************************************************************
+// *                                  Addon                                  *
+// ***************************************************************************
+
 Addon::Addon(std::string id, AddonVersion version, SGPath basePath,
              std::string minFGVersionRequired, std::string maxFGVersionRequired,
              SGPropertyNode* addonNode)
@@ -506,6 +534,29 @@ Addon::parseLicenseNode(const SGPath& addonPath, SGPropertyNode* addonNode)
   return std::make_tuple(licenseDesignation, licenseFile, licenseUrl);
 }
 
+std::map<UrlType, QualifiedUrl> Addon::getUrls() const
+{
+  std::map<UrlType, QualifiedUrl> res;
+
+  auto appendIfNonEmpty = [&res](UrlType type, const string& url) {
+    if (!url.empty()) {
+      auto emplaceRetval = res.emplace(type, QualifiedUrl(type, url));
+      // We start with an empty std::map<> and don't call this lambda more
+      // than once for the same type, therefore the same key can't be seen
+      // twice.
+      assert(emplaceRetval.second);
+      SG_UNUSED(emplaceRetval); // 'cause asserts are removed in Release builds
+    }
+  };
+
+  appendIfNonEmpty(UrlType::homePage, getHomePage());
+  appendIfNonEmpty(UrlType::download, getDownloadUrl());
+  appendIfNonEmpty(UrlType::support, getSupportUrl());
+  appendIfNonEmpty(UrlType::codeRepository, getCodeRepositoryUrl());
+  appendIfNonEmpty(UrlType::license, getLicenseUrl());
+
+  return res;
+}
 
 // Static method
 void Addon::setupGhost(nasal::Hash& addonsModule)

src/Add-ons/Addon.hxx

@@ -20,6 +20,7 @@
 #ifndef FG_ADDON_HXX
 #define FG_ADDON_HXX
 
+#include <map>
 #include <ostream>
 #include <string>
 #include <tuple>
@@ -40,6 +41,29 @@ namespace flightgear
 namespace addons
 {
 
+enum class UrlType {
+  homePage,
+  download,
+  support,
+  codeRepository,
+  license
+};
+
+class QualifiedUrl {
+public:
+  QualifiedUrl(UrlType type, std::string url);
+
+  UrlType getType() const;
+  void setType(UrlType type);
+
+  std::string getUrl() const;
+  void setUrl(const std::string& url);
+
+private:
+  UrlType _type;
+  std::string _url;
+};
+
 class Addon : public SGReferenced {
 public:
   // Default constructor. 'minFGVersionRequired' is initialized to "2017.4.0"
@@ -131,6 +155,9 @@ public:
   int getLoadSequenceNumber() const;
   void setLoadSequenceNumber(int num);
 
+  // Get all non-empty URLs pertaining to this add-on
+  std::map<UrlType, QualifiedUrl> getUrls() const;
+
   // Simple string representation
   std::string str() const;
 

src/Add-ons/addon_fwd.hxx

@@ -34,6 +34,9 @@ class AddonManager;
 class AddonVersion;
 class AddonVersionSuffix;
 
+enum class UrlType;
+class QualifiedUrl;
+
 using AddonRef = SGSharedPtr<Addon>;
 using AddonVersionRef = SGSharedPtr<AddonVersion>;