Improve proxy initialization

Simplify and make the code in AppInit2 more clear.

This provides a straightforward flow, gets rid of .count() (which makes
it possible to override an earlier provided proxy option to nothing), as
well as comments the different cases.

src/init.cpp

@@ -1136,31 +1136,36 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         }
     }
 
-    proxyType addrProxy;
-    bool fProxy = false;
-    if (mapArgs.count("-proxy")) {
-        addrProxy = proxyType(CService(mapArgs["-proxy"], 9050), GetBoolArg("-proxyrandomize", true));
+    bool proxyRandomize = GetBoolArg("-proxyrandomize", true);
+    // -proxy sets a proxy for all outgoing network traffic
+    // -noproxy (or -proxy=0) as well as the empty string can be used to not set a proxy, this is the default
+    std::string proxyArg = GetArg("-proxy", "");
+    if (proxyArg != "" && proxyArg != "0") {
+        proxyType addrProxy = proxyType(CService(proxyArg, 9050), proxyRandomize);
         if (!addrProxy.IsValid())
-            return InitError(strprintf(_("Invalid -proxy address: '%s'"), mapArgs["-proxy"]));
+            return InitError(strprintf(_("Invalid -proxy address: '%s'"), proxyArg));
 
         SetProxy(NET_IPV4, addrProxy);
         SetProxy(NET_IPV6, addrProxy);
+        SetProxy(NET_TOR, addrProxy);
         SetNameProxy(addrProxy);
-        fProxy = true;
+        SetReachable(NET_TOR); // by default, -proxy sets onion as reachable, unless -noonion later
     }
 
-    // -onion can override normal proxy, -noonion disables connecting to .onion entirely
-    if (!(mapArgs.count("-onion") && mapArgs["-onion"] == "0") &&
-        (fProxy || mapArgs.count("-onion"))) {
-        proxyType addrOnion;
-        if (!mapArgs.count("-onion"))
-            addrOnion = addrProxy;
-        else
-            addrOnion = proxyType(CService(mapArgs["-onion"], 9050), GetBoolArg("-proxyrandomize", true));
-        if (!addrOnion.IsValid())
-            return InitError(strprintf(_("Invalid -onion address: '%s'"), mapArgs["-onion"]));
-        SetProxy(NET_TOR, addrOnion);
-        SetReachable(NET_TOR);
+    // -onion can be used to set only a proxy for .onion, or override normal proxy for .onion addresses
+    // -noonion (or -onion=0) disables connecting to .onion entirely
+    // An empty string is used to not override the onion proxy (in which case it defaults to -proxy set above, or none)
+    std::string onionArg = GetArg("-onion", "");
+    if (onionArg != "") {
+        if (onionArg == "0") { // Handle -noonion/-onion=0
+            SetReachable(NET_TOR, false); // set onions as unreachable
+        } else {
+            proxyType addrOnion = proxyType(CService(onionArg, 9050), proxyRandomize);
+            if (!addrOnion.IsValid())
+                return InitError(strprintf(_("Invalid -onion address: '%s'"), onionArg));
+            SetProxy(NET_TOR, addrOnion);
+            SetReachable(NET_TOR);
+        }
     }
 
     // see Step 2: parameter interactions for more information about these