add try_fetch_addon_with_checks fcn, use when gui installs addons

Extending the 'try_fetch_addon' fcn, this fcn also calls the dep
check and the check for dev overwrite functions beforehand. Thus it
does a fully 'smart' download of an add-on and tidies up many of the
details.

We plan to call this function also as part of the code path when we
do addon auto-downloads from the mp lobby.

src/addon/manager_ui.cpp

@@ -136,17 +136,23 @@ static bool try_fetch_addon(display & disp, addons_client & client, const addon_
 	}
 }
 
+enum OUTCOME { SUCCESS, FAILURE, ABORT };
+
 // A structure which summarizes the outcome of one or more add-on install operations.
 struct ADDON_OP_RESULT {
-	bool continue_;
+	OUTCOME outcome_;
 	bool wml_changed_;
 };
 
-/** Warns the user about unresolved dependencies and installs them if they choose to do so. */
+/** Warns the user about unresolved dependencies and installs them if they choose to do so. 
+ * Returns: outcome: ABORT in case the user chose to abort because of an issue
+ *                   SUCCESS otherwise
+ *          wml_change: indicates if new wml content was installed
+ */
 ADDON_OP_RESULT do_resolve_addon_dependencies(display& disp, addons_client& client, const addons_list& addons, const addon_info& addon)
 {
 	ADDON_OP_RESULT result;
-	result.continue_ = true;
+	result.outcome_ = SUCCESS;
 	result.wml_changed_ = false;
 
 	boost::scoped_ptr<cursor::setter> cursor_setter(new cursor::setter(cursor::WAIT));
@@ -185,7 +191,7 @@ ADDON_OP_RESULT do_resolve_addon_dependencies(display& disp, addons_client& clie
 		}
 
 		if(gui2::show_message(disp.video(), _("Broken Dependencies"), broken_deps_report, gui2::tmessage::yes_no_buttons) != gui2::twindow::OK) {
-			result.continue_ = false;
+			result.outcome_ = ABORT;
 			return result; // canceled by user
 		}
 	}
@@ -273,7 +279,7 @@ ADDON_OP_RESULT do_resolve_addon_dependencies(display& disp, addons_client& clie
 			"The following dependencies could not be installed. Do you still wish to continue?",
 			failed_titles.size()) + std::string("\n\n") + utils::bullet_list(failed_titles);
 
-		result.continue_ = gui2::show_message(disp.video(), _("Dependencies Installation Failed"), failed_deps_report, gui2::tmessage::yes_no_buttons) == gui2::twindow::OK; // Only continue if the user chooses to ignore the failures
+		result.outcome_ = gui2::show_message(disp.video(), _("Dependencies Installation Failed"), failed_deps_report, gui2::tmessage::yes_no_buttons) == gui2::twindow::OK ? SUCCESS : ABORT; // If the user cancels, return ABORT. Otherwise, return SUCCESS, since the user chose to ignore the failure.
 		return result;
 	}
 
@@ -314,6 +320,38 @@ bool do_check_before_overwriting_addon(CVideo& video, const addon_info& addon)
 	return gui2::show_message(video, _("Confirm"), text, gui2::tmessage::yes_no_buttons) == gui2::twindow::OK;
 }
 
+/** Do a 'smart' fetch of an add-on, checking to avoid overwrites for devs and resolving dependencies, using gui interaction to handle issues that arise
+ * Returns: outcome: ABORT in case the user chose to abort because of an issue
+ *                   FAILURE in case we resolved checks and dependencies, but fetching this particular add-on failed
+ *                   SUCCESS otherwise
+ *          wml_changed: indicates if new wml content was installed at any point
+ */
+static ADDON_OP_RESULT try_fetch_addon_with_checks(display & disp, addons_client& client, const addons_list& addons, const addon_info& addon)
+{
+	if(!(do_check_before_overwriting_addon(disp.video(), addon))) {
+		// Just do nothing and leave.
+		ADDON_OP_RESULT result;
+		result.outcome_ = ABORT;
+		result.wml_changed_ = false;
+
+		return result;
+	}
+
+	// Resolve any dependencies
+	ADDON_OP_RESULT res = do_resolve_addon_dependencies(disp, client, addons, addon);
+	if (res.outcome_ != SUCCESS) { // this function only returns SUCCESS and ABORT as outcomes
+		return res; // user aborted
+	}
+
+	if(!try_fetch_addon(disp, client, addon)) {
+		res.outcome_ = FAILURE;
+		return res; //wml_changed should have whatever value was obtained in resolving dependencies
+	} else {
+		res.wml_changed_ = true;
+		return res; //we successfully installed something, so now the wml was definitely changed
+	}
+}
+
 /** Performs all backend and UI actions for taking down the specified add-on. */
 void do_remote_addon_delete(CVideo& video, addons_client& client, const std::string& addon_id)
 {
@@ -887,21 +925,13 @@ void show_addons_manager_dialog(display& disp, addons_client& client, addons_lis
 	BOOST_FOREACH(const std::string& id, ids_to_install) {
 		const addon_info& addon = addon_at(id, addons);
 
-		if(!(do_check_before_overwriting_addon(disp.video(), addon))) {
-			// Just do nothing and leave.
-			return;
-		}
-
-		// Resolve any dependencies
-		ADDON_OP_RESULT res = do_resolve_addon_dependencies(disp, client, addons, addon);
-		wml_changed |= res.wml_changed_; // Take note if this op changed the wml.
-		if (!res.continue_) {
-			return; // abort
-		}
-
-		if(!try_fetch_addon(disp, client, addon)) {
-			failed_titles.push_back(addon.title);
-		} else {
+		ADDON_OP_RESULT res = try_fetch_addon_with_checks(disp, client, addons, addon);
+		wml_changed |= res.wml_changed_; // take note if any wml_changes occurred
+		if (res.outcome_ == ABORT) {
+			return; // the user aborted because of some issue encountered
+		} else if (res.outcome_ == FAILURE) {
+			failed_titles.push_back(addon.title); // we resolved dependencies, but fetching this particular addon failed.
+		} else { // res.outcome == SUCCESS
 			wml_changed = true;
 		}
 	}