From d640ec248ca8bf86a03007a0f8df352df696cf92 Mon Sep 17 00:00:00 2001
From: Edwin Mons <edwin.mons@isode.com>
Date: Wed, 13 Nov 2019 13:03:22 +0100
Subject: Support application-supplied logging

This adds a method to set a logging callback.  If such a callback is
set, all SWIFT_LOG calls will invoke this callback instead of writing to
either stderr or the swift logging file.

Test-Information:

Updated unit tests pass.
Checked that logs generated by Swift and Sluift (which do not set the
callback) resulted in logging in the expected location.

Change-Id: I0eb2a1057aa77839e1b8d5f320205eb9d5fdc253

diff --git a/Swiften/Base/Log.cpp b/Swiften/Base/Log.cpp
index 9b16531..abfd2bc 100644
--- a/Swiften/Base/Log.cpp
+++ b/Swiften/Base/Log.cpp
@@ -17,6 +17,7 @@ namespace Swift {
 
 static Log::Severity logLevel = Log::warning;
 std::unique_ptr<FILE, Log::LogFileClose> Log::logfile;
+Log::Callback Log::logCallback;
 
 Log::Log() {
 }
@@ -26,7 +27,10 @@ Log::~Log() {
     __android_log_print(ANDROID_LOG_VERBOSE, "Swift", stream.str().c_str(), 1);
 #else
     // Using stdio for thread safety (POSIX file i/o calls are guaranteed to be atomic)
-    if (logfile) {
+    if (logCallback) {
+        logCallback(severity_, std::move(file_), line_, std::move(function_), stream.str());
+    }
+    else if (logfile) {
         fwrite(stream.str().c_str(), sizeof(char), stream.str().size(), logfile.get());
         fflush(logfile.get());
     }
@@ -38,12 +42,20 @@ Log::~Log() {
 }
 
 std::ostringstream& Log::getStream(
-        Severity /*severity*/,
-        const std::string& severityString,
-        const std::string& file,
+        Severity severity,
+        std::string severityString,
+        std::string file,
         int line,
-        const std::string& function) {
-    stream << "[" << severityString << "] " << file << ":" << line << " " << function << ": ";
+        std::string function) {
+    if (logCallback) {
+        severity_ = severity;
+        file_ = std::move(file);
+        line_ = line;
+        function_ = std::move(function);
+    }
+    else {
+        stream << "[" << severityString << "] " << file << ":" << line << " " << function << ": ";
+    }
     return stream;
 }
 
@@ -61,4 +73,8 @@ void Log::setLogFile(const std::string& fileName) {
     }
 }
 
+void Log::setLogCallback(Callback callback) {
+    Log::logCallback = callback;
+}
+
 }
diff --git a/Swiften/Base/Log.h b/Swiften/Base/Log.h
index e3e04a5..255e478 100644
--- a/Swiften/Base/Log.h
+++ b/Swiften/Base/Log.h
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <cstdio>
+#include <functional>
 #include <memory>
 #include <sstream>
 
@@ -18,20 +19,22 @@ namespace Swift {
             enum Severity {
                 error, warning, info, debug
             };
+            using Callback = std::function<void(Severity severity, std::string file, int line, std::string function, std::string message)>;
 
             Log();
             ~Log();
 
             std::ostringstream& getStream(
                     Severity severity,
-                    const std::string& severityString,
-                    const std::string& file,
+                    std::string severityString,
+                    std::string file,
                     int line,
-                    const std::string& function);
+                    std::string function);
 
             static Severity getLogLevel();
             static void setLogLevel(Severity level);
             static void setLogFile(const std::string& fileName);
+            static void setLogCallback(Callback callback);
 
         private:
             struct LogFileClose {
@@ -43,6 +46,11 @@ namespace Swift {
             };
             std::ostringstream stream;
             static std::unique_ptr<FILE, LogFileClose> logfile;
+            static Callback logCallback;
+            Severity severity_;
+            std::string file_;
+            int line_;
+            std::string function_;
     };
 }
 
diff --git a/Swiften/Base/UnitTest/LogTest.cpp b/Swiften/Base/UnitTest/LogTest.cpp
new file mode 100644
index 0000000..5d710db
--- /dev/null
+++ b/Swiften/Base/UnitTest/LogTest.cpp
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2019 Isode Limited.
+ * All rights reserved.
+ * See the COPYING file for more information.
+ */
+
+#include <vector>
+
+#include <boost/algorithm/string/predicate.hpp>
+
+#include <gtest/gtest.h>
+
+#include <Swiften/Base/Log.h>
+
+using namespace Swift;
+
+struct LogEntry {
+    LogEntry(Log::Severity severity, std::string file, int line, std::string function, std::string message) : severity(severity), file(std::move(file)), line(line), function(std::move(function)), message(std::move(message)) {}
+
+    Log::Severity severity;
+    std::string file;
+    int line;
+    std::string function;
+    std::string message;
+};
+
+// Helper class to set the logging callback.  Using this class to set it will ensure the
+// logCallback is reset to empty (its default state) after each test.
+class LogCallbackSetter {
+public:
+    LogCallbackSetter(Log::Callback callback) {
+        Log::setLogCallback(callback);
+    }
+    ~LogCallbackSetter() {
+        Log::setLogCallback({});
+    }
+};
+
+TEST(LogTest, testCallback) {
+    std::vector<LogEntry> logEntries;
+    LogCallbackSetter callbackSetter = {[&](Log::Severity severity, const std::string& file, int line, const std::string& function, const std::string& message) {
+        logEntries.emplace_back(severity, file, line, function, message);
+    }};
+
+    SWIFT_LOG(error) << "An error";
+    ASSERT_EQ(1, logEntries.size());
+    ASSERT_EQ(Log::error, logEntries[0].severity);
+    ASSERT_EQ("An error", logEntries[0].message);
+}
diff --git a/Swiften/SConscript b/Swiften/SConscript
index 5705113..7ea7355 100644
--- a/Swiften/SConscript
+++ b/Swiften/SConscript
@@ -383,6 +383,7 @@ if env["SCONS_STAGE"] == "build" :
             File("Avatars/UnitTest/CombinedAvatarProviderTest.cpp"),
             File("Avatars/UnitTest/AvatarManagerImplTest.cpp"),
             File("Base/UnitTest/IDGeneratorTest.cpp"),
+            File("Base/UnitTest/LogTest.cpp"),
             File("Base/UnitTest/LRUCacheTest.cpp"),
             File("Base/UnitTest/SimpleIDGeneratorTest.cpp"),
             File("Base/UnitTest/StringTest.cpp"),
-- 
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