/** 
 * @file llerror.h
 * @date   December 2006
 * @brief error message system
 *
 * $LicenseInfo:firstyear=2006&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 * 
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef LL_LLERROR_H
#define LL_LLERROR_H

#include <sstream>
#include <typeinfo>

#include "stdtypes.h"

#include "llpreprocessor.h"
#include <boost/static_assert.hpp>

const int LL_ERR_NOERR = 0;

// Define one of these for different error levels in release...
// #define RELEASE_SHOW_DEBUG // Define this if you want your release builds to show lldebug output.
#define RELEASE_SHOW_INFO // Define this if you want your release builds to show llinfo output
#define RELEASE_SHOW_WARN // Define this if you want your release builds to show llwarn output.

#ifdef _DEBUG
#define SHOW_DEBUG
#define SHOW_WARN
#define SHOW_INFO
#define SHOW_ASSERT
#else // _DEBUG

#ifdef LL_RELEASE_WITH_DEBUG_INFO
#define SHOW_ASSERT
#endif // LL_RELEASE_WITH_DEBUG_INFO

#ifdef RELEASE_SHOW_DEBUG
#define SHOW_DEBUG
#endif

#ifdef RELEASE_SHOW_WARN
#define SHOW_WARN
#endif

#ifdef RELEASE_SHOW_INFO
#define SHOW_INFO
#endif

#ifdef RELEASE_SHOW_ASSERT
#define SHOW_ASSERT
#endif

#endif // !_DEBUG

#define llassert_always_msg(func, msg) if (LL_UNLIKELY(!(func))) LL_ERRS() << "ASSERT (" << msg << ")" << LL_ENDL

#define llassert_always(func)	llassert_always_msg(func, #func)

#ifdef SHOW_ASSERT
#define llassert(func)			llassert_always_msg(func, #func)
#define llverify(func)			llassert_always_msg(func, #func)
#else
#define llassert(func)
#define llverify(func)			do {if (func) {}} while(0)
#endif

#ifdef LL_WINDOWS
#define LL_STATIC_ASSERT(func, msg) static_assert(func, msg)
#define LL_BAD_TEMPLATE_INSTANTIATION(type, msg) static_assert(false, msg)
#else
#define LL_STATIC_ASSERT(func, msg) BOOST_STATIC_ASSERT(func)
#define LL_BAD_TEMPLATE_INSTANTIATION(type, msg) BOOST_STATIC_ASSERT(sizeof(type) != 0 && false);
#endif


/** Error Logging Facility

	Information for most users:
	
	Code can log messages with constructions like this:
	
		LL_INFOS("StringTag") << "request to fizzbip agent " << agent_id
			<< " denied due to timeout" << LL_ENDL;
		
	Messages can be logged to one of four increasing levels of concern,
	using one of four "streams":

		LL_DEBUGS("StringTag")	- debug messages that are normally suppressed
		LL_INFOS("StringTag")	- informational messages that are normal shown
		LL_WARNS("StringTag")	- warning messages that signal a problem
		LL_ERRS("StringTag")	- error messages that are major, unrecoverable failures
		
	The later (LL_ERRS("StringTag")) automatically crashes the process after the message
	is logged.
	
	Note that these "streams" are actually #define magic.  Rules for use:
		* they cannot be used as normal streams, only to start a message
		* messages written to them MUST be terminated with LL_ENDL
		* between the opening and closing, the << operator is indeed
		  writing onto a std::ostream, so all conversions and stream
		  formating are available
	
	These messages are automatically logged with function name, and (if enabled)
	file and line of the message.  (Note: Existing messages that already include
	the function name don't get name printed twice.)
	
	If you have a class, adding LOG_CLASS line to the declaration will cause
	all messages emitted from member functions (normal and static) to be tagged
	with the proper class name as well as the function name:
	
		class LLFoo
		{
			LOG_CLASS(LLFoo);
		public:
			...
		};
	
		void LLFoo::doSomething(int i)
		{
			if (i > 100)
			{
				LL_WARNS("FooBarTag") << "called with a big value for i: " << i << LL_ENDL; 
			}
			...
		}
	
	will result in messages like:
	
		WARN #FooBarTag# llcommon/llfoo(100) LLFoo::doSomething : called with a big value for i: 283
	
    the syntax is:
        <timestamp> SPACE <level> SPACE <tags> SPACE <location> SPACE <function> SPACE COLON SPACE <message>

    where each SPACE is a single space character; note that if a field is empty (such as when no
    tags are specified), all the SPACEs are still present.

    The tags must be a single word (may not contain a space); if more than one tag is specified,
    they are all surrounded by '#' ( #FooTag#BarTag# ).

	Which messages are logged and which are suppressed can be controlled at run
	time from the configuration file. The default configuration is in newview/app_settings/logcontrol.xml
    A copy of that file named logcontrol-dev.xml can be made in the users personal settings
    directory; that will override the installed default file.  See the logcontrol.xml
    file or http://wiki.secondlife.com/wiki/Logging_System_Overview for configuration details.
	
	Lastly, logging is now very efficient in both compiled code and execution
	when skipped.  There is no need to wrap messages, even debugging ones, in
	#ifdef _DEBUG constructs.  LL_DEBUGS("StringTag") messages are compiled into all builds,
	even release.  Which means you can use them to help debug even when deployed
	to a real grid.
*/
namespace LLError
{
	enum ELevel
	{
		LEVEL_ALL = 0,
			// used to indicate that all messages should be logged
			
		LEVEL_DEBUG = 0,
		LEVEL_INFO = 1,
		LEVEL_WARN = 2,
		LEVEL_ERROR = 3,	// used to be called FATAL
		
		LEVEL_NONE = 4
			// not really a level
			// used to indicate that no messages should be logged
	};
	// If you change ELevel, please update llvlog() macro below.

	/*	Macro support
		The classes CallSite and Log are used by the logging macros below.
		They are not intended for general use.
	*/

	struct CallSite;

	class LL_COMMON_API Log
	{
	public:
		static bool shouldLog(CallSite&);
		static std::ostringstream* out();
		static void flush(std::ostringstream* out, char* message);
		static void flush(std::ostringstream*, const CallSite&);
		static std::string demangle(const char* mangled);
		/// classname<TYPE>()
		template <typename T>
		static std::string classname()             { return demangle(typeid(T).name()); }
		/// classname(some_pointer)
		template <typename T>
		static std::string classname(T* const ptr) { return ptr? demangle(typeid(*ptr).name()) : "nullptr"; }
		/// classname(some_reference)
		template <typename T>
		static std::string classname(const T& obj) { return demangle(typeid(obj).name()); }
	};

	struct LL_COMMON_API CallSite
	{
		// Represents a specific place in the code where a message is logged
		// This is public because it is used by the macros below.  It is not
		// intended for public use.
		CallSite(ELevel level, 
				const char* file, 
				int line,
				const std::type_info& class_info, 
				const char* function, 
				bool print_once, 
				const char** tags, 
				size_t tag_count);

		~CallSite();

#ifdef LL_LIBRARY_INCLUDE
		bool shouldLog();
#else // LL_LIBRARY_INCLUDE
		bool shouldLog()
		{ 
			return mCached 
					? mShouldLog 
					: Log::shouldLog(*this); 
		}
			// this member function needs to be in-line for efficiency
#endif // LL_LIBRARY_INCLUDE
		
		void invalidate();
		
		// these describe the call site and never change
		const ELevel			mLevel;
		const char* const		mFile;
		const int				mLine;
		const std::type_info&   mClassInfo;
		const char* const		mFunction;
		const char**			mTags;
		size_t					mTagCount;
		const bool				mPrintOnce;
		const char*				mLevelString;
		std::string				mLocationString,
								mFunctionString,
								mTagString;
		bool					mCached,
								mShouldLog;
		
		friend class Log;
	};
	
	
	class End { };
	inline std::ostream& operator<<(std::ostream& s, const End&)
		{ return s; }
		// used to indicate the end of a message
		
	class LL_COMMON_API NoClassInfo { };
		// used to indicate no class info known for logging

    //LLCallStacks keeps track of call stacks and output the call stacks to log file
    //when LLAppViewer::handleViewerCrash() is triggered.
    //
    //Note: to be simple, efficient and necessary to keep track of correct call stacks, 
    //LLCallStacks is designed not to be thread-safe.
    //so try not to use it in multiple parallel threads at same time.
    //Used in a single thread at a time is fine.
    class LL_COMMON_API LLCallStacks
    {
    private:
        static char**  sBuffer ;
        static S32     sIndex ;

        static void allocateStackBuffer();
        static void freeStackBuffer();
              
    public:   
        static void push(const char* function, const int line) ;
        static std::ostringstream* insert(const char* function, const int line) ;
        static void print() ;
        static void clear() ;
        static void end(std::ostringstream* _out) ;
        static void cleanup();
    };

    // class which, when streamed, inserts the current stack trace
    struct LLStacktrace
    {
        friend std::ostream& operator<<(std::ostream& out, const LLStacktrace&);
    };
}

//this is cheaper than llcallstacks if no need to output other variables to call stacks. 
#define LL_PUSH_CALLSTACKS() LLError::LLCallStacks::push(__FUNCTION__, __LINE__)

#define llcallstacks                                                                      \
	{                                                                                     \
       std::ostringstream* _out = LLError::LLCallStacks::insert(__FUNCTION__, __LINE__) ; \
       (*_out)

#define llcallstacksendl                   \
		LLError::End();                    \
		LLError::LLCallStacks::end(_out) ; \
	}

#define LL_CLEAR_CALLSTACKS() LLError::LLCallStacks::clear()
#define LL_PRINT_CALLSTACKS() LLError::LLCallStacks::print() 

/*
	Class type information for logging
 */

#define LOG_CLASS(s)	typedef s _LL_CLASS_TO_LOG
	// Declares class to tag logged messages with.
	// See top of file for example of how to use this
	
typedef LLError::NoClassInfo _LL_CLASS_TO_LOG;
	// Outside a class declaration, or in class without LOG_CLASS(), this
	// typedef causes the messages to not be associated with any class.

/////////////////////////////////
// Error Logging Macros
// See top of file for common usage.
/////////////////////////////////

// Instead of using LL_DEBUGS(), LL_INFOS() et al., it may be tempting to
// directly code the lllog() macro so you can pass in the LLError::ELevel as a
// variable. DON'T DO IT! The reason is that the first time control passes
// through lllog(), it initializes a local static LLError::CallSite with that
// *first* ELevel value. All subsequent visits will decide whether or not to
// emit output based on the *first* ELevel value bound into that static
// CallSite instance. Use LL_VLOGS() instead. lllog() assumes its ELevel
// argument never varies.

// this macro uses a one-shot do statement to avoid parsing errors when
// writing control flow statements without braces:
// if (condition) LL_INFOS() << "True" << LL_ENDL; else LL_INFOS()() << "False" << LL_ENDL;

#define lllog(level, once, ...)                                         \
	do {                                                                \
		const char* tags[] = {"", ##__VA_ARGS__};                       \
		static LLError::CallSite _site(lllog_site_args_(level, once, tags)); \
		lllog_test_()

#define lllog_test_()                                       \
		if (LL_UNLIKELY(_site.shouldLog()))                 \
		{                                                   \
			std::ostringstream* _out = LLError::Log::out(); \
			(*_out)

#define lllog_site_args_(level, once, tags)                 \
	level, __FILE__, __LINE__, typeid(_LL_CLASS_TO_LOG),    \
	__FUNCTION__, once, &tags[1], LL_ARRAY_SIZE(tags)-1

//Use this construct if you need to do computation in the middle of a
//message:
//	
//	LL_INFOS("AgentGesture") << "the agent " << agend_id;
//	switch (f)
//	{
//		case FOP_SHRUGS:	LL_CONT << "shrugs";				break;
//		case FOP_TAPS:		LL_CONT << "points at " << who;	break;
//		case FOP_SAYS:		LL_CONT << "says " << message;	break;
//	}
//	LL_CONT << " for " << t << " seconds" << LL_ENDL;
//	
//Such computation is done iff the message will be logged.
#define LL_CONT	(*_out)

#define LL_NEWLINE '\n'

// Use this only in LL_ERRS or in a place that LL_ERRS may not be used
#define LLERROR_CRASH         \
{                             \
    int* make_me_crash = NULL;\
    *make_me_crash = 0;       \
    exit(*make_me_crash);     \
}

#define LL_ENDL                                         \
            LLError::End();                             \
            LLError::Log::flush(_out, _site);           \
            if (_site.mLevel == LLError::LEVEL_ERROR)   \
            {                                           \
                LLERROR_CRASH                           \
            }                                           \
        }                                               \
    } while(0)

// NEW Macros for debugging, allow the passing of a string tag

// Pass comma separated list of tags (currently only supports up to 0, 1, or 2)
#define LL_DEBUGS(...)	lllog(LLError::LEVEL_DEBUG, false, ##__VA_ARGS__)
#define LL_INFOS(...)	lllog(LLError::LEVEL_INFO, false, ##__VA_ARGS__)
#define LL_WARNS(...)	lllog(LLError::LEVEL_WARN, false, ##__VA_ARGS__)
#define LL_ERRS(...)	lllog(LLError::LEVEL_ERROR, false, ##__VA_ARGS__)
// alternative to llassert_always that prints explanatory message
// note ## token paste operator hack used above will only work in gcc following
// a comma and is completely unnecessary in VS since the comma is automatically
// suppressed
// https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html
// https://docs.microsoft.com/en-us/cpp/preprocessor/variadic-macros?view=vs-2015
#define LL_WARNS_IF(exp, ...)	if (exp) LL_WARNS(__VA_ARGS__) << "(" #exp ")"
#define LL_ERRS_IF(exp, ...)	if (exp) LL_ERRS(__VA_ARGS__) << "(" #exp ")"

// Only print the log message once (good for warnings or infos that would otherwise
// spam the log file over and over, such as tighter loops).
#define LL_DEBUGS_ONCE(...)	lllog(LLError::LEVEL_DEBUG, true, ##__VA_ARGS__)
#define LL_INFOS_ONCE(...)	lllog(LLError::LEVEL_INFO, true, ##__VA_ARGS__)
#define LL_WARNS_ONCE(...)	lllog(LLError::LEVEL_WARN, true, ##__VA_ARGS__)

// Use this if you need to pass LLError::ELevel as a variable.
#define LL_VLOGS(level, ...)      llvlog(level, false, ##__VA_ARGS__)
#define LL_VLOGS_ONCE(level, ...) llvlog(level, true,  ##__VA_ARGS__)

// The problem with using lllog() with a variable level is that the first time
// through, it initializes a static CallSite instance with whatever level you
// pass. That first level is bound into the CallSite; the level parameter is
// never again examined. One approach to variable level would be to
// dynamically construct a CallSite instance every call -- which could get
// expensive, depending on context. So instead, initialize a static CallSite
// for each level value we support, then dynamically select the CallSite
// instance for the passed level value.
// Compare implementation to lllog() above.
#define llvlog(level, once, ...)                                        \
	do {                                                                \
		const char* tags[] = {"", ##__VA_ARGS__};                       \
		/* Need a static CallSite instance per expected ELevel value. */ \
		/* Since we intend to index this array with the ELevel, */      \
		/* _sites[0] should be ELevel(0), and so on -- avoid using */   \
		/* ELevel symbolic names when initializing -- except for */     \
		/* the last entry, which handles anything beyond the end. */    \
		/* (Commented ELevel value names are from 2016-09-01.) */       \
		/* Passing an ELevel past the end of this array is itself */    \
		/* a fatal error, so ensure the last is LEVEL_ERROR. */         \
		static LLError::CallSite _sites[] =                             \
		{                                                               \
			/* LEVEL_DEBUG */                                           \
			LLError::CallSite(lllog_site_args_(LLError::ELevel(0), once, tags)), \
			/* LEVEL_INFO */                                            \
			LLError::CallSite(lllog_site_args_(LLError::ELevel(1), once, tags)), \
			/* LEVEL_WARN */                                            \
			LLError::CallSite(lllog_site_args_(LLError::ELevel(2), once, tags)), \
			/* LEVEL_ERROR */                                           \
			LLError::CallSite(lllog_site_args_(LLError::LEVEL_ERROR, once, tags)) \
		};                                                              \
		/* Clamp the passed 'level' to at most last entry */            \
		std::size_t which((std::size_t(level) >= LL_ARRAY_SIZE(_sites)) ? \
						  (LL_ARRAY_SIZE(_sites) - 1) : std::size_t(level)); \
		/* selected CallSite *must* be named _site for LL_ENDL */       \
		LLError::CallSite& _site(_sites[which]);                        \
		lllog_test_()

// Check at run-time whether logging is enabled, without generating output
bool debugLoggingEnabled(const std::string& tag);

#endif // LL_LLERROR_H