/**
 * A massively over-engineered logging system.  The basic idea here
 * is to set up logging that can be changed at compile time, so that
 * durign development you have lots of logging and the in production
 * very little, WITH NO CODE CHANGE. More, when logging at the ERROR level
 * all logging is to stderr, so it has delivery guaranteed.
 * 
 * I used a system very similar to this for several years at one of my jobs.
 * 
 * @author gtowell
 * Created: Sep 2019
 * Modified (heavily): March 2021
 * **/  

#include<stdio.h>
 
/**
 * To change the log level
 * gcc -D LOG_LEVEL=v logging.c
 * 
 * where v = 0,1,5,10
 * 
 * If the log level is not wrapped in an ifndef, then the 
 * compile time setting is overwritten
 * **/
#ifndef LOG_LEVEL
#define LOG_LEVEL 0
#endif

#define LOG_VERBOSE 1
#define LOG_INFO 5
#define LOG_ERROR 10

// basic logging comment
#define LOG(level, ...) if (LOG_LEVEL <= level) fprintf(LOG_LEVEL>=LOG_ERROR?stderr:stdout , __VA_ARGS__)

// a logger to check for possible divide by zero errors
#define CHECK_ZERO(d) if (d==0) LOG(LOG_ERROR, "Divide by zero line:%d  file:%s\n", __LINE__, __FILE__)

// log the start of a function ... arguably should include the args
#define FUNC_START() if (LOG_LEVEL <= LOG_INFO) fprintf(LOG_LEVEL>=LOG_ERROR?stderr:stdout , "start %s\n", __func__)

// log the end of a function
#define FUNC_END() if (LOG_LEVEL <= LOG_INFO) fprintf(LOG_LEVEL>=LOG_ERROR?stderr:stdout , "finish %s\n", __func__)

//Covert a character to upper case.  Not clear that having this as a define
//makes any sense.
#define TO_UPPER(c) (c>='a' &&c<='z')?c+('A'-'a'):c

/**
 * A function, just to illustrate everything
 * **/
void v1()
{
    FUNC_START();
    for (int i=0; i<10; i++)
    {
	CHECK_ZERO(i);
	LOG(LOG_VERBOSE, "%d %c %c\n", i, 'a'+i, TO_UPPER('a'+i));
    }
    FUNC_END();
}

int main(int argc, char * argv[])
{
    for (int i=0; i<argc; i++) {
	    LOG(LOG_INFO, "%s\n", argv[i]);
    }
    v1();
    
}