/* 5-2
 * Tanel Toova
 * Faili operatsioonid ja vőtmete kasutamine
 *
 */
 
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>

int Inp=0;
int Prnt=0;
int SizeB=0;
int SizeMB=0;
int Otp=0;

//next procedure writes usage help to stderr and exits with eCode
int usage(FILE *stream, int eCode)
{
    fprintf(stream, "Options:\n"
                    "  -f --input           Name of input file\n"
                    "  -s --sizeB           Size in bytes\n"
                    "  -S --sizeMB          Size in megabytes\n"
                    "  -p --print           Put contence of input file to screen\n"
                    "  -o --output          Name of output file\n"
                );
    exit(eCode);
}
//next procedure writes contents of inputfile to stdout
int FtoS(FILE *inputstream) 
{
    while(!feof(inputstream)){
        fputc(fgetc(inputstream),stdout);
    }
    fprintf(stdout,"\n");
    fclose(inputstream);
    exit(0);
}

//next procedure writes size of input file in bytes or megabytes to outputstream (screen of file)
int Failisuurus(FILE *inputstream, FILE *outputstream)
{
    long size;
    fseek(inputstream,0,SEEK_END);
    size=(ftell(inputstream));
    if(SizeB==1){fprintf(outputstream,"The size of file is %i B\n", size);}
    if(SizeMB==1){fprintf(outputstream,"The size of file is %i MB\n", size/1024/1024);}
    if(Otp==1){fclose(outputstream);}
    fclose(inputstream);
    exit(0);
}


int main(int argc, char **argv)
{
    FILE *inputfile;
    FILE *outputfile;
    char in[80]; //asked name of inputfile if key -f is not used
    int option;
    char *short_options = {"f:sSpo:"};
    static struct option long_options[] =
        {
                {"input", 1, NULL, 'f'},
                {"sizeB", 0, NULL, 's'},
                {"sizeMB", 0, NULL, 'S'},
                {"print", 0, NULL, 'p'},
                {"output", 1, NULL, 'o'},
                {NULL, 0, NULL, 0}
        };
    
    while(1){
        option = getopt_long(argc, argv, short_options, long_options, NULL); 
        
        if(option == -1){break;} //if there are no more keys
        
        switch(option){
                case 'f': //checks if -f has an argument and tries to open new stream
                        Inp=1;
                        if(!optarg){
                             fprintf(stderr,"-f needs an argument\n");
                             usage(stderr,2);
                        };
                        inputfile = fopen(optarg,"r");
                        if(!inputfile){
                             fprintf(stderr,"Error opening file %s\n",optarg);
                             usage(stderr,3);
                        };
			break;
                case 'p':
                        Prnt=1;
			break;
                case 's':
                        SizeB=1;
			break;
                case 'S':
                        SizeMB=1;
			break;
                case 'o': //checks if -o has an argument and creates new stream(file)
                        Otp=1;
                        if(!optarg){
                             fprintf(stderr,"-o needs an argument\n");
                             usage(stderr,2);
                        };
                        outputfile = fopen(optarg,"w");
			break;
                default: //if unknown key is used
                        usage(stderr,1);
                               
        } //switch
    } //while
    
    if(!Inp){ //if -f was not used then asks user to give inputfile name and tries to open new stream
        fprintf(stdout,"Enter the input file: ");
        scanf("%s",in);
        inputfile = fopen(in,"r");
        if(!in){
                fprintf(stderr,"Error opening file %s\n",in);
                usage(stderr,3);
        }
    }

    //fallowing if-statements check the improper use of keys
    if(SizeB==1 && SizeMB==1){
	fprintf(stderr,"Invalid use of keys -s and -S\n");
	usage(stderr,4);
    }

    if(SizeB==1 && Prnt==1){
	fprintf(stderr,"invalid use of keys -s and -p\n");
	usage(stderr,4);
    }

    if(SizeMB==1 && Prnt==1){
	fprintf(stderr,"Invalid use of keys -S and -p\n");
	usage(stderr,4);
    }

    if(Otp==1 && Prnt==1){
	fprintf(stderr,"Invalid use of keys -o and -p\n");
	usage(stderr,4);
    }

    if(Otp==1 && SizeB==0 && SizeMB==0){
	fprintf(stderr,"Invalid use of key -o, -s or -S must be used with it\n");
	usage(stderr,4);
    }

    if(SizeB==0 && SizeMB==0 && Prnt==0){Prnt=1;}
    
    //if -o key is given then size of inputfile is writen into outputfile (either in B or MB)
    if(Otp==1){Failisuurus(inputfile,outputfile);}
    //if -o is not given but -s or -S is then the size of inputile is writen to stdout (either in B or MB)
    if(SizeB==1 || SizeMB==1){Failisuurus(inputfile,stdout);}
    //the default action of writing contents of inputfile to stdout
    if(Prnt ==1){FtoS(inputfile);}
    
}