#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/********************************************/
#define FPS_IN 25.0 // FPS ENTRADA
#define FPS_OUT 23.978 // FPS SALIDA
/********************************************/
int lookAhead(FILE *F, int n){
    // PRE: F=<r, d_1..d_n, x>
    // POST:  lookAhead=d_x AND F=<r, d_1..d_n, x>
	int c;
	for(c=1;c<n;c++) fgetc(F); 
	c = fgetc(F);
	fseek(F, -n, SEEK_CUR);
	return c;
}

int end_of_file(FILE *F){
    // PRE: F=<r, d_1..d_n, x>
    // POST: end_of_file = (x>n)
	return (0xffffffff==lookAhead(F,1));
}
int end_of_line(FILE *F){
    // indica si estamos final de linea, valido para formato WIN/UNIX/MAX
	int c;
	c = lookAhead(F,1);

	if (c == 0x0D) c = lookAhead(F, 2);
	return (c == 0x0A);
}

void skip_line(FILE *F){
     // salta la linea actual, valido para formato WIN/UNIX/MAX
	int c;
	while (!end_of_line(F))
		fgetc(F);
	
	if (end_of_line(F)){
		c = fgetc(F);
		if (c == 0x0D)	c = fgetc(F);		
	}
}

int esNum(int character){
	return (character>=48 && character<=57);
}

int leeNum(FILE *F, int n){
	int veces;
	int ok=1;
	for(veces=0; veces<n; veces++)
		if (!esNum(fgetc(F)))
			ok = 0;
	return ok;
}

char linea_OK(FILE *F){
    // comprueba si estamos en una linea que indica "tiempo"
    // segun el formato de ficheros *.SRT
	int i;
	int leidos = 0;
	
	for (i=1;i<=3;i++){
		leidos += 2;
		if (!leeNum(F, 2)){
			fseek(F, -leidos, SEEK_CUR);
			return 0;
		}
	
		if ((i=lookAhead(F,1)) == ':'){
			leidos++; 
			fgetc(F);
		}else if ((i == ',') && (i==3)){
			leidos++; 
			fgetc(F);
		}else{
			fseek(F, -leidos, SEEK_CUR);
			return 0;
		}
	}
	fseek(F, -leidos, SEEK_CUR);
	return 1;
}

void new_line(FILE *out){
	fputc(0x0D, out); fputc(0x0A,out);
}

void clonaLinea(FILE *in, FILE *out){
	
	while(!end_of_line(in))
		fputc(fgetc(in), out);	

		
	skip_line(in);
	new_line(out);
}

void pilla_tiempo(FILE *F, int *h, int *m, int *s, int *ms){
	char num[3];
	num[2]=0;
	fread(num, sizeof(char), 2, F);
	(*h)=atoi(num);
	fgetc(F);
	fread(num, sizeof(char), 2, F);
	(*m)=atoi(num);
	fgetc(F);
	fread(num, sizeof(char), 2, F);
	(*s)=atoi(num);
	fgetc(F);
	fread(num, sizeof(char), 3, F);
	(*ms)=atoi(num);
}
void pon_tiempo(FILE *F, int h, int m, int s, float ms){
	char cad[5];
	cad[2]=0;
	sprintf(cad, "%d",h);
	if (!cad[1]){ cad[1]=cad[0]; cad[0]='0'; cad[2]=0;}
	fwrite(cad, 2,sizeof(char), F);
	fwrite(":", 1,sizeof(char), F);
	sprintf(cad,"%d",m);
	if (!cad[1]){ cad[1]=cad[0]; cad[0]='0'; cad[2]=0;}
	fwrite(cad, 2,sizeof(char), F);
	fwrite(":", 1,sizeof(char), F);
	sprintf(cad,"%d",s);
	if (!cad[1]){ cad[1]=cad[0]; cad[0]='0'; cad[2]=0;}
	fwrite(cad, 2,sizeof(char), F);
	fwrite(",", 1,sizeof(char), F);
	sprintf(cad,"%.3f",ms);
	fwrite(cad+2, 3,sizeof(char), F);
}
void convertir(int h, int m, int s, int ms, int *h2, int *m2, int *s2, float *ms2){
	float segT=0.0;
	
	segT = (float)(ms)/1000.0 + (float)(s)+60.0*m + 3600.0*h;
	segT *= (float)(FPS_IN) / (float)(FPS_OUT);
	
	(*h2) = (int)(segT / 3600.0); 
	segT -= *h2*3600.0;
	(*m2) = (int)(segT / 60.0); segT -= *m2*60.0;
	(*s2) = (int)(segT); segT -= *s2*1.0;
	(*ms2) = segT;
}
void Convierte_Linea(FILE *F, FILE *Fout){
	int h,h2,m2,s2,m,s,ms,i;
	float ms2;
	
	pilla_tiempo(F, &h, &m, &s, &ms);
	convertir(h,m,s,ms, &h2, &m2, &s2, &ms2);
	pon_tiempo(Fout, h2, m2, s2, ms2);
	
	for(i=0;i<5;i++,fgetc(F));
	fwrite(" --> ", 5, sizeof(char), Fout);
	
	pilla_tiempo(F, &h, &m, &s, &ms);
	convertir(h,m,s,ms, &h2, &m2, &s2, &ms2);
	pon_tiempo(Fout, h2, m2, s2, ms2);
	
	new_line(Fout);	skip_line(F);
}

void abrirFicheros(FILE *in, FILE *out, char *f1, char *f2){
    	in=fopen(f1, "r");
		out = fopen(f2, "w");
}

int main(int argc, char **argv){
	FILE *F, *Fout;
	
	if (argc != 3 && argc != 2){
        printf("ERROR:\tUSO %s SUB_ENTRADA.srt SUB_SALIDA.srt\n", argv[0]);
        exit(1);
    }else
    	abrirFicheros( F, 
		               Fout, 
		               argv[1],
					   (argc==3 ? argv[2] : strcat(argv[1], ".srt"))
					  );

	
	while (!end_of_file(F))

		if (linea_OK(F))			
			Convierte_Linea(F, Fout);			
		else
			clonaLinea(F, Fout);			
					
	fclose(F); fclose(Fout);	
}