// ******************************************
// * unTar - razpakiranje datotek iz arhiva	*
// * 										*
// * 		Jernej Virag					*
// ******************************************
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct
{
	char ime[FILENAME_MAX];
	long offset;
} F_Info;

int main(int argc,char* argv[])
{
	if (argc<2)
		{printf("Manjkajo argumenti.\n"); return -1;}
	
	FILE *arhiv;
	FILE *output;
	char *buffer;
	F_Info *fileinfo;
	int i=0,j=0;
	
	long headerpos; //položaj začetka fileinfoja
	
	arhiv=fopen(argv[1],"rb");
	if (arhiv==NULL)
		{printf("Napaka pri odpiranju arhiva."); return -1;}
	//najprej preverimo, če je arhiv sploh legalen
	buffer=(char*)malloc(4*sizeof(char));
	memset(buffer,'\0',4); //inicializiramo 
	fread(buffer,sizeof(char),3,			 arhiv);
	if(strcmp(buffer,"ARH\0"))
		{printf("Datoteka ni veljaven arhiv!\n"); return -1;}
	//pogledamo kje se začnejo informacije o datotekah
	fseek(arhiv,-sizeof(long),SEEK_END);
	fread(&headerpos,sizeof(long),1,arhiv);
	//pomaknemo se na začetek infoja
	fseek(arhiv,headerpos,SEEK_SET);	
	fileinfo=(F_Info*)malloc(sizeof(F_Info));
	buffer=realloc(buffer,sizeof(char)); //zmanjšamo buffer na velikost 
										 //enega znaka
	i=0;
	*buffer=fgetc(arhiv);
	while(!feof(arhiv))
	{			
		
		fileinfo=(F_Info*)realloc(fileinfo,(i+1)*sizeof(F_Info));
		fileinfo[i].ime[0]='\0';
		do
		{
			*buffer=fgetc(arhiv);
			strncat(fileinfo[i].ime,buffer,1);
		} while(*buffer!='\0'&&!feof(arhiv));
		fread(&fileinfo[i].offset,sizeof(long),1,arhiv);
		printf("Najdena datoteka %s z offsetfom %ld.\n",fileinfo[i].ime,fileinfo[i].offset);
	i++;
	};
	i--;
	fileinfo[i].offset=headerpos;
	//gremo pisat fajle... končno
	for(j=0;j<i;j++)
	{
		output=fopen(fileinfo[j].ime,"wb");
		if (output==NULL)
			{printf("Napaka pri pisanju!"); break;};
		fseek(arhiv,fileinfo[j].offset,SEEK_SET);
		printf("Pišem %s na mestu %ld.\n",fileinfo[j].ime,ftell(arhiv));
		while(ftell(arhiv)!=fileinfo[j+1].offset)
		{
			fread(buffer,sizeof(char),1,arhiv);
			fwrite(buffer,sizeof(char),1,output);
		}
		fclose(output);
	}
	printf("Končano!\n");
	return 0;
	
}