/*
 * Loader Implementation
 *
 * 2018, Operating Systems
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <signal.h>
#include <fcntl.h>
#include <unistd.h>

#include "exec_parser.h"

static so_exec_t *exec;

static struct sigaction old_action;
static int pageSize;
int fd;
static void segv_handler(int signum, siginfo_t *info, void *context)
{
	uintptr_t *addr;
	int rc;
	int i;
	char* p;
	ssize_t bytes_read;

	if (signum != SIGSEGV && info->si_code == SEG_ACCERR) {
		old_action.sa_sigaction(signum, info, context);
		return;
	}

	addr = (uintptr_t *)info->si_addr;

	for( i=0; i<exec->segments_no; i++){
		//pagina mapata
		if(addr>exec->segments[i].vaddr && addr<exec->segments[i].vaddr+exec->segments[i].mem_size){
			int page = ( addr - exec->segments[i].vaddr ) / getpagesize();
			if( page * pageSize < exec->segments[i].file_size && (page+1)*pageSize > exec->segments[i].file_size) {
				p = mmap(page*pageSize,pageSize, PROT_WRITE, MAP_SHARED | MAP_PRIVATE | MAP_FIXED, fd, exec->segments[i].offset);
				rc = lseek(fd, exec->segments[i].offset, SEEK_SET);
				DIE(rc < 0, "lseek");

				bytes_read = read(fd, page*pageSize, exec->segments[i].mem_size-pageSize*page);
				DIE(bytes_read < 0, "read");

				p = mprotect(page*pageSize, (page+1)*pageSize - exec->segments[i].mem_size, exec->segments[i].perm);
				//mapezi cu doar perm de write
				// lseek cu offset(il ai in struct).
				// read din fisier prima bucata si scrii la inceputul paginii problema(doar pana la problema)
				// mprot(cu permisiunea din struct) pe a doua bucata

			}
			else if( page*pageSize < exec->segments[i].file_size ){
				p = mmap(page*pageSize,pageSize, exec->segments[i].perm, MAP_SHARED | MAP_PRIVATE | MAP_FIXED, fd, exec->segments[i].offset);
				DIE(p == (char *)-1, "mmap");
				// start=inceputul paginii problema
				// length = pagesize
				// prot= permisiuni, vezi structura seg
				// flags= map shared, private, fixed
				// fd
				//offset= vezzi struct seg
			}
			else{
				// ca in primul caz, dar pui 0,0 la final
				p = mmap(page*pageSize,pageSize, exec->segments[i].perm, MAP_SHARED | MAP_PRIVATE | MAP_FIXED, 0, 0);
				DIE(p == (char *)-1, "else mmap");
			}

		}

	}


	int page = (addr - exec->segments[i].vaddr) / getpagesize();


}

int so_init_loader(void)
{
	/* TODO: initialize on-demand loader */
	struct sigaction action;
	int rc;
	pageSize = getpagesize();

	action.sa_sigaction = segv_handler;
	sigemptyset(&action.sa_mask);
	sigaddset(&action.sa_mask, SIGSEGV);
	action.sa_flags = SA_SIGINFO;

	rc = sigaction(SIGSEGV, &action, &old_action);
	DIE(rc == -1, "sigaction");

	return 0;
}

int so_execute(char *path, char *argv[])
{
	//deschizi fisier, salvezi fd, folosesti fd in mmap

	exec = so_parse_exec(path);
	if (!exec)
		return -1;
	fd=open(path,O_RDONLY,0644);
	so_start_exec(exec, auintptr_trgv);

	return -1;
}