//printf needs following syscalls: sbrk write close fstat isatty lseek read
//

#include <sys/stat.h>
#include <string.h>
#include <stdint.h>
#include "../fs/fs.h"

static int preread;
static int alloc;
easywrite(char *c);

void syscalls_init()
{
    preread=0;
    alloc=0xff0000;
}

int close(int file) 
{
// easywrite("syscall: close\n");
    return -1;
}

int fstat(int file, struct stat *st)
{
//    easywrite("syscall: fstat\n");
    st->st_mode = S_IFCHR;
    return 0;
}

int isatty(int file) 
{
//  easywrite("syscall: isatty\n");
    return 1;
}

int lseek(int file, int ptr, int dir) 
{
//    printf("syscall: lseek %i %i %i",file,ptr,dir);
    if(dir==0)preread=ptr;
    else{ puts("other modes unsupported sorry"); while(1);}
    return preread;
}



int read(int file, char *ptr, int len)
{
	int ebx; // will hold return value;

	asm("pusha");

	// select syscall
	asm("mov $62,%eax"); 

	// pass params
	asm("mov %0,%%edx"::"m"(file));
	asm("mov %0,%%ecx"::"m"(ptr));
	asm("mov %0,%%ebx"::"m"(len));

	// interrrupt
	asm("int $0x80");

	// get return value
        asm("mov %%ebx, %0": "=b" (ebx));

	asm("popa");

	return ebx;
}

int readdir(const char *name,fs_dirent  *dirs,int max)
{

	int ebx; // WILL Hold return value;

	asm("pusha");

	// select syscall
	asm("mov $63,%eax"); 

	// pass params
	asm("mov %0,%%edx"::"m"(name));
	asm("mov %0,%%ecx"::"m"(dirs));
	asm("mov %0,%%ebx"::"m"(max));

	// interrrupt
	asm("int $0x80");

	// get return value
        asm("mov %%ebx, %0": "=b" (ebx));

	asm("popa");

	return ebx;
}

int open(const char *name, int flags, int mode)
{
//   easywrite("syscall: open\n");
    return 99;
    return -1;
}

int write(int file, char *ptr, int len) 
{

	int ebx; // will hold return value;

	asm("pusha");
	
	// select syscall
	asm("mov $61,%eax"); 

	// pass params
	asm("mov %0,%%edx"::"m"(file));
	asm("mov %0,%%ecx"::"m"(ptr));
	asm("mov %0,%%ebx"::"m"(len));

	// interrupt
	asm("int $0x80");         

	// get return value	
	asm("mov %%ebx, %0": "=b" (ebx));

	asm("popa");
	
	return ebx;
}



caddr_t sbrk(int incr) 
{
//	    easywrite("syscall: sbrk!!\n");
	    int oldalloc=alloc;
	    alloc+=incr;
	    return oldalloc;
	    /*
	    
            extern char end;	    
//	    char _end;
            static char *heap_end;
            char *prev_heap_end;
          
            if (heap_end == 0) {
              heap_end = &end;
            }
            prev_heap_end = heap_end;

            if (heap_end + incr > stack_ptr) {
              write (1, "Heap and stack collision\n", 25);
              abort ();
            }
          
            heap_end += incr;
            return (caddr_t) prev_heap_end;
	    */
}

//

// helpers
easywrite(char *c)
{
    write(1,c,strlen(c));
}