#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <time.h>

#define nil NULL
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned int u32;

char *argv0 = "tp";
u8 boot[512];
typedef struct {
	char name[32];
	u16 mode;
	u8 uid, gid;
	u8 unused;
	u8 s1; u16 s2;
	u32 mtime;
	u16 addr;
	u8 unused2[16];
	u16 chk;
} Dirent;
Dirent dir[496];
u8 *files[496];
int dirsz;
int changed;

#define SZ(d) ((d->s1<<16)|d->s2)
#define NBLK(sz) (((sz)+511)/512)

void
usage(void)
{
	fprintf(stderr, "%s filename [rtx] [files ...]\n", argv0);
	exit(1);
}

void
readtape(FILE *f)
{
	fread(boot, 1, 512, f);
	fread(dir, 1, dirsz*sizeof(Dirent), f);

	int sz;
	u8 **fp = files;
	for(Dirent *d = dir; d < &dir[dirsz]; d++, fp++) {
		if(d->name[0] == '\0')
			continue;
		fseek(f, d->addr*512, 0);
		*fp = malloc(sz = SZ(d));
		fread(*fp, 1, sz, f);
	}
}

void
writetape(FILE *f)
{
	fwrite(boot, 1, 512, f);
	fwrite(dir, 1, dirsz*sizeof(Dirent), f);

	u8 **fp = files;
	for(Dirent *d = dir; d < &dir[dirsz]; d++, fp++) {
		if(d->name[0] == '\0')
			continue;
		fseek(f, d->addr*512, 0);
		fwrite(*fp, 1, SZ(d), f);
	}
}

void
table(void)
{
	for(Dirent *d = dir; d < &dir[dirsz]; d++) {
		if(d->name[0] == '\0')
			continue;
		u16 s = 0;
		for(u16 *w = (u16*)d; w < (u16*)(d+1); w++) s += *w;
		printf("%.32s\t%06o %o %o\t%d\t(%d) %u\t%06o %06o %06o\n", d->name,
			d->mode, d->uid, d->gid,
			SZ(d), NBLK(SZ(d)), d->mtime, d->addr, d->chk, s);
	}
}

void
extract(void)
{
	FILE *f;
	char name[33];

	name[32] = '\0';
	u8 **fp = files;
	for(Dirent *d = dir; d < &dir[dirsz]; d++, fp++) {
		if(d->name[0] == '\0')
			continue;
		memcpy(name, d->name, 32);
		f = fopen(name, "wb");
		if(f == nil) {
			fprintf(stderr, "couldn't open %s\n", name);
		} else {
			fwrite(*fp, 1, SZ(d), f);
			fclose(f);
		}
	}
}

void
addfile(char *path)
{
	printf("add file %s\n", path);

	Dirent *d;
	u8 **fp = files;
	for(d = dir; d < &dir[dirsz]; d++, fp++)
		if(d->name[0] == '\0')
			goto found;
	fprintf(stderr, "directory full\n");
	return;

found:
	FILE *f = fopen(path, "rb");
	if(f == nil) {
		fprintf(stderr, "can't open file %s\n", path);
		return;
	}
	fseek(f, 0, 2);
	int sz = ftell(f);
	fseek(f, 0, 0);
	*fp = malloc(sz);
	fread(*fp, 1, sz, f);
	fclose(f);
	strncpy(d->name, path, 32);
	// TMP
	d->mode = 0644;
	d->uid = 3;
	d->gid = 1;
	d->s1 = sz>>16;
	d->s2 = sz;
	d->mtime = time(NULL);
	changed = 1;
}

void
recalc(void)
{
	int block = dirsz/8 + 1;

	printf("first %o\n", block);
	for(Dirent *d = dir; d < &dir[dirsz]; d++) {
		if(d->name[0] == '\0')
			continue;
		d->addr = block;
		block += NBLK(SZ(d));

		u16 s = 0;
		for(u16 *w = (u16*)d; w < &d->chk; w++) s += *w;
		d->chk = -s;
	}
	printf("last %o\n", block);
}

int
main(int argc, char *argv[])
{
	FILE *f;
	char key = 't';
	char *filename;

	assert(sizeof(Dirent) == 64);

	argv++; argc--;
	if(argc < 2)
		usage();

	filename = *argv++; argc--;
	f = fopen(filename, "rb");
	if(f == nil) {
		fprintf(stderr, "can't open file %s\n", filename);
		return 1;
	}

	int m = 0;	// 1 for magtape
	dirsz = m ? 496 : 192;
	readtape(f);

	key = **argv++; argc--;
	switch(key) {
	case 't':
		table();
		break;
	case 'x':
		extract();
		break;
	case 'r':
		while(argc--)
			addfile(*argv++);
		break;
	}
	fclose(f);

	if(changed) {
		recalc();

		f = fopen(filename, "wb");
		if(f == nil) {
			fprintf(stderr, "can't open file %s\n", filename);
			return 1;
		}
		writetape(f);
		fclose(f);
	}
	return 0;
}