/* See LICENSE file for copyright and license details. */
#include "common.h"
#include <libsimple-arg.h>

/* TODO why has the program started to freeze (since multithreading?)*/


USAGE("[-o offset] [-l length | -e postend] device [< random-source]");


static _Atomic volatile sig_atomic_t exiting = 0;

static struct span *spans = NULL;
static size_t nspans = 0;
static size_t spans_size = 0;

static off_t shredded = 0;
static off_t total_size = 0;

static char total_size_1000[256];
static char total_size_1024[256];

static uintmax_t bad_writes = 0;
static uintmax_t bad_sections = 0;
static off_t bad_bytes = 0;

static clockid_t clck = CLOCK_MONOTONIC_COARSE;
static const char *clkcstr = "CLOCK_MONOTONIC_COARSE";
static struct timespec last_success = {-1, 0};
static struct timespec max_success = {-1, 0};
static struct timespec start_time;

static const struct timespec progress_print_interval = {0, MILLISECONDS(500)};
static const struct timespec poll_timeout            = {0, MILLISECONDS(500)};
static int progress_print_sig_pipe[2];
static pthread_mutex_t progress_mutex;

static enum direction direction = FORWARDS; /* TODO add option (-b) to switch start direction */
static uintmax_t pass_nr = 1;


static void
signal_handler(int signo)
{
	(void) signo;
	exiting = 1;
}


static void
add_span(off_t off, off_t amount, size_t blocksize, int try_join)
{
	off_t end = off + amount;

	while ((off_t)(blocksize >> 1) >= amount)
		blocksize >>= 1;

	if (try_join) {
		if (off == spans[nspans - 1U].end || end == spans[nspans - 1U].start) {
			spans[nspans - 1U].start = MIN(off, spans[nspans - 1U].start);
			spans[nspans - 1U].end = MAX(end, spans[nspans - 1U].end);
			spans[nspans - 1U].bad += amount;
			spans[nspans - 1U].blocksize = MAX(blocksize, spans[nspans - 1U].blocksize);
			return;
		}
	}

	if (nspans == spans_size) {
		spans_size += 1024;
		spans = ereallocarray(spans, spans_size, sizeof(*spans));
	}

	spans[nspans].start = off;
	spans[nspans].end = end;
	spans[nspans].bad = amount;
	spans[nspans].blocksize = blocksize;
	nspans++;
}


static void
print_progress(int done, const struct timespec *now)
{
	static char buf1[2048] = {0};
	static char buf2[2048] = {0};
	static int bufi = 0;

	char subbuf1[256];
	char subbuf2[256];
	char subbuf3[256];
	char subbuf4[256];
	char subbuf5[256];
	char subbuf6[256];
	char subbuf7[256];
	struct timespec since_success = {-1, 0};
	struct timespec time_spent;

	if (last_success.tv_sec >= 0) {
		libsimple_difftimespec(&since_success, now, &last_success);
		if (libsimple_cmptimespec(&since_success, &max_success) > 0)
			max_success = since_success;
	}

	/* TODO deal with machine and process suspension */
	libsimple_difftimespec(&time_spent, now, &start_time);

	sprintf(bufi == 0 ? buf1 : buf2,
	        "%ji bytes (%s, %s, %.2lf %%) of %s (%s) shredded\033[K\n"
	        "failed writes: %ju; bad sections: %ju (%ji bytes, %s, %s)\033[K\n"
	        "time spent shredding: %s; performance: %s\033[K\n"
	        "time since last successful write: %s\033[K\n"
	        "maximum time until a successful write: %s\033[K\n"
	        "pass: %ju; pass direction: %s\033[K\n"
	        "%s",
	        /* line 1 { */
	        (intmax_t)shredded,
	        humansize1000(shredded, subbuf1),
	        humansize1024(shredded, subbuf2),
	        100 * (double)shredded / (double)total_size,
	        total_size_1000,
	        total_size_1024,
	        /* } line 2 { */
	        bad_writes,
	        bad_sections,
	        (intmax_t)bad_bytes,
	        humansize1000(bad_bytes, subbuf3),
	        humansize1024(bad_bytes, subbuf4),
	        /* } line 3 { */
	        durationstr(&time_spent, subbuf5, 1),
	        wravg_get(now),
	        /* } line 4 { */
	        durationstr(&since_success, subbuf6, 2),
	        /* } line 5 { */
	        durationstr(&max_success, subbuf7, 2),
	        /* } line 6 { */
	        pass_nr,
	        direction == FORWARDS ? "forwards" : "backwards",
	        /* } */
	        done ? "" : "\033[6A");

	if (strcmp(buf1, buf2)) {
		fprintf(stderr, "%s", bufi == 0 ? buf1 : buf2);
		fflush(stderr);
	}

	bufi ^= 1;
}


static void *
progress_print_loop(void *user)
{
	struct pollfd pfd = {.fd = progress_print_sig_pipe[0], .events = POLLOUT};
	struct timespec now;
	ssize_t r;
	int terminate = 0;
	sigset_t sigset;

	(void) user;

	sigemptyset(&sigset);
	sigaddset(&sigset, SIGTERM);
	sigaddset(&sigset, SIGINT);
	errno = pthread_sigmask(SIG_UNBLOCK, &sigset, NULL);
	if (errno)
		eprintf("pthread_sigmask SIG_UNBLOCK {SIGTERM, SIGINT} NULL:");

	do {
		switch (ppoll(&pfd, 1U, &poll_timeout, NULL)) {
		case -1:
			if (errno != EINTR)
				eprintf("ppoll:");
			if (exiting)
				break;
			continue;
		case 0:
			break;
		default:
			r = read(progress_print_sig_pipe[0], &now, sizeof(now));
			if (r == (ssize_t)sizeof(now)) {
				goto have_time;
			} else if (!r) {
				terminate = 1;
			} else if (r < 0) {
				if (errno == EINTR)
					continue;
				eprintf("read <internal pipe>:");
			}
			break;
		}
		if (clock_gettime(clck, &now))
			eprintf("clock_gettime %s:", clkcstr);
	have_time:
		pthread_mutex_lock(&progress_mutex);
		if (exiting) {
			fprintf(stderr, "\033[K\nTermination initialised by user...\033[K\n\033[K\n");
			terminate = 1;
		}
		print_progress(0, &now);
		wravg_update_time(&now);
		pthread_mutex_unlock(&progress_mutex);
	} while (!terminate);

	return NULL;
}


static void
shredspan(int fd, struct span *span, const char *fname)
{
	off_t off, n;
	ssize_t r;
	struct timespec now, when = {0, 0};
	int bad = span->bad > 0;
	int first_fail = 1;
	const char *random_data;

	pthread_mutex_lock(&progress_mutex);

	off = (direction == FORWARDS ? span->start : span->end);
	while (direction == FORWARDS ? off < span->end : off > span->start) {
		if (exiting) {
		userexit:
			if (direction == FORWARDS)
				span->start = off;
			else
				span->end = off;
			close(progress_print_sig_pipe[1]);
			progress_print_sig_pipe[1] = -1;
			goto out;
		}

		if (clock_gettime(clck, &now))
			eprintf("clock_gettime %s:", clkcstr);
		if (libsimple_cmptimespec(&now, &when) >= 0) {
			libsimple_sumtimespec(&when, &now, &progress_print_interval);
			write(progress_print_sig_pipe[1], &now, sizeof(now));
		}
		if (direction == FORWARDS) {
			n = MIN((off_t)span->blocksize, span->end - off);
		} else {
			n = off--;
			off &= ~(off_t)(span->blocksize - 1U);
			if (off < span->start)
				off = span->start;
			n -= off;
			if (!n)
				break;
		}
		random_data = get_random(span->blocksize);
		pthread_mutex_unlock(&progress_mutex);
	pwrite_again:
		r = pwrite(fd, random_data, (size_t)n, off);
		if (r < 0) {
			if (errno == EINTR) {
				if (exiting) {
					pthread_mutex_lock(&progress_mutex);
					goto userexit;
				}
				goto pwrite_again;
			}
			pthread_mutex_lock(&progress_mutex);
			if (errno != EIO)
				weprintf("pwrite %s <buffer> %zu %ji:", fname, (size_t)n, (intmax_t)off);
			add_span(off, n, span->blocksize == 1U ? 1U : span->blocksize >> 1, !first_fail);
			first_fail = 0;
			if (direction == FORWARDS)
				off += n;
			if (!span->bad)
				bad_bytes += n;
			if (bad)
				bad = 0;
			else
				bad_sections += 1U;
			when.tv_sec = 0;
			when.tv_nsec = 0;
			bad_writes += 1U;
			continue;
		}
		pthread_mutex_lock(&progress_mutex);
		if (direction == FORWARDS) {
			off += (off_t)r;
		} else if ((off_t)r < n) {
			n -= (off_t)r;
			add_span(off + (off_t)r, n, span->blocksize == 1U ? 1U : span->blocksize >> 1, !first_fail);
			first_fail = 0;
			if (direction == FORWARDS)
				off += n;
			if (!span->bad)
				bad_bytes += n;
			if (bad)
				bad = 0;
			else
				bad_sections += 1U;
			when.tv_sec = 0;
			when.tv_nsec = 0;
			bad_writes += 1U;
		}
		shredded += (off_t)r;
		used_random(r);
		wravg_update_write(r);
		last_success = now;
		if (span->bad) {
			bad_bytes -= (off_t)r;
			span->bad -= (off_t)r;
		}
	}

	if (bad && !span->bad)
		bad_sections -= 1U;

out:
	pthread_mutex_unlock(&progress_mutex);
}


static void
dump_map(int fd, const char *fname)
{
	size_t i;
	int r;

	if (!nspans)
		return;

	for (i = 0; i < nspans; i++) {
		r = dprintf(fd, "%s%jx-%jx/%zx",
		            i ? "," : "0x",
		            (uintmax_t)spans[i].start,
		            (uintmax_t)spans[i].end,
		            spans[i].blocksize);
		if (r < 0)
			goto fail;
	}
	r = dprintf(fd, "\n");
	if (r < 0)
		goto fail;

	return;

fail:
	eprintf("dprintf %s:", fname);
}


int
main(int argc, char *argv[])
{
	off_t off = -1, len = -1, end = -1;
	size_t i, j;
	int fd;
	struct timespec now;
	struct sigaction sa;
	pthread_t progress_print_thread;
	sigset_t sigset;

	ARGBEGIN {
	case 'o':
		if (off >= 0)
			usage();
		off = unhumansize(ARG(), FLAG());
		break;
	case 'l':
		if (len >= 0 || end >= 0)
			usage();
		len = unhumansize(ARG(), FLAG());
		break;
	case 'e':
		if (len >= 0 || end >= 0)
			usage();
		end = unhumansize(ARG(), FLAG());
		break;
	default:
		usage();
	} ARGEND;

	if (argc != 1)
		usage();

	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = &signal_handler;
	sigemptyset(&sa.sa_mask);
	if (sigaction(SIGTERM, &sa, NULL))
		eprintf("sigaction SIGTERM {.sa_handler=<function>, .sa_mask={}, .sa_flags=0} NULL:");
	if (sigaction(SIGINT, &sa, NULL))
		eprintf("sigaction SIGINT {.sa_handler=<function>, .sa_mask={}, .sa_flags=0} NULL:");

	sigemptyset(&sigset);
	sigaddset(&sigset, SIGTERM);
	sigaddset(&sigset, SIGINT);
	errno = pthread_sigmask(SIG_BLOCK, &sigset, NULL);
	if (errno)
		eprintf("pthread_sigmask SIG_BLOCK {SIGTERM, SIGINT} NULL:");

	fd = open(argv[0], O_WRONLY | O_DSYNC);
	if (fd < 0)
		eprintf("open %s O_WRONLY|O_DSYNC:", argv[0]);

	init_random(STDIN_FILENO, "<stdin>");

	spans = emalloc(sizeof(*spans));
	spans[0].start = 0;
	spans[0].end = filesize(fd, argv[0]);
	spans[0].bad = 0;
	spans[0].blocksize = max_blksize();
	nspans = 1U;
	spans_size = 1U;

	if (off >= 0) {
		if (off > spans[0].end)
			eprintf("value of -o flag is beyond the end of the file");
		spans[0].start = off;
	}
	if (len >= 0) {
		if (len > OFF_MAX - spans[0].start)
			eprintf("the sum of the values of -o and -l flag is too large");
		end = spans[0].start + len;
		if (end > spans[0].end)
			eprintf("the sum of the values of -o and -l flag is beyond the end of the file");
		spans[0].end = end;
	} else if (end >= 0) {
		if (end > spans[0].end)
			eprintf("the value of -e flag is beyond the end of the file");
		spans[0].end = end;
	}

	total_size = spans[0].end - spans[0].start;
	humansize1000(total_size, total_size_1000);
	humansize1024(total_size, total_size_1024);

	if (pipe(progress_print_sig_pipe))
		eprintf("pipe:");

	errno = pthread_mutex_init(&progress_mutex, NULL);
	if (errno)
		eprintf("pthread_mutex_init NULL:");
	errno = pthread_create(&progress_print_thread, NULL, &progress_print_loop, NULL);
	if (errno)
		eprintf("pthread_create NULL:");

	if (clock_gettime(clck, &start_time)) {
		clck = CLOCK_MONOTONIC;
		clkcstr = "CLOCK_MONOTONIC";
		if (clock_gettime(clck, &start_time))
			eprintf("clock_gettime %s:", clkcstr);
	}
	wravg_init(&start_time);
	last_success = start_time;

	while (nspans) {
		size_t old_nspans = nspans;
		for (i = 0; i < old_nspans && !exiting; i++)
			shredspan(fd, &spans[i], argv[0]);
		if (exiting) {
			memmove(&spans[0], &spans[i], (nspans -= i) * sizeof(*spans));
			break;
		}
		/* TODO bug: this is sometimes reached immediately on write failure */
		for (i = 0, j = nspans, nspans -= old_nspans; i < nspans;)
			spans[i++] = spans[--j];
		direction ^= 1;
		pass_nr++;
	}

	close(fd);
	if (progress_print_sig_pipe[1] >= 0)
		close(progress_print_sig_pipe[1]);

	errno = pthread_join(progress_print_thread, NULL);
	if (errno)
		weprintf("pthread_join:");
	pthread_mutex_destroy(&progress_mutex);

	if (clock_gettime(clck, &now))
		eprintf("clock_gettime %s:", clkcstr);
	print_progress(1, &now);

	if (nspans) {
		/* TODO document in man page */
		dump_map(STDOUT_FILENO, "<stdout>");
		if (close(STDOUT_FILENO))
			eprintf("write <stdout>");
	}
	return 0;
}