/* SPDX-License-Identifier: LGPL-2.1-only */

/* Copyright (C) 2020 Gediminas Jakutis */

#include <sys/types.h>
#include <sys/stat.h>
#include <linux/limits.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include "io.h"
#include "defs.h"
#include "datagen.h"
#include "cache.h"

static int stream_open_in(struct stream * const in, const struct settings * const s);
static int stream_open_out(struct stream * const in, const struct settings * const s);
static int stream_open_special(struct stream * const in);

int stream_open(struct stream * const in, const struct settings * const s)
{
	int ret = 0;

	try(!in || in->fd > 0 || !in->name || !s, err, EINVAL);

	if (in->out == 1) {
		ret = stream_open_out(in, s);
	} else if (!in->out) {
		ret = stream_open_in(in, s);
	} else {
		ret = stream_open_special(in);
	}

err:
	return ret;
}

int stream_close(struct stream * const in)
{
	int ret = 0;

	try(!in || in->fd < 0, early_err, EINVAL);

	if (!in->out) {
		goto out;
	}

	if (in->name) {
		char path[PATH_MAX];
		struct stat st;

		snprintf(path, PATH_MAX, "/proc/self/fd/%i", in->fd);

		if (!stat(in->name, &st)) {
			if (st.st_mode & S_IFREG) {
				unlink(in->name);
			} else {
				ret = EINVAL;
				/* TODO: error message */
				goto err;
			}
		}

		try(linkat(AT_FDCWD, path, AT_FDCWD, in->name, AT_SYMLINK_FOLLOW), err, errno);
	} else {
		ret = EINVAL;
		goto err;
	}

out:
err:
	close(in->fd);
	in->fd = -1;
early_err:
	return ret;
}

static int stream_open_out(struct stream * const in, const struct settings * const s)
{
	struct stat st;
	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP;
	char *dname = NULL;
	char *tmp[2];
	int ret = 0;

	tmp[0] = strdup(in->name);
	tmp[1] = dirname(tmp[0]);
	dname = strdup(tmp[1]);
	free(tmp[0]);

	try(stat(dname, &st), err, errno);
	try(!(st.st_mode & S_IFDIR), err, EINVAL); /* TODO: err msg */

	if (!stat(in->name, &st)) {
		try(!(st.st_mode & S_IFREG), err, EINVAL); /* TODO: err msg */
		mode = st.st_mode;
	}

	in->fd = open(dname, O_TMPFILE | O_WRONLY, mode);
	try(in->fd < 0, err, errno); /* TODO: err msg */
	try(ftruncate(in->fd, s->stride * in->n), err, errno); /* TODO: err msg */

err:
	free(dname);
	return ret;
}

static int stream_open_in(struct stream * const in, const struct settings * const s)
{
	struct stat st;
	int ret = 0;

	try(stat(in->name, &st), err, errno); /* TODO: err msg */
	try(!(st.st_mode & S_IFREG) || !st.st_size || (st.st_size % s->stride), err, EINVAL); /* TODO: err msg */
	in->n = st.st_size / s->stride;
	in->fd = open(in->name, O_RDONLY | O_NOATIME);
	try(in->fd < 0, err, errno); /* TODO: err msg */
	if (in->cached) {
		cache_create(in, s);
		cache_populate(in);
	}

err:
	return ret;
}

static int stream_open_special(struct stream * const in)
{
	struct stat st;
	int ret = 0;

	try(stat(in->name, &st), err, errno); /* TODO: err msg */
	in->fd = open(in->name, O_RDONLY | O_NOATIME);
	try(in->fd < 0, err, errno); /* TODO: err msg */

err:
	return ret;
}