/* 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_out(struct stream * const in);
static int stream_open_out_lite(struct stream * const in);
static int stream_open_in(struct stream * const in);
static int stream_open_chardev(struct stream * const in);
static int stream_flush(struct stream * const in);
static int stream_flush_array(struct stream * const in);
static int stream_flush_list(struct stream * const in);

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

	try(!in || in->fd > 0 || !in->name, err, EINVAL, "invalid argunent");

	switch (in->type) {
	case (stream_outlite):
		ret = stream_open_out_lite(in);
		break;
	case (stream_out):
		try(!in->name, err, EINVAL, "no filename given");
		ret = stream_open_out(in);
		break;
	case (stream_in):
		try(!in->name, err, EINVAL, "no filename given");
		ret = stream_open_in(in);
		break;
	case (stream_chardev):
		ret = stream_open_chardev(in);
		break;
	default:
		try(0, err, EINVAL, "cannot open stream: stream is invalid");
	}

err:
	return ret;
}

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

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

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

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

		try_s((ret = stream_flush(in)), err);

		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;
				rin_err("the given output file already exists and is not a regular file");
				goto err;
			}
		}

		try(linkat(AT_FDCWD, path, AT_FDCWD, in->name, AT_SYMLINK_FOLLOW), err, errno, "error linking output file to filesystem: %s", strerror(ret));
	} else {
		rin_err("no output filename given");
		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)
{
	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, "stat failed: %s", strerror(ret));
	try(!(st.st_mode & S_IFDIR), err, EINVAL, "invalid output path");

	if (!stat(in->name, &st)) {
		try(!(st.st_mode & S_IFREG), err, EINVAL, "the given output file already exists and is not a regular file");
		mode = st.st_mode;
	}

	in->fd = open(dname, O_TMPFILE | O_RDWR, mode);
	try(in->fd < 0, err, errno, "failed creating temporary output file: %s", strerror(ret));
	try(ftruncate(in->fd, in->settings->stride * in->n), err, errno, "failed setting output file size: %s", strerror(ret));

err:
	free(dname);
	return ret;
}

static int stream_open_out_lite(struct stream * const in)
{
	struct stat st;
	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, "stat failed: %s", strerror(ret));
	try(!(st.st_mode & S_IFDIR), err, EINVAL, "invalid output path");

	in->fd = open(dname, O_TMPFILE | O_RDWR, S_IRUSR | S_IWUSR);
	try(in->fd < 0, err, errno, "failed creating temporary output file: %s", strerror(ret));
	try(ftruncate(in->fd, in->settings->stride * in->n), err, errno, "failed setting output file size: %s", strerror(ret));

err:
	free(dname);
	return ret;
}

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

	try(stat(in->name, &st), err, errno, "stat failed: %s", strerror(ret));
	try(!(st.st_mode & S_IFREG) || !st.st_size || (st.st_size % in->settings->stride), err, EINVAL, "invalid input file");
	in->n = st.st_size / in->settings->stride;
	in->fd = open(in->name, O_RDONLY | O_NOATIME);
	try(in->fd < 0, err, errno, "failed opening input file: %s", strerror(ret));

err:
	return ret;
}

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

	try(stat(in->name, &st), err, errno, "stat failed: %s", strerror(ret));
	in->fd = open(in->name, O_RDONLY);
	try(in->fd < 0, err, errno, "failed opening input file: %s", strerror(ret));

err:
	return ret;
}

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

	try(in->settings->access != cached, err, EINVAL, "cannot flush an uncached stream");
	try(in->type != stream_out, err, EINVAL, "cannot flush a non-output cache");

	if (in->settings->format == array) {
		ret = stream_flush_array(in);
	} else {
		ret = stream_flush_list(in);
	}
err:
	return ret;
}

int stream_flush_array(struct stream * const in)
{
	ssize_t ret = 0;
	size_t remaining = in->n * in->settings->stride;
	ssize_t written = 0;

	do {
		ret = write(in->fd, in->cache + written, remaining);
		if (ret < 0) {
			try(errno != EAGAIN, err, errno, "Writing to stream failed with %zi", ret);
		} else {
			written += ret;
			remaining -= ret;
			ret = 0;
		}
	} while (remaining);

err:
	return ret;
}

int stream_flush_list(struct stream * const in)
{
	ssize_t ret = 0;
	size_t remaining;
	ssize_t written;
	size_t i;

	/* adjust pointers to have a base starting at 0, to cater to disk storage format.
	 * File offsets are otherwise 1:1 to memory addresses, which is neat.
	 * Just don't process the last offset, as that is always NULL/zero.
	 * */

	for (i = 0; i < (in->n - 1); ++i) {
		in->cache_l[i].offset = (char *) in->cache_l[i].next - in->cache;
	}

	/* dump the bloody list */
	written = 0;
	remaining = in->n * in->settings->stride;

	do {
		ret = write(in->fd, in->cache + written, remaining);
		if (ret < 0) {
			try(errno != EAGAIN, err, errno, "Writing to stream failed with %zi", ret);
		} else {
			written += ret;
			remaining -= ret;
			ret = 0;
		}
	} while (remaining);

err:
	return ret;
}