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

/* Copyright (C) 2020-2021 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 "stream.h"
#include "defs.h"
#include "datagen.h"
#include "cache.h"
#include "util.h"

static int stream_open_out(struct stream * const in);
static int stream_open_lite(struct stream * const in);
static int stream_open_in(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 && in->type != stream_randread), err, EINVAL, "invalid argunent");

	switch (in->type) {
	case (stream_lite):
		ret = stream_open_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_randread):
		; /* NOOP */
		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;

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

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

		if (in->settings->access == cached) {
			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:
	if (in->settings && in->settings->access == cached) {
		cache_destroy(in);
	}
err:
	in->fd > 2 ? close(in->fd) : 0;
	in->fd = -1;
	return ret;
}

struct entry_l *file_get_array(struct stream * const in, struct entry_l * const store)
{
	struct entry ent;
	struct entry_l *ret = NULL;
	ssize_t bytes_read;

	if (in->index < in->n) {
		do {
			try(0 > (bytes_read = pread(in->fd, &ent, sizeof(ent), in->index * in->settings->stride)), err, NULL, "Writing to stream failed with %i", errno);
		} while (bytes_read != sizeof(ent));

		++in->index;
		store->val = ent.val;
		ret = store;
	}

err:
	return ret;
}

struct entry_l *file_get_list(struct stream * const in, struct entry_l * const store)
{
	struct entry_l ent;
	struct entry_l *ret = NULL;
	ssize_t bytes_read;

	if (in->index < in->n) {
		in->cnode = in->cnode ? in->cnode : &in->cnode_f;
		do {
			try(0 > (bytes_read = pread(in->fd, &ent, sizeof(ent), in->cnode->file_offset)), err, NULL, "Writing to stream failed with %i", errno);
		} while (bytes_read != sizeof(ent));

		in->cnode->file_offset = ent.file_offset;
		++in->index;
		store->val = ent.val;
		ret = store;
	}

err:
	return ret;
}

int file_put_array(struct stream * const in, const struct entry_l * const data)
{
	int ret = 0;
	ssize_t bytes_written;

	if (in->index < in->n) {
		do {
			try(0 > (bytes_written = pwrite(in->fd, data, sizeof(data->val), in->index * in->settings->stride)), err, errno, "Writing to stream failed with %i", ret);
		} while (bytes_written != sizeof(data->val));
		++in->index;
	}

err:
	return ret;
}

int file_put_list(struct stream * const in, const struct entry_l * const node)
{
	int ret = 0;
	ssize_t bytes_written;
	struct entry_l tmp = {0};

	try(in->index >= in->n, err, EINVAL, "can't add element: out of cache bounds");

	if (!in->cnode) { /* if this is the very first one */
		in->cnode = &in->cnode_f;
	} else {
		in->cnode->file_offset += sizeof(*node);
		/* writing the offset of the node being added to the current node's offset field */
		do {
			try(0 > (bytes_written = pwrite(in->fd, &in->cnode->file_offset, sizeof(in->cnode->file_offset), in->cnode->file_offset - sizeof(*node) + sizeof(node->val))), err, errno, "Writing to stream failed with %i", ret);
		} while (bytes_written != sizeof(in->cnode->file_offset));
	}

	tmp.val = node->val;

	if (in->index < in->n) {
		do {
			try(0 > (bytes_written = pwrite(in->fd, &tmp, sizeof(tmp), in->cnode->file_offset)), err, errno, "Writing to stream failed with %i", ret);
		} while (bytes_written != sizeof(tmp));
	}

	++in->index;
err:
	return ret;
}

int file_transfer(struct stream * const src, struct stream * const dest)
{
	int ret = 0;
	int tmp;

	/* just a simple switcheroo of file descriptors */

	tmp = src->fd;
	src->fd = dest->fd;
	dest->fd = tmp;

	return ret;
}

/* generic, naïve and slow copy routine when an optimized one cannot be used */
int stream_copy_range(struct stream * const restrict src, struct stream * const restrict dest)
{
	int ret = 0;
	size_t ss;
	struct entry_l tmp_store;

	try(src->n < dest->settings->to, err, EINVAL, "invalid copy size");

	ss = dest->settings->ss;

	/* skip over to start position */
	while (ss--) {
		src->get(src, &tmp_store);
	}

	do {
		dest->put(dest, src->get(src, &tmp_store));
	} while (dest->index < (dest->n));

	stream_rewind(src);
	stream_rewind(dest);

err:
	return ret;
}

int stream_shallow_copy(struct stream const * const restrict src, struct stream * const dest)
{
	int ret = 0;

	dest->n = src->n;
	dest->settings = src->settings;
	dest->index = 0;

	dest->get = src->get;
	dest->put = src->put;
	dest->copy = src->copy;

	if (src->settings->access == cached) {
		dest->fd = -1;
		dest->type = stream_lite;
		try_s((ret = cache_create(dest)), err);
	} else {
		dest->name = src->name;
		dest->type = stream_lite;
		try_s((ret = stream_open_lite(dest)), err);
	}

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_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_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;
}

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

	try(in->fd < 3, err, EINVAL, "can't dump without an open file");

	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;
}

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