/*
 * Copyright 2023, Vincent Douillet <vincent@vdouillet.fr>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its contributors
 * may be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/mman.h>
#include <sys/stat.h>

#include <fcntl.h>
#include <limits.h>
#include <unistd.h>

#include "cgi.h"
#include "config.h"
#include "download.h"
#include "http.h"
#include "url.h"

void
download(struct kreq * r)
{
	void   *buffer;
	struct stat st;
	int 	st_ret, fd;
	char 	file_path[PATH_MAX];
	size_t 	path_size;

	/* check that the requested URL can be safely processed */
	if (!check_request_path(r->path))
		http_exit(r, KHTTP_400, "download: Invalid request path");

	/* build requested file path */
	path_size = url_build(file_path, PATH_MAX, DATA_DIR, "File.txt",
			      NULL);
	if (path_size == 0)
		http_exit(r, KHTTP_404, "download: Unable to build file path");
	if (path_size >= PATH_MAX)
		http_exit(r, KHTTP_414, NULL);

	/* memory map the file */
	fd = open(file_path, O_RDONLY);
	if (fd < 0)
		http_exit(r, KHTTP_404, "download: Unable to open file");
	st_ret = fstat(fd, &st);
	if (st_ret != 0)
		http_exit(r, KHTTP_404, "download: Unable to open file");

	/* TODO mmap does not work with empty file: st_size = 0 */
	buffer = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	if (buffer == MAP_FAILED)
		http_exit(r, KHTTP_500, "download: mmap failed");

	/* write the file */
	/* TODO proper filename & MIME type detection */
	K_OK(khttp_head(r, kresps[KRESP_CONTENT_DISPOSITION], "attachment; filename=\"File.txt\""), r);
	http_open(r, KHTTP_200, KMIME_TEXT_PLAIN);
	K_OK(khttp_write(r, (const char *) buffer, st.st_size), r);

	/* cleanup */
	munmap(buffer, st.st_size);
	close(fd);
}