/*
 * 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 <stdlib.h>
#include <string.h>
#include <unistd.h>

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

/*
 * download url = r->pname / DOWNLOAD_URL / file->path / file->name
 */
size_t
build_download_url(struct kreq * r, struct file * file)
{
	char 	action_url[PATH_MAX];
	size_t 	action_url_len;

	/* don't download directories */
	if (file->is_dir)
		return 0;

	action_url_len = url_build(action_url, PATH_MAX, r->pname, DOWNLOAD_URL,
				   file->path, file->name, NULL);
	if (action_url_len == 0 || action_url_len >= PATH_MAX) {
		kutil_warn(r, NULL,
			   "download: action URL overflow: %s", action_url);
		return 0;
	}
	file->action_url = strndup(action_url, action_url_len);
	if (file->action_url == NULL) {
		kutil_warn(r, NULL,
			   "download: unable to allocate file url buffer: %s",
			   action_url);
		return 0;
	}
	return action_url_len;
}

static char *
strsplit(char * str, char c) {
	char	*right, *result;
	size_t	right_len;

	right = strrchr(str, c);
	if(!right || right == str)
		return NULL;

	// move right part to new buffer
	right_len = strlen(right);
	result = malloc(sizeof(char) * right_len);
	if(result == NULL)
		return NULL;

	if(strlcpy(result, right + 1, right_len) >= right_len) {
		free(result);
		return NULL;
	}

	// remove right part from src buffer
	*right = '\0';

	return result;
}

void
download(struct kreq * r)
{
	char   *file_name;
	void   *buffer;
	struct file* f;
	int	fd;
	char 	file_path[PATH_MAX], request_path[PATH_MAX];
	size_t 	path_size;

	/* check that the requested URL can be safely processed */
	if (strlen(r->path) == 0 || !check_request_path(r->path, r->suffix))
		http_exit(r, KHTTP_400, "download: invalid request path");

	/* build requested file path */
	if(strlen(r->suffix) > 0) {
		/* request with suffix */
		if(snprintf(request_path, sizeof(request_path), "%s.%s", r->path, r->suffix)
				>= (int) sizeof(request_path))
			http_exit(r, KHTTP_414, NULL);
	}
	else {
		if(snprintf(request_path, sizeof(request_path), "%s", r->path) >= (int) sizeof(request_path))
			http_exit(r, KHTTP_414, NULL);
	}

	path_size = url_build(file_path, PATH_MAX, DATA_DIR, request_path,
			      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);

	/* build file metadata */
	file_name = strsplit(request_path, '/');
	if(file_name == NULL)
		f = file_new("/", 1, request_path, strlen(request_path)); /* ROOT file */
	else {
		f = file_new(request_path, strlen(request_path), file_name,
				strlen(file_name));
		free(file_name); /* copied in file_new */
	}
	if(f == NULL)
		http_exit(r, KHTTP_404, "download: file metadata failure");

	/* memory map the file */
	fd = open(file_path, O_RDONLY);
	if(fd < 0)
		http_exit(r, KHTTP_404, "download: unable to open file");
	/* mmap does not work with empty file: st_size = 0 */
	if(f->size > 0) {
		buffer = mmap(NULL, f->size, PROT_READ, MAP_PRIVATE, fd, 0);
		if (buffer == MAP_FAILED)
			http_exit(r, KHTTP_500, "download: mmap failed");
	}

	/* write the file */
	http_open_file(r, KHTTP_200, f);
	if(f->size > 0)
		K_OK(khttp_write(r, (const char *) buffer, f->size), r);

	/* cleanup */
	if(f->size > 0)
		munmap(buffer, f->size);
	free(f);
}