/*
 * 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 <stdio.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 "str.h"
#include "url.h"

/*
 * download url = r->pname / DOWNLOAD_URL / file->path
 */
size_t
build_download_url(const 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, 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;
}

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

	/* initialize empty file and return struct to success */
	f = NULL;
	ret = (struct http_ret) {
		KHTTP_200, ""
	};

	/* check that the requested URL can be safely processed */
	if (strlen(r->path) == 0 || !check_request_path(r->path, r->suffix)) {
		ret = (struct http_ret) {
			KHTTP_400,
			"download: invalid request path"
		};
		goto end;
	}
	/* build requested file path, with suffix or without */
	if (strlen(r->suffix) > 0) {
		if (snprintf(request_path, sizeof(request_path), "%s.%s", r->path, r->suffix)
		    >= (int) sizeof(request_path)) {
			ret = (struct http_ret) {
				KHTTP_414,
				"download: request too long"
			};
			goto end;
		}
	} else {
		if (snprintf(request_path, sizeof(request_path), "%s", r->path)
		    >= (int) sizeof(request_path)) {
			ret = (struct http_ret) {
				KHTTP_414,
				"download: request too long"
			};
			goto end;
		}
	}
	/* build file metadata */
	f = file_new(request_path);
	if (f == NULL) {
		ret = (struct http_ret) {
			KHTTP_404,
			"download: file metadata failure"
		};
		goto end;
	}
	path_size = file_get_data_path(f, file_path, PATH_MAX, NULL);
	if (path_size == 0 || path_size >= PATH_MAX) {
		ret = (struct http_ret) {
			KHTTP_404,
			"download: unable to build file path"
		};
		goto end;
	}
	/* memory map the file */
	fd = open(file_path, O_RDONLY);
	if (fd < 0) {
		ret = (struct http_ret) {
			KHTTP_404,
			"download: unable to open file"
		};
		goto end;
	}
	/* 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) {
			ret = (struct http_ret) {
				KHTTP_500,
				"download: mmap failed"
			};
			goto end;
		}
	}
	/* write the file */
	if (!http_open_file(r, KHTTP_200, f)) {
		ret = (struct http_ret) {
			KHTTP_500,
			"download: filename url encoding failed"
		};
		goto end;
	}
	if (f->size > 0)
		K_OK(khttp_write(r, (const char *) buffer, f->size), r);

	/* cleanup */
end:
	if (f != NULL && f->size > 0)
		munmap(buffer, f->size);
	file_free(f);
	return ret;
}