/*
 * uhttpd - Tiny single-threaded httpd - Static file handler
 *
 *   Copyright (C) 2010 Jo-Philipp Wich <xm@subsignal.org>
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#define _XOPEN_SOURCE 500	/* strptime() */
#define _BSD_SOURCE			/* scandir(), timegm() */

#include "uhttpd.h"
#include "uhttpd-utils.h"
#include "uhttpd-file.h"

#include "uhttpd-mimetypes.h"


static const char * uh_file_mime_lookup(const char *path)
{
	struct mimetype *m = &uh_mime_types[0];
	const char *e;

	while( m->extn )
	{
		e = &path[strlen(path)-1];

		while( e >= path )
		{
			if( (*e == '.') && !strcasecmp(&e[1], m->extn) )
				return m->mime;

			e--;
		}

		m++;
	}

	return "application/octet-stream";
}

static const char * uh_file_mktag(struct stat *s)
{
	static char tag[128];

	snprintf(tag, sizeof(tag), "\"%x-%x-%x\"",
		(unsigned int) s->st_ino,
		(unsigned int) s->st_size,
		(unsigned int) s->st_mtime
	);

	return tag;
}

static time_t uh_file_date2unix(const char *date)
{
	struct tm t;

	memset(&t, 0, sizeof(t));

	if( strptime(date, "%a, %d %b %Y %H:%M:%S %Z", &t) != NULL )
		return timegm(&t);

	return 0;
}

static char * uh_file_unix2date(time_t ts)
{
	static char str[128];
	struct tm *t = gmtime(&ts);

	strftime(str, sizeof(str), "%a, %d %b %Y %H:%M:%S GMT", t);

	return str;
}

static char * uh_file_header_lookup(struct http_request *req, const char *name)
{
	int i;

	foreach_header(i, req->headers)
	{
		if( ! strcasecmp(req->headers[i], name) )
			return req->headers[i+1];
	}

	return NULL;
}

#define ensure_ret(x) \
	do { if( x < 0 ) return -1; } while(0)

static int uh_file_response_ok_hdrs(struct client *cl, struct http_request *req, struct stat *s)
{
	ensure_ret(uh_http_sendf(cl, NULL, "Connection: close\r\n"));

	if( s )
	{
		ensure_ret(uh_http_sendf(cl, NULL, "ETag: %s\r\n", uh_file_mktag(s)));
		ensure_ret(uh_http_sendf(cl, NULL, "Last-Modified: %s\r\n", uh_file_unix2date(s->st_mtime)));
	}

	return uh_http_sendf(cl, NULL, "Date: %s\r\n", uh_file_unix2date(time(NULL)));
}

static int uh_file_response_200(struct client *cl, struct http_request *req, struct stat *s)
{
	ensure_ret(uh_http_sendf(cl, NULL, "HTTP/%.1f 200 OK\r\n", req->version));
	return uh_file_response_ok_hdrs(cl, req, s);
}

static int uh_file_response_304(struct client *cl, struct http_request *req, struct stat *s)
{
	ensure_ret(uh_http_sendf(cl, NULL, "HTTP/%.1f 304 Not Modified\r\n", req->version));
	return uh_file_response_ok_hdrs(cl, req, s);
}

static int uh_file_response_412(struct client *cl, struct http_request *req)
{
	return uh_http_sendf(cl, NULL,
		"HTTP/%.1f 412 Precondition Failed\r\n"
		"Connection: close\r\n", req->version);
}

static int uh_file_if_match(struct client *cl, struct http_request *req, struct stat *s)
{
	const char *tag = uh_file_mktag(s);
	char *hdr = uh_file_header_lookup(req, "If-Match");
	char *p;
	int i;

	if( hdr )
	{
		p = &hdr[0];

		for( i = 0; i < strlen(hdr); i++ )
		{
			if( (hdr[i] == ' ') || (hdr[i] == ',') )
			{
				hdr[i++] = 0;
				p = &hdr[i];
			}
			else if( !strcmp(p, "*") || !strcmp(p, tag) )
			{
				return 1;
			}
		}

		uh_file_response_412(cl, req);
		return 0;
	}

	return 1;
}

static int uh_file_if_modified_since(struct client *cl, struct http_request *req, struct stat *s)
{
	char *hdr = uh_file_header_lookup(req, "If-Modified-Since");

	if( hdr )
	{
		if( uh_file_date2unix(hdr) < s->st_mtime )
		{
			return 1;
		}
		else
		{
			uh_file_response_304(cl, req, s);
			return 0;
		}
	}

	return 1;
}

static int uh_file_if_none_match(struct client *cl, struct http_request *req, struct stat *s)
{
	const char *tag = uh_file_mktag(s);
	char *hdr = uh_file_header_lookup(req, "If-None-Match");
	char *p;
	int i;

	if( hdr )
	{
		p = &hdr[0];

		for( i = 0; i < strlen(hdr); i++ )
		{
			if( (hdr[i] == ' ') || (hdr[i] == ',') )
			{
				hdr[i++] = 0;
				p = &hdr[i];
			}
			else if( !strcmp(p, "*") || !strcmp(p, tag) )
			{
				if( (req->method == UH_HTTP_MSG_GET) ||
				    (req->method == UH_HTTP_MSG_HEAD) )
					uh_file_response_304(cl, req, s);
				else
					uh_file_response_412(cl, req);

				return 0;
			}
		}
	}

	return 1;
}

static int uh_file_if_range(struct client *cl, struct http_request *req, struct stat *s)
{
	char *hdr = uh_file_header_lookup(req, "If-Range");

	if( hdr )
	{
		uh_file_response_412(cl, req);
		return 0;
	}

	return 1;
}

static int uh_file_if_unmodified_since(struct client *cl, struct http_request *req, struct stat *s)
{
	char *hdr = uh_file_header_lookup(req, "If-Unmodified-Since");

	if( hdr )
	{
		if( uh_file_date2unix(hdr) <= s->st_mtime )
		{
			uh_file_response_412(cl, req);
			return 0;
		}
	}

	return 1;
}


#define ensure_out(x) \
	do { if( x < 0 ) goto out; } while(0)

static int uh_file_scandir_filter_dir(const struct dirent *e)
{
	return strcmp(e->d_name, ".") ? 1 : 0;
}

static void uh_file_dirlist(struct client *cl, struct http_request *req, struct path_info *pi)
{
	int i;
	int count = 0;
	char filename[PATH_MAX];
	char *pathptr;
	struct dirent **files = NULL;
	struct stat s;

	ensure_out(uh_http_sendf(cl, req,
		"<html><head><title>Index of %s</title></head>"
		"<body><h1>Index of %s</h1><hr /><ol>",
			pi->name, pi->name
	));

	if( (count = scandir(pi->phys, &files, uh_file_scandir_filter_dir, alphasort)) > 0 )
	{
		memset(filename, 0, sizeof(filename));
		memcpy(filename, pi->phys, sizeof(filename));
		pathptr = &filename[strlen(filename)];

		/* list subdirs */
		for( i = 0; i < count; i++ )
		{
			strncat(filename, files[i]->d_name,
				sizeof(filename) - strlen(files[i]->d_name));

			if( !stat(filename, &s) &&
			    (s.st_mode & S_IFDIR) && (s.st_mode & S_IXOTH)
			)
				ensure_out(uh_http_sendf(cl, req,
					"<li><strong><a href='%s%s'>%s</a>/</strong><br />"
					"<small>modified: %s<br />directory - %.02f kbyte"
					"<br /><br /></small></li>",
						pi->name, files[i]->d_name, files[i]->d_name,
						uh_file_unix2date(s.st_mtime), s.st_size / 1024.0
				));

			*pathptr = 0;
		}

		/* list files */
		for( i = 0; i < count; i++ )
		{
			strncat(filename, files[i]->d_name,
				sizeof(filename) - strlen(files[i]->d_name));

			if( !stat(filename, &s) &&
			    !(s.st_mode & S_IFDIR) && (s.st_mode & S_IROTH)
			)
				ensure_out(uh_http_sendf(cl, req,
					"<li><strong><a href='%s%s'>%s</a></strong><br />"
					"<small>modified: %s<br />%s - %.02f kbyte<br />"
					"<br /></small></li>",
						pi->name, files[i]->d_name, files[i]->d_name,
						uh_file_unix2date(s.st_mtime),
						uh_file_mime_lookup(filename), s.st_size / 1024.0
				));

			*pathptr = 0;
		}
	}

	ensure_out(uh_http_sendf(cl, req, "</ol><hr /></body></html>"));
	ensure_out(uh_http_sendf(cl, req, ""));

out:
	if( files )
	{
		for( i = 0; i < count; i++ )
			free(files[i]);

		free(files);
	}
}


void uh_file_request(struct client *cl, struct http_request *req, struct path_info *pi)
{
	int rlen;
	int fd = -1;
	char buf[UH_LIMIT_MSGHEAD];

	/* we have a file */
	if( (pi->stat.st_mode & S_IFREG) && ((fd = open(pi->phys, O_RDONLY)) > 0) )
	{
		/* test preconditions */
		if(
			uh_file_if_modified_since(cl, req, &pi->stat)  	&&
			uh_file_if_match(cl, req, &pi->stat)           	&&
			uh_file_if_range(cl, req, &pi->stat)           	&&
			uh_file_if_unmodified_since(cl, req, &pi->stat)	&&
			uh_file_if_none_match(cl, req, &pi->stat)
		) {
			/* write status */
			ensure_out(uh_file_response_200(cl, req, &pi->stat));

			ensure_out(uh_http_sendf(cl, NULL, "Content-Type: %s\r\n", uh_file_mime_lookup(pi->name)));
			ensure_out(uh_http_sendf(cl, NULL, "Content-Length: %i\r\n", pi->stat.st_size));

			/* if request was HTTP 1.1 we'll respond chunked */
			if( (req->version > 1.0) && (req->method != UH_HTTP_MSG_HEAD) )
				ensure_out(uh_http_send(cl, NULL, "Transfer-Encoding: chunked\r\n", -1));

			/* close header */
			ensure_out(uh_http_send(cl, NULL, "\r\n", -1));

			/* send body */
			if( req->method != UH_HTTP_MSG_HEAD )
			{
				/* pump file data */
				while( (rlen = read(fd, buf, sizeof(buf))) > 0 )
					ensure_out(uh_http_send(cl, req, buf, rlen));

				/* send trailer in chunked mode */
				ensure_out(uh_http_send(cl, req, "", 0));
			}
		}

		/* one of the preconditions failed, terminate opened header and exit */
		else
		{
			ensure_out(uh_http_send(cl, NULL, "\r\n", -1));
		}
	}

	/* directory */
	else if( (pi->stat.st_mode & S_IFDIR) && !cl->server->conf->no_dirlists )
	{
		/* write status */
		ensure_out(uh_file_response_200(cl, req, NULL));

		if( req->version > 1.0 )
			ensure_out(uh_http_send(cl, NULL, "Transfer-Encoding: chunked\r\n", -1));

		ensure_out(uh_http_send(cl, NULL, "Content-Type: text/html\r\n\r\n", -1));

		/* content */
		uh_file_dirlist(cl, req, pi);
	}

	/* 403 */
	else
	{
		ensure_out(uh_http_sendhf(cl, 403, "Forbidden",
			"Access to this resource is forbidden"));
	}

out:
	if( fd > -1 )
		close(fd);
}