/*
 * Copyright (C) 2014, 2016  J. Ali Harlow <ali@juiblex.co.uk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "config.h"
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "razor.h"
#include "razor-internal.h"
#include "uri.h"

static int valid_unicode(unsigned unicode)
{
	/*
	 * Within the U+0000..U+10FFFF range defined by RFC3629
	 * but not in the U+D800..U+DFFF range prohibited in UTF-8.
	 */
	return unicode < 0xD800 || (unicode >= 0xE000 && unicode < 0x110000);
}

char *razor_path_from_parsed_uri(const struct razor_uri *ru,
  struct razor_error **error)
{
	int continuation_bytes = 0;
	char *path, *p, *s, *uri;
	unsigned char c;
	unsigned unicode;

	if (!ru->scheme) {
		uri = razor_uri_recompose(ru);
		razor_set_error(error, RAZOR_GENERAL_ERROR,
				RAZOR_GENERAL_ERROR_BAD_URI, uri,
				"URI does not include a scheme");
		free(uri);
		return NULL;
	}

	if (strcmp(ru->scheme, "file")) {
		uri = razor_uri_recompose(ru);
		razor_set_error(error, RAZOR_GENERAL_ERROR,
				RAZOR_GENERAL_ERROR_UNSUPPORTED_URI, uri,
				"Not a file URI");
		free(uri);
		return NULL;
	}

	if (ru->host && *ru->host && strcmp(ru->host, "localhost") ||
	    ru->userinfo || ru->port) {
		uri = razor_uri_recompose(ru);
		razor_set_error(error, RAZOR_GENERAL_ERROR,
				RAZOR_GENERAL_ERROR_UNSUPPORTED_URI, uri,
				"URI refers to a non-local file");
		free(uri);
		return NULL;
	}

	s = ru->path;
#ifdef MSWIN_API
	/*
	 * Under MS-Windows, a path of /c:/xxx maps to c:/xxx
	 * Note that PathCreateFromUrl converts / to \ as well.
	 */
	if (s[0] == '/' && is_alpha(s[1]) && s[2] == ':' && s[3] == '/')
		s++;
#endif

	p = path = malloc(strlen(s) + 1);

	while (*s) {
		if (*s >= 0x7F || *s < 0x20)
			break;
		else if (*s != '%') {
			if (continuation_bytes)
				break;
			else
				*p++ = *s++;
		} else {
			c = pchar_get_char(s);
#ifdef MSWIN_API
			if (c == '/' || c == '\\')
#else
			if (c == '/')
#endif
				break;
			else if (!continuation_bytes) {
				if (c >= 0xF5 || c == 0xC0 || c == 0xC1)
					break;
				else if (c >= 0xF0) {
					unicode = c & 7;
					continuation_bytes = 3;
				} else if (c >= 0xE0) {
					unicode = c & 3;
					continuation_bytes = 2;
				} else if (c >= 0xC0) {
					unicode = c & 1;
					continuation_bytes = 1;
				}
			} else if ((c & 0xC0) != 0x80)
				break;
			else {
				unicode <<= 6;
				unicode |= (c & 0x3F);

				if (!--continuation_bytes &&
				    !valid_unicode(unicode))
					break;
			}

			*p++ = c;
			s += 3;
		}
	}

	if (*s || continuation_bytes) {
		uri = razor_uri_recompose(ru);
		razor_set_error(error, RAZOR_GENERAL_ERROR,
				RAZOR_GENERAL_ERROR_BAD_URI,
				uri, "Illegal character in file URI path");
		free(uri);
		free(path);
		return NULL;
	}

	*p++ = '\0';

	return realloc(path, p - path);
}

RAZOR_EXPORT char *razor_path_from_uri(const char *uri,
  struct razor_error **error)
{
	struct razor_uri ru;
	char *path;

	if (razor_uri_parse(&ru, uri, error))
		return NULL;

	path = razor_path_from_parsed_uri(&ru, error);

	razor_uri_destroy(&ru);

	return path;
}

RAZOR_EXPORT char *razor_path_to_uri(const char *path)
{
	char *uri, *s;
	const char *p;
	int check_dotdot, len;
	struct razor_uri ru;

	uri = malloc(5 + (4 - 3) + 4 + 3 * strlen(path) + 1);

	strcpy(uri, "file:");

	s = uri + 5;

#ifdef MSWIN_API
	check_dotdot = path[0] != '/' && path[0] != '\\';
#else
	check_dotdot = path[0] != '/';
#endif

	p = path;

#ifdef MSWIN_API
	/*
	 * Under MS-Windows, c:/xxx maps to a path of /c:/xxx
	 * Relative paths that include a drive letter (eg., c:xxx)
	 * can't be handled directly and have to be converted
	 * to absolute form.
	 */
	if (is_alpha(p[0]) && p[1] == ':') {
		if (p[2] == '/' || p[2] == '\\') {
			*s++ = '/';
			*s++ = p[0];
			*s++ = ':';
			*s++ = '/';
			p += 3;
			/*
			 * We need to take care that ".." segments don't remove
			 * the drive letter (eg., c:/../xxx -> file:/c:/../xxx
			 * which normalizes to file:/xxx).
			 */
			check_dotdot = 2;
		} else {
			s = razor_abspath(p);
			uri = razor_path_to_uri(s);
			free(s);
			return uri;
		}
	}
#endif

	/*
	 * Relative paths are complicated. URIs can't have dot segments
	 * so these will be removed during normalization. That often does
	 * the right thing, but where a relative path traverses up the
	 * tree then the result is a URI that points to somewhere quite
	 * different to path: eg., file:../dir normalizes to file:dir
	 * We solve this by inserting a sentinel segment at the beginning.
	 * If the segment is still present after normalization, then it
	 * can just be removed. If it is missing, then we need to create
	 * an absolute path and redo the conversion.
	 */
	if (check_dotdot) {
		*s++ = '%';
		*s++ = '2';
		*s++ = 'F';
		*s++ = '/';
	}

	while(*p) {
		if (*p == '/' || is_unreserved(*p) || is_sub_delim(*p) ||
		    *p == ':' || *p == '@')
			*s++ = *p;
#ifdef MSWIN_API
		else if (*p == '\\')
			*s++ = '/';
#endif
		else {
			*s++ = '%';
			*s++ = "0123456789ABCDEF"[(*(unsigned char *)p)/16];
			*s++ = "0123456789ABCDEF"[(*(unsigned char *)p)%16];
		}
		p++;
	}
	*s++ = '\0';

	if (razor_uri_parse(&ru, uri, NULL) < 0) {
		free(uri);
		return NULL;
	}
	free(uri);

	razor_uri_normalize(&ru);

	uri = razor_uri_recompose(&ru);

	razor_uri_destroy(&ru);

	if (check_dotdot == 2) {
		s = strdup("file:/x:/%2F/");
		s[6] = path[0];
		if (str_has_prefix(uri, s)) {
			free(s);
			memmove(uri + 5 + 3, uri + 9 + 3,
				strlen(uri + 9 + 3) + 1);
			uri = realloc(uri, strlen(uri) + 1);
		} else {
			free(s);
			free(uri);
			s = razor_abspath(path);
			uri = razor_path_to_uri(s);
			free(s);
		}
	} else if (check_dotdot) {
		if (str_has_prefix(uri, "file:%2F/")) {
			memmove(uri + 5, uri + 9, strlen(uri + 9) + 1);
			uri = realloc(uri, strlen(uri) + 1);
		} else {
			free(uri);
			s = razor_abspath(path);
			uri = razor_path_to_uri(s);
			free(s);
		}
	}

	return uri;
}

RAZOR_EXPORT char *
razor_path_relative_to_uri(const char *uri, const char *path,
			   struct razor_error **error)
{
	char *rel_uri, *result;

	/* Strictly wrong if uri isn't a file URI, but probably okay */
	rel_uri = razor_path_to_uri(path);

	result = razor_resolve_uri_root(uri, rel_uri + 5, 1, error);

	free(rel_uri);

	return result;
}