/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */

#include "common.h"
#include "path.h"
#include "path_w32.h"
#include "utf-conv.h"

#define PATH__NT_NAMESPACE     L"\\\\?\\"
#define PATH__NT_NAMESPACE_LEN 4

#define PATH__ABSOLUTE_LEN     3

#define path__is_dirsep(p) ((p) == '/' || (p) == '\\')

#define path__is_absolute(p) \
	(git__isalpha((p)[0]) && (p)[1] == ':' && ((p)[2] == '\\' || (p)[2] == '/'))

#define path__is_nt_namespace(p) \
	(((p)[0] == '\\' && (p)[1] == '\\' && (p)[2] == '?' && (p)[3] == '\\') || \
	 ((p)[0] == '/' && (p)[1] == '/' && (p)[2] == '?' && (p)[3] == '/'))

#define path__is_unc(p) \
	(((p)[0] == '\\' && (p)[1] == '\\') || ((p)[0] == '/' && (p)[1] == '/'))

GIT_INLINE(int) path__cwd(wchar_t *path, int size)
{
	int len;

	if ((len = GetCurrentDirectoryW(size, path)) == 0) {
		errno = GetLastError() == ERROR_ACCESS_DENIED ? EACCES : ENOENT;
		return -1;
	} else if (len > size) {
		errno = ENAMETOOLONG;
		return -1;
	}

	/* The Win32 APIs may return "\\?\" once you've used it first.
	 * But it may not.  What a gloriously predictible API!
	 */
	if (wcsncmp(path, PATH__NT_NAMESPACE, PATH__NT_NAMESPACE_LEN))
		return len;

	len -= PATH__NT_NAMESPACE_LEN;

	memmove(path, path + PATH__NT_NAMESPACE_LEN, sizeof(wchar_t) * len);
	return len;
}

static wchar_t *path__skip_server(wchar_t *path)
{
	wchar_t *c;

	for (c = path; *c; c++) {
		if (path__is_dirsep(*c))
			return c + 1;
	}

	return c;
}

static wchar_t *path__skip_prefix(wchar_t *path)
{
	if (path__is_nt_namespace(path)) {
		path += PATH__NT_NAMESPACE_LEN;

		if (wcsncmp(path, L"UNC\\", 4) == 0)
			path = path__skip_server(path + 4);
		else if (path__is_absolute(path))
			path += PATH__ABSOLUTE_LEN;
	} else if (path__is_absolute(path)) {
		path += PATH__ABSOLUTE_LEN;
	} else if (path__is_unc(path)) {
		path = path__skip_server(path + 2);
	}

	return path;
}

int git_win32_path_canonicalize(git_win32_path path)
{
	wchar_t *base, *from, *to, *next;
	size_t len;

	base = to = path__skip_prefix(path);

	/* Unposixify if the prefix */
	for (from = path; from < to; from++) {
		if (*from == L'/')
			*from = L'\\';
	}

	while (*from) {
		for (next = from; *next; ++next) {
			if (*next == L'/') {
				*next = L'\\';
				break;
			}

			if (*next == L'\\')
				break;
		}

		len = next - from;

		if (len == 1 && from[0] == L'.')
			/* do nothing with singleton dot */;

		else if (len == 2 && from[0] == L'.' && from[1] == L'.') {
			if (to == base) {
				/* no more path segments to strip, eat the "../" */
				if (*next == L'\\')
					len++;

				base = to;
			} else {
				/* back up a path segment */
				while (to > base && to[-1] == L'\\') to--;
				while (to > base && to[-1] != L'\\') to--;
			}
		} else {
			if (*next == L'\\' && *from != L'\\')
				len++;

			if (to != from)
				memmove(to, from, sizeof(wchar_t) * len);

			to += len;
		}

		from += len;

		while (*from == L'\\') from++;
	}

	/* Strip trailing backslashes */
	while (to > base && to[-1] == L'\\') to--;

	*to = L'\0';

	return (to - path);
}

int git_win32_path__cwd(wchar_t *out, size_t len)
{
	int cwd_len;

	if ((cwd_len = path__cwd(out, len)) < 0)
		return -1;

	/* UNC paths */
	if (wcsncmp(L"\\\\", out, 2) == 0) {
		/* Our buffer must be at least 5 characters larger than the
		 * current working directory:  we swallow one of the leading
		 * '\'s, but we we add a 'UNC' specifier to the path, plus
		 * a trailing directory separator, plus a NUL.
		 */
		if (cwd_len > MAX_PATH - 4) {
			errno = ENAMETOOLONG;
			return -1;
		}

		memmove(out+2, out, sizeof(wchar_t) * cwd_len);
		out[0] = L'U';
		out[1] = L'N';
		out[2] = L'C';

		cwd_len += 2;
	}

	/* Our buffer must be at least 2 characters larger than the current
	 * working directory.  (One character for the directory separator,
	 * one for the null.
	 */
	else if (cwd_len > MAX_PATH - 2) {
		errno = ENAMETOOLONG;
		return -1;
	}

	return cwd_len;
}

int git_win32_path_from_utf8(git_win32_path out, const char *src)
{
	wchar_t *dest = out;

	/* All win32 paths are in NT-prefixed format, beginning with "\\?\". */
	memcpy(dest, PATH__NT_NAMESPACE, sizeof(wchar_t) * PATH__NT_NAMESPACE_LEN);
	dest += PATH__NT_NAMESPACE_LEN;

	/* See if this is an absolute path (beginning with a drive letter) */
	if (path__is_absolute(src)) {
		if (git__utf8_to_16(dest, MAX_PATH, src) < 0)
			return -1;
	}
	/* File-prefixed NT-style paths beginning with \\?\ */
	else if (path__is_nt_namespace(src)) {
		/* Skip the NT prefix, the destination already contains it */
		if (git__utf8_to_16(dest, MAX_PATH, src + PATH__NT_NAMESPACE_LEN) < 0)
			return -1;
	}
	/* UNC paths */
	else if (path__is_unc(src)) {
		memcpy(dest, L"UNC\\", sizeof(wchar_t) * 4);
		dest += 4;

		/* Skip the leading "\\" */
		if (git__utf8_to_16(dest, MAX_PATH - 2, src + 2) < 0)
			return -1;
	}
	/* Absolute paths omitting the drive letter */
	else if (src[0] == '\\' || src[0] == '/') {
		if (path__cwd(dest, MAX_PATH) < 0)
			return -1;

		if (!path__is_absolute(dest)) {
			errno = ENOENT;
			return -1;
		}

		/* Skip the drive letter specification ("C:") */	
		if (git__utf8_to_16(dest + 2, MAX_PATH - 2, src) < 0)
			return -1;
	}
	/* Relative paths */
	else {
		int cwd_len;

		if ((cwd_len = git_win32_path__cwd(dest, MAX_PATH)) < 0)
			return -1;

		dest[cwd_len++] = L'\\';

		if (git__utf8_to_16(dest + cwd_len, MAX_PATH - cwd_len, src) < 0)
			return -1;
	}

	return git_win32_path_canonicalize(out);
}

int git_win32_path_to_utf8(git_win32_utf8_path dest, const wchar_t *src)
{
	char *out = dest;
	int len;

	/* Strip NT namespacing "\\?\" */
	if (path__is_nt_namespace(src)) {
		src += 4;

		/* "\\?\UNC\server\share" -> "\\server\share" */
		if (wcsncmp(src, L"UNC\\", 4) == 0) {
			src += 4;

			memcpy(dest, "\\\\", 2);
			out = dest + 2;
		}
	}

	if ((len = git__utf16_to_8(out, GIT_WIN_PATH_UTF8, src)) < 0)
		return len;

	git_path_mkposix(dest);

	return len;
}
