#include "ruby/ruby.h"
#include "ruby/encoding.h"
#include <winbase.h>
#include <wchar.h>
#include <shlwapi.h>

#ifndef INVALID_FILE_ATTRIBUTES
# define INVALID_FILE_ATTRIBUTES ((DWORD)-1)
#endif

/* cache 'encoding name' => 'code page' into a hash */
static VALUE rb_code_page;

#define IS_DIR_SEPARATOR_P(c) (c == L'\\' || c == L'/')
#define IS_DIR_UNC_P(c) (IS_DIR_SEPARATOR_P(c[0]) && IS_DIR_SEPARATOR_P(c[1]))

/* MultiByteToWideChar() doesn't work with code page 51932 */
#define INVALID_CODE_PAGE 51932
#define PATH_BUFFER_SIZE MAX_PATH * 2

#define insecure_obj_p(obj, level) ((level) >= 4 || ((level) > 0 && OBJ_TAINTED(obj)))

static inline void
replace_wchar(wchar_t *s, int find, int replace)
{
    while (*s != 0) {
	if (*s == find)
	    *s = replace;
	s++;
    }
}

/* Convert str from multibyte char to wchar with specified code page */
static inline void
convert_mb_to_wchar(VALUE str, wchar_t **wstr, wchar_t **wstr_pos, size_t *wstr_len, UINT code_page)
{
    size_t len;

    if (NIL_P(str))
	return;

    len = MultiByteToWideChar(code_page, 0, RSTRING_PTR(str), -1, NULL, 0) + 1;
    *wstr = (wchar_t *)xmalloc(len * sizeof(wchar_t));
    if (wstr_pos)
	*wstr_pos = *wstr;

    MultiByteToWideChar(code_page, 0, RSTRING_PTR(str), -1, *wstr, len);
    *wstr_len = len - 2;
}

static inline void
convert_wchar_to_mb(const wchar_t *wstr, char **str, size_t *str_len, UINT code_page)
{
    size_t len;

    len = WideCharToMultiByte(code_page, 0, wstr, -1, NULL, 0, NULL, NULL);
    *str = (char *)xmalloc(len * sizeof(char));
    WideCharToMultiByte(code_page, 0, wstr, -1, *str, len, NULL, NULL);

    /* do not count terminator as part of the string length */
    *str_len = len - 1;
}

/*
  Return user's home directory using environment variables combinations.
  Memory allocated by this function should be manually freed afterwards.

  Try:
  HOME, HOMEDRIVE + HOMEPATH and USERPROFILE environment variables
  TODO: Special Folders - Profile and Personal
*/
static wchar_t *
home_dir(void)
{
    wchar_t *buffer = NULL;
    size_t buffer_len = 0, len = 0;
    size_t home_env = 0;

    /*
      GetEnvironmentVariableW when used with NULL will return the required
      buffer size and its terminating character.
      http://msdn.microsoft.com/en-us/library/windows/desktop/ms683188(v=vs.85).aspx
    */

    if (len = GetEnvironmentVariableW(L"HOME", NULL, 0)) {
	buffer_len = len;
	home_env = 1;
    }
    else if (len = GetEnvironmentVariableW(L"HOMEDRIVE", NULL, 0)) {
	buffer_len = len;
	if (len = GetEnvironmentVariableW(L"HOMEPATH", NULL, 0)) {
	    buffer_len += len;
	    home_env = 2;
	}
	else {
	    buffer_len = 0;
	}
    }
    else if (len = GetEnvironmentVariableW(L"USERPROFILE", NULL, 0)) {
	buffer_len = len;
	home_env = 3;
    }

    /* allocate buffer */
    if (home_env)
	buffer = (wchar_t *)xmalloc(buffer_len * sizeof(wchar_t));

    switch (home_env) {
      case 1:
	/* HOME */
	GetEnvironmentVariableW(L"HOME", buffer, buffer_len);
	break;
      case 2:
	/* HOMEDRIVE + HOMEPATH */
	len = GetEnvironmentVariableW(L"HOMEDRIVE", buffer, buffer_len);
	GetEnvironmentVariableW(L"HOMEPATH", buffer + len, buffer_len - len);
	break;
      case 3:
	/* USERPROFILE */
	GetEnvironmentVariableW(L"USERPROFILE", buffer, buffer_len);
	break;
      default:
	break;
    }

    if (home_env) {
	/* sanitize backslashes with forwardslashes */
	replace_wchar(buffer, L'\\', L'/');

	return buffer;
    }

    return NULL;
}

/* Remove trailing invalid ':$DATA' of the path. */
static inline size_t
remove_invalid_alternative_data(wchar_t *wfullpath, size_t size)
{
    static const wchar_t prime[] = L":$DATA";
    enum { prime_len = (sizeof(prime) / sizeof(wchar_t)) -1 };

    if (size <= prime_len || _wcsnicmp(wfullpath + size - prime_len, prime, prime_len) != 0)
	return size;

    /* alias of stream */
    /* get rid of a bug of x64 VC++ */
    if (wfullpath[size - (prime_len + 1)] == ':') {
	/* remove trailing '::$DATA' */
	size -= prime_len + 1; /* prime */
	wfullpath[size] = L'\0';
    }
    else {
	/* remove trailing ':$DATA' of paths like '/aa:a:$DATA' */
	wchar_t *pos = wfullpath + size - (prime_len + 1);
	while (!IS_DIR_SEPARATOR_P(*pos) && pos != wfullpath) {
	    if (*pos == L':') {
		size -= prime_len; /* alternative */
		wfullpath[size] = L'\0';
		break;
	    }
	    pos--;
	}
    }
    return size;
}

/* Return system code page. */
static inline UINT
system_code_page(void)
{
    return AreFileApisANSI() ? CP_ACP : CP_OEMCP;
}

/*
  Return code page number of the encoding.
  Cache code page into a hash for performance since finding the code page in
  Encoding#names is slow.
*/
static UINT
code_page(rb_encoding *enc)
{
    VALUE code_page_value, name_key;
    VALUE encoding, names_ary = Qundef, name;
    char *enc_name;
    struct RString fake_str;
    ID names;
    long i;

    if (!enc)
	return system_code_page();

    enc_name = (char *)rb_enc_name(enc);

    fake_str.basic.flags = T_STRING|RSTRING_NOEMBED;
    fake_str.basic.klass = rb_cString;
    fake_str.as.heap.len = strlen(enc_name);
    fake_str.as.heap.ptr = enc_name;
    fake_str.as.heap.aux.capa = fake_str.as.heap.len;
    name_key = (VALUE)&fake_str;
    ENCODING_CODERANGE_SET(name_key, rb_usascii_encindex(), ENC_CODERANGE_7BIT);

    code_page_value = rb_hash_lookup(rb_code_page, name_key);
    if (code_page_value != Qnil)
	return (UINT)FIX2INT(code_page_value);

    name_key = rb_usascii_str_new2(enc_name);

    encoding = rb_enc_from_encoding(enc);
    if (!NIL_P(encoding)) {
	CONST_ID(names, "names");
	names_ary = rb_funcall(encoding, names, 0);
    }

    /* map US-ASCII and ASCII-8bit as code page 20127 (us-ascii) */
    if (enc == rb_usascii_encoding() || enc == rb_ascii8bit_encoding()) {
	UINT code_page = 20127;
	rb_hash_aset(rb_code_page, name_key, INT2FIX(code_page));
	return code_page;
    }

    if (names_ary != Qundef) {
	for (i = 0; i < RARRAY_LEN(names_ary); i++) {
	    name = RARRAY_PTR(names_ary)[i];
	    if (strncmp("CP", RSTRING_PTR(name), 2) == 0) {
		int code_page = atoi(RSTRING_PTR(name) + 2);
		if (code_page != 0) {
		    rb_hash_aset(rb_code_page, name_key, INT2FIX(code_page));
		    return (UINT)code_page;
		}
	    }
	}
    }

    rb_hash_aset(rb_code_page, name_key, INT2FIX(INVALID_CODE_PAGE));
    return INVALID_CODE_PAGE;
}

static inline VALUE
fix_string_encoding(VALUE str, rb_encoding *encoding)
{
    VALUE result, tmp;

    tmp = rb_enc_str_new(RSTRING_PTR(str), RSTRING_LEN(str), encoding);
    result = rb_str_encode(tmp, rb_enc_from_encoding(rb_utf8_encoding()), 0, Qnil);

    return result;
}

/*
  Replace the last part of the path to long name.
  We try to avoid to call FindFirstFileW() since it takes long time.
*/
static inline size_t
replace_to_long_name(wchar_t **wfullpath, size_t size, int heap)
{
    WIN32_FIND_DATAW find_data;
    HANDLE find_handle;

    /*
      Skip long name conversion if the path is already long name.
      Short name is 8.3 format.
      http://en.wikipedia.org/wiki/8.3_filename
      This check can be skipped for directory components that have file
      extensions longer than 3 characters, or total lengths longer than
      12 characters.
      http://msdn.microsoft.com/en-us/library/windows/desktop/aa364980(v=vs.85).aspx
    */
    size_t const max_short_name_size = 8 + 1 + 3;
    size_t const max_extension_size = 3;
    size_t path_len = 1, extension_len = 0;
    wchar_t *pos = *wfullpath;

    if (size == 3 && pos[1] == L':' && pos[2] == L'\\' && pos[3] == L'\0') {
	/* root path doesn't need short name expansion */
	return size;
    }

    pos = *wfullpath + size - 1;
    while (!IS_DIR_SEPARATOR_P(*pos) && pos != *wfullpath) {
	if (!extension_len && *pos == L'.') {
	    extension_len = path_len - 1;
	}
	if (path_len > max_short_name_size || extension_len > max_extension_size) {
	    return size;
	}
	path_len++;
	pos--;
    }

    find_handle = FindFirstFileW(*wfullpath, &find_data);
    if (find_handle != INVALID_HANDLE_VALUE) {
	size_t trail_pos = wcslen(*wfullpath);
	size_t file_len = wcslen(find_data.cFileName);

	FindClose(find_handle);
	while (trail_pos > 0) {
	    if (IS_DIR_SEPARATOR_P((*wfullpath)[trail_pos]))
		break;
	    trail_pos--;
	}
	size = trail_pos + 1 + file_len;
	if ((size + 1) > sizeof(*wfullpath) / sizeof((*wfullpath)[0])) {
	    wchar_t *buf = (wchar_t *)xmalloc((size + 1) * sizeof(wchar_t));
	    wcsncpy(buf, *wfullpath, trail_pos + 1);
	    if (heap)
		xfree(*wfullpath);
	    *wfullpath = buf;
	}
	wcsncpy(*wfullpath + trail_pos + 1, find_data.cFileName, file_len + 1);
    }
    return size;
}

VALUE
rb_file_expand_path_internal(VALUE fname, VALUE dname, int abs_mode, int long_name, VALUE result)
{
    size_t size = 0, wpath_len = 0, wdir_len = 0, whome_len = 0;
    size_t buffer_len = 0;
    char *fullpath = NULL;
    wchar_t *wfullpath = NULL, *wpath = NULL, *wpath_pos = NULL, *wdir = NULL;
    wchar_t *whome = NULL, *buffer = NULL, *buffer_pos = NULL;
    UINT path_cp, cp;
    VALUE path = fname, dir = dname;
    wchar_t wfullpath_buffer[PATH_BUFFER_SIZE];
    wchar_t path_drive = L'\0', dir_drive = L'\0';
    int ignore_dir = 0;
    rb_encoding *path_encoding;
    int tainted = 0;

    /* tainted if path is tainted */
    tainted = OBJ_TAINTED(path);

    /* get path encoding */
    if (NIL_P(dir)) {
	path_encoding = rb_enc_get(path);
    }
    else {
	path_encoding = rb_enc_check(path, dir);
    }

    cp = path_cp = code_page(path_encoding);

    /* workaround invalid codepage */
    if (path_cp == INVALID_CODE_PAGE) {
	cp = CP_UTF8;
	if (!NIL_P(path)) {
	    path = fix_string_encoding(path, path_encoding);
	}
    }

    /* convert char * to wchar_t */
    convert_mb_to_wchar(path, &wpath, &wpath_pos, &wpath_len, cp);

    /* determine if we need the user's home directory */
    /* expand '~' only if NOT rb_file_absolute_path() where `abs_mode` is 1 */
    if (abs_mode == 0 && wpath_len > 0 && wpath_pos[0] == L'~' &&
	(wpath_len == 1 || IS_DIR_SEPARATOR_P(wpath_pos[1]))) {
	/* tainted if expanding '~' */
	tainted = 1;

	whome = home_dir();
	if (whome == NULL) {
	    xfree(wpath);
	    rb_raise(rb_eArgError, "couldn't find HOME environment -- expanding `~'");
	}
	whome_len = wcslen(whome);

	if (PathIsRelativeW(whome) && !(whome_len >= 2 && IS_DIR_UNC_P(whome))) {
	    xfree(wpath);
	    rb_raise(rb_eArgError, "non-absolute home");
	}

	/* use filesystem encoding if expanding home dir */
	path_encoding = rb_filesystem_encoding();
	cp = path_cp = system_code_page();

	/* ignores dir since we are expading home */
	ignore_dir = 1;

	/* exclude ~ from the result */
	wpath_pos++;
	wpath_len--;

	/* exclude separator if present */
	if (wpath_len && IS_DIR_SEPARATOR_P(wpath_pos[0])) {
	    wpath_pos++;
	    wpath_len--;
	}
    }
    else if (wpath_len >= 2 && wpath_pos[1] == L':') {
	if (wpath_len >= 3 && IS_DIR_SEPARATOR_P(wpath_pos[2])) {
	    /* ignore dir since path contains a drive letter and a root slash */
	    ignore_dir = 1;
	}
	else {
	    /* determine if we ignore dir or not later */
	    path_drive = wpath_pos[0];
	}
    }
    else if (abs_mode == 0 && wpath_len >= 2 && wpath_pos[0] == L'~') {
	wchar_t *wuser = wpath_pos + 1;
	wchar_t *pos = wuser;
	char *user;

	/* tainted if expanding '~' */
	tainted = 1;

	while (!IS_DIR_SEPARATOR_P(*pos) && *pos != '\0')
	    pos++;

	*pos = '\0';
	convert_wchar_to_mb(wuser, &user, &size, cp);

	/* convert to VALUE and set the path encoding */
	if (path_cp == INVALID_CODE_PAGE) {
	    VALUE tmp = rb_enc_str_new(user, size, rb_utf8_encoding());
	    result = rb_str_encode(tmp, rb_enc_from_encoding(path_encoding), 0, Qnil);
	    rb_str_resize(tmp, 0);
	}
	else {
	    result = rb_enc_str_new(user, size, path_encoding);
	}

	xfree(wpath);
	if (user)
	    xfree(user);

	rb_raise(rb_eArgError, "can't find user %s", StringValuePtr(result));
    }

    /* convert dir */
    if (!ignore_dir && !NIL_P(dir)) {
	/* fix string encoding */
	if (path_cp == INVALID_CODE_PAGE) {
	    dir = fix_string_encoding(dir, path_encoding);
	}

	/* convert char * to wchar_t */
	convert_mb_to_wchar(dir, &wdir, NULL, &wdir_len, cp);

	if (wdir_len >= 2 && wdir[1] == L':') {
	    dir_drive = wdir[0];
	    if (wpath_len && IS_DIR_SEPARATOR_P(wpath_pos[0])) {
		wdir_len = 2;
	    }
	}
	else if (wdir_len >= 2 && IS_DIR_UNC_P(wdir)) {
	    /* UNC path */
	    if (wpath_len && IS_DIR_SEPARATOR_P(wpath_pos[0])) {
		/* cut the UNC path tail to '//host/share' */
		size_t separators = 0;
		size_t pos = 2;
		while (pos < wdir_len && separators < 2) {
		    if (IS_DIR_SEPARATOR_P(wdir[pos])) {
			separators++;
		    }
		    pos++;
		}
		if (separators == 2)
		    wdir_len = pos - 1;
	    }
	}
    }

    /* determine if we ignore dir or not */
    if (!ignore_dir && path_drive && dir_drive) {
	if (towupper(path_drive) == towupper(dir_drive)) {
	    /* exclude path drive letter to use dir */
	    wpath_pos += 2;
	    wpath_len -= 2;
	}
	else {
	    /* ignore dir since path drive is different from dir drive */
	    ignore_dir = 1;
	    wdir_len = 0;
	}
    }

    if (!ignore_dir && wpath_len >= 2 && IS_DIR_UNC_P(wpath)) {
	/* ignore dir since path has UNC root */
	ignore_dir = 1;
	wdir_len = 0;
    }
    else if (!ignore_dir && wpath_len >= 1 && IS_DIR_SEPARATOR_P(wpath[0]) &&
	     !dir_drive && !(wdir_len >= 2 && IS_DIR_UNC_P(wdir))) {
	/* ignore dir since path has root slash and dir doesn't have drive or UNC root */
	ignore_dir = 1;
	wdir_len = 0;
    }

    buffer_len = wpath_len + 1 + wdir_len + 1 + whome_len + 1;

    buffer = buffer_pos = (wchar_t *)xmalloc((buffer_len + 1) * sizeof(wchar_t));

    /* add home */
    if (whome_len) {
	wcsncpy(buffer_pos, whome, whome_len);
	buffer_pos += whome_len;
    }

    /* Add separator if required */
    if (whome_len && wcsrchr(L"\\/:", buffer_pos[-1]) == NULL) {
	buffer_pos[0] = L'\\';
	buffer_pos++;
    }

    if (wdir_len) {
	/* tainted if dir is used and dir is tainted */
	if (!tainted && OBJ_TAINTED(dir))
	    tainted = 1;

	wcsncpy(buffer_pos, wdir, wdir_len);
	buffer_pos += wdir_len;
    }

    /* add separator if required */
    if (wdir_len && wcsrchr(L"\\/:", buffer_pos[-1]) == NULL) {
	buffer_pos[0] = L'\\';
	buffer_pos++;
    }

    /* now deal with path */
    if (wpath_len) {
	wcsncpy(buffer_pos, wpath_pos, wpath_len);
	buffer_pos += wpath_len;
    }

    /* GetFullPathNameW requires at least "." to determine current directory */
    if (wpath_len == 0) {
	buffer_pos[0] = L'.';
	buffer_pos++;
    }

    /* Ensure buffer is NULL terminated */
    buffer_pos[0] = L'\0';

    /* tainted if path is relative */
    if (!tainted && PathIsRelativeW(buffer) && !(buffer_len >= 2 && IS_DIR_UNC_P(buffer)))
	tainted = 1;

    /* FIXME: Make this more robust */
    /* Determine require buffer size */
    size = GetFullPathNameW(buffer, PATH_BUFFER_SIZE, wfullpath_buffer, NULL);
    if (size > PATH_BUFFER_SIZE) {
	/* allocate more memory than alloted originally by PATH_BUFFER_SIZE */
	wfullpath = (wchar_t *)xmalloc(size * sizeof(wchar_t));
	size = GetFullPathNameW(buffer, size, wfullpath, NULL);
    }
    else {
	wfullpath = wfullpath_buffer;
    }

    /* Remove any trailing slashes */
    if (IS_DIR_SEPARATOR_P(wfullpath[size - 1]) &&
	wfullpath[size - 2] != L':' &&
	!(size == 2 && IS_DIR_UNC_P(wfullpath))) {
	size -= 1;
	wfullpath[size] = L'\0';
    }

    /* Remove any trailing dot */
    if (wfullpath[size - 1] == L'.') {
	size -= 1;
	wfullpath[size] = L'\0';
    }

    /* removes trailing invalid ':$DATA' */
    size = remove_invalid_alternative_data(wfullpath, size);

    /* Replace the trailing path to long name */
    if (long_name)
	size = replace_to_long_name(&wfullpath, size, (wfullpath != wfullpath_buffer));

    /* sanitize backslashes with forwardslashes */
    replace_wchar(wfullpath, L'\\', L'/');

    /* convert to char * */
    size = WideCharToMultiByte(cp, 0, wfullpath, size, NULL, 0, NULL, NULL);
    if (size > (size_t)RSTRING_LEN(result)) {
	rb_str_modify(result);
	rb_str_resize(result, size);
    }

    WideCharToMultiByte(cp, 0, wfullpath, size, RSTRING_PTR(result), size, NULL, NULL);
    rb_str_set_len(result, size);

    /* convert to VALUE and set the path encoding */
    if (path_cp == INVALID_CODE_PAGE) {
	VALUE tmp;
	size_t len;

	rb_enc_associate(result, rb_utf8_encoding());
	ENC_CODERANGE_CLEAR(result);
	tmp = rb_str_encode(result, rb_enc_from_encoding(path_encoding), 0, Qnil);
	len = RSTRING_LEN(tmp);
	rb_str_modify(result);
	rb_str_resize(result, len);
	memcpy(RSTRING_PTR(result), RSTRING_PTR(tmp), len);
	rb_str_resize(tmp, 0);
    }
    rb_enc_associate(result, path_encoding);
    ENC_CODERANGE_CLEAR(result);

    /* makes the result object tainted if expanding tainted strings or returning modified path */
    if (tainted)
	OBJ_TAINT(result);

    /* TODO: better cleanup */
    if (buffer)
	xfree(buffer);

    if (wpath)
	xfree(wpath);

    if (wdir)
	xfree(wdir);

    if (whome)
	xfree(whome);

    if (wfullpath && wfullpath != wfullpath_buffer)
	xfree(wfullpath);

    if (fullpath)
	xfree(fullpath);

    return result;
}

int
rb_file_load_ok(const char *path)
{
    int ret = 1;
    DWORD attr = GetFileAttributes(path);
    if (attr == INVALID_FILE_ATTRIBUTES ||
	attr & FILE_ATTRIBUTE_DIRECTORY) {
	ret = 0;
    }
    else {
	HANDLE h = CreateFile(path, GENERIC_READ,
			      FILE_SHARE_READ | FILE_SHARE_WRITE,
			      NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if (h != INVALID_HANDLE_VALUE) {
	    CloseHandle(h);
	}
	else {
	    ret = 0;
	}
    }
    return ret;
}

void
rb_w32_init_file(void)
{
    rb_code_page = rb_hash_new();

    /* prevent GC removing rb_code_page */
    rb_gc_register_mark_object(rb_code_page);
}
