//
// Filename expansion routines for the Fast Light Tool Kit (FLTK).
//
// Copyright 1998-2023 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file.  If this
// file is missing or damaged, see the license at:
//
//     https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
//     https://www.fltk.org/bugs.php
//

/* expand a file name by prepending current directory, deleting . and
   .. (not really correct for symbolic links) between the prepended
   current directory.  Use $PWD if it exists.
   Returns true if any changes were made.
*/

#include <FL/filename.H>
#include <FL/Fl.H>
#include <FL/fl_string_functions.h>
#include "Fl_System_Driver.H"
#include <stdlib.h>
#include "flstring.h"

static inline int isdirsep(int c) {return c == '/';}

/** Makes a filename absolute from a relative filename to the current working directory.
    \code
    #include <FL/filename.H>
    [..]
    fl_chdir("/var/tmp");
    fl_filename_absolute(out, sizeof(out), "foo.txt");         // out="/var/tmp/foo.txt"
    fl_filename_absolute(out, sizeof(out), "./foo.txt");       // out="/var/tmp/foo.txt"
    fl_filename_absolute(out, sizeof(out), "../log/messages"); // out="/var/log/messages"
    \endcode
    \param[out] to resulting absolute filename
    \param[in]  tolen size of the absolute filename buffer
    \param[in]  from relative filename
    \return 0 if no change, non zero otherwise
 */
int fl_filename_absolute(char *to, int tolen, const char *from) {
  char cwd_buf[FL_PATH_MAX];    // Current directory
  // get the current directory and return if we can't
  if (!fl_getcwd(cwd_buf, sizeof(cwd_buf))) {
    strlcpy(to, from, tolen);
    return 0;
  }
  return Fl::system_driver()->filename_absolute(to, tolen, from, cwd_buf);
}

/** Concatenate the absolute path `base` with `from` to form the new absolute path in `to`.
 \code
 #include <FL/filename.H>
 char out[FL_PATH_MAX];
 fl_filename_absolute(out, sizeof(out), "../foo.txt", "/var/tmp");   // out="/var/foo.txt"
 fl_filename_absolute(out, sizeof(out), "../local/bin", "/usr/bin");  // out="/usr/local/bin"
 \endcode
 \param[out] to resulting absolute filename
 \param[in]  tolen size of the absolute filename buffer
 \param[in]  from relative filename
 \param[in]  base `from` is relative to this absolute file path
 \return 0 if no change, non zero otherwise
 */
int fl_filename_absolute(char *to, int tolen, const char *from, const char *base) {
  return Fl::system_driver()->filename_absolute(to, tolen, from, base);
}

/**
 \cond DriverDev
 \addtogroup DriverDeveloper
 \{
 */
int Fl_System_Driver::filename_absolute(char *to, int tolen, const char *from, const char *base) {
  if (isdirsep(*from) || *from == '|' || !base) {
    strlcpy(to, from, tolen);
    return 0;
  }
  char *a;
  char *temp = new char[tolen];
  const char *start = from;
  strlcpy(temp, base, tolen);
  a = temp+strlen(temp);
  /* remove trailing '/' in current working directory */
  if (isdirsep(*(a-1))) a--;
  /* remove intermediate . and .. names: */
  while (*start == '.') {
    if (start[1]=='.' && (isdirsep(start[2]) || start[2]==0) ) {
      // found "..", remove the last directory segment form cwd
      char *b;
      for (b = a-1; b >= temp && !isdirsep(*b); b--) {/*empty*/}
      if (b < temp) break;
      a = b;
      if (start[2]==0)
        start += 2; // Skip to end of path
      else
        start += 3; // Skip over dir separator
    } else if (isdirsep(start[1])) {
      // found "./" in path, just skip it
      start += 2;
    } else if (!start[1]) {
      // found "." at end of path, just skip it
      start ++;
      break;
    } else
      break;
  }
  *a++ = '/';
  strlcpy(a,start,tolen - (a - temp));
  strlcpy(to, temp, tolen);
  delete[] temp;
  return 1;
}

/**
 \}
 \endcond
 */


/** Makes a filename relative to the current working directory.

  Return the \a from path made relative to the working directory, similar to
  C++17 `std::filesystem::path::lexically_relative`. This function can also be
  called with a fourth argument for a user supplied \a base directory path

  These conversions are purely lexical. They do not check that the paths exist,
  do not follow symlinks, and do not access the filesystem at all.

  Path arguments must be absolute (start at the root directory) and must not
  contain `.` or `..` segments, or double separators. A single trailing
  separator is ok.

  On Windows, path arguments must start with a drive name, e.g. `c:\`.
  Windows network paths and other special paths starting
  with a double separator are not supported (`\\cloud\drive\path`,
  `\\?\`, etc.) . Separators can be `\` and `/` and will be preserved.
  Newly created separators are alway the forward slash `/`.

  On Windows and macOS, the path segment tests are case insensitive.

  If the path can not be generated, \a from path is copied into the \a to
  buffer and 0 is returned.

  \code
  #include <FL/filename.H>
  [..]
  fl_chdir("/var/tmp/somedir");       // set cwd to /var/tmp/somedir
  [..]
  char out[FL_PATH_MAX];
  fl_filename_relative(out, sizeof(out), "/var/tmp/somedir/foo.txt");  // out="foo.txt",    return=1
  fl_filename_relative(out, sizeof(out), "/var/tmp/foo.txt");          // out="../foo.txt", return=1
  fl_filename_relative(out, sizeof(out), "foo.txt");                   // out="foo.txt",    return=0 (no change)
  fl_filename_relative(out, sizeof(out), "./foo.txt");                 // out="./foo.txt",  return=0 (no change)
  fl_filename_relative(out, sizeof(out), "../foo.txt");                // out="../foo.txt", return=0 (no change)
  \endcode

  \param[out] to resulting relative filename
  \param[in]  tolen size of the relative filename buffer
  \param[in]  from absolute filename
  \return 0 if no change, non zero otherwise
  \see fl_filename_relative(char *to, int tolen, const char *from, const char *base)
  <!-- FIXME: added in 1.5 or higher ...
    \see fl_filename_relative(const std::string &from, const std::string &base)
    \see fl_filename_relative(const std::string &from)
  -->
 */
int fl_filename_relative(char *to, int tolen, const char *from)
{
  char cwd_buf[FL_PATH_MAX];    // Current directory
  // get the current directory and return if we can't
  if (!fl_getcwd(cwd_buf, sizeof(cwd_buf))) {
    strlcpy(to, from, tolen);
    return 0;
  }
  return fl_filename_relative(to, tolen, from, cwd_buf);
}


/** Makes a filename relative to any other directory.

 \param[out] to resulting relative filepath
 \param[in]  tolen size of the relative filename buffer
 \param[in]  from absolute filepath
 \param[in]  base generate filepath relative to this absolute filepath
 \return 0 if no change, non zero otherwise
 \see fl_filename_relative(char *to, int tolen, const char *from)
 */
int fl_filename_relative(char *to, int tolen, const char *from, const char *base) {
  return Fl::system_driver()->filename_relative(to, tolen, from, base);
}


/**
 \cond DriverDev
 \addtogroup DriverDeveloper
 \{
 */

int Fl_System_Driver::filename_relative(char *to, int tolen, const char *dest_dir, const char *base_dir) {
  return filename_relative_(to, tolen, dest_dir, base_dir, true);
}


int Fl_System_Driver::filename_relative_(char *to, int tolen, const char *dest_dir, const char *base_dir, bool case_sensitive)
{
  // Find the relative path from base_dir to dest_dir.
  // Both paths must be absolute and well formed (contain no /../ and /./ segments).
  const char *base_i = base_dir;    // iterator through the base directory string
  const char *base_s = base_dir;    // pointer to the last dir separator found
  const char *dest_i = dest_dir;    // iterator through the destination directory
  const char *dest_s = dest_dir;    // pointer to the last dir separator found

  // return if any of the pointers is NULL
  if (!to || !dest_dir || !base_dir) {
    return 0;
  }

  // return if `base_dir` or `dest_dir` is not an absolute path
  if (!isdirsep(*base_dir) || !isdirsep(*dest_dir)) {
    strlcpy(to, dest_dir, tolen);
    return 0;
  }

  // compare both path names until we find a difference
  for (;;) {
    int b, d;
    if (case_sensitive) { // case sensitive
      base_i++;
      dest_i++;
      b = *base_i, d = *dest_i;
    } else { // case insensitive
      base_i += fl_utf8len1(*base_i);
      b = fl_tolower(fl_utf8decode(base_i, NULL, NULL));
      dest_i += fl_utf8len1(*dest_i);
      d = fl_tolower(fl_utf8decode(dest_i, NULL, NULL));
    }
    int b0 = (b==0) || (isdirsep(b));
    int d0 = (d==0) || (isdirsep(d));
    if (b0 && d0) {
      base_s = base_i;
      dest_s = dest_i;
    }
    if (b==0 || d==0) break;
    if (b!=d) break;
  }
  // base_s and dest_s point at the last separator we found
  // base_i and dest_i point at the first character that differs

  // test for the exact same string and return "." if so
  if (   (base_i[0] == 0 || (isdirsep(base_i[0]) && base_i[1] == 0))
      && (dest_i[0] == 0 || (isdirsep(dest_i[0]) && dest_i[1] == 0))) {
    strlcpy(to, ".", tolen);
    return 0;
  }

  // prepare the destination buffer
  to[0]         = '\0';
  to[tolen - 1] = '\0';

  // count the directory segments remaining in `base_dir`
  int n_up = 0;
  for (;;) {
    char b = *base_s++;
    if (b==0) break;
    if (isdirsep(b) && *base_s) n_up++;
  }

  // now add a "previous dir" sequence for every following slash in the cwd
  if (n_up>0)
    strlcat(to, "..", tolen);
  for (; n_up>1; --n_up)
    strlcat(to, "/..", tolen);

  // finally add the differing path from "from"
  if (*dest_s) {
    if (n_up)
      strlcat(to, "/", tolen);
    strlcat(to, dest_s+1, tolen);
  }

  return 1;
}

/**
 \}
 \endcond
 */