<?php
// Read files on disk to establish the proper navigation links.
// Set globals with found information: $levels

$navfile    = 'NAVIGATION.php'; // looked for in each directory
$maxrecurse = 20;               // avoid infinite loops
$debug      = 0;

# Args: message string, optional depth of indentation
function nav_debug()
{
  global $debug;
  if ( ! $debug ) return;

  $arg_list = func_get_args();
  $msg      = array_shift($arg_list);
  $indent   = array_shift($arg_list);
  if ( ! isset($msg)    ) $msg    = '';
  if ( ! isset($indent) ) $indent = 0;

  printf(str_repeat('  ', $indent)."<!-- DEBUG: $msg -->\n");
}

// set information for navigation based on the current URL (file path)
// and the navfiles in the filesystem.  Returned array $levels will
// contain each level of "navbar" information, starting with the top of
// htdocs, down as far as we can go, along the path indicated by our URL.
function where_am_i()
{
  global $navfile, $maxrecurse; // import
  global $levels, $season;      // export
  $subst_count = 1; // for use in string replacements

  $top  = $_SERVER['DOCUMENT_ROOT']; // full path to top of site
  $file = $_SERVER['SCRIPT_FILENAME']; // full path to this page
  nav_debug("where_am_i file is '$file'");
  // We're using % as a regexp delimiter below; abort if any in our path:
  if ( preg_match('/%/', $file ) )
  {
    trigger_error("file path contains illegal char '%': '$file'");
    return;
  }

  // strip top off our path, as well as remaining leading slash
  $rest = preg_replace("%^$top/?%",'',$file,$subst_count);
  // for comparison, strip off a trailing index.php, prepend slash:
  $our_location = preg_replace('%/index\.php$%','/',$rest,$subst_count);
  $our_location = "/$our_location";
  nav_debug("where_am_i our location for comparison is '$our_location'");

  // we'll walk down from the top
  $curdir_url   = '/';
  $curdir_path  = $top;

  // recurse down our path, reading and processing navigation files,
  // until we run out of directories or we find one without a
  // navigation file.
  $recurse = 0;
  $season  = 'unknown';
  $levels = array();
  while ( $recurse < $maxrecurse ) // expect to break out before then
  {
    $recurse++; // to avoid infinite loops, e.g. if symlinks up

    // figure out what the next level down will be; need it to check current
    $nextdir = preg_replace('%/.*%',"",$rest,$subst_count); // next component
    $rest    = preg_replace("%^$nextdir/?%","",$rest,$subst_count);
    nav_debug("where_am_i ********** "
             ."under '$curdir_url' at dir '$nextdir' "
             ."with rest '$rest'");

    // if $nextdir looks like a season and the season is not set, set it
    if ( ( $season == 'unknown' ) and
         preg_match('/^20\d\d(?:-20\d\d)?-[sfw]$/', $nextdir, $matches) )
    {
      $season = $matches[0];
      nav_debug("where_am_i set the season: '$season'");
    }

    // grab the navfile data
    $navigation = array();
    if (     file_exists("$curdir_path/$navfile") 
         and is_readable("$curdir_path/$navfile") )
    {
      include("$curdir_path/$navfile"); // sets array $navigation
    }
    else
    {
      nav_debug("where_am_i breaks, no navfile");
      break;
    }
    if ( ! $navigation )
    {
      nav_debug("where_am_i breaks, navfile did not set array");
      break;
    }
    // okay, we have some navigation items for this level:
    $navitems = array();

    // mark the one corresponding to us, and stack them into an array
    // for use by the navbar-generating code.
    foreach ( $navigation as $navitem )
    {
      list( $is_active, $do_expand, $label, $item_url ) = $navitem;

      // if this is a foreign URL, cannot "canonify":
      if ( preg_match('%^https?:%', $item_url) )
      {
        nav_debug("where_am_i: foreign URL '$item_url' cannot be current");
        $is_current = false;
        $canon_url = $item_url;
      }
      else
      {
        // put the URL into a canonical form so we can check if it is "us":
        //   CANON-1:  if relative URLs, prepend current directory's URL,
        //             being careful not to introduce a double leading slash
        $canon_url = $item_url;
        if ( ! preg_match('%^/%', $canon_url) )
        {
          $canon_url = "$curdir_url/$canon_url";
          $canon_url = preg_replace('%//%','/',$canon_url);
        }
        //   CANON-2:  remove any trailing slash
        $canon_url = preg_replace('%/$%','',$canon_url,$subst_count);
        //   CANON-3:  if the result is a directory then re-append slash
        if ( is_dir("$top$canon_url") )
        {
          $canon_url = "$canon_url/";
        }
  
        nav_debug("where_am_i checking item '$item_url' "
                 ."canonical '$canon_url' "
                 ."against location '$our_location'"
                 );

        // is this "us" so far?
        if ( preg_match("%^$canon_url%",$our_location) )
        {
          $is_current = true;
          nav_debug("where_am_i: is CURRENT");
        }
        else
        {
          $is_current = false;
        }
      }
      // stack this item onto the array for this level only if it is
      // marked as active *or* corresponds to the current URL:
      if ( $is_active or $is_current )
      {
        array_push($navitems, 
                   array($is_current,$do_expand,$label,$canon_url) );
        nav_debug("where_am_i: KEEPING '$canon_url' ('$label')");
      }
      else
      {
        nav_debug("where_am_i: is DISCARDED");
      }
    }
    array_push($levels, $navitems); // push this level
    // once we've processed all the items in the navfile, set up for
    // next directory down:
    if ( ! is_dir("$curdir_path/$nextdir") )
    {
      nav_debug("where_am_i breaks, not a directory: '$curdir_path/$nextdir'");
      break;
    }
    // ready for next iteration:
    $curdir_url  = "$curdir_url/$nextdir";
    $curdir_path = "$curdir_path/$nextdir";
  }
  
  return;
}

function issue_nav_level($depth,$levels)
{
  nav_debug("issue_nav_level called with depth '$depth'", $depth);

  print(str_repeat('  ', $depth)); // depth determines indentation
  if ( $depth == 0 )
  {
    print('<div id="links" class="NOPRINT"><!-- navigation links start -->'."\n");
    $issue_end_nav_links = true;
  }
  else
  {
    print('<div class="sublinks">'."\n");
  }


  // process the first level
  $navitems = array_shift($levels);

  foreach ( $navitems as $navitem )
  {
    list( $is_current, $do_expand, $label, $item_url ) = $navitem;

    print(str_repeat('  ', $depth+1)); // depth determines indentation
    print('<a');
    if ( $is_current )
      print(' class="current"');
    else
      print('                ');
    print(' href="'.$item_url.'">'.$label.'</a>'."\n");
    if ( $is_current )
    {
      // if there's more, call ourselves recursively, unless we were
      // asked not to expand this item:
      if ( $levels )
      {
        if ( $do_expand )
        {
          issue_nav_level($depth+1,$levels);
        }
        else
        {
          print(str_repeat('  ', $depth+2)); // depth determines indentation
          print("<!-- Expansion disabled for '$label' -->\n");
        }
      }
      else
      {
        nav_debug("No deeper levels for '$label'", $depth+2);
      }
    }
  }

  print(str_repeat('  ', $depth)); // depth determines indentation
  if ( $depth == 0 )
  {
    print('</div><!-- div#links, navigation links end -->'."\n");
  }
  else
  {
    print('</div><!-- class=sublinks -->'."\n");
  }
  nav_debug("issue_nav_level returned from depth '$depth'", $depth);
}

?>