## Copyright (C) 2009-2011 Søren Hauberg
##
## This file is part of Octave.
##
## Octave 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 3 of the License, or (at
## your option) any later version.
##
## Octave 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 Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn  {Command} {} lookfor @var{str}
## @deftypefnx {Command} {} lookfor -all @var{str}
## @deftypefnx {Function File} {[@var{func}, @var{helpstring}] =} lookfor (@var{str})
## @deftypefnx {Function File} {[@var{func}, @var{helpstring}] =} lookfor ('-all', @var{str})
## Search for the string @var{str} in all functions found in the current
## function search path.  By default, @code{lookfor} searches for @var{str}
## in the first sentence of the help string of each function found.  The entire
## help text of each function can be searched if the '-all' argument is
## supplied.  All searches are case insensitive.
##
## Called with no output arguments, @code{lookfor} prints the list of
## matching functions to the terminal.  Otherwise, the output arguments
## @var{func} and @var{helpstring} define the matching functions and the
## first sentence of each of their help strings.
##
## The ability of @code{lookfor} to correctly identify the first
## sentence of the help text is dependent on the format of the
## function's help.  All Octave core functions are correctly
## formatted, but the same can not be guaranteed for external packages and
## user-supplied functions.  Therefore, the use of the '-all' argument may
## be necessary to find related functions that are not a part of Octave.
## @seealso{help, doc, which}
## @end deftypefn

function [out_fun, out_help_text] = lookfor (str, arg2)
  if (strcmpi (str, "-all"))
    ## The difference between using '-all' and not, is which part of the caches
    ## we search. The cache is organised such that its first column contains
    ## the function name, its second column contains the full help text, and its
    ## third column contains the first sentence of the help text.
    str = arg2;
    search_type = 2; # when using caches, search its second column
  else
    search_type = 3; # when using caches, search its third column
  endif
  str = lower (str);

  ## Search functions, operators, and keywords that come with Octave
  cache_file = doc_cache_file ();
  if (exist (cache_file, "file"))
    [fun, help_text] = search_cache (str, cache_file, search_type);
    had_core_cache = true;
  else
    fun = help_text = {};
    had_core_cache = false;
  endif

  ## Search functions in new path dirs.
  orig_path = strsplit (__pathorig__ (), pathsep ());

  ## ditto for path.
  new_path = strsplit (path (), pathsep ());

  ## scratch out directories already covered by orig_path.
  if (had_core_cache)
    new_path = setdiff (new_path, orig_path);
  endif

  for n = 1:numel (new_path)
    elt = new_path{n};
    cache_file = fullfile (elt, "doc-cache");
    if (exist (cache_file, "file"))
      ## We have a cache in the directory, then read it and search it!
      [funs, hts] = search_cache (str, cache_file, search_type);
      fun (end+1:end+length (funs)) = funs;
      help_text (end+1:end+length (hts)) = hts;
    else
    ## We don't have a cache. Search files
      funs_in_f = __list_functions__ (elt);
      for m = 1:length (funs_in_f)
        fn = funs_in_f {m};

        ## Skip files that start with __
        if (length (fn) > 2 && strcmp (fn (1:2), "__"))
          continue;
        endif

        ## Extract first sentence
        try
          warn_state = warning ();
          unwind_protect
            warning ("off");
            first_sentence = get_first_help_sentence (fn);
            status = 0;
          unwind_protect_cleanup
            warning (warn_state);
          end_unwind_protect
        catch
          status = 1;
        end_try_catch

        if (search_type == 2) # search entire help text
          try
            warn_state = warning ();
            unwind_protect
              warning ("off");
              [text, fmt] = get_help_text (fn);
              status = 0;
            unwind_protect_cleanup
              warning (warn_state);
            end_unwind_protect
          catch
            status = 1;
          end_try_catch

          ## Take action depending on help text fmt
          switch (lower (fmt))
            case "plain text"
              status = 0;
            case "texinfo"
              [text, status] = __makeinfo__ (text, "plain text");
            case "html"
              [text, status] = strip_html_tags (text);
            otherwise
              status = 1;
          endswitch

        elseif (status == 0) # only search the first sentence of the help text
          text = first_sentence;
        endif

        ## Search the help text, if we can
        if (status == 0 && !isempty (strfind (text, str)))
          fun (end+1) = fn;
          help_text (end+1) = first_sentence;
        endif
      endfor
    endif
  endfor

  if (nargout == 0)
    ## Print the results (FIXME: improve this to make it look better.
    indent = 20;
    term_width = terminal_size() (2);
    desc_width = term_width - indent - 2;
    indent_space = repmat (" ", 1, indent);
    for k = 1:length (fun)
      f = fun {k};
      f (end+1:indent) = " ";
      printf (f);
      desc = strtrim (strrep (help_text {k}, "\n", " "));
      ldesc = length (desc);
      printf ("%s\n", desc (1:min (desc_width, ldesc)));
      for start = desc_width+1:desc_width:ldesc
        stop = min (start + desc_width, ldesc);
        printf ("%s%s\n", indent_space, strtrim (desc (start:stop)));
      endfor
    endfor

  else
    ## Return the results instead of displaying them
    out_fun = fun;
    out_help_text = help_text;
  endif
endfunction

function [funs, help_texts] = search_cache (str, cache_file, search_type)
  load (cache_file);
  if (! isempty (cache))
    t1 = strfind (cache (1, :), str);
    t2 = strfind (cache (search_type, :), str);
    cache_idx = find (! (cellfun ("isempty", t1) & cellfun ("isempty", t2)));
    funs = cache (1, cache_idx);
    help_texts = cache (3, cache_idx);
  else
    funs = help_texts = {};
  endif
endfunction
