## Copyright (C) 2009-2012 S�ren 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 {Function File} {} gen_doc_cache (@var{out_file}, @var{directory})
## Generate documentation caches for all functions in a given directory.
##
## A documentation cache is generated for all functions in @var{directory}.
## The
## resulting cache is saved in the file @var{out_file}.
## The cache is used to speed up @code{lookfor}.
##
## If no directory is given (or it is the empty matrix), a cache for builtin
## operators, etc. is generated.
##
## @seealso{lookfor, path}
## @end deftypefn

function gen_doc_cache (out_file = "doc-cache", directory = [])

  ## Check input
  if (!ischar (out_file))
    print_usage ();
  endif

  ## Generate cache
  if (isempty (directory))
    cache = gen_builtin_cache ();
  elseif (ischar (directory))
    cache = gen_doc_cache_in_dir (directory);
  else
    error ("gen_doc_cache: second input argument must be a string");
  endif

  ## Save cache
  if (! isempty (cache))
    save ("-text", out_file, "cache");
  endif
endfunction

function [text, first_sentence, status] = handle_function (f, text, format)
  first_sentence = "";
  ## Skip functions that start with __ as these shouldn't be searched by lookfor
  if (length (f) > 2 && all (f (1:2) == "_"))
    status = 1;
    return;
  endif

  ## Take action depending on help text format
  switch (lower (format))
    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

  ## Did we get the help text?
  if (status != 0 || isempty (text))
    warning ("gen_doc_cache: unusable help text found in file '%s'", f);
    return;
  endif

  ## Get first sentence of help text
  first_sentence = get_first_help_sentence (f);
endfunction

function cache = create_cache (list)
  cache = {};

  ## For each function:
  for n = 1:length (list)
    f = list {n};

    ## Get help text
    [text, format] = get_help_text (f);

    [text, first_sentence, status] = handle_function (f, text, format);

    ## Did we get the help text?
    if (status != 0)
      continue;
    endif

    ## Store the help text
    cache (1, end+1) = f;
    cache (2, end) = text;
    cache (3, end) = first_sentence;
  endfor
endfunction

function cache = gen_doc_cache_in_dir (directory)
  ## If 'directory' is not in the current path, add it so we search it
  dir_in_path = false;
  p = path ();
  idx = find (p == pathsep ());
  prev_idx = 1;
  for n = 1:length (idx)
    f = p (prev_idx:idx (n)-1);
    if (strcmp (f, directory))
      dir_in_path = true;
      break;
    endif
    prev_idx = idx (n) + 1;
  endfor

  if (!dir_in_path)
    addpath (directory);
  endif

  ## Get list of functions in directory and create cache
  list = __list_functions__ (directory);
  cache = create_cache (list);

  if (!dir_in_path)
    rmpath (directory);
  endif
endfunction

function cache = gen_builtin_cache ()
  operators = __operators__ ();
  keywords = __keywords__ ();
  builtins = __builtins__ ();
  list = {operators{:}, keywords{:}, builtins{:}};

  cache = create_cache (list);
endfunction


%% No true tests desirable for this function.
%% Test input validation
%!error gen_doc_cache (1)