GeanyLua: get selected filename as module

-- Get selected filename (as module)
-- 2018.11.17
--
-- Based on "on_menu_open_selected_file1_activate()" (Ctrl+Shift+O) and "document_open_file_full()"

local gsfn = {}

local function path_is_absolute(p)
  if (geany.dirsep == '\\') then
    if (string.match(string.sub(p, 1, 3), '[A-Za-z]:[\\\\/]') ~= nil) then
      return true;
    end
  else
    if (string.sub(p, 1, 1) == geany.dirsep) then return true end;
  end
  return false;
end

local function file_is_exists(p)
  local f = geany.stat(p);
  if (f ~= nil) then
    if (f.type == 'r') then return true end;
  end
  return false;
end

local function tidy_path(fp)
  local c1, c2, ii, fd, td
  -- Remove relative junk
  if (geany.dirsep == '\\') then
    fp = string.gsub(fp, '/', geany.dirsep);
  end
  -- Replace "/./" and "//"
  fp = string.gsub(fp, geany.dirsep .. '%.' .. geany.dirsep, geany.dirsep);
  fp = string.gsub(fp, geany.dirsep .. geany.dirsep, geany.dirsep);
  -- Replace "/../"
  while true do
    c1 = string.find(fp, geany.dirsep .. '..' .. geany.dirsep, 1, true);
    if (c1 == nil) then break end;
    if (c1 <= 4) then return nil end; -- Bad path
    fd = string.sub(fp, 1, c1 - 1);
    ii = 1;
    while true do
      -- Search for last "/" before found "/../"
      c2 = string.find(fd, geany.dirsep, ii, true);
      if (c2 == nil) then
        if (ii == 1) then
          return nil; -- Bad path
        else
          break;
        end
      end
      ii = c2 + 1;
    end
    fd = string.sub(fd, 1, ii - 2);
    td = string.sub(fp, c1 + 4, -1);
    fp = string.gsub(fd .. geany.dirsep .. td, geany.dirsep .. geany.dirsep, geany.dirsep);
  end
  return fp;
end

local function get_sel_filename()
  local wc = geany.wordchars
  local sel = geany.selection()
  local ai, fn, pn, tm

  if (sel == nil) then return end;
  if (sel == '') then
    if (geany.dirsep == '\\') then
      geany.wordchars = wc .. './-\\:'; --Win
    elseif (geany.dirsep == '/') then
      geany.wordchars = wc .. './-'; --Unix
    else
      geany.message('Where are you?');
      return;
    end
    sel = geany.word();
    geany.wordchars = wc;
    if (string.len(sel) == 0) then return end;
  end
  if path_is_absolute(sel) then
    fn = sel;
  else
    -- Relative filename, add the path of the current file
    tm = geany.filename();
    if (tm ~= nil) then
      pn = geany.dirname(tm);
    else
      pn = geany.wkdir();
    end
    fn = pn .. geany.dirsep .. sel;
    if not file_is_exists(fn) then
      -- Try the project's base path
      ai = geany.appinfo();
      if (ai.project ~= nil) then
        if path_is_absolute(ai.project.base) then
          pn = ai.project.base;
        else
          -- Build path out of project file name's dir and base path
          tm = geany.dirname(ai.project.file);
          if (ai.project.base == './') or (ai.project.base == '.\\') then
            pn = tm;
          else
            pn = tm .. geany.dirsep .. ai.project.base;
          end
        end
        fn = pn .. geany.dirsep .. sel;
        if (geany.dirsep == '/') then
          if not file_is_exists(fn) then fn = '/usr/local/include/' .. sel end;
          if not file_is_exists(fn) then fn = '/usr/include/' .. sel end;
        end
      end
    end
  end
  fn = tidy_path(fn);
  if (fn ~= nil) and (file_is_exists(fn)) then
    return fn;
  else
    return nil;
  end
end

gsfn.get_sel_filename = get_sel_filename;
gsfn.file_is_exists   = file_is_exists;
gsfn.path_is_absolute = path_is_absolute;
gsfn.tidy_path        = tidy_path;

return gsfn;