return function(config)
   local fmt = string.format

   --------------------------------
   --
   -- basics
   --
   --------------------------------

   function Set(array, transform)
      if type(array) ~= 'table' then return nil end

      local transform = transform or function(x) return x end

      local set = {}
      for _, element in ipairs(array) do
	 set[transform(element)] = true
      end
      return set
   end

   function set_tostring(set)
      local str = '[empty]'
      for element in pairs(set) do
	 if str == '[empty]' then
	    str = tostring(element)
	 else
	    str = str .. '; '.. tostring(element)
	 end
      end

      return str
   end


   function add_end_slash(str)
      if type(str) ~= 'string' then return nil end
      if string.match(str, '/$') then return str end
      return str .. '/'
   end


   function strip_end_slash(str)
      if string.match(str, '/$') then return string.sub(str, 1, #str-1) end
      return str
   end


   function load_layouts(directory, parent, layouts)
      local directory = add_end_slash(directory) or ''
      local parent = parent or ''
      local layouts = layouts or {}

      local fullpath = parent..directory
      local dirs, files = argent.scanDirectory(argent.config.layout_directory..fullpath)

      for _, file in ipairs(files) do
	 if string.match(file, '%.lua$') then
	    local basename = string.gsub(file, '%.lua$', '')
	    local id = string.gsub(fullpath..basename, '/', '.')
	    argent.log('debug', fmt('loading layout %q', id))
	    success, result = pcall(loadfile(argent.config.layout_directory..fullpath..file), 0, 1)
	    if not success then
	       argent.log('error', result)
	       argent.log('warn', fmt('layout %q will not be available', id))
	    else
	       layouts[id] = result
	    end
	 end
      end

      for _, dir in ipairs(dirs) do
	 if dir ~= '.' and dir ~= '..' then
	    argent.log('debug', fmt('loading layouts from %q', parent..directory))
	    load_layouts(dir, parent..directory, layouts)
	 end
      end

      return layouts
   end


   function setup(config)
      argent.log('debug', 'begin setup')
      
      argent.config = {
	 site_directory = add_end_slash(config.site_directory) or 'site/',
	 output_directory = add_end_slash(config.output_directory) or 'public/',
	 layout_directory = add_end_slash(config.layout_directory) or nil,
	 plugin_directory = add_end_slash(config.plugin_directory) or nil,
	 exclude = Set(config.exclude, strip_end_slash) or {},
	 include = Set(config.include, strip_end_slash) or {},
	 keep = Set(config.keep, strip_end_slash) or {},
	 noprocess = Set(config.noprocess, strip_end_slash) or {},
	 rss_include = Set(config.rss_include, strip_end_slash) or {},
      }

      argent.log('info', fmt('site directory: %s', argent.config.site_directory))
      argent.log('info', fmt('output directory: %s', argent.config.output_directory))
      argent.log('info', fmt('layout directory: %s', tostring(argent.config.layout_directory)))
      argent.log('info', fmt('plugin directory: %s', tostring(argent.config.plugin_directory)))

      argent.log('info', 'exclusions: '..set_tostring(argent.config.exclude))
      argent.log('info', 'inclusions: '..set_tostring(argent.config.include))
      argent.log('info', 'files to keep: '..set_tostring(argent.config.keep))
      argent.log('info', 'noprocess: '..set_tostring(argent.config.noprocess))
      argent.log('info', 'rss files: '..set_tostring(argent.config.rss_include))

      if argent.config.layout_directory then
	 argent.layouts = load_layouts()
      else
	 argent.layouts = {}
      end
      argent.log('info', fmt('available layouts: %s', set_tostring(argent.layouts)))
      
      if argent.config.plugin_directory then
	 package.path =
	    add_end_slash(argent.currentWorkingDirectory())
	    ..argent.config.plugin_directory..'?.lua;'..package.path
      end
      argent.log('debug', 'end setup')
   end


   function is_dotfile(filename)
      if string.match(filename, '^%.') then return true end
      return false
   end


   function directory_exists(directory, parent)
      local directory = directory or ''
      local parent = parent or ''
      local dirs = argent.scanDirectory(argent.config.output_directory..parent)
      for _, dir in ipairs(dirs) do
	 if strip_end_slash(directory) == dir then return true end
      end
      return false
   end


   function output_directory_exists()
      local dirs = argent.scanDirectory('./')
      for _, dir in ipairs(dirs) do
	 if add_end_slash(dir) == argent.config.output_directory then
	    return true
	 end
      end
      return false
   end


   --------------------------------
   --
   -- obliterating
   --
   --------------------------------

   function obliterate_file(file, parent)
      if argent.config.keep[file] then
	 argent.log('debug', fmt('retaining file %q', parent..file))
	 return true
      end

      argent.log('debug', fmt('removing file %q', parent..file))
      os.remove(argent.config.output_directory..parent..file)
      return false
   end


   function obliterate_dir(dir, parent)
      if argent.config.keep[strip_end_slash(dir)] then
	 argent.log('debug', fmt('retaining directory %q', parent..dir))
	 return true
      end

      argent.log('debug', fmt('obliterating files in %q', parent..dir))
      return obliterate_directory(dir, parent)
   end


   function obliterate_directory(dirname, parent)
      local dirname = add_end_slash(dirname) or ''
      local parent = parent or ''

      if argent.config.keep[dirname] then return true end

      local keep_self = (dirname == '')

      local dirs, files = argent.scanDirectory(argent.config.output_directory..parent..dirname)
      for _, file in ipairs(files) do
	 keep_self = obliterate_file(file, parent..dirname) or keep_self
      end
      for _, dir in ipairs(dirs) do
	 if dir ~= '.' and dir ~= '..' then
	    keep_self = obliterate_dir(dir, parent..dirname) or keep_self
	 end
      end

      if not keep_self then
	 os.remove(argent.config.output_directory..parent..dirname)
	 return false
      else
	 return true
      end
   end


   --------------------------------
   --
   -- processing
   --
   --------------------------------

   function should_include(filename, parent)
      for pattern in pairs(argent.config.include) do
	 if string.match(filename, pattern) or string.match(parent..filename, pattern) then
	    return true
	 end
      end
      return false
   end

   function should_ignore(filename, parent)
      if is_dotfile(filename) and not should_include(filename, parent) then
	 return false
      end

      for pattern in pairs(argent.config.exclude) do
	 if string.match(filename, pattern)
	    or string.match(parent..filename, pattern) then
	    return true
	 end
      end

      return false
   end

   function should_process(filename, parent)
      if not string.match(filename, '%.lua$') then
	 return false
      end
      
      if should_ignore(filename, parent) then
	 return false
      end

      for pattern in pairs(argent.config.noprocess) do
	 if string.match(filename, pattern)
	    or string.match(parent..filename, pattern) then
	    return false
	 end
      end

      return true
   end

   function process_file(filename, parent)
      if should_ignore(filename, parent) then
	 argent.log('debug', fmt('will not process file %q', parent..filename))
	 return
      end

      if should_process(filename, parent) then
	 argent.log('debug', fmt('processing %q as lua file', parent..filename))
	 process_lua_file(filename, parent)
      else
	 argent.log('debug', fmt('processing %q as regular file', parent..filename))
	 argent.copyFile(
	    argent.config.site_directory..parent..filename,
	    argent.config.output_directory..parent..filename
	 )
      end
   end


   function process_lua_file(filename, parent)
      local success, result = pcall(loadfile(argent.config.site_directory..parent..filename))
      if not success then
	 print('WARNING: '..result)
	 return
      end

      if not type(result) == 'table' then
	 argent.log('error', fmt('%q returned %q instead of %q', filename, type(result), 'table'))
	 argent.log('warn', fmt('%q will not result in file output!', filename))
	 return
      end

      local html
      if result.html then
	 html = result.html
      elseif result.markdown then
	 html = argent.markdown(result.markdown)
      else
	 argent.log('error', fmt('%q did not specify any content!', filename))
	 argent.log('warn', fmt('%q will not result in file output!', filename))
	 return
      end

      if not result.title then
	 result.title = string.gsub(filename, '%.lua$', '')
	 argent.log('warn', fmt('%q did not specify a title; using default title of %q',
				filename, result.title))
      end

      local layout = function(html, tbl) return html end
      if result.layout then
	 if not argent.layouts[result.layout] then
	    argent.log('error', fmt('%q requested nonexistent layout %q', filename, result.layout))
	    argent.log('warn', fmt('%q will not result in file output!', filename))
	    return
	 else
	    layout = argent.layouts[result.layout]
	 end
      else -- no layout specified
	 argent.log('warn', fmt(
		       '%q did not specify a layout; output will be naked content!',
		       filename))
      end

      local output_data = layout(html, result)
      local output_name = string.gsub(filename, '%.lua$', '.html')
      local output_file = io.open(argent.config.output_directory..parent..output_name, 'w')
      output_file:write(output_data)
      output_file:close()
   end


   function process_dir(directory, parent)
      if should_ignore(directory, parent) then
	 argent.log('debug', fmt('will not process directory %q', parent..directory))
	 return
      end

      if not directory_exists(directory, parent) then
	 argent.createDirectory(argent.config.output_directory..parent..directory)
      end
      process_directory(directory, parent)
   end


   function process_directory(directory, parent)
      local directory = add_end_slash(directory) or ''
      local parent = add_end_slash(parent) or ''
      local dirs, files = argent.scanDirectory(argent.config.site_directory..parent..directory)
      for _, file in ipairs(files) do
	 process_file(file, parent..directory)
      end

      for _, dir in ipairs(dirs) do
	 if dir ~= '.' and dir ~= '..' then
	    process_dir(dir, parent..directory)
	 end
      end
   end


   --------------------------------
   --
   -- putting it all together
   --
   --------------------------------

   setup(config)
   if not output_directory_exists() then
      argent.createDirectory(argent.config.output_directory)
   else
      obliterate_directory()
   end
   process_directory()
end