module Sass::Files

def find_file_to_import(filename, load_paths)
  was_sass = false
  original_filename = filename
  if filename[-5..-1] == ".sass"
    filename = filename[0...-5]
    was_sass = true
  elsif filename[-4..-1] == ".css"
    return filename
  end
  new_filename = find_full_path("#{filename}.sass", load_paths)
  return new_filename if new_filename
  return filename + '.css' unless was_sass
  raise SyntaxError.new("File to import not found or unreadable: #{original_filename}.", @line)
end

def find_full_path(filename, load_paths)
  partial_name = File.join(File.dirname(filename), "_#{File.basename(filename)}")
  if Pathname.new(filename).absolute?
    [partial_name, filename].each do |name|
      return name if File.readable?(name)
    end
    return nil
  end
  load_paths.each do |path|
    [partial_name, filename].each do |name|
      full_path = File.join(path, name)
      if File.readable?(full_path)
        return full_path
      end
    end
  end
  nil
end

def sassc_filename(filename, options)
  File.join(options[:cache_location],
    Digest::SHA1.hexdigest(File.dirname(File.expand_path(filename))),
    File.basename(filename) + 'c')
end

def tree_for(filename, options)
  options = Sass::Engine::DEFAULT_OPTIONS.merge(options)
  text = File.read(filename)
  if options[:cache]
    compiled_filename = sassc_filename(filename, options)
    sha = Digest::SHA1.hexdigest(text)
    if root = try_to_read_sassc(filename, compiled_filename, sha)
      root.options = options.merge(:filename => filename)
      return root
    end
  end
  engine = Sass::Engine.new(text, options.merge(:filename => filename))
  begin
    root = engine.to_tree
  rescue Sass::SyntaxError => err
    err.add_backtrace_entry(filename)
    raise err
  end
  try_to_write_sassc(root, compiled_filename, sha, options) if options[:cache]
  root
end

def try_to_read_sassc(filename, compiled_filename, sha)
  return unless File.readable?(compiled_filename)
  File.open(compiled_filename, "rb") do |f|
    return unless f.readline("\n").strip == Sass::VERSION
    return unless f.readline("\n").strip == sha
    return Marshal.load(f.read)
  end
rescue TypeError, ArgumentError => e
  warn "Warning. Error encountered while reading cache #{compiled_filename}: #{e}"
end

def try_to_write_sassc(root, compiled_filename, sha, options)
  return unless File.writable?(File.dirname(options[:cache_location]))
  return if File.exists?(options[:cache_location]) && !File.writable?(options[:cache_location])
  return if File.exists?(File.dirname(compiled_filename)) && !File.writable?(File.dirname(compiled_filename))
  return if File.exists?(compiled_filename) && !File.writable?(compiled_filename)
  FileUtils.mkdir_p(File.dirname(compiled_filename))
  File.open(compiled_filename, "wb") do |f|
    f.write(Sass::VERSION)
    f.write("\n")
    f.write(sha)
    f.write("\n")
    f.write(Marshal.dump(root))
  end
end