class Importmap::Paths

def absolute_root_of(path)
  (pathname = Pathname.new(path)).absolute? ? pathname : Rails.root.join(path)
end

def asset(name, path: nil)
  @files[name] = path || "#{name}.js"
end

def assets_in(path, append_base_path: false)
  @directories[path] = append_base_path
end

def expand_directories_into(paths)
  @directories.each do |(path, append_base_path)|
    if (absolute_path = absolute_root_of(path)).exist?
      find_javascript_files_in_tree(absolute_path).each do |filename|
        module_filename = filename.relative_path_from(absolute_path)
        module_name     = module_name_from(module_filename)
        module_path     = append_base_path ? absolute_path.basename.join(module_filename).to_s : module_filename.to_s
        paths[module_name] = module_path
      end
    end
  end
end

def expanded_files_and_directories
  @files.dup.tap { |expanded| expand_directories_into expanded }
end

def find_javascript_files_in_tree(path)
  Dir[path.join("**/*.js{,m}")].collect { |file| Pathname.new(file) }.select(&:file?)
end

def initialize
  @files = {}
  @directories = {}
end

def map_to_asset_paths(resolver)
  expanded_files_and_directories.transform_values { |path| resolver.asset_path(path) }
end

def module_name_from(filename)
  filename.to_s.remove(filename.extname).remove("/index").split("@").first
end

def to_json(resolver)
  { "imports" => map_to_asset_paths(resolver) }.to_json
end