class Importmap::Map

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

def cache_as(name)
  if (cached && result = instance_variable_get("@cached_#{name}"))
    result
  else
    instance_variable_set("@cached_#{name}", yield)
  end
end

def draw(&block)
  instance_eval(&block)
end

def expand_directories_into(paths)
  @directories.values.each do |mapping|
    if (absolute_path = absolute_root_of(mapping.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, mapping.under)
        module_path     = mapping.under ? absolute_path.basename.join(module_filename).to_s : module_filename.to_s
        paths[module_name] = MappedFile.new(name: module_name, path: module_path, preload: mapping.preload)
      end
    end
  end
end

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

def expanded_preloading_files_and_directories
  expanded_files_and_directories.select { |name, mapping| mapping.preload }
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 module_name_from(filename, under)
  filename_without_ext = filename.to_s.remove(filename.extname)
  if filename_without_ext == "index" && under
    under
  else
    module_name = filename_without_ext.split("@").first
    under ? "#{under}/#{module_name}" : module_name
  end
end

def pin(name, to: nil, preload: false)
  @files[name] = MappedFile.new(name: name, path: to || "#{name}.js", preload: preload)
end

def pin_all_from(path, under: nil, preload: false)
  @directories[path] = MappedDir.new(path: path, under: under, preload: preload)
end

def preloaded_module_paths(resolver:)
  cache_as(:preloaded_module_paths) do
    resolve_asset_paths(expanded_preloading_files_and_directories, resolver: resolver).values
  end
end

def resolve_asset_paths(paths, resolver:)
  paths.transform_values do |mapping|
    begin
      resolver.asset_path(mapping.path)
    rescue Sprockets::Rails::Helper::AssetNotFound
      Rails.logger.warn "Importmap skipped missing path: #{mapping.path}"
      nil
    end
  end.compact
end

def to_json(resolver:)
  cache_as(:json) do
    { "imports" => resolve_asset_paths(expanded_files_and_directories, resolver: resolver) }.to_json
  end
end