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.dir)).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)
        module_path     = module_path_from(module_filename, mapping)
        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, mapping)
  filename_without_ext_and_version = filename.to_s.remove(filename.extname).split("@").first
  case
  when filename_without_ext_and_version == "index" && mapping.under
    mapping.under
  when mapping.under
    "#{mapping.under}/#{filename_without_ext_and_version}"
  else
    module_name
  end
end

def module_path_from(filename, mapping)
  [ mapping.path || mapping.under, filename.to_s ].join("/")
end

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

def pin_all_from(dir, under: nil, to: nil, preload: true)
  @directories[dir] = MappedDir.new(dir: dir, under: under, path: to, 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