class Rack::Files

def call(env)
  # HEAD requests drop the response body, including 4xx error messages.
  @head.call env
end

def fail(status, body, headers = {})
  body += "\n"
  [
    status,
    {
      CONTENT_TYPE   => "text/plain",
      CONTENT_LENGTH => body.size.to_s,
      "x-cascade" => "pass"
    }.merge!(headers),
    [body]
  ]
end

def filesize(path)
  #   We check via File::size? whether this file provides size info
  #   via stat (e.g. /proc files often don't), otherwise we have to
  #   figure it out by reading the whole file into memory.
  ::File.size?(path) || ::File.read(path).bytesize
end

def get(env)
  request = Rack::Request.new env
  unless ALLOWED_VERBS.include? request.request_method
    return fail(405, "Method Not Allowed", { 'allow' => ALLOW_HEADER })
  end
  path_info = Utils.unescape_path request.path_info
  return fail(400, "Bad Request") unless Utils.valid_path?(path_info)
  clean_path_info = Utils.clean_path_info(path_info)
  path = ::File.join(@root, clean_path_info)
  available = begin
    ::File.file?(path) && ::File.readable?(path)
  rescue SystemCallError
    # Not sure in what conditions this exception can occur, but this
    # is a safe way to handle such an error.
    # :nocov:
    false
    # :nocov:
  end
  if available
    serving(request, path)
  else
    fail(404, "File not found: #{path_info}")
  end
end

def initialize(root, headers = {}, default_mime = 'text/plain')
  @root = (::File.expand_path(root) if root)
  @headers = headers
  @default_mime = default_mime
  @head = Rack::Head.new(lambda { |env| get env })
end

def mime_type(path, default_mime)
  Mime.mime_type(::File.extname(path), default_mime)
end

def serving(request, path)
  if request.options?
    return [200, { 'allow' => ALLOW_HEADER, CONTENT_LENGTH => '0' }, []]
  end
  last_modified = ::File.mtime(path).httpdate
  return [304, {}, []] if request.get_header('HTTP_IF_MODIFIED_SINCE') == last_modified
  headers = { "last-modified" => last_modified }
  mime_type = mime_type path, @default_mime
  headers[CONTENT_TYPE] = mime_type if mime_type
  # Set custom headers
  headers.merge!(@headers) if @headers
  status = 200
  size = filesize path
  ranges = Rack::Utils.get_byte_ranges(request.get_header('HTTP_RANGE'), size)
  if ranges.nil?
    # No ranges:
    ranges = [0..size - 1]
  elsif ranges.empty?
    # Unsatisfiable. Return error, and file size:
    response = fail(416, "Byte range unsatisfiable")
    response[1]["content-range"] = "bytes */#{size}"
    return response
  else
    # Partial content
    partial_content = true
    if ranges.size == 1
      range = ranges[0]
      headers["content-range"] = "bytes #{range.begin}-#{range.end}/#{size}"
    else
      headers[CONTENT_TYPE] = "multipart/byteranges; boundary=#{MULTIPART_BOUNDARY}"
    end
    status = 206
    body = BaseIterator.new(path, ranges, mime_type: mime_type, size: size)
    size = body.bytesize
  end
  headers[CONTENT_LENGTH] = size.to_s
  if request.head?
    body = []
  elsif !partial_content
    body = Iterator.new(path, ranges, mime_type: mime_type, size: size)
  end
  [status, headers, body]
end