defmodule Dragon.Serve.Plug.RuntimeStatic do
@moduledoc """
Clone of Plug.Static, adjusted to handle runtime root folder, rather than
compile time.
NOTE: Copyright on this file is from the core Elixir Plug library, not the Dragon.
"""
@behaviour Plug
@allowed_methods ~w(GET HEAD)
import Plug.Conn
alias Plug.Conn
# In this module, the `:prim_file` Erlang module along with the `:file_info`
# record are used instead of the more common and Elixir-y `File` module and
# `File.Stat` struct, respectively. The reason behind this is performance: all
# the `File` operations pass through a single process in order to support node
# operations that we simply don't need when serving assets.
require Record
Record.defrecordp(:file_info, Record.extract(:file_info, from_lib: "kernel/include/file.hrl"))
defmodule InvalidPathError do
defexception message: "invalid path for static asset", plug_status: 400
end
@impl true
def init(opts) do
encodings =
opts
|> Keyword.get(:encodings, [])
|> maybe_add("br", ".br", Keyword.get(opts, :brotli, false))
|> maybe_add("gzip", ".gz", Keyword.get(opts, :gzip, false))
%{
encodings: encodings,
only_rules: {Keyword.get(opts, :only, []), Keyword.get(opts, :only_matching, [])},
qs_cache: Keyword.get(opts, :cache_control_for_vsn_requests, "public, max-age=31536000"),
et_cache: Keyword.get(opts, :cache_control_for_etags, "public"),
et_generation: Keyword.get(opts, :etag_generation, nil),
headers: Keyword.get(opts, :headers, %{}),
content_types: Keyword.get(opts, :content_types, %{}),
from: nil,
at: opts |> Keyword.fetch!(:at) |> Plug.Router.Utils.split()
}
end
@impl true
def call(
conn = %Conn{method: meth},
%{at: at, encodings: encodings} = options
)
when meth in @allowed_methods do
{:ok, from} = Dragon.get(:build)
segments = subset(at, conn.path_info)
segments = Enum.map(segments, &uri_decode/1)
{path, segments} = path(from, segments) |> folder_to_index(segments)
if invalid_path?(segments) do
raise InvalidPathError, "invalid path for static asset: #{conn.request_path}"
end
range = get_req_header(conn, "range")
encoding = file_encoding(conn, path, range, encodings)
serve_static(encoding, conn, segments, range, options)
end
defp folder_to_index(path, segments) do
if File.dir?(path) do
path = Path.join(path, "index.html")
[_ | segments] = Path.split(path)
{path, segments}
else
{path, segments}
end
end
defp uri_decode(path) do
# TODO: Remove rescue as this can't fail from Elixir v1.13
try do
URI.decode(path)
rescue
ArgumentError ->
raise InvalidPathError
end
end
defp serve_static({content_encoding, file_info, path}, conn, segments, _range, options) do
%{
qs_cache: qs_cache,
et_cache: et_cache,
et_generation: et_generation,
headers: headers,
content_types: types
} = options
case put_cache_header(conn, qs_cache, et_cache, et_generation, file_info, path) do
{:stale, conn} ->
filename = List.last(segments)
content_type = Map.get(types, filename) || MIME.from_path(filename)
conn
|> put_resp_header("content-type", content_type)
|> put_resp_header("accept-ranges", "bytes")
|> put_resp_header("access-control-allow-origin", "*")
|> maybe_add_encoding(content_encoding)
|> merge_headers(headers)
|> send_entire_file(path, options)
{:fresh, conn} ->
conn
|> maybe_add_vary(options)
|> send_resp(304, "")
|> halt()
end
end
defp serve_static(:error, conn, _segments, _range, _options) do
conn
end
defp send_entire_file(conn, path, options) do
IO.write(".")
conn
|> maybe_add_vary(options)
|> send_file(200, path)
|> halt()
end
defp maybe_add_encoding(conn, nil), do: conn
defp maybe_add_encoding(conn, ce), do: put_resp_header(conn, "content-encoding", ce)
defp maybe_add_vary(conn, %{encodings: encodings}) do
# If we serve gzip or brotli at any moment, we need to set the proper vary
# header regardless of whether we are serving gzip content right now.
# See: http://www.fastly.com/blog/best-practices-for-using-the-vary-header/
if encodings != [] do
update_in(conn.resp_headers, &[{"vary", "Accept-Encoding"} | &1])
else
conn
end
end
defp put_cache_header(
%Conn{query_string: "vsn=" <> _} = conn,
qs_cache,
_et_cache,
_et_generation,
_file_info,
_path
)
when is_binary(qs_cache) do
{:stale, put_resp_header(conn, "cache-control", qs_cache)}
end
defp put_cache_header(conn, _qs_cache, et_cache, et_generation, file_info, path)
when is_binary(et_cache) do
etag = etag_for_path(file_info, et_generation, path)
conn =
conn
|> put_resp_header("cache-control", et_cache)
|> put_resp_header("etag", etag)
if etag in get_req_header(conn, "if-none-match") do
{:fresh, conn}
else
{:stale, conn}
end
end
defp put_cache_header(conn, _, _, _, _, _) do
{:stale, conn}
end
defp etag_for_path(file_info, et_generation, path) do
case et_generation do
{module, function, args} ->
apply(module, function, [path | args])
nil ->
file_info(size: size, mtime: mtime) = file_info
<<?", {size, mtime} |> :erlang.phash2() |> Integer.to_string(16)::binary, ?">>
end
end
defp file_encoding(conn, path, [_range], _encodings) do
# We do not support compression for range queries.
file_encoding(conn, path, nil, [])
end
defp file_encoding(conn, path, _range, encodings) do
encoded =
Enum.find_value(encodings, fn {encoding, ext} ->
if file_info = accept_encoding?(conn, encoding) && regular_file_info(path <> ext) do
{encoding, file_info, path <> ext}
end
end)
cond do
not is_nil(encoded) ->
encoded
file_info = regular_file_info(path) ->
{nil, file_info, path}
true ->
:error
end
end
defp regular_file_info(path) do
case :prim_file.read_file_info(path) do
{:ok, file_info(type: :regular) = file_info} ->
file_info
_ ->
nil
end
end
defp accept_encoding?(conn, encoding) do
encoding? = &String.contains?(&1, [encoding, "*"])
Enum.any?(get_req_header(conn, "accept-encoding"), fn accept ->
accept |> Plug.Conn.Utils.list() |> Enum.any?(encoding?)
end)
end
defp maybe_add(list, key, value, true), do: list ++ [{key, value}]
defp maybe_add(list, _key, _value, false), do: list
defp path({module, function, arguments}, segments)
when is_atom(module) and is_atom(function) and is_list(arguments),
do: Enum.join([apply(module, function, arguments) | segments], "/")
defp path({app, from}, segments) when is_atom(app) and is_binary(from),
do: Enum.join([Application.app_dir(app), from | segments], "/")
defp path(from, segments),
do: Enum.join([from | segments], "/")
defp subset([h | expected], [h | actual]), do: subset(expected, actual)
defp subset([], actual), do: actual
defp subset(_, _), do: []
defp invalid_path?(list) do
invalid_path?(list, :binary.compile_pattern(["/", "\\", ":", "\0"]))
end
defp invalid_path?([h | _], _match) when h in [".", "..", ""], do: true
defp invalid_path?([h | t], match), do: String.contains?(h, match) or invalid_path?(t)
defp invalid_path?([], _match), do: false
defp merge_headers(conn, {module, function, args}) do
merge_headers(conn, apply(module, function, [conn | args]))
end
defp merge_headers(conn, headers) do
merge_resp_headers(conn, headers)
end
end
