add headers_lib

src/headers.ml

@@ -42,84 +42,3 @@ let select_encoding headers =
   | `Identity :: _ -> None
   | `DEFLATE :: _ -> Some `DEFLATE
   | `Gzip :: _ -> Some `Gzip
-
-(* TODO(etag)
-   - test
-   - don't ignore invalid_etag
-   - can still bypass this module and directly set Etag header
-     but its fine *)
-module Etag : sig
-  (* https://httpwg.org/specs/rfc9110.html#field.etag
-       module to parse < "*" / #entity-tag >,
-       used for If-Match and If-None-Match headers *)
-  type t
-  type header_value
-
-  val parse : string -> (header_value, string) result
-  val of_crockford32 : string -> (t, string) result
-  val to_field_value : t -> string
-  val evaluate : t -> header_value -> bool
-end = struct
-  (* raw etag *)
-  type t = string
-
-  (* type for the value of header field *)
-  type header_etag_item = { weak: bool; value: string }
-  type header_value = Any_etag | Etag_list of header_etag_item list
-
-  let pp_header_etag_item ppf { weak; value } =
-    if weak then Fmt.pf ppf {|W/"%s"|} value else Fmt.pf ppf {|"%s"|} value
-
-  let to_field_value t =
-    (* always weak comparison for If-None-Match header *)
-    let v = { weak= true; value= t } in
-    Fmt.str "%a" pp_header_etag_item v
-
-  let invalid_etag = Error "invalid etag field"
-
-  let has_valid_charset s =
-    let f c =
-      let n = Char.code c in
-      (n >= 0x21 && n <= 0x7E && n <> 0x22) || (n >= 0x80 && n <= 0xFF)
-    in
-    String.for_all f s
-
-  let of_crockford32 s =
-    match has_valid_charset s with false -> invalid_etag | true -> Ok s
-
-  let trim_dquote s =
-    let len = String.length s in
-    if len >= 2 && s.[0] = '"' && s.[len - 1] = '"' then
-      Ok (String.sub s 1 (len - 2))
-    else invalid_etag
-
-  let parse s =
-    if String.trim s = "*" then Ok Any_etag
-    else
-      String.split_on_char ',' s
-      |> List.map String.trim
-      |> List.filter (( <> ) "")
-      |> Syntax.list_map (fun s ->
-             (* "W/" is the weak comparison indicator *)
-             let weak, s =
-               if String.starts_with ~prefix:"W/" s then
-                 (true, String.sub s 2 (String.length s - 2))
-               else (false, s)
-             in
-             Result.bind (trim_dquote s) (fun s ->
-                 if has_valid_charset s then Ok { weak; value= s }
-                 else invalid_etag))
-      |> Result.map (fun l -> Etag_list l)
-
-  (* To evaluate a received If-None-Match header field:
-     - If the field value is "*", the condition is false
-       if the origin server has a current representation for the target resource.
-     - If the field value is a list of entity tags, the condition is false
-       if one of the listed tags matches the entity tag of the selected representation.
-     - Otherwise, the condition is true. *)
-  let evaluate t header_value =
-    match header_value with
-    | Any_etag -> false
-    | Etag_list l ->
-        not @@ List.exists (fun { weak= _; value } -> String.equal t value) l
-end