(** HTTP-date parsing and formatting per RFC 7231 Section 7.1.1.1. *)

(** {1 Types} *)

(** Parse status. *)
type status =
  | Valid    (** Successfully parsed *)
  | Invalid  (** Invalid date format *)

(** {1 Parsing} *)

(** Parse HTTP-date from span.
    Accepts all three formats (IMF-fixdate, RFC 850, asctime).
    Returns (status, timestamp) where timestamp is Unix seconds since epoch.
    Only valid if status = Valid. *)
val parse : Base_bigstring.t -> Span.t -> status * float

(** {1 Formatting} *)

(** Format Unix timestamp as IMF-fixdate string (allocates).
    Example: ["Sun, 06 Nov 1994 08:49:37 GMT"] *)
val format : float -> string

(** {1 Response Writing} *)

(** Write [Date: <timestamp>\r\n] header. Returns new offset. *)
val write_date_header : Base_bigstring.t -> off:int -> float -> int

(** Write [Last-Modified: <timestamp>\r\n] header. Returns new offset. *)
val write_last_modified : Base_bigstring.t -> off:int -> float -> int

(** Write [Expires: <timestamp>\r\n] header. Returns new offset. *)
val write_expires : Base_bigstring.t -> off:int -> float -> int

(** Write formatted HTTP-date at offset (no header name, no CRLF).
    Returns new offset. Used internally by header writers. *)
val write_http_date : Base_bigstring.t -> off:int -> float -> int

(** {2 Comparison Helpers} *)

(** Check if resource was modified since the given date. *)
val is_modified_since : last_modified:float -> if_modified_since:float -> bool

(** Check if resource was not modified since the given date. *)
val is_unmodified_since : last_modified:float -> if_unmodified_since:float -> bool