(** JMAP Primitive Data Types

    This module defines the primitive data types used in JMAP:
    - Int (signed 53-bit integer)
    - UnsignedInt (unsigned integer 0 to 2^53-1)
    - Date (RFC 3339 date-time)
    - UTCDate (RFC 3339 date-time with Z timezone)

    Reference: RFC 8620 Section 1.3
*)

(** Signed 53-bit integer (-2^53 + 1 to 2^53 - 1)
    JavaScript's safe integer range *)
module Int53 = struct
  type t = int

  let min_value = -9007199254740991  (* -(2^53 - 1) *)
  let max_value = 9007199254740991   (* 2^53 - 1 *)

  let of_int i =
    if i < min_value || i > max_value then
      raise (Invalid_argument "Int53 out of range")
    else
      i

  let to_int t = t

  (** Parse from JSON.
      Test files: test/data/core/request_query.json (position, anchorOffset) *)
  let of_json = function
    | `Float f ->
        let i = int_of_float f in
        if Float.is_integer f then
          of_int i
        else
          raise (Jmap_error.Parse_error "Int53 must be an integer")
    | _ -> raise (Jmap_error.Parse_error "Int53 must be a JSON number")

  let to_json t = `Float (float_of_int t)
end

(** Unsigned integer (0 to 2^53 - 1) *)
module UnsignedInt = struct
  type t = int

  let min_value = 0
  let max_value = 9007199254740991  (* 2^53 - 1 *)

  let of_int i =
    if i < min_value || i > max_value then
      raise (Invalid_argument "UnsignedInt out of range")
    else
      i

  let to_int t = t

  (** Parse from JSON.
      Test files:
      - test/data/mail/mailbox_get_response.json (totalEmails, unreadEmails, etc.)
      - test/data/core/request_query.json (limit)
  *)
  let of_json = function
    | `Float f ->
        let i = int_of_float f in
        if Float.is_integer f && i >= 0 then
          of_int i
        else
          raise (Jmap_error.Parse_error "UnsignedInt must be a non-negative integer")
    | _ -> raise (Jmap_error.Parse_error "UnsignedInt must be a JSON number")

  let to_json t = `Float (float_of_int t)
end

(** RFC 3339 date-time (with or without timezone)
    Examples: "2014-10-30T14:12:00+08:00", "2014-10-30T06:12:00Z"
*)
module Date = struct
  type t = string

  (** Basic validation of RFC 3339 format *)
  let validate s =
    (* Simple check: contains 'T' and has reasonable length *)
    String.contains s 'T' && String.length s >= 19

  let of_string s =
    if validate s then s
    else raise (Invalid_argument "Invalid RFC 3339 date-time format")

  let to_string t = t

  (** Parse from JSON.
      Test files: test/data/mail/email_get_response.json (sentAt field) *)
  let of_json = function
    | `String s -> of_string s
    | _ -> raise (Jmap_error.Parse_error "Date must be a JSON string")

  let to_json t = `String t
end

(** RFC 3339 date-time with Z timezone (UTC)
    Example: "2014-10-30T06:12:00Z"

    MUST have "Z" suffix to indicate UTC.
*)
module UTCDate = struct
  type t = string

  (** Validate that string is RFC 3339 with Z suffix *)
  let validate s =
    String.contains s 'T' &&
    String.length s >= 20 &&
    s.[String.length s - 1] = 'Z'

  let of_string s =
    if validate s then s
    else raise (Invalid_argument "Invalid RFC 3339 UTCDate format (must end with Z)")

  let to_string t = t

  (** Parse from JSON.
      Test files:
      - test/data/mail/email_get_response.json (receivedAt field)
      - test/data/mail/email_submission_get_response.json (sendAt field)
  *)
  let of_json = function
    | `String s -> of_string s
    | _ -> raise (Jmap_error.Parse_error "UTCDate must be a JSON string")

  let to_json t = `String t

  (** Get current UTC time as UTCDate *)
  let now () =
    let open Unix in
    let tm = gmtime (time ()) in
    Printf.sprintf "%04d-%02d-%02dT%02d:%02d:%02dZ"
      (tm.tm_year + 1900)
      (tm.tm_mon + 1)
      tm.tm_mday
      tm.tm_hour
      tm.tm_min
      tm.tm_sec
end