path: root/lib/session.ml

(* Session: outermost connection object.
   Each user connection mints a session registered in RNT at
   /system/sessions/<id>. The session owns exactly one branch at a time;
   DDL / DML / DRL sublanguages operate through that branch. *)

module Make (NT : Nt.S) = struct
  module B = Branch.Make (NT)

  let ( let* ) = Result.bind

  class session ~(sid : string) ~(branch : B.branch) =
    object
      val mutable br : B.branch = branch
      method id = sid
      method branch = br
      method snapshot = br#tip
      method tip = br#tip

      (* Switch to a different branch within the same session. *)
      method set_branch (b : B.branch) = br <- b

      method close () =
        let* () = br#close () in
        NT.session_close sid
    end

  (* Open a session on a live (mutable) branch.
     Creates the branch if it does not exist yet. *)
  let open_session claims ~branch_name =
    let* sid = NT.session_open () in
    let* branch = B.open_branch claims branch_name in
    Ok (new session ~sid ~branch)

  (* Open a session pinned to a specific snapshot hash (detached / read-only).
     Mutations through the returned branch are refused. *)
  let open_snapshot_session claims ~branch_name ~snapshot_hash =
    let* sid = NT.session_open () in
    let* branch = B.open_snapshot claims ~branch_name ~snapshot_hash in
    (* Inform RNT of the session's snapshot override so future session-path
       resolution (once NamespaceReferenceManager handles /system/sessions/...)
       can route queries through the pinned snapshot. *)
    let* () = NT.session_set_branch sid branch_name snapshot_hash in
    Ok (new session ~sid ~branch)
end