open Format

type tracer = string
type level = int

let tracers = [ "top-down-run"; "top-down-approx"; "result-set"; "level2-jit"; "res-jit"; "grammar" ]
let active_tracers : (tracer, int) Hashtbl.t = Hashtbl.create 17

let available () = tracers

let is_tracer s = List.mem s tracers
let level s = try Hashtbl.find active_tracers s with Not_found -> 0
let is_active s = Hashtbl.mem active_tracers s
let activate s lvl = if not (is_active s) then Hashtbl.add active_tracers s lvl
let deactivate s = Hashtbl.remove active_tracers s

let tracer_output = ref err_formatter
let set_output f = tracer_output := f

let trace t l s =
  if l <= level t
  then begin
    fprintf !tracer_output "%s: " t;
    fprintf !tracer_output "%s%!" s
  end