type step = Prepare | Work | Rest | End

let prettyPrint step =
  match step with
  | Prepare -> "Prepare"
  | Work -> "Work"
  | Rest -> "Rest"
  | End -> "End"

type state = { step : step; remaining : int; tabata : int; cycle : int }

let getAt (config : Config.config) elapsed =
  let cycleDuration = config.work + config.rest in
  let tabataDuration = config.prepare + (config.cycles * cycleDuration) in
  if elapsed >= tabataDuration * config.tabatas then
    {
      step = End;
      remaining = 0;
      tabata = config.tabatas;
      cycle = config.cycles;
    }
  else
    let currentTabataElapsed = elapsed mod tabataDuration in
    let step, remaining =
      if currentTabataElapsed < config.prepare then
        (Prepare, config.prepare - currentTabataElapsed)
      else
        let currentCycleElapsed =
          (currentTabataElapsed - config.prepare) mod cycleDuration
        in
        if currentCycleElapsed < config.work then
          (Work, config.work - currentCycleElapsed)
        else (Rest, config.work + config.rest - currentCycleElapsed)
    in
    let tabata = (elapsed / tabataDuration) + 1 in
    let cycle =
      if currentTabataElapsed < config.prepare then 1
      else ((currentTabataElapsed - config.prepare) / cycleDuration) + 1
    in
    { step; remaining; tabata; cycle }