-- ---------------------------------------------------------------- [ Perf.idr ]
-- Module    : Perf.idr
-- Copyright : (c) Jan de Muijnck-Hughes
-- License   : see LICENSE
-- --------------------------------------------------------------------- [ EOH ]
||| A naive performance effect for gathering data about the
||| performance of effectful programmes.
module Effect.Perf

import System

import Effects
import Effect.Default

%access public export

-- ---------------------------------------------------- [ Timer Data Structure ]

||| A Simple timer.
record Timer where
  constructor MkTimer
  desc   : String
  start  : Integer
  stop   : Integer
  splits : List (Integer, Maybe String)

displayTimer : Timer -> String
displayTimer (MkTimer d a z bcd) = unlines
      [ unwords ["Timer:", d]
      , unwords ["\tStart:\t", show a, (displaySplits bcd)]
      , unwords ["\tStop:\t",  show z]
      , unwords ["\tDifference:\t", show (z - a)]
      ]
    where
      displaySplit : (Integer, Maybe String) -> String
      displaySplit (v, Nothing)  = with List unwords ["\tSplit:\t",show v]
      displaySplit (v, Just msg) = with List unwords ["\tSplit:\t",show v, show msg]

      displaySplits : List (Integer, Maybe String) -> String
      displaySplits Nil = ""
      displaySplits ss  = "\n" ++ unlines (map displaySplit $ reverse ss)


defaultTimer : String -> Timer
defaultTimer n = MkTimer n 0 0 Nil

-- ---------------------------------------------------------------- [ Resource ]

||| Performance Metrics to keep during program lifetime.
record PMetrics where
  constructor MkPMetrics
  canPerf  : Bool
  livePerf : Bool
  counters : List (String, Nat)
  timers   : List (String, Timer)
  stime    : Integer
  stamps   : List (String, Integer)


implementation Default PMetrics where
  default = MkPMetrics False False Nil Nil 0 Nil

displayPerfMetrics : PMetrics -> String
displayPerfMetrics (MkPMetrics c l cs ts _ ss) =
    unlines [ "Perf Data:"
            , unlines $ map displayMarker cs
            , unlines $ map (\(x,y) => displayTimer y) ts
            , unlines $ map displayMarker ss]
  where
    displayMarker : Show a => Pair String a -> String
    displayMarker (d,v) = unwords [show v, "\t<==\t", show d]

-- ------------------------------------------------------- [ Utility functions ]

incCounter' : String -> PMetrics -> PMetrics
incCounter' x st = record {counters = cs} st
  where
    cs : List (String, Nat)
    cs = map (\(y,c) => if x == y then (y,S c) else (y,c)) (counters st)


data TOpt = START | STOP | SPLIT

displayTimerOpt : TOpt -> String
displayTimerOpt START = "Starting"
displayTimerOpt STOP  = "Stopping"
displayTimerOpt SPLIT = "Splitting"

timerStuff' : TOpt -> Integer -> String -> Maybe String -> PMetrics -> PMetrics
timerStuff' opt val x msg st = record {timers = ts} st
  where
    doThing : (String,Timer) -> (String,Timer)
    doThing (y,t) =
      if not (x == y)
        then (y, t)
        else case opt of
          START => MkPair y $ record {start  = val} t
          STOP  => MkPair y $ record {stop   = val} t
          SPLIT => MkPair y $ record {splits = (val, msg) :: splits t} t

    ts : List (String, Timer)
    ts = map doThing (timers st)


perfLog : PMetrics -> String -> IO ()
perfLog res msg =
    if livePerf res
      then putStrLn $ unwords ["PERF:", msg]
      else pure ()

-- ------------------------------------------------------- [ Effect Definition ]

data Perf : Effect where
  GetMetrics  : sig Perf (PMetrics) (PMetrics)
  TurnOn      : Bool -> sig Perf () (PMetrics) (PMetrics)
  MkCounter   : String -> sig Perf () (PMetrics) (PMetrics)
  IncCounter  : String -> sig Perf () (PMetrics) (PMetrics)
  Timestamp   : String -> sig Perf () (PMetrics) (PMetrics)
  MkStopWatch : String -> sig Perf () (PMetrics) (PMetrics)
  TimerStuff  : TOpt -> String -> Maybe String -> sig Perf () (PMetrics) (PMetrics)

-- ---------------------------------------------------------- [ Handler for IO ]

implementation Handler Perf IO where
  handle res (TurnOn b) k = do
      v <- time
      let res' = record {canPerf = True, livePerf = b, stime = v} res
      perfLog res' $ unwords [ "Turning on Perf with at", show v]
      k () (res')

  handle res (GetMetrics)  k = k res res

  handle res (MkCounter n) k = do
      if not (canPerf res)
        then k () res
        else do
          let res' = record {counters = (n,Z) :: counters res} res
          perfLog res' $ unwords ["Creating counter:", show n]
          k () (res')

  handle res (IncCounter n) k = do
      if not (canPerf res)
        then k () res
        else do
          let res' = incCounter' n res
          perfLog res' $ unwords ["Incriminating counter:", show n]
          k () (res')

  handle res (MkStopWatch n) k = do
      if not (canPerf res)
        then k () res
        else do
          let res' = record {timers = (n, defaultTimer n) :: timers res} res
          perfLog res' $ unwords ["Creating Timer:", show n]
          k () (res')

  handle res (TimerStuff opt n msg) k = do
      v <- time
      if not (canPerf res)
        then k () res
        else do
          let res' = timerStuff' opt v n msg res
          perfLog res' $ unwords [displayTimerOpt opt, "timer", show n, "at", show v, fromMaybe "" msg]
          k () (res')

  handle res (Timestamp s) k = do
      v <- time
      let stamp = v - (stime res)
      if not (canPerf res)
        then k () res
        else do
          let res' = record {stamps = (s,stamp) :: stamps res} res
          perfLog res' $ unlines [ "Creating Timestamp:"
                                 , "\tTIMESTAMP:", show v
                                 , "\tMESSAGE:", show s]
          k () (res')

-- ------------------------------------------------------- [ Effect Descriptor ]

PERF : EFFECT
PERF = MkEff PMetrics Perf

-- --------------------------------------------------------------------- [ API ]

||| Turn on performance metrics.
collectPMetricsOnly : Eff () [PERF]
collectPMetricsOnly = call $ TurnOn False

collectPMetrics : Bool -> Eff () [PERF]
collectPMetrics b = call $ TurnOn b

||| Turn on performance metrics and show during operation
collectPMetricsAndShow : Eff () [PERF]
collectPMetricsAndShow = call $ TurnOn True

||| Return gatheres metrics
getPerfMetrics : Eff PMetrics [PERF]
getPerfMetrics = call $ GetMetrics

||| Create a counter
mkCounter : String -> Eff () [PERF]
mkCounter n = call $ MkCounter n

||| Increment the counter
incCounter : String -> Eff () [PERF]
incCounter n = call $ IncCounter n

mkTimer : String -> Eff () [PERF]
mkTimer n = call $ MkStopWatch n

||| Stop a timer
stopTimer : String -> Eff () [PERF]
stopTimer n = call $ TimerStuff STOP n Nothing

||| Start a timer
startTimer : String -> Eff () [PERF]
startTimer n = call $ TimerStuff START n Nothing

||| Split a timer
splitTimer : String -> Eff () [PERF]
splitTimer n = call $ TimerStuff SPLIT n Nothing

splitTimerMsg : String -> String -> Eff () [PERF]
splitTimerMsg n msg = call $ TimerStuff SPLIT n (Just msg)

||| Create a time stamp.
timestamp : String -> Eff () [PERF]
timestamp msg = call $ Timestamp msg

-- --------------------------------------------------------------------- [ EOF ]