-- |
-- Module      : Criterion.Types
-- Copyright   : (c) Bryan O'Sullivan 2009
--
-- License     : BSD-style
-- Maintainer  : bos@serpentine.com
-- Stability   : experimental
-- Portability : GHC
--
-- Types for benchmarking.
--
-- The core class is 'Benchmarkable', which admits both pure functions
-- and 'IO' actions.
--
-- For a pure function of type @Int -> a@, the benchmarking harness
-- calls this function repeatedly, each time with a different 'Int'
-- argument, and reduces the result the function returns to weak head
-- normal form.  If you need the result reduced to normal form, that
-- is your responsibility.
--
-- For an action of type @IO a@, the benchmarking harness calls the
-- action repeatedly, but does not reduce the result.

{-# LANGUAGE FlexibleInstances, GADTs #-}
module Criterion.Types
    (
      Benchmarkable(..)
    , Benchmark(..)
    , bench
    , bgroup
    , benchNames
    ) where

import Control.Exception (evaluate)

-- | A benchmarkable function or action.
class Benchmarkable b where
    run :: b -> Int -> IO ()

instance Benchmarkable (Int -> a) where
    run f u = evaluate (f u) >> return ()

instance Benchmarkable (IO a) where
    run a _ = a >> return ()

-- | A benchmark may consist of either a single 'Benchmarkable' item
-- with a name, created with 'bench', or a (possibly nested) group of
-- 'Benchmark's, created with 'bgroup'.
data Benchmark where
    Benchmark  :: Benchmarkable b => String -> b -> Benchmark
    BenchGroup :: String -> [Benchmark] -> Benchmark

-- | Create a single benchmark.
bench :: Benchmarkable b =>
         String                 -- ^ A name to identify the benchmark.
      -> b
      -> Benchmark
bench = Benchmark

-- | Group several benchmarks together under a common name.
bgroup :: String                -- ^ A name to identify the group of benchmarks.
       -> [Benchmark]           -- ^ Benchmarks to group under this name.
       -> Benchmark
bgroup = BenchGroup

-- | Retrieve the names of all benchmarks.  Grouped benchmarks are
-- prefixed with the name of the group they're in.
benchNames :: Benchmark -> [String]
benchNames (Benchmark d _)   = [d]
benchNames (BenchGroup d bs) = map ((d ++ "/") ++) . concatMap benchNames $ bs

instance Show Benchmark where
    show (Benchmark d _)  = ("Benchmark " ++ show d)
    show (BenchGroup d _) = ("BenchGroup " ++ show d)