import Control.Monad     (unless)
import Test.Hspec        (Spec, describe, expectationFailure, it, shouldBe)
import Test.Hspec.Runner (configFastFail, defaultConfig, hspecWith)

import Beer (song)

main :: IO ()
main = hspecWith defaultConfig {configFastFail = True} specs

specs :: Spec

specs = describe "beer-song" $

          describe "song" $ do

            -- First we test the input, line by line, to give more
            -- useful error messages.

            it "matches lines" $ sequence_ lineAssertions

            -- Finally, because testing lines we are unable
            -- to detect a missing newline at the end of the
            -- lyrics, we test the full song.

            it "matches full song" $ song `shouldBe` lyrics
  where

    lineAssertions = zipWith checkLine [1 :: Int ..] $ zipMaybe (lines song) (lines lyrics)

    checkLine lineno (got, want) =
      unless (got == want) $
        expectationFailure $ "mismatch at line " ++ show lineno ++ "\nexpected: " ++ show want ++ "\n but got: " ++ show got

    zipMaybe    []     []  = []
    zipMaybe (x:xs)    []  = (Just x , Nothing) : zipMaybe xs []
    zipMaybe    []  (y:ys) = (Nothing, Just y ) : zipMaybe [] ys
    zipMaybe (x:xs) (y:ys) = (Just x , Just y ) : zipMaybe xs ys

-- Lyrics extracted from `exercism/x-common` on 2016-10-03.

lyrics :: String
lyrics = "99 bottles of beer on the wall, 99 bottles of beer.\n\
         \Take one down and pass it around, 98 bottles of beer on the wall.\n\
         \\n\
         \98 bottles of beer on the wall, 98 bottles of beer.\n\
         \Take one down and pass it around, 97 bottles of beer on the wall.\n\
         \\n\
         \97 bottles of beer on the wall, 97 bottles of beer.\n\
         \Take one down and pass it around, 96 bottles of beer on the wall.\n\
         \\n\
         \96 bottles of beer on the wall, 96 bottles of beer.\n\
         \Take one down and pass it around, 95 bottles of beer on the wall.\n\
         \\n\
         \95 bottles of beer on the wall, 95 bottles of beer.\n\
         \Take one down and pass it around, 94 bottles of beer on the wall.\n\
         \\n\
         \94 bottles of beer on the wall, 94 bottles of beer.\n\
         \Take one down and pass it around, 93 bottles of beer on the wall.\n\
         \\n\
         \93 bottles of beer on the wall, 93 bottles of beer.\n\
         \Take one down and pass it around, 92 bottles of beer on the wall.\n\
         \\n\
         \92 bottles of beer on the wall, 92 bottles of beer.\n\
         \Take one down and pass it around, 91 bottles of beer on the wall.\n\
         \\n\
         \91 bottles of beer on the wall, 91 bottles of beer.\n\
         \Take one down and pass it around, 90 bottles of beer on the wall.\n\
         \\n\
         \90 bottles of beer on the wall, 90 bottles of beer.\n\
         \Take one down and pass it around, 89 bottles of beer on the wall.\n\
         \\n\
         \89 bottles of beer on the wall, 89 bottles of beer.\n\
         \Take one down and pass it around, 88 bottles of beer on the wall.\n\
         \\n\
         \88 bottles of beer on the wall, 88 bottles of beer.\n\
         \Take one down and pass it around, 87 bottles of beer on the wall.\n\
         \\n\
         \87 bottles of beer on the wall, 87 bottles of beer.\n\
         \Take one down and pass it around, 86 bottles of beer on the wall.\n\
         \\n\
         \86 bottles of beer on the wall, 86 bottles of beer.\n\
         \Take one down and pass it around, 85 bottles of beer on the wall.\n\
         \\n\
         \85 bottles of beer on the wall, 85 bottles of beer.\n\
         \Take one down and pass it around, 84 bottles of beer on the wall.\n\
         \\n\
         \84 bottles of beer on the wall, 84 bottles of beer.\n\
         \Take one down and pass it around, 83 bottles of beer on the wall.\n\
         \\n\
         \83 bottles of beer on the wall, 83 bottles of beer.\n\
         \Take one down and pass it around, 82 bottles of beer on the wall.\n\
         \\n\
         \82 bottles of beer on the wall, 82 bottles of beer.\n\
         \Take one down and pass it around, 81 bottles of beer on the wall.\n\
         \\n\
         \81 bottles of beer on the wall, 81 bottles of beer.\n\
         \Take one down and pass it around, 80 bottles of beer on the wall.\n\
         \\n\
         \80 bottles of beer on the wall, 80 bottles of beer.\n\
         \Take one down and pass it around, 79 bottles of beer on the wall.\n\
         \\n\
         \79 bottles of beer on the wall, 79 bottles of beer.\n\
         \Take one down and pass it around, 78 bottles of beer on the wall.\n\
         \\n\
         \78 bottles of beer on the wall, 78 bottles of beer.\n\
         \Take one down and pass it around, 77 bottles of beer on the wall.\n\
         \\n\
         \77 bottles of beer on the wall, 77 bottles of beer.\n\
         \Take one down and pass it around, 76 bottles of beer on the wall.\n\
         \\n\
         \76 bottles of beer on the wall, 76 bottles of beer.\n\
         \Take one down and pass it around, 75 bottles of beer on the wall.\n\
         \\n\
         \75 bottles of beer on the wall, 75 bottles of beer.\n\
         \Take one down and pass it around, 74 bottles of beer on the wall.\n\
         \\n\
         \74 bottles of beer on the wall, 74 bottles of beer.\n\
         \Take one down and pass it around, 73 bottles of beer on the wall.\n\
         \\n\
         \73 bottles of beer on the wall, 73 bottles of beer.\n\
         \Take one down and pass it around, 72 bottles of beer on the wall.\n\
         \\n\
         \72 bottles of beer on the wall, 72 bottles of beer.\n\
         \Take one down and pass it around, 71 bottles of beer on the wall.\n\
         \\n\
         \71 bottles of beer on the wall, 71 bottles of beer.\n\
         \Take one down and pass it around, 70 bottles of beer on the wall.\n\
         \\n\
         \70 bottles of beer on the wall, 70 bottles of beer.\n\
         \Take one down and pass it around, 69 bottles of beer on the wall.\n\
         \\n\
         \69 bottles of beer on the wall, 69 bottles of beer.\n\
         \Take one down and pass it around, 68 bottles of beer on the wall.\n\
         \\n\
         \68 bottles of beer on the wall, 68 bottles of beer.\n\
         \Take one down and pass it around, 67 bottles of beer on the wall.\n\
         \\n\
         \67 bottles of beer on the wall, 67 bottles of beer.\n\
         \Take one down and pass it around, 66 bottles of beer on the wall.\n\
         \\n\
         \66 bottles of beer on the wall, 66 bottles of beer.\n\
         \Take one down and pass it around, 65 bottles of beer on the wall.\n\
         \\n\
         \65 bottles of beer on the wall, 65 bottles of beer.\n\
         \Take one down and pass it around, 64 bottles of beer on the wall.\n\
         \\n\
         \64 bottles of beer on the wall, 64 bottles of beer.\n\
         \Take one down and pass it around, 63 bottles of beer on the wall.\n\
         \\n\
         \63 bottles of beer on the wall, 63 bottles of beer.\n\
         \Take one down and pass it around, 62 bottles of beer on the wall.\n\
         \\n\
         \62 bottles of beer on the wall, 62 bottles of beer.\n\
         \Take one down and pass it around, 61 bottles of beer on the wall.\n\
         \\n\
         \61 bottles of beer on the wall, 61 bottles of beer.\n\
         \Take one down and pass it around, 60 bottles of beer on the wall.\n\
         \\n\
         \60 bottles of beer on the wall, 60 bottles of beer.\n\
         \Take one down and pass it around, 59 bottles of beer on the wall.\n\
         \\n\
         \59 bottles of beer on the wall, 59 bottles of beer.\n\
         \Take one down and pass it around, 58 bottles of beer on the wall.\n\
         \\n\
         \58 bottles of beer on the wall, 58 bottles of beer.\n\
         \Take one down and pass it around, 57 bottles of beer on the wall.\n\
         \\n\
         \57 bottles of beer on the wall, 57 bottles of beer.\n\
         \Take one down and pass it around, 56 bottles of beer on the wall.\n\
         \\n\
         \56 bottles of beer on the wall, 56 bottles of beer.\n\
         \Take one down and pass it around, 55 bottles of beer on the wall.\n\
         \\n\
         \55 bottles of beer on the wall, 55 bottles of beer.\n\
         \Take one down and pass it around, 54 bottles of beer on the wall.\n\
         \\n\
         \54 bottles of beer on the wall, 54 bottles of beer.\n\
         \Take one down and pass it around, 53 bottles of beer on the wall.\n\
         \\n\
         \53 bottles of beer on the wall, 53 bottles of beer.\n\
         \Take one down and pass it around, 52 bottles of beer on the wall.\n\
         \\n\
         \52 bottles of beer on the wall, 52 bottles of beer.\n\
         \Take one down and pass it around, 51 bottles of beer on the wall.\n\
         \\n\
         \51 bottles of beer on the wall, 51 bottles of beer.\n\
         \Take one down and pass it around, 50 bottles of beer on the wall.\n\
         \\n\
         \50 bottles of beer on the wall, 50 bottles of beer.\n\
         \Take one down and pass it around, 49 bottles of beer on the wall.\n\
         \\n\
         \49 bottles of beer on the wall, 49 bottles of beer.\n\
         \Take one down and pass it around, 48 bottles of beer on the wall.\n\
         \\n\
         \48 bottles of beer on the wall, 48 bottles of beer.\n\
         \Take one down and pass it around, 47 bottles of beer on the wall.\n\
         \\n\
         \47 bottles of beer on the wall, 47 bottles of beer.\n\
         \Take one down and pass it around, 46 bottles of beer on the wall.\n\
         \\n\
         \46 bottles of beer on the wall, 46 bottles of beer.\n\
         \Take one down and pass it around, 45 bottles of beer on the wall.\n\
         \\n\
         \45 bottles of beer on the wall, 45 bottles of beer.\n\
         \Take one down and pass it around, 44 bottles of beer on the wall.\n\
         \\n\
         \44 bottles of beer on the wall, 44 bottles of beer.\n\
         \Take one down and pass it around, 43 bottles of beer on the wall.\n\
         \\n\
         \43 bottles of beer on the wall, 43 bottles of beer.\n\
         \Take one down and pass it around, 42 bottles of beer on the wall.\n\
         \\n\
         \42 bottles of beer on the wall, 42 bottles of beer.\n\
         \Take one down and pass it around, 41 bottles of beer on the wall.\n\
         \\n\
         \41 bottles of beer on the wall, 41 bottles of beer.\n\
         \Take one down and pass it around, 40 bottles of beer on the wall.\n\
         \\n\
         \40 bottles of beer on the wall, 40 bottles of beer.\n\
         \Take one down and pass it around, 39 bottles of beer on the wall.\n\
         \\n\
         \39 bottles of beer on the wall, 39 bottles of beer.\n\
         \Take one down and pass it around, 38 bottles of beer on the wall.\n\
         \\n\
         \38 bottles of beer on the wall, 38 bottles of beer.\n\
         \Take one down and pass it around, 37 bottles of beer on the wall.\n\
         \\n\
         \37 bottles of beer on the wall, 37 bottles of beer.\n\
         \Take one down and pass it around, 36 bottles of beer on the wall.\n\
         \\n\
         \36 bottles of beer on the wall, 36 bottles of beer.\n\
         \Take one down and pass it around, 35 bottles of beer on the wall.\n\
         \\n\
         \35 bottles of beer on the wall, 35 bottles of beer.\n\
         \Take one down and pass it around, 34 bottles of beer on the wall.\n\
         \\n\
         \34 bottles of beer on the wall, 34 bottles of beer.\n\
         \Take one down and pass it around, 33 bottles of beer on the wall.\n\
         \\n\
         \33 bottles of beer on the wall, 33 bottles of beer.\n\
         \Take one down and pass it around, 32 bottles of beer on the wall.\n\
         \\n\
         \32 bottles of beer on the wall, 32 bottles of beer.\n\
         \Take one down and pass it around, 31 bottles of beer on the wall.\n\
         \\n\
         \31 bottles of beer on the wall, 31 bottles of beer.\n\
         \Take one down and pass it around, 30 bottles of beer on the wall.\n\
         \\n\
         \30 bottles of beer on the wall, 30 bottles of beer.\n\
         \Take one down and pass it around, 29 bottles of beer on the wall.\n\
         \\n\
         \29 bottles of beer on the wall, 29 bottles of beer.\n\
         \Take one down and pass it around, 28 bottles of beer on the wall.\n\
         \\n\
         \28 bottles of beer on the wall, 28 bottles of beer.\n\
         \Take one down and pass it around, 27 bottles of beer on the wall.\n\
         \\n\
         \27 bottles of beer on the wall, 27 bottles of beer.\n\
         \Take one down and pass it around, 26 bottles of beer on the wall.\n\
         \\n\
         \26 bottles of beer on the wall, 26 bottles of beer.\n\
         \Take one down and pass it around, 25 bottles of beer on the wall.\n\
         \\n\
         \25 bottles of beer on the wall, 25 bottles of beer.\n\
         \Take one down and pass it around, 24 bottles of beer on the wall.\n\
         \\n\
         \24 bottles of beer on the wall, 24 bottles of beer.\n\
         \Take one down and pass it around, 23 bottles of beer on the wall.\n\
         \\n\
         \23 bottles of beer on the wall, 23 bottles of beer.\n\
         \Take one down and pass it around, 22 bottles of beer on the wall.\n\
         \\n\
         \22 bottles of beer on the wall, 22 bottles of beer.\n\
         \Take one down and pass it around, 21 bottles of beer on the wall.\n\
         \\n\
         \21 bottles of beer on the wall, 21 bottles of beer.\n\
         \Take one down and pass it around, 20 bottles of beer on the wall.\n\
         \\n\
         \20 bottles of beer on the wall, 20 bottles of beer.\n\
         \Take one down and pass it around, 19 bottles of beer on the wall.\n\
         \\n\
         \19 bottles of beer on the wall, 19 bottles of beer.\n\
         \Take one down and pass it around, 18 bottles of beer on the wall.\n\
         \\n\
         \18 bottles of beer on the wall, 18 bottles of beer.\n\
         \Take one down and pass it around, 17 bottles of beer on the wall.\n\
         \\n\
         \17 bottles of beer on the wall, 17 bottles of beer.\n\
         \Take one down and pass it around, 16 bottles of beer on the wall.\n\
         \\n\
         \16 bottles of beer on the wall, 16 bottles of beer.\n\
         \Take one down and pass it around, 15 bottles of beer on the wall.\n\
         \\n\
         \15 bottles of beer on the wall, 15 bottles of beer.\n\
         \Take one down and pass it around, 14 bottles of beer on the wall.\n\
         \\n\
         \14 bottles of beer on the wall, 14 bottles of beer.\n\
         \Take one down and pass it around, 13 bottles of beer on the wall.\n\
         \\n\
         \13 bottles of beer on the wall, 13 bottles of beer.\n\
         \Take one down and pass it around, 12 bottles of beer on the wall.\n\
         \\n\
         \12 bottles of beer on the wall, 12 bottles of beer.\n\
         \Take one down and pass it around, 11 bottles of beer on the wall.\n\
         \\n\
         \11 bottles of beer on the wall, 11 bottles of beer.\n\
         \Take one down and pass it around, 10 bottles of beer on the wall.\n\
         \\n\
         \10 bottles of beer on the wall, 10 bottles of beer.\n\
         \Take one down and pass it around, 9 bottles of beer on the wall.\n\
         \\n\
         \9 bottles of beer on the wall, 9 bottles of beer.\n\
         \Take one down and pass it around, 8 bottles of beer on the wall.\n\
         \\n\
         \8 bottles of beer on the wall, 8 bottles of beer.\n\
         \Take one down and pass it around, 7 bottles of beer on the wall.\n\
         \\n\
         \7 bottles of beer on the wall, 7 bottles of beer.\n\
         \Take one down and pass it around, 6 bottles of beer on the wall.\n\
         \\n\
         \6 bottles of beer on the wall, 6 bottles of beer.\n\
         \Take one down and pass it around, 5 bottles of beer on the wall.\n\
         \\n\
         \5 bottles of beer on the wall, 5 bottles of beer.\n\
         \Take one down and pass it around, 4 bottles of beer on the wall.\n\
         \\n\
         \4 bottles of beer on the wall, 4 bottles of beer.\n\
         \Take one down and pass it around, 3 bottles of beer on the wall.\n\
         \\n\
         \3 bottles of beer on the wall, 3 bottles of beer.\n\
         \Take one down and pass it around, 2 bottles of beer on the wall.\n\
         \\n\
         \2 bottles of beer on the wall, 2 bottles of beer.\n\
         \Take one down and pass it around, 1 bottle of beer on the wall.\n\
         \\n\
         \1 bottle of beer on the wall, 1 bottle of beer.\n\
         \Take it down and pass it around, no more bottles of beer on the wall.\n\
         \\n\
         \No more bottles of beer on the wall, no more bottles of beer.\n\
         \Go to the store and buy some more, 99 bottles of beer on the wall.\n"