{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE NumericUnderscores #-}
-- GHC wants us to remove `Err never` branches from case statements, because it
-- knows we'll never end up in those branches. We like them though, because
-- missing such a branch in a case statement looks like a problem and so is
-- distracting.
{-# OPTIONS_GHC -fno-warn-overlapping-patterns #-}

module Test.Internal where

import qualified Control.Concurrent.MVar as MVar
import qualified Control.Exception.Safe as Exception
import qualified Control.Monad.IO.Class
import qualified Data.Either
import qualified Data.IORef as IORef
import qualified Dict
import qualified GHC.Stack as Stack
import qualified Hedgehog
import qualified Hedgehog.Internal.Property
import qualified Hedgehog.Internal.Report
import qualified Hedgehog.Internal.Runner
import qualified Hedgehog.Internal.Seed
import qualified List
import qualified Maybe
import NriPrelude
import Platform (TracingSpan)
import qualified Platform
import qualified Platform.Internal
import qualified Task
import qualified Tuple
import qualified Prelude

data SingleTest a = SingleTest
  { describes :: [Text],
    name :: Text,
    label :: Label,
    loc :: Maybe Stack.SrcLoc,
    body :: a
  }
  deriving (Prelude.Functor)

data Label = None | Skip | Only | Todo
  deriving (Eq, Ord)

data TestResult
  = Succeeded
  | Failed Failure

data Failure
  = FailedAssertion Text (Maybe Stack.SrcLoc)
  | ThrewException Exception.SomeException
  | TookTooLong
  | TestRunnerMessedUp Text
  deriving (Show)

instance Exception.Exception Failure

data SuiteResult
  = AllPassed [SingleTest TracingSpan]
  | OnlysPassed [SingleTest TracingSpan] [SingleTest NotRan]
  | PassedWithSkipped [SingleTest TracingSpan] [SingleTest NotRan]
  | TestsFailed [SingleTest TracingSpan] [SingleTest NotRan] [SingleTest (TracingSpan, Failure)]
  | NoTestsInSuite

data NotRan = NotRan

-- | A test which has yet to be evaluated. When evaluated, it produces one
-- or more 'Expect.Expectation's.
-- See 'test' and 'fuzz' for some ways to create a @Test@.
newtype Test = Test {unTest :: [SingleTest Expectation]}

-- | The result of a single test run: either a 'pass' or a 'fail'.
type Expectation = Expectation' ()

-- | The type of a test that runs some script with multiple expectations in
-- between.
newtype Expectation' a = Expectation {unExpectation :: Task Failure a}
  deriving (Prelude.Functor, Prelude.Applicative, Prelude.Monad)

-- | A @Fuzzer a@ knows how to produce random values of @a@ and how to "shrink"
-- a value of @a@, that is turn a value into another that is slightly simpler.
newtype Fuzzer a = Fuzzer {unFuzzer :: Hedgehog.Gen a}
  deriving (Prelude.Functor, Prelude.Applicative)

-- | Apply a description to a list of tests.
--
-- > import Test (describe, test, fuzz)
-- > import Fuzz (int)
-- > import Expect
-- >
-- > describe "List"
-- >     [ describe "reverse"
-- >         [ test "has no effect on an empty list" <|
-- >             \_ ->
-- >                 List.reverse []
-- >                     |> Expect.equal []
-- >         , fuzz int "has no effect on a one-item list" <|
-- >             \num ->
-- >                  List.reverse [ num ]
-- >                     |> Expect.equal [ num ]
-- >         ]
-- >     ]
--
-- Passing an empty list will result in a failing test, because you either made a
-- mistake or are creating a placeholder.
describe :: Text -> [Test] -> Test
describe description tests =
  tests
    |> List.concatMap unTest
    |> List.map (\test' -> test' {describes = description : describes test'})
    |> Test

-- | Returns a 'Test' that is "todo" (not yet implemented). These tests always
-- fail.
--
-- These tests aren't meant to be committed to version control. Instead, use
-- them when you're brainstorming lots of tests you'd like to write, but you
-- can't implement them all at once. When you replace @todo@ with a real test,
-- you'll be able to see if it fails without clutter from tests still not
-- implemented. But, unlike leaving yourself comments, you'll be prompted to
-- implement these tests because your suite will fail.
--
-- > describe "a new thing"
-- >     [ todo "does what is expected in the common case"
-- >     , todo "correctly handles an edge case I just thought of"
-- >     ]
--
-- This functionality is similar to "pending" tests in other frameworks, except
-- that a todo test is considered failing but a pending test often is not.
todo :: Stack.HasCallStack => Text -> Test
todo name =
  Test
    [ SingleTest
        { describes = [],
          name = name,
          loc = Stack.withFrozenCallStack getFrame,
          label = Todo,
          body = Expectation (Task.succeed ())
        }
    ]

-- | Return a 'Test' that evaluates a single
-- 'Expect.Expectation'
--
-- > import Test (fuzz)
-- > import Expect
-- > test "the empty list has 0 length" <|
-- >     \_ ->
-- >         List.length []
-- >             |> Expect.equal 0
test :: Stack.HasCallStack => Text -> (() -> Expectation) -> Test
test name expectation =
  Test
    [ SingleTest
        { describes = [],
          name = name,
          loc = Stack.withFrozenCallStack getFrame,
          label = None,
          body = handleUnexpectedErrors (expectation ())
        }
    ]

-- | Take a function that produces a test, and calls it several (usually 100)
-- times, using a randomly-generated input from a 'Fuzzer' each time. This
-- allows you to test that a property that should always be true is indeed true
-- under a wide variety of conditions. The function also takes a string
-- describing the test.
--
-- These are called "fuzz tests" because of the randomness. You may find them
-- elsewhere called property-based tests, generative tests, or QuickCheck-style
-- tests.
fuzz :: (Stack.HasCallStack, Show a) => Fuzzer a -> Text -> (a -> Expectation) -> Test
fuzz fuzzer name expectation =
  Test
    [ SingleTest
        { describes = [],
          name = name,
          loc = Stack.withFrozenCallStack getFrame,
          label = None,
          body = fuzzBody fuzzer expectation
        }
    ]

-- | Run a fuzz test using two random inputs.
fuzz2 :: (Stack.HasCallStack, Show a, Show b) => Fuzzer a -> Fuzzer b -> Text -> (a -> b -> Expectation) -> Test
fuzz2 (Fuzzer genA) (Fuzzer genB) name expectation =
  Test
    [ SingleTest
        { describes = [],
          name = name,
          loc = Stack.withFrozenCallStack getFrame,
          label = None,
          body =
            fuzzBody
              (Fuzzer (map2 (,) genA genB))
              (\(a, b) -> expectation a b)
        }
    ]

-- | Run a fuzz test using three random inputs.
fuzz3 :: (Stack.HasCallStack, Show a, Show b, Show c) => Fuzzer a -> Fuzzer b -> Fuzzer c -> Text -> (a -> b -> c -> Expectation) -> Test
fuzz3 (Fuzzer genA) (Fuzzer genB) (Fuzzer genC) name expectation =
  Test
    [ SingleTest
        { describes = [],
          name = name,
          loc = Stack.withFrozenCallStack getFrame,
          label = None,
          body =
            fuzzBody
              (Fuzzer (map3 (,,) genA genB genC))
              (\(a, b, c) -> expectation a b c)
        }
    ]

fuzzBody :: Show a => Fuzzer a -> (a -> Expectation) -> Expectation
fuzzBody (Fuzzer gen) expectation = do
  Expectation
    <| Platform.Internal.Task
      ( \_log -> do
          -- For the moment we're not recording traces in fuzz tests. Because
          -- the test body runs a great many times, we'd record a ton of data
          -- that's not all that useful.
          --
          -- Ideally we'd only keep the recording of the most significant run,
          -- but we have to figure out how to do that first.
          silentLog <- Platform.silentHandler
          seed <- Hedgehog.Internal.Seed.random
          failureRef <- IORef.newIORef Nothing
          hedgehogResult <-
            Hedgehog.Internal.Runner.checkReport
              Hedgehog.Internal.Property.defaultConfig
              0 -- Same value used as in Hedgehog internals.
              seed
              ( do
                  generated <- Hedgehog.forAll gen
                  result <-
                    expectation generated
                      |> handleUnexpectedErrors
                      |> unExpectation
                      |> Task.map Ok
                      |> Task.onError (Task.succeed << Err)
                      |> Task.perform silentLog
                      |> Control.Monad.IO.Class.liftIO
                  case result of
                    Ok () -> Prelude.pure ()
                    Err failure -> do
                      IORef.writeIORef failureRef (Just failure)
                        |> Control.Monad.IO.Class.liftIO
                      Hedgehog.failure
              )
              (\_ -> Prelude.pure ())
          case Hedgehog.Internal.Report.reportStatus hedgehogResult of
            Hedgehog.Internal.Report.Failed _ -> do
              maybeFailure <- IORef.readIORef failureRef
              case maybeFailure of
                Nothing ->
                  TestRunnerMessedUp "I lost the error report of a failed fuzz test test."
                    |> Err
                    |> Prelude.pure
                Just failure ->
                  Err failure
                    |> Prelude.pure
            Hedgehog.Internal.Report.GaveUp ->
              TestRunnerMessedUp "I couldn't generate any values for a fuzz test."
                |> Err
                |> Prelude.pure
            Hedgehog.Internal.Report.OK ->
              Ok ()
                |> Prelude.pure
      )

-- | Returns a 'Test' that gets skipped.
--
-- Calls to @skip@ aren't meant to be committed to version control. Instead,
-- use it when you want to focus on getting a particular subset of your tests
-- to pass. If you use @skip@, your entire test suite will fail, even if each
-- of the individual tests pass. This is to help avoid accidentally committing
-- a @skip@ to version control.
--
-- See also 'only'. Note that @skip@ takes precedence over @only@; if you use a
-- @skip@ inside an @only@, it will still get skipped, and if you use an @only@
-- inside a @skip@, it will also get skipped.
--
-- > describe "List"
-- >     [ skip <|
-- >         describe "reverse"
-- >             [ test "has no effect on an empty list" <|
-- >                 \_ ->
-- >                     List.reverse []
-- >                         |> Expect.equal []
-- >             , fuzz int "has no effect on a one-item list" <|
-- >                 \num ->
-- >                     List.reverse [ num ]
-- >                         |> Expect.equal [ num ]
-- >             ]
-- >     , test "This is the only test that will get run; the other was skipped!" <|
-- >         \_ ->
-- >             List.length []
-- >                 |> Expect.equal 0
-- >     ]
skip :: Test -> Test
skip (Test tests) =
  Test <| List.map (\test' -> test' {label = Skip}) tests

-- | Returns a 'Test' that causes other tests to be skipped, and only runs the given one.
--
-- Calls to @only@ aren't meant to be committed to version control. Instead,
-- use them when you want to focus on getting a particular subset of your tests
-- to pass.  If you use @only@, your entire test suite will fail, even if each
-- of the individual tests pass. This is to help avoid accidentally committing
-- a @only@ to version control.
--
-- If you you use @only@ on multiple tests, only those tests will run. If you
-- put a @only@ inside another @only@, only the outermost @only@ will affect
-- which tests gets run. See also 'skip'. Note that @skip@ takes precedence
-- over @only@; if you use a @skip@ inside an @only@, it will still get
-- skipped, and if you use an @only@ inside a @skip@, it will also get skipped.
--
-- > describe "List"
-- >     [ only <|
-- >         describe "reverse"
-- >             [ test "has no effect on an empty list" <|
-- >                 \_ ->
-- >                     List.reverse []
-- >                         |> Expect.equal []
-- >             , fuzz int "has no effect on a one-item list" <|
-- >                 \num ->
-- >                     List.reverse [ num ]
-- >                         |> Expect.equal [ num ]
-- >             ]
-- >     , test "This will not get run, because of the @only@ above!" <|
-- >         \_ ->
-- >             List.length []
-- >                 |> Expect.equal 0
-- >     ]
only :: Test -> Test
only (Test tests) =
  Test <| List.map (\test' -> test' {label = Only}) tests

run :: Test -> Task e SuiteResult
run (Test all) = do
  let grouped = groupBy label all
  let skipped = Dict.get Skip grouped |> Maybe.withDefault []
  let todos = Dict.get Todo grouped |> Maybe.withDefault []
  let containsOnlys =
        case Dict.get Only grouped |> Maybe.withDefault [] of
          [] -> False
          _ -> True
  let doRun label =
        if containsOnlys
          then label == Only
          else label == None
  let (toRun, notToRun') =
        Dict.toList grouped
          |> List.partition (doRun << Tuple.first)
          |> Tuple.mapBoth (List.concatMap Tuple.second) (List.concatMap Tuple.second)
  let notToRun = List.map (\test' -> test' {body = NotRan}) notToRun'
  results <- Task.parallel (List.map runSingle toRun)
  let (failed, passed) =
        results
          |> List.map
            ( \test' ->
                case body test' of
                  (tracingSpan, Failed failure) ->
                    Prelude.Left test' {body = (tracingSpan, failure)}
                  (tracingSpan, Succeeded) ->
                    Prelude.Right test' {body = tracingSpan}
            )
          |> Data.Either.partitionEithers
  let summary =
        Summary
          { noTests = List.isEmpty all,
            allPassed = List.isEmpty failed,
            anyOnlys = containsOnlys,
            noneSkipped = List.isEmpty (skipped ++ todos)
          }
  Task.succeed <| case summary of
    Summary {noTests = True} -> NoTestsInSuite
    Summary {allPassed = False} -> TestsFailed passed notToRun failed
    Summary {anyOnlys = True} -> OnlysPassed passed notToRun
    Summary {noneSkipped = False} -> PassedWithSkipped passed notToRun
    Summary {} -> AllPassed passed

data Summary = Summary
  { noTests :: Bool,
    allPassed :: Bool,
    anyOnlys :: Bool,
    noneSkipped :: Bool
  }

handleUnexpectedErrors :: Expectation -> Expectation
handleUnexpectedErrors (Expectation task') =
  task'
    |> onException (Task.fail << ThrewException)
    |> Task.timeout 10_000 TookTooLong
    |> Task.onError Task.fail
    |> Expectation

runSingle :: SingleTest Expectation -> Task e (SingleTest (TracingSpan, TestResult))
runSingle test' =
  Platform.Internal.Task
    ( \_ -> do
        spanVar <- MVar.newEmptyMVar
        res <-
          Platform.Internal.rootTracingSpanIO
            ""
            (MVar.putMVar spanVar)
            "test"
            ( \log ->
                body test'
                  |> unExpectation
                  |> Task.map Ok
                  |> Task.onError (Task.succeed << Err)
                  |> Task.perform log
            )
        let testRest =
              case res of
                Ok () -> Succeeded
                -- If you remove this branch, consider also removing the
                -- -fno-warn-overlapping-patterns warning above.
                Err err -> Failed err
        span' <- MVar.takeMVar spanVar
        let span =
              span'
                { Platform.Internal.summary = Just (name test'),
                  Platform.Internal.frame = map (\loc -> ("", loc)) (loc test'),
                  Platform.Internal.succeeded = case testRest of
                    Succeeded -> Platform.Internal.Succeeded
                    Failed failure ->
                      Exception.toException failure
                        |> Platform.Internal.FailedWith
                }
        test' {body = (span, testRest)}
          |> Ok
          |> Prelude.pure
    )

ioToTask :: Prelude.IO a -> Task Exception.SomeException a
ioToTask io =
  Platform.Internal.Task <| \_ ->
    Exception.handleAny (Prelude.pure << Err) (map Ok io)

onException :: (Exception.SomeException -> Task e a) -> Task e a -> Task e a
onException f (Platform.Internal.Task run') =
  Platform.Internal.Task
    ( \log ->
        run' log
          |> Exception.handleAny (Task.attempt log << f)
    )

getFrame :: Stack.HasCallStack => Maybe Stack.SrcLoc
getFrame =
  Stack.callStack
    |> Stack.getCallStack
    |> List.head
    |> map Tuple.second

groupBy :: Ord key => (a -> key) -> [a] -> Dict.Dict key [a]
groupBy key xs =
  List.foldr
    ( \x acc ->
        Dict.update
          (key x)
          ( \val ->
              Just
                <| case val of
                  Nothing -> [x]
                  Just ys -> x : ys
          )
          acc
    )
    Dict.empty
    xs

append :: Expectation -> Expectation -> Expectation
append (Expectation task1) (Expectation task2) =
  Expectation <| do
    task1
    task2

-- Assertion constructors
-- All exposed assertion functions should call these functions internally and
-- never each other, to ensure a single unnested 'expectation' entry from
-- appearing in log-explorer traces.

pass :: Stack.HasCallStack => Text -> a -> Expectation' a
pass name a = Stack.withFrozenCallStack traceExpectation name (Task.succeed a)

failAssertion :: Stack.HasCallStack => Text -> Text -> Expectation' a
failAssertion name err =
  FailedAssertion err (Stack.withFrozenCallStack getFrame)
    |> Task.fail
    |> Stack.withFrozenCallStack traceExpectation name

traceExpectation :: Stack.HasCallStack => Text -> Task Failure a -> Expectation' a
traceExpectation name task =
  Stack.withFrozenCallStack
    Platform.tracingSpan
    name
    task
    |> Expectation