use Test Success Status Report Test Scope
use Test.Status Failed Expected Unexpected Pending
use Test.Success Passed Proved
use Test.Report Report
use Test.Test Test
use Test passed proved failed expected unexpected pending finished label
use Test.Scope Scope
use List flatMap

type Test.Success = Passed Nat | Proved

type Test.Status = Failed
                 | Expected Test.Success
                 | Unexpected Test.Success
                 | Pending

-- Current scope together with accumulated test report.
type Test.Report = Report (Trie Text Test.Status)

type Test.Test = Test (Test.Scope -> Test.Report)

unique type Test.Scope = Scope [Text]

foldSuccess : (Nat -> r) -> r -> Success -> r
foldSuccess passed proved = cases
  Passed n -> passed n
  Proved -> proved

foldStatus : r -> (Success -> r) -> (Success -> r) -> r -> Status -> r
foldStatus failed expected unexpected pending = cases
  Failed -> failed
  Expected s -> expected s
  Unexpected s -> unexpected s
  Pending -> pending

foldReport : (Trie Text Test.Status -> r) -> Report -> r
foldReport k r = case r of Report t -> k t

foldScope : ([Text] -> r) -> Scope -> r
foldScope k = cases Scope ss -> k ss

Scope.cons : Text -> Scope -> Scope
Scope.cons n = foldScope (Scope . List.cons n)

-- Basic building blocks of tests
Test.finished : Status -> Test
Test.finished st =
  Test (Report . foldScope (sc -> Trie.singleton sc st))

Test.failed : Test
Test.failed = finished Failed

Test.proved : Test
Test.proved = finished <| Expected Proved

Test.passed : Test
Test.passed = finished . Expected <| Passed 1

Test.passedUnexpectedly : Test
Test.passedUnexpectedly = finished . Unexpected <| Passed 1

Test.provedUnexpectedly : Test
Test.provedUnexpectedly = finished <| Unexpected Proved

-- Basic test combinators

Test.modifyStatus : (Status -> Status) -> Test -> Test
Test.modifyStatus f =
  cases Test k -> Test (foldReport (Report . map f) . k)

Test.label : Text -> Test -> Test
Test.label n = cases
  Test.Test.Test k -> Test (scope -> k <| Scope.cons n scope)

use Test.Report combine

(Test.&&) : Test -> Test -> Test
(Test.&&) a b = match (a,b) with
  (Test k1, Test k2) ->
    Test (
      scope ->
        let r1 = k1 scope
            r2 = k2 scope
            combine r1 r2)

Test.passedWith : Text -> Test
Test.passedWith m = label m passed

Test.provedWith : Text -> Test
Test.provedWith m = label m proved

Test.failedWith : Text -> Test
Test.failedWith m = Test.label m Test.failed

-- Report combinators

Test.Report.combine : Report -> Report -> Report
Test.Report.combine r1 r2 = match (r1, r2) with
  (Test.Report.Report t1, Test.Report.Report t2) ->
    Report <| Trie.unionWith Status.combine t1 t2

Test.Report.empty : Report
Test.Report.empty = Report empty

Test.Report.toCLIResult : Report -> [Test.Result]
Test.Report.toCLIResult r =
  descend scope = cases (k, t) ->
    go ((if scope != "" then (scope ++ ".") else "") ++ k) t
  convert : Text -> Test.Status -> Test.Result
  convert scope = cases
    Test.Status.Failed -> Test.Result.Fail scope
    Test.Status.Expected (Test.Success.Passed n) ->
      Test.Result.Ok (scope ++ " : Passed " ++ Nat.toText n ++ " tests.")
    Test.Status.Expected (Test.Success.Proved) ->
      Test.Result.Ok (scope ++ " : Proved.")
  go : Text -> Trie Text Test.Status -> [Test.Result]
  go scope t =
    rest = flatMap (descend scope) (Map.toList (tail t))
    match head t with
      Optional.Some status ->
        cons (convert scope status) rest
      Optional.None -> rest
  match r with Test.Report.Report t -> go "" t

Test.report : Test -> Report
Test.report = cases Test k -> k (Scope [])

-- Running tests

Test.run : Test -> [Test.Result]
Test.run = Test.Report.toCLIResult . Test.report

Test.runAll : [Test] -> [Test.Result]
Test.runAll = flatMap Test.run

-- Status combinators

Status.combine : Test.Status -> Test.Status -> Test.Status
Status.combine s1 s2 = match (s1, s2) with
  (_, Pending) -> Pending
  (Pending, _) -> Pending
  (Failed, _) -> Failed
  (_, Failed) -> Failed
  (Unexpected a, Unexpected b) -> Unexpected (Success.combine a b)
  (Unexpected a, _) -> Unexpected a
  (_, Unexpected b) -> Unexpected b
  (Expected a, Expected b) -> Expected (Success.combine a b)


Status.pending : Test.Status -> Test.Status
Status.pending = cases
  Failed -> Pending
  Expected s -> Unexpected s
  Unexpected s -> Pending
  Pending -> Pending

-- Make a test pending
Test.pending : Test -> Test
Test.pending = modifyStatus Status.pending

Test.modifyScope : (Scope -> Scope) -> Test -> Test
Test.modifyScope f = cases Test k -> Test (k . f)

Success.combine s1 s2 = match (s1, s2) with
  (Passed n, Passed m) -> Passed (n + m)
  (Passed n, Proved) -> Passed n
  (Proved, Passed n) -> Passed n
  (Proved, Proved) -> Proved

-- Test case generation

-- A domain is either small, in which case we can exhaustively list all the
-- values in the domain, or it's large, in which case we can ask for a value
-- of a particular size.
type Domain a = Small [a] | Large (Weighted a)

-- The domain of natural numbers is large.
Domain.nats : Domain Nat
Domain.nats = Large Weighted.nats

-- The domain of all integers
Domain.ints : Domain Int
Domain.ints = let
  go n = yield n <|> weight 1
          '(go (if n > +0 then negate n else increment (negate n)))
  Large (List.foldl (a n -> a <|> yield n)
                    Weighted.Fail
                    [+0, +1, -1, maxInt, minInt] <|> go +2)

use Universal == < >

namespace Domain where

  -- The threshold of "small" domains.
  smallSize = 10000

  -- The Boolean domain is small
  boolean : Domain Boolean
  boolean = Small [false, true]

  -- The domain of lists of arbitrary data is large
  listsOf : Domain a -> Domain [a]
  listsOf d =
    Large (Weighted.lists match d with
      Domain.Small as -> Weighted.fromList as
      Domain.Large w -> w)

  lists : Domain [()]
  lists = Domain.listsOf (Small [()])

  sample : Nat -> Domain a -> [a]
  sample n = cases
    Domain.Large w -> Weighted.sample n w
    Domain.Small xs -> take n xs

  map : (a -> b) -> Domain a -> Domain b
  map f = cases
    Domain.Large w -> Domain.Large (Weighted.map f w)
    Domain.Small as -> Domain.Small (List.map f as)

  pairs : Domain a -> Domain (a,a)
  pairs d = lift2 (a b -> (a,b)) d d

  tuples : Domain a -> Domain b -> Domain (Pair a b)
  tuples = lift2 (a b -> Pair a b)

  lift2 : (a -> b -> c) -> Domain a -> Domain b -> Domain c
  lift2 f da db = let
    wa = weighted da
    wb = weighted db
    wc = mergeWith (a1 a2 -> f a1 a2) wa wb
    match (da, db) with
      (Domain.Small as, Domain.Small bs) | size as + size bs < smallSize ->
        Small (Weighted.sample smallSize wc)
      _ -> Large wc

  weighted : Domain a -> Weighted a
  weighted = cases
    Domain.Small as -> Weighted.fromList as
    Domain.Large w -> w

-- Test a property for a given domain up to a maximum size
Test.forAll' : Nat -> Domain a -> (a -> Boolean) -> Test
Test.forAll' maxSize domain property =
  check xs s =
    List.map (
      cases (c, i) ->
             if property c then finished (Expected s)
             else label ("test case " ++ Nat.toText i) (finished Failed)
                 ) (indexed xs)
  List.foldb id (Test.&&) proved <|
    match domain with
      Domain.Small xs -> check (take maxSize xs) Proved
      Domain.Large _ -> check (sample maxSize domain) (Passed 1)

Test.check' : Boolean -> Test
Test.check' b = if b then Test.proved else Test.failed

Test.forAll : Nat -> Domain a -> (a -> Boolean) -> [Test.Result]
Test.forAll n d p = Test.run (Test.forAll' n d p)

Test.check : Boolean -> [Test.Result]
Test.check = Test.run . Test.check'