diff --git a/CHANGELOG.md b/CHANGELOG.md
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+++ b/CHANGELOG.md
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+Changelog
+
+# 1.0.0 (2025-07-28)
+
+
+### Bug Fixes
+
+* fix date parser with day short names ([64f3229](https://github.com/drlkf/megaparsec-utils/commit/64f3229dcfd660bdd770938da0bbacbf84c02dc3))
+* fix invalid generation of TimeOfDay ([6bc728e](https://github.com/drlkf/megaparsec-utils/commit/6bc728ea31e2cfb380927c53ee544f44b399ece7))
+* fix type errors in boundedEnumShowParser ([9c0fe3d](https://github.com/drlkf/megaparsec-utils/commit/9c0fe3db132bfe123be2d71e7c92f5928113cc26))
+
+
+### Features
+
+* add aeson parser transformer ([84857eb](https://github.com/drlkf/megaparsec-utils/commit/84857eb2d5221f8547e9130c2b8503e7e59888a4))
+* add date parser ([357d03f](https://github.com/drlkf/megaparsec-utils/commit/357d03f265e053f128be8711aec53e0b7659e563))
+* add duration parsers ([a89bd88](https://github.com/drlkf/megaparsec-utils/commit/a89bd885b867b65cb7db3fcad4635cd38cba2227))
+* add gregorian day parser ([46d4178](https://github.com/drlkf/megaparsec-utils/commit/46d4178945ad8bff5b309b95d9a2901a53b60ef9))
+* add parser for decimal numbers ([42de75f](https://github.com/drlkf/megaparsec-utils/commit/42de75fec47b29caf1de59334b7a9c5e05f87a2f))
+* add time parsers ([f267ffd](https://github.com/drlkf/megaparsec-utils/commit/f267ffd718f701046965318f99aa73b7f9e7b335))
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+ END OF TERMS AND CONDITIONS
+
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+
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+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
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+to attach them to the start of each source file to most effectively
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+ (at your option) any later version.
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+if any, to sign a "copyright disclaimer" for the program, if necessary.
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+.
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+into proprietary programs. If your program is a subroutine library, you
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diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,17 @@
+# megaparsec-utils
+Utilities to use on top of the
+[Megaparsec](https://hackage.haskell.org/package/megaparsec) library.
+
+# Running tests
+Make sure your build passes tests using [Stack](https://docs.haskellstack.org/en/stable/).
+
+# Contributing
+This repository uses [Conventional
+Commits](https://www.conventionalcommits.org/en/v1.0.0/) to generate versions
+with [Semantic Release](https://github.com/semantic-release/semantic-release),
+so make sure your commits are compliant. Pull requests are rebased, not
+squashed, so make sure your commits make sense as well.
+
+It is preferrable that you format code using
+[fourmolu](https://github.com/fourmolu/fourmolu), a configuration is available
+at the root of the repository.
diff --git a/megaparsec-utils.cabal b/megaparsec-utils.cabal
new file mode 100644
--- /dev/null
+++ b/megaparsec-utils.cabal
@@ -0,0 +1,68 @@
+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.37.0.
+--
+-- see: https://github.com/sol/hpack
+
+name: megaparsec-utils
+version: 0.1.0.0
+synopsis: Parsers and utilities for the Megaparsec library.
+description: Common parsers and utilities to use with the Megaparsec library.
+category: Parsing
+homepage: https://github.com/drlkf/megaparsec-utils
+bug-reports: https://github.com/drlkf/megaparsec-utils/issues
+author: drlkf
+maintainer: drlkf@drlkf.net
+copyright: 2024 drlkf
+license: GPL-3
+license-file: LICENSE
+build-type: Simple
+tested-with:
+ GHC == 9.8
+ , GHC == 9.6
+ , GHC == 9.4
+extra-source-files:
+ README.md
+ CHANGELOG.md
+
+source-repository head
+ type: git
+ location: https://github.com/drlkf/megaparsec-utils
+
+library
+ exposed-modules:
+ Text.Megaparsec.Utils
+ other-modules:
+ Paths_megaparsec_utils
+ hs-source-dirs:
+ src
+ ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
+ build-depends:
+ aeson >=2.0 && <3
+ , base >=4.7 && <5
+ , megaparsec >=9.0 && <10
+ , parser-combinators >=1.0 && <2
+ , text >=2.0 && <3
+ , uuid >=1.3 && <2
+ default-language: Haskell2010
+
+test-suite megaparsec-utils-test
+ type: exitcode-stdio-1.0
+ main-is: Spec.hs
+ other-modules:
+ Text.Megaparsec.UtilsSpec
+ Paths_megaparsec_utils
+ hs-source-dirs:
+ test
+ ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+ build-depends:
+ QuickCheck
+ , aeson >=2.0 && <3
+ , base >=4.7 && <5
+ , hspec
+ , megaparsec >=9.0 && <10
+ , megaparsec-utils
+ , parser-combinators >=1.0 && <2
+ , text >=2.0 && <3
+ , uuid >=1.3 && <2
+ default-language: Haskell2010
diff --git a/src/Text/Megaparsec/Utils.hs b/src/Text/Megaparsec/Utils.hs
new file mode 100644
--- /dev/null
+++ b/src/Text/Megaparsec/Utils.hs
@@ -0,0 +1,167 @@
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeFamilies #-}
+
+-- |
+-- Module : Text.Megaparsec.Utils
+-- Description : Various generic parsers and combinators.
+-- Copyright : (c) drlkf, 2024
+-- License : GPL-3
+-- Maintainer : drlkf@drlkf.net
+-- Stability : experimental
+module Text.Megaparsec.Utils (
+ boolParser,
+ boundedEnumShowParser,
+ commaSeparated,
+ numParser,
+ occurrence,
+ occurrences,
+ parsecToJSONParser,
+ parsecToReadsPrec,
+ posDecNumParser,
+ posNumParser,
+ uuidParser,
+) where
+
+import Control.Applicative (many, some, (<|>))
+import Control.Applicative.Combinators (choice)
+import Control.Monad (replicateM)
+import Control.Monad.Combinators (optional)
+import Data.Aeson.Types (Parser, Value, withText)
+import Data.Functor (($>))
+import Data.List (intercalate, sortOn)
+import Data.List.NonEmpty (NonEmpty ((:|)))
+import Data.Maybe (fromJust)
+import qualified Data.Text as T (unpack)
+import Data.UUID (UUID)
+import qualified Data.UUID as U (fromString)
+import Text.Megaparsec (
+ Parsec,
+ ShowErrorComponent,
+ anySingle,
+ errorBundlePretty,
+ runParser,
+ try,
+ )
+import Text.Megaparsec.Char (
+ char,
+ digitChar,
+ hexDigitChar,
+ string',
+ )
+import Text.Read (readMaybe)
+
+-- | Parse a case-insensitive human-readable boolean, including C-style numbers
+-- and English yes-no.
+boolParser
+ :: Ord e
+ => Parsec e String Bool
+boolParser = true <|> false
+ where
+ true = True <$ choice (map string' ["true", "y", "yes", "1"])
+ false = False <$ choice (map string' ["false", "n", "no", "0"])
+
+-- | Parse a 'Bounded' 'Enum' type that has a 'Show' instance, trying all
+-- possibilities, case-insensitive, in the 'Enum' order.
+boundedEnumShowParser
+ :: forall a e
+ . Ord e
+ => Bounded a
+ => Enum a
+ => Show a
+ => Parsec e String a
+boundedEnumShowParser =
+ choice . map parseShow $ sortOn (negate . length . show) [(minBound :: a) ..]
+ where
+ parseShow a = string' (show a) $> a
+
+-- | Parse a comma-separated list of items.
+commaSeparated
+ :: Ord e
+ => Parsec e String a
+ -> Parsec e String (NonEmpty a)
+commaSeparated p = (:|) <$> p <*> many (char ',' >> p)
+
+-- | Parse any occurrence of a given parser. Consumes any input before occurrence.
+occurrence
+ :: Ord e
+ => Parsec e String a
+ -> Parsec e String a
+occurrence p = go
+ where
+ go = p <|> (anySingle >> go)
+
+-- | Parse all occurrences of a given parser.
+occurrences
+ :: Ord e
+ => Parsec e String a
+ -> Parsec e String [a]
+occurrences = some . try . occurrence . try
+
+-- | Parse a positive number, with or without decimals prefixed by a @.@.
+posDecNumParser
+ :: Ord e
+ => Read a
+ => Parsec e String a
+posDecNumParser = do
+ num <- some digitChar
+ dec <- maybe "" ("." <>) <$> optional (char '.' >> some digitChar)
+
+ let str = num <> dec
+
+ maybe (fail ("could not read from input: " <> str)) pure (readMaybe str)
+
+-- | Parse a positive integer.
+posNumParser
+ :: Ord e
+ => Read a
+ => Parsec e String a
+posNumParser = do
+ digits <- some digitChar
+ maybe
+ (fail ("could not read from digits: " <> digits))
+ pure
+ (readMaybe digits)
+
+-- | Parse an integer, without any space between minus sign and digits.
+numParser
+ :: Ord e
+ => Num a
+ => Read a
+ => Parsec e String a
+numParser = (char '-' >> negate <$> posNumParser) <|> posNumParser
+
+-- | Convert a 'Parsec' parser into a 'Parser' suited for 'Data.Aeson.FromJSON'
+-- instances.
+parsecToJSONParser
+ :: ShowErrorComponent e
+ => String
+ -- ^ Parser name.
+ -> Parsec e String a
+ -- ^ Parser.
+ -> (Value -> Parser a)
+parsecToJSONParser n p =
+ withText n (either (fail . errorBundlePretty) pure . runParser p n . T.unpack)
+
+-- | Convert a 'Parsec' parser into a 'ReadS' parser. Useful for defining 'Read'
+-- instances with 'Text.Megaparsec'.
+parsecToReadsPrec
+ :: Parsec e String a
+ -> ReadS a
+parsecToReadsPrec p = either (const []) (\x -> [(x, "")]) . runParser p "string"
+
+-- | Parse a RFC4122-compliant UUID.
+uuidParser
+ :: Ord e
+ => Parsec e String UUID
+uuidParser = do
+ part1 <- replicateM 8 hexDigitChar <* char '-'
+ part2 <- replicateM 4 hexDigitChar <* char '-'
+ part3 <- replicateM 4 hexDigitChar <* char '-'
+ part4 <- replicateM 4 hexDigitChar <* char '-'
+ part5 <- replicateM 12 hexDigitChar
+
+ pure
+ (fromJust
+ (U.fromString
+ (intercalate "-" [part1, part2, part3, part4, part5])))
diff --git a/test/Spec.hs b/test/Spec.hs
new file mode 100644
--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1,2 @@
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}
+{-# OPTIONS_GHC -Wno-missing-export-lists #-}
diff --git a/test/Text/Megaparsec/UtilsSpec.hs b/test/Text/Megaparsec/UtilsSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Text/Megaparsec/UtilsSpec.hs
@@ -0,0 +1,251 @@
+{-# LANGUAGE TypeApplications #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
+
+module Text.Megaparsec.UtilsSpec (
+ spec,
+) where
+
+import Control.Applicative (some)
+import Control.Applicative.Combinators (choice)
+import Control.Monad (void)
+import Data.Bifunctor (first)
+import Data.Char (isAlphaNum, toUpper)
+import Data.Either (isLeft)
+import Data.List (intercalate)
+import Data.List.NonEmpty (NonEmpty ((:|)))
+import qualified Data.List.NonEmpty as N (toList)
+import Data.Void (Void)
+import Test.Hspec (
+ Expectation,
+ Spec,
+ SpecWith,
+ context,
+ describe,
+ it,
+ shouldBe,
+ shouldSatisfy,
+ )
+import Test.QuickCheck (
+ Arbitrary (..),
+ Gen,
+ elements,
+ forAll,
+ listOf,
+ listOf1,
+ property,
+ suchThat,
+ )
+import Text.Megaparsec (
+ Parsec,
+ eof,
+ errorBundlePretty,
+ parseMaybe,
+ runParser,
+ )
+import Text.Megaparsec.Char (
+ alphaNumChar,
+ char,
+ digitChar,
+ string,
+ )
+import Text.Megaparsec.Utils (
+ boundedEnumShowParser,
+ commaSeparated,
+ numParser,
+ occurrence,
+ occurrences,
+ posDecNumParser,
+ posNumParser,
+ )
+import Text.Printf (printf)
+
+newtype SomeData = SomeData Int
+ deriving Eq
+
+instance Show SomeData where
+ show (SomeData i) = show i
+
+instance Arbitrary SomeData where
+ arbitrary = SomeData . abs <$> arbitrary
+
+someDataParser :: Parsec Void String SomeData
+someDataParser = SomeData . read <$> some digitChar
+
+data SomeEnum
+ = SomeA
+ | SomeB
+ | SomeC
+ deriving (Eq, Show, Enum, Bounded)
+
+instance Arbitrary SomeEnum where
+ arbitrary = elements [SomeA, SomeB, SomeC]
+
+showableParser :: Show a => a -> Parsec Void String a
+showableParser a = string (show a) >> pure a
+
+someEnumParser :: Parsec Void String SomeEnum
+someEnumParser = choice $ map showableParser [(minBound :: SomeEnum) ..]
+
+data SomeADT = SomeADT
+ { _id :: Int
+ , _name :: String
+ , _type :: SomeEnum
+ }
+ deriving Eq
+
+instance Show SomeADT where
+ show (SomeADT i n t) = intercalate "," [show i, n, show t]
+
+instance Arbitrary SomeADT where
+ arbitrary =
+ SomeADT . abs
+ <$> arbitrary
+ <*> listOf1 (arbitrary `suchThat` isAlphaNum)
+ <*> arbitrary
+
+someADTParser :: Parsec Void String SomeADT
+someADTParser = do
+ i <- read <$> some digitChar
+ void $ char ','
+ n <- some alphaNumChar
+ void $ char ','
+ SomeADT i n <$> someEnumParser
+
+input :: Arbitrary a => Gen (String, a, String)
+input =
+ (,,)
+ <$> listOf (arbitrary `suchThat` flip notElem forbiddenChars)
+ <*> arbitrary
+ <*> listOf (arbitrary `suchThat` flip notElem forbiddenChars)
+ where
+ forbiddenChars = ['0' .. '9'] ++ concatMap show [(minBound :: SomeEnum) ..]
+
+exhaustive
+ :: Show a
+ => Enum a
+ => Bounded a
+ => (a -> Expectation)
+ -> SpecWith ()
+exhaustive f = foldl1 (>>) $ mkIt <$> values
+ where
+ mkIt v = it (pad (show v)) $ f v
+ padNum = foldr (max . length . show) 0 values
+ pad s = s ++ replicate (padNum - length s) ' '
+ values = [minBound ..]
+
+instance Arbitrary a => Arbitrary (NonEmpty a) where
+ arbitrary = (:|) <$> arbitrary <*> arbitrary
+
+parseOrPrettyError
+ :: Parsec Void String a
+ -> String
+ -> Either String a
+parseOrPrettyError p = first errorBundlePretty . runParser p "test"
+
+spec :: Spec
+spec = do
+ let parseMaybe' = parseMaybe @Void
+
+ describe "parsers" $ do
+ it "SomeData" . property $ \v ->
+ parseMaybe' someDataParser (show (v :: SomeData)) `shouldBe` Just v
+
+ it "SomeEnum" . property $ \v ->
+ parseMaybe' someEnumParser (show (v :: SomeEnum)) `shouldBe` Just v
+
+ it "SomeADT" . property $ \v ->
+ parseMaybe' someADTParser (show (v :: SomeADT)) `shouldBe` Just v
+
+ context "posDecNumParser" $ do
+ it "no decimals" . property $ \v ->
+ parseMaybe' posDecNumParser (show (abs (v :: Int)))
+ `shouldBe` Just (fromIntegral (abs v))
+
+ it "decimals" . property $ \v ->
+ parseMaybe' posDecNumParser (printf "%f" (abs (v :: Double)))
+ `shouldBe` Just (abs v)
+
+ it "posNumParser" . property $ \v ->
+ parseMaybe' posNumParser (show (abs (v :: Int))) `shouldBe` Just (abs v)
+
+ it "numParser" . property $ \v ->
+ parseMaybe' numParser (show (v :: Int)) `shouldBe` Just v
+
+ describe "boundedEnumShowParser" $ do
+ context "lowercase" . exhaustive $ \v ->
+ parseMaybe' (boundedEnumShowParser <* eof) (show v) `shouldBe` Just (v :: SomeEnum)
+
+ context "uppercase" . exhaustive $ \v ->
+ parseMaybe' (boundedEnumShowParser <* eof) (map toUpper (show v))
+ `shouldBe` Just (v :: SomeEnum)
+
+ context "mixed" . exhaustive $ \v -> do
+ let capitalize i x
+ | even i = toUpper x
+ | otherwise = x
+
+ mixCase = zipWith capitalize [(0 :: Int) ..]
+ parseMaybe' (boundedEnumShowParser <* eof) (mixCase (show v))
+ `shouldBe` Just (v :: SomeEnum)
+
+ describe "occurrence" $ do
+ it "SomeData" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeData), suffix]
+ parseOrPrettyError (occurrence someDataParser) s `shouldBe` Right v
+
+ it "SomeEnum" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeEnum), suffix]
+ parseOrPrettyError (occurrence someEnumParser) s `shouldBe` Right v
+
+ it "SomeADT" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeADT), suffix]
+ parseOrPrettyError (occurrence someADTParser) s `shouldBe` Right v
+
+ describe "occurrences" $ do
+ it "SomeData" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeData), suffix]
+ parseOrPrettyError (occurrences someDataParser) s `shouldBe` Right [v]
+
+ context "SomeEnum" $ do
+ it "words" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeEnum), suffix]
+ parseOrPrettyError (occurrences someEnumParser) s `shouldBe` Right [v]
+
+ it "with partial" $
+ parseOrPrettyError (occurrences someEnumParser) "a [Some] SomeA yo"
+ `shouldBe` Right [SomeA]
+
+ it "SomeADT" . forAll input $ \(prefix, v, suffix) -> do
+ let s = unwords [prefix, show (v :: SomeADT), suffix]
+ parseOrPrettyError (occurrences someADTParser) s `shouldBe` Right [v]
+
+ describe "comma-separated" $ do
+ context "valid" $ do
+ it "single" . property $ \x -> do
+ let y = abs x
+ parseOrPrettyError (commaSeparated numParser) (show y)
+ `shouldBe` Right (y :| [] :: NonEmpty Int)
+
+ it "multiple" . property $ \xs -> do
+ let ys = fmap abs xs
+ s = intercalate "," (map show (N.toList ys))
+
+ parseOrPrettyError (commaSeparated numParser) s
+ `shouldBe` Right (ys :: NonEmpty Int)
+
+ context "invalid" $ do
+ it "empty" $
+ parseOrPrettyError (commaSeparated (numParser @Void @Int)) ""
+ `shouldSatisfy` isLeft
+
+ it "first" $
+ parseOrPrettyError (commaSeparated (numParser @Void @Int)) "test"
+ `shouldSatisfy` isLeft
+
+ it "first partially correct" $
+ parseOrPrettyError (commaSeparated ((numParser @Void @Int) <* eof)) "test"
+ `shouldSatisfy` isLeft
+
+ it "second" $
+ parseOrPrettyError (commaSeparated (numParser @Void @Int)) "test"
+ `shouldSatisfy` isLeft