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|
{-# LANGUAGE TupleSections #-}
{-|
Module : Text.Edifact.Parsing.Combinators
Description : High level combinators
-}
module Text.Edifact.Parsing.Combinators
( -- * Combinators
-- ** Values parsers
message
, segmentGroup
, segment
, composite
, simple
-- ** Position and strictness
, position
, (.@)
, (@.)
, mandatory
, optional
-- ** Repetition of segments and segment groups
, repeated
, repeatedAtLeastOnce
, once
, maybeOnce
) where
import Text.Edifact.Parsing.Commons
import Text.Edifact.Types
import Text.Parsec (lookAhead, many1, optionMaybe,
string, try)
import qualified Text.Parsec as P (many)
-- | Parses a 'Message'.
--
-- > messageABCDEF :: Parser Value
-- > messageABCDEF =
-- > let simple1234 = simple "1234" (alphaNumeric `upTo` 35)
-- > c101 = composite "C101" [ position "010" (mandatory simple1234)
-- > , position "020" (optional simple1234)
-- > ]
-- > segmentABC = segment "ABC" [ position "010" (mandatory c101)
-- > ]
-- > in message "ABCDEF" [ position "0010" (mandatory segmentABC)
-- > ]
message :: MessageCode -> [Parser (Position, [Value])] -> Parser Value
message code ps =
let description = "message " <> show code
in Message code <$> sequence ps <??> description
-- | Parses a 'Group'.
--
-- A Segment Group is the way Edifact format represents hierarchy. One can view
-- a segment group as a sub message. A segment group can be repeated like
-- segments. A segment group wraps segments and segment groups.
segmentGroup :: GroupCode -> [Parser (Position, [Value])] -> Parser Value
segmentGroup code ps =
let description = "segment-group " <> show code
in Group code <$> sequence ps <??> description
-- | Parses a 'Segment'.
--
-- Following parser:
--
-- > segmentABC :: Parser Value
-- > segmentABC =
-- > let simple1234 = simple "1234" (alphaNumeric `upTo` 35)
-- > simple2001 = simple "2001" (alphaNumeric `exactly` 3)
-- > c101 = composite "C101" [ position "010" (mandatory simple1234)
-- > , position "020" (optional simple1234)
-- > , position "030" (optional simple1234)
-- > ]
-- > in segment "ABC" [ position "010" (mandatory simple2001)
-- > , position "020" (optional c101)
-- > ]
--
-- would parse strings such as:
--
-- >>> parse segmentABC "ABC+123'"
-- Segment "ABC" [ ("010", Just (Simple "2001" "123"))
-- ]
-- >>> parse segmentABC "ABC+123+abcdefgh'"
-- Segment "ABC" [ ("010", Just (Simple "2001" "123"))
-- , ("020", Just (Composite "C101" [ ("010", Just (Simple "1234" "abcdefgh"))
-- ]
-- ))
-- ]
-- >>> parse segmentABC "ABC+123+abcdefgh:ijklmno'"
-- Segment "ABC" [ ("010", Just (Simple "2001" "123"))
-- , ("020", Just (Composite "C101" [ ("010", Just (Simple "1234" "abcdefgh"))
-- , ("020", Just (Simple "1234" "ijklmno"))
-- ]
-- ))
-- ]
segment :: SegmentCode -> [Parser (Position, Maybe Value)] -> Parser Value
segment code parsers =
let go [] = [] <$ parseSegmentSeparator
go (p:ps) =
tries [ [] <$ parseSegmentSeparator
, (:) <$> (parseElementSeparator *> p)
<*> go ps
]
description = "segment " <> show code
in Segment <$> parseSegmentCode code
<*> go parsers
<??> description
parseSegmentCode :: SegmentCode -> Parser SegmentCode
parseSegmentCode (SegmentCode code) =
let description = "segment code " <> show code
in SegmentCode <$> string code <??> description
-- | Parses a 'Composite' element.
--
-- Following parser:
--
-- > compositeC101 :: Parser Value
-- > compositeC101 =
-- > let simple1234 = simple "1234" (alphaNumeric `upTo` 35)
-- > in composite "C101" [ position "010" (mandatory simple1234)
-- > , position "020" (optional simple1234)
-- > , position "030" (optional simple1234)
-- > ]
--
-- would parse strings such as:
--
-- >>> parse compositeC101 "abcdefgh"
-- Composite "C101" [ ("010", Just (Simple "1234" "abcdefgh"))
-- ]
-- >>> parse compositeC101 "abcdefgh:ijklmno"
-- Composite "C101" [ ("010", Just (Simple "1234" "abcdefgh"))
-- , ("020", Just (Simple "1234" "ijklmno"))
-- ]
-- >>> parse compositeC101 "abcdefgh::pqrstu"
-- Composite "C101" [ ("010", Just (Simple "1234" "abcdefgh"))
-- , ("020", Just (Simple "1234" ""))
-- , ("030", Just (Simple "1234" "pqrstu"))
-- ]
composite :: CompositeCode -> [Parser (Position, Maybe Value)] -> Parser Value
composite code parsers =
let go [] = pure []
go (p:ps) = do
let parseSeparator = tries [ parseCompositeSeparator
, lookAhead parseElementSeparator
, lookAhead parseSegmentSeparator
]
(value, continuation) <- tries [ (, ps) <$> p <* parseSeparator
, (, []) <$> p
]
(:) value <$> go continuation
description = "composite element " <> show code
in Composite code <$> go parsers <??> description
-- | Parses a 'Simple' element.
--
-- Following parser would parse strings of size between 0 and 35 characters.
--
-- > simple1234 :: Parser Value
-- > simple1234 = simple "1234" (alphaNumeric `upTo` 35)
simple :: SimpleCode -> Parser Primitive -> Parser Value
simple code p =
let description = "simple element " <> show code
in Simple code <$> p <??> description
-- | Makes the parsing of the element optional, which doesn't consume input if the given parser doesn't succeed.
optional :: Parser Value -> Parser (Maybe Value)
optional = optionMaybe
-- | Makes the parsing of the element mandatory.
mandatory :: Parser Value -> Parser (Maybe Value)
mandatory = fmap Just
-- | Sets the current 'Position'. This is relevant for segment in a message, for composite or simple element in a segment, and for simple element in a composite.
position :: Position -> Parser (f Value) -> Parser (Position, f Value)
position pos p =
let decorated = (pos,) <$> p
in setCurrentPosition pos *> decorated <* resetCurrentPosition
-- | Alias to 'position'.
--
-- > compositeC101 :: Parser Value
-- > compositeC101 =
-- > let simple1234 = simple "1234" (alphaNumeric `upTo` 35)
-- > in composite "C101" [ "010" .@ mandatory simple1234
-- > , "020" .@ optional simple1234
-- > , "030" .@ optional simple1234
-- > ]
(.@) :: Position -> Parser (f Value) -> Parser (Position, f Value)
(.@) = position
-- | Flipped alias to 'position'.
--
-- > compositeC101 :: Parser Value
-- > compositeC101 =
-- > let simple1234 = simple "1234" (alphaNumeric `upTo` 35)
-- > in composite "C101" [ mandatory simple1234 @. "010"
-- > , optional simple1234 @. "020"
-- > , optional simple1234 @. "030"
-- > ]
(@.) :: Parser (f Value) -> Position -> Parser (Position, f Value)
(@.) = flip position
-- | For segments or segment groups, let you express how many occurrences.
repeated :: Int -> Parser a -> Parser [a]
repeated limit p = do
values <- P.many (try p)
let parsed = length values
if parsed > limit
then failWithPosition ("expected up to " <> show limit <> " items, but encountered " <> show parsed)
else pure values
-- | For segments or segment groups, let you express how many occurrences with at least one occurrence.
repeatedAtLeastOnce :: Int -> Parser a -> Parser [a]
repeatedAtLeastOnce limit p = do
values <- many1 (try p)
let parsed = length values
if parsed > limit
then failWithPosition ("expected up to " <> show limit <> " items, but encountered " <> show parsed)
else pure values
-- | For segments or segment groups, let you express you expect only one occurrence.
once :: Parser a -> Parser [a]
once = fmap pure
-- | For segments or segment groups, let you express you expect one or no occurrence.
maybeOnce :: Parser a -> Parser [a]
maybeOnce = fmap (maybe [] pure) . optionMaybe
|
