48 lines
1.5 KiB
Haskell
48 lines
1.5 KiB
Haskell
{-# LANGUAGE NamedFieldPuns #-}
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module PDF.Update (
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unify
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) where
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import Data.Map (member)
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import qualified Data.Map as Map (empty, union)
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import PDF.Object (
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Content(..), IndexedObjects, IndirectObjCoordinates(..), Occurrence(..)
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, Structure(..)
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)
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emptyContent :: Content
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emptyContent = Content {
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docStructure = Structure {xRef = Map.empty, trailer = Map.empty}
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, objects = Map.empty
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, occurrences = []
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}
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unify :: [Content] -> Content
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unify = foldl complete emptyContent
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where
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complete tmpContent older =
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let mergedObjects = Map.union (objects tmpContent) (objects older) in
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Content {
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docStructure =
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unifyDocStructure (docStructure tmpContent) (docStructure older)
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, objects = mergedObjects
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, occurrences =
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unifyOccurrences mergedObjects (occurrences tmpContent) (occurrences older)
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}
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unifyDocStructure :: Structure -> Structure -> Structure
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unifyDocStructure update original = Structure {
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xRef = Map.union (xRef update) (xRef original)
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, trailer = Map.union (trailer update) (trailer original)
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}
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unifyOccurrences :: IndexedObjects -> [Occurrence] -> [Occurrence] -> [Occurrence]
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unifyOccurrences objects update = foldr addOlder update
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where
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addOlder occurrence@(Comment _) existing = occurrence : existing
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addOlder occurrence@(Indirect indirect) existing =
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if objectId indirect `member` objects
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then occurrence : existing
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else existing
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