src/Tools/Haskell/XML.hs

clarified signature;

{- generated by Isabelle -}

{-  Title:      Tools/Haskell/XML.hs
    Author:     Makarius
    LICENSE:    BSD 3-clause (Isabelle)

Untyped XML trees and representation of ML values.

See also "$ISABELLE_HOME/src/Pure/PIDE/xml.ML".
-}

module Isabelle.XML (Attributes, Body, Tree(..), wrap_elem, unwrap_elem, content_of)
where

import qualified Data.List as List

import Isabelle.Library
import qualified Isabelle.Properties as Properties
import qualified Isabelle.Markup as Markup
import qualified Isabelle.Buffer as Buffer


{- types -}

type Attributes = Properties.T
type Body = [Tree]
data Tree = Elem Markup.T Body | Text String


{- wrapped elements -}

wrap_elem (((a, atts), body1), body2) =
  Elem ("xml_elem", ("xml_name", a) : atts) (Elem ("xml_body", []) body1 : body2)

unwrap_elem
  (Elem ("xml_elem", ("xml_name", a) : atts) (Elem ("xml_body", []) body1 : body2)) =
  Just (((a, atts), body1), body2)
unwrap_elem _ = Nothing


{- text content -}

add_content tree =
  case unwrap_elem tree of
    Just (_, ts) -> fold add_content ts
    Nothing ->
      case tree of
        Elem _ ts -> fold add_content ts
        Text s -> Buffer.add s

content_of body = Buffer.empty |> fold add_content body |> Buffer.content


{- string representation -}

encode '<' = "&lt;"
encode '>' = "&gt;"
encode '&' = "&amp;"
encode '\'' = "&apos;"
encode '\"' = "&quot;"
encode c = [c]

instance Show Tree where
  show tree =
    Buffer.empty |> show_tree tree |> Buffer.content
    where
      show_tree (Elem (name, atts) []) =
        Buffer.add "<" #> Buffer.add (show_elem name atts) #> Buffer.add "/>"
      show_tree (Elem (name, atts) ts) =
        Buffer.add "<" #> Buffer.add (show_elem name atts) #> Buffer.add ">" #>
        fold show_tree ts #>
        Buffer.add "</" #> Buffer.add name #> Buffer.add ">"
      show_tree (Text s) = Buffer.add (show_text s)

      show_elem name atts =
        unwords (name : map (\(a, x) -> a ++ "=\"" ++ show_text x ++ "\"") atts)

      show_text = concatMap encode