KML.hs

{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances, EmptyDataDecls #-}
-- |Author: Thomas DuBuisson
-- Copyright: Thomas DuBuisson
-- License: BSD3
module Data.GPS.KML
	(  -- * KML Operations (Open format used by GoogleEarth, among others)
	  KML
	, trailToKML
	, pointsToKML
	, kmlToString
	) where

import Text.XML.Light
import Data.GPS

-- |The KML type and operations might be moved into a Data.KML module in the future
type KML = Element

-- |Converts the KML elements to a string and prepends the proper XML header,
-- thus making it the correct format for saving as a file and opening it
-- with other programs such as GoogleEarth.
kmlToString :: KML -> String
kmlToString = (++) xml_header . ppElement

kmlTop = Element (QName "kml" Nothing Nothing) [Attr (basicName "xmlns") "http://www.opengis.net/kml/2.2"] [] Nothing

addElem :: Element -> Element -> Element
addElem top child = top { elContent = Elem child : elContent top }

basicName :: String -> QName
basicName n = QName n Nothing Nothing

basicElem :: String -> Element
basicElem n = Element (basicName n) [] [] Nothing

filledElem :: String -> String -> Element
filledElem name val = Element (basicName name) [] [Text (CData CDataText val Nothing)] Nothing

-- |converts a given set of coordinates to a trail in KML format.
-- Useful for saving as a file.
trailToKML :: Coordinate a => String -> Trail a -> KML
trailToKML name ps = addElem kmlTop doc
 where
  doc = foldl addElem (basicElem "Document") (nameElem : trailElem : [])
  nameElem = filledElem "name" name
  trailName = filledElem "name" (name ++ " trail")
  trailElem = foldl addElem (basicElem "Placemark") [trailName, pointsElem]
  pointsElem = addElem (basicElem "LineString") (filledElem "coordinates" points)
  points :: String
  points = concatMap packCoordinate ps
  packCoordinate :: Coordinate a => a -> String
  packCoordinate x =
	let (lat, lon) = getDegreeLatLon x
	in concat [lon, ",", lat, ",0 "]

-- |converts a given set of coordinates to points in KML format.
-- Useful for saving as a file.
pointsToKML :: Coordinate a => String -> [a] -> [String] -> KML
pointsToKML name ps pointNames = addElem kmlTop doc
 where
  doc = foldl addElem (basicElem "Document") (nameElem : placemarkElems)
  nameElem = filledElem "name" name
  placemarkElems = map buildPoint (zip ps pointNames)
  buildPoint (p,n) =
	let (t,g) = getDegreeLatLon p
	in foldl addElem (basicElem "Placemark")
	[ filledElem "name" n
	, foldl addElem (basicElem "LookAt")
		[ filledElem "longitude" g
		, filledElem "latitude" t
		, filledElem "altitude" "0"
		, filledElem "range" "500"
		]
	, addElem (basicElem "Point") (filledElem "coordinates" (g ++ "," ++ t))
	]

-- |Gets a pair of lat lon bytestrings (in degrees)
getDegreeLatLon :: Coordinate a => a -> (String,String)
getDegreeLatLon x =
	let (lat,lon) = dmsToRadianPair . toDMS $ x
	    f = show . (*) (180 / pi)
	in (f lat, f lon)