uvmeter: new plugin showing UV data (Australia)

This patch adds a new optional plugin showing UV data for Australian
users. The data is aquired by simple HTTP request from the Australian
Radiation Protection and Nuclear Safety Agencies XML data feed.

The uvmeter plugin can be configured ovserving multiple different
station across the country. The alias now defaults to 'uv <stationid>'.

1 files changed, 150 insertions, 0 deletions

diff --git a/src/Plugins/Monitors/UVMeter.hs b/src/Plugins/Monitors/UVMeter.hs
new file mode 100644
index 0000000..5fa0b82
--- /dev/null
+++ b/src/Plugins/Monitors/UVMeter.hs
@@ -0,0 +1,150 @@
+{-# LANGUAGE OverloadedStrings #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Plugins.Monitors.UVMeter
+-- Copyright   :  (c) Róman Joost
+-- License     :  BSD-style (see LICENSE)
+--
+-- Maintainer  :  Róman Joost
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- An australian uv monitor for Xmobar
+--
+-----------------------------------------------------------------------------
+
+module Plugins.Monitors.UVMeter where
+
+import Plugins.Monitors.Common
+
+import qualified Control.Exception as CE
+import Control.Applicative hiding ((<|>),many)
+import Network.HTTP
+import Text.Read (readMaybe)
+import Text.Parsec
+import Text.Parsec.String
+
+
+uvConfig :: IO MConfig
+uvConfig = mkMConfig
+       "<station>" -- template
+       ["station"                               -- available replacements
+       ]
+
+data UvInfo = UV { index :: String }
+    deriving (Show)
+
+uvURL :: String
+uvURL = "http://www.arpansa.gov.au/uvindex/realtime/xml/uvvalues.xml"
+
+getData :: IO String
+getData = do
+    let request = getRequest uvURL
+    CE.catch (simpleHTTP request >>= getResponseBody) errHandler
+    where errHandler :: CE.IOException -> IO String
+          errHandler _ = return "<Could not retrieve data>"
+
+textToXMLDocument :: String -> Either ParseError [XML]
+textToXMLDocument = parse document ""
+
+formatUVRating :: Maybe Float -> Monitor String
+formatUVRating Nothing = getConfigValue naString
+formatUVRating (Just x) = do
+    uv <- showWithColors show x
+    parseTemplate [uv]
+
+getUVRating :: String -> [XML] ->  Maybe Float
+getUVRating locID (Element "stations" _ y:_) = getUVRating locID y
+getUVRating locID (Element "location" [Attribute attr] ys:xs)
+    | locID == snd attr = getUVRating locID ys
+    | otherwise = getUVRating locID xs
+getUVRating _ (Element "index" [] [Body rate]:_) = readMaybe rate
+getUVRating locID (_:xs) = getUVRating locID xs
+getUVRating _ [] = Nothing
+
+
+runUVMeter :: [String] -> Monitor String
+runUVMeter [] = return "N.A."
+runUVMeter (s:_) = do
+    resp <- io getData
+    case textToXMLDocument resp of
+        Right doc -> formatUVRating (getUVRating s doc)
+        Left _ -> getConfigValue naString
+
+-- | XML Parsing code comes here.
+-- This is a very simple XML parser to just deal with the uvvalues.xml
+-- provided by ARPANSA. If you work on a new plugin which needs an XML
+-- parser perhaps consider using a real XML parser and refactor this
+-- plug-in to us it as well.
+--
+-- Note: This parser can not deal with short tags.
+--
+-- Kudos to: Charlie Harvey for his article about writing an XML Parser
+-- with Parsec.
+--
+
+type AttrName  = String
+type AttrValue = String
+
+data Attribute = Attribute (AttrName, AttrValue)
+    deriving (Show)
+
+data XML = Element String [Attribute] [XML]
+         | Decl String
+         | Body String
+    deriving (Show)
+
+-- | parse the document
+--
+document :: Parser [XML]
+document = do
+    spaces
+    y <- try xmlDecl <|> tag
+    spaces
+    x <- many tag
+    spaces
+    return (y : x)
+
+-- | parse any tags
+--
+tag :: Parser XML
+tag  = do
+    char '<'
+    spaces
+    name <- many (letter <|> digit)
+    spaces
+    attr <- many attribute
+    spaces
+    string ">"
+    eBody <- many elementBody
+    endTag name
+    spaces
+    return (Element name attr eBody)
+
+xmlDecl :: Parser XML
+xmlDecl = do
+    string "<?xml"
+    decl <- many (noneOf "?>")
+    string "?>"
+    return (Decl decl)
+
+elementBody :: Parser XML
+elementBody = spaces *> try tag <|> text
+
+endTag :: String -> Parser String
+endTag str = string "</" *> string str <* char '>'
+
+text :: Parser XML
+text = Body <$> many1 (noneOf "><")
+
+attribute :: Parser Attribute
+attribute = do
+    name <- many (noneOf "= />")
+    spaces
+    char '='
+    spaces
+    char '"'
+    value <- many (noneOf "\"")
+    char '"'
+    spaces
+    return (Attribute (name, value))