Count.hs

{-# LANGUAGE BangPatterns      #-}
{-# LANGUAGE OverloadedStrings #-}

module App.Commands.Count
  ( cmdCount
  ) where

import App.Options
import Control.Lens
import Control.Monad
import Data.Generics.Product.Any
import Data.Succinct.Xml.DecodeResult
import Data.Succinct.Xml.RawDecode
import Data.Succinct.Xml.RawValue
import Data.Succinct.Xml.Succinct.Cursor.Load
import Data.Succinct.Xml.Succinct.Cursor.MMap
import Data.Succinct.Xml.Succinct.Index
import Data.Succinct.Xml.Value
import Data.Text                                  (Text)
import GHC.Generics
import HaskellWorks.Data.TreeCursor
import Options.Applicative                        hiding (columns)

import qualified App.Commands.Types as Z
import qualified App.Naive          as NAIVE
import qualified App.XPath.Parser   as XPP
import qualified System.Exit        as IO
import qualified System.IO          as IO

-- | Document model.  This does not need to be able to completely represent all
-- the data in the XML document.  In fact, having a smaller model may improve
-- Count performance.
data Plant = Plant
  { common :: String
  , price  :: String
  } deriving (Eq, Show, Generic)

newtype Catalog = Catalog
  { plants :: [Plant]
  } deriving (Eq, Show, Generic)

tags :: Value -> Text -> [Value]
tags xml@(XmlElement n _ _) elemName = if n == elemName
  then [xml]
  else []
tags _ _ = []

kids :: Value -> [Value]
kids (XmlElement _ _ cs) = cs
kids _                   = []

countAtPath :: [Text] -> Value -> DecodeResult Int
countAtPath []  _   = return 0
countAtPath [t] xml = return (length (tags xml t))
countAtPath (t:ts) xml = do
  counts <- forM (tags xml t >>= kids) $ countAtPath ts
  return (sum counts)

runCount :: Z.CountOptions -> IO ()
runCount opt = do
  let input   = opt ^. the @"input"
  let xpath   = opt ^. the @"xpath"
  let method  = opt ^. the @"method"

  IO.putStrLn $ "XPath: " <> show xpath

  cursorResult <- case method of
    "mmap"   -> Right <$> mmapFastCursor input
    "memory" -> Right <$> loadFastCursor input
    "naive"  -> Right <$> NAIVE.loadFastCursor input
    unknown  -> return (Left ("Unknown method " <> show unknown))

  case cursorResult of
    Right !cursor -> do
      -- Skip the XML declaration to get to the root element cursor
      case nextSibling cursor of
        Just rootCursor -> do
          -- Get the root raw XML value at the root element cursor
          let rootValue = rawValueAt (xmlIndexAt rootCursor)
          -- Show what we have at this cursor
          putStrLn $ "Raw value: " <> take 100 (show rootValue)
          -- Decode the raw XML value
          case countAtPath (xpath ^. the @"path") (rawDecode rootValue) of
            DecodeOk count   -> putStrLn $ "Count: " <> show count
            DecodeFailed msg -> putStrLn $ "Error: " <> show msg
        Nothing -> do
          putStrLn "Could not read XML"
          return ()
    Left msg -> do
      IO.putStrLn $ "Error: " <> msg
      IO.exitFailure

optsCount :: Parser Z.CountOptions
optsCount = Z.CountOptions
  <$> strOption
      (   long "input"
      <>  help "Input file"
      <>  metavar "FILE"
      )
  <*> optionParser XPP.path
      (   long "xpath"
      <>  help "XPath expression"
      <>  metavar "XPATH"
      )
  <*> textOption
      (   long "method"
      <>  help "Read method"
      <>  metavar "METHOD"
      )

cmdCount :: Mod CommandFields (IO ())
cmdCount = command "count"  $ flip info idm $ runCount <$> optsCount