    {-|

    This is the entry point to hledger's reading system, which can read
    Journals from various data formats. Use this module if you want to parse
    journal data or read journal files. Generally it should not be necessary
    to import modules below this one.
    -}

    {-# LANGUAGE ScopedTypeVariables, OverloadedStrings #-}

    module Hledger.Read (

      -- * Journal files
      PrefixedFilePath,
      defaultJournal,
      defaultJournalPath,
      readJournalFiles,
      readJournalFile,
      requireJournalFileExists,
      ensureJournalFileExists,
      splitReaderPrefix,

      -- * Journal parsing
      readJournal,
      readJournal',

      -- * Re-exported
      JournalReader.accountaliasp,
      JournalReader.postingp,
      module Hledger.Read.Common,

      -- * Tests
      samplejournal,
      tests_Hledger_Read,

    ) where

    import Control.Applicative ((<|>))
    import Control.Arrow (right)
    import qualified Control.Exception as C
    import Control.Monad.Except
    import Data.List
    import Data.Maybe
    import Data.Text (Text)
    import qualified Data.Text as T
    import Safe
    import System.Directory (doesFileExist, getHomeDirectory)
    import System.Environment (getEnv)
    import System.Exit (exitFailure)
    import System.FilePath ((</>), takeExtension)
    import System.IO (stderr)
    import Test.HUnit
    import Text.Printf

    import Hledger.Data.Dates (getCurrentDay)
    import Hledger.Data.Types
    import Hledger.Read.Common
    import qualified Hledger.Read.JournalReader   as JournalReader
    -- import qualified Hledger.Read.LedgerReader    as LedgerReader
    import qualified Hledger.Read.TimedotReader   as TimedotReader
    import qualified Hledger.Read.TimeclockReader as TimeclockReader
    import qualified Hledger.Read.CsvReader       as CsvReader
    import Hledger.Utils
    import Prelude hiding (getContents, writeFile)
    import Hledger.Utils.UTF8IOCompat (writeFile)

    journalEnvVar           = "LEDGER_FILE"
    journalEnvVar2          = "LEDGER"
    journalDefaultFilename  = ".hledger.journal"

    -- The available journal readers, each one handling a particular data format.
    readers :: [Reader]
    readers = [
      JournalReader.reader
     ,TimeclockReader.reader
     ,TimedotReader.reader
     ,CsvReader.reader
    --  ,LedgerReader.reader
     ]

    readerNames :: [String]
    readerNames = map rFormat readers

    -- | A file path optionally prefixed by a reader name and colon
    -- (journal:, csv:, timedot:, etc.).
    type PrefixedFilePath = FilePath

    -- | Read the default journal file specified by the environment, or raise an error.
    defaultJournal :: IO Journal
    defaultJournal = defaultJournalPath >>= readJournalFile Nothing Nothing True >>= either error' return

    -- | Get the default journal file path specified by the environment.
    -- Like ledger, we look first for the LEDGER_FILE environment
    -- variable, and if that does not exist, for the legacy LEDGER
    -- environment variable. If neither is set, or the value is blank,
    -- return the hard-coded default, which is @.hledger.journal@ in the
    -- users's home directory (or in the current directory, if we cannot
    -- determine a home directory).
    defaultJournalPath :: IO String
    defaultJournalPath = do
      s <- envJournalPath
      if null s then defaultJournalPath else return s
        where
          envJournalPath =
            getEnv journalEnvVar
             `C.catch` (\(_::C.IOException) -> getEnv journalEnvVar2
                                                `C.catch` (\(_::C.IOException) -> return ""))
          defaultJournalPath = do
                      home <- getHomeDirectory `C.catch` (\(_::C.IOException) -> return "")
                      return $ home </> journalDefaultFilename

    -- | @readJournalFiles mformat mrulesfile assrt prefixedfiles@
    --
    -- Read a Journal from each specified file path and combine them into one.
    -- Or, return the first error message.
    --
    -- Combining Journals means concatenating them, basically.
    -- The parse state resets at the start of each file, which means that
    -- directives & aliases do not cross file boundaries.
    -- (The final parse state saved in the Journal does span all files, however.)
    --
    -- As with readJournalFile,
    -- file paths can optionally have a READER: prefix,
    -- and the @mformat@, @mrulesfile, and @assrt@ arguments are supported
    -- (and these are applied to all files).
    --
    readJournalFiles :: Maybe StorageFormat -> Maybe FilePath -> Bool -> [PrefixedFilePath] -> IO (Either String Journal)
    readJournalFiles mformat mrulesfile assrt prefixedfiles = do
      (right mconcat1 . sequence)
        <$> mapM (readJournalFile mformat mrulesfile assrt) prefixedfiles
      where mconcat1 :: Monoid t => [t] -> t
            mconcat1 [] = mempty
            mconcat1 x = foldr1 mappend x

    -- | @readJournalFile mformat mrulesfile assrt prefixedfile@
    --
    -- Read a Journal from this file, or from stdin if the file path is -,
    -- or return an error message. The file path can have a READER: prefix.
    --
    -- The reader (data format) is chosen based on (in priority order):
    -- the @mformat@ argument;
    -- the file path's READER: prefix, if any;
    -- a recognised file name extension (in readJournal);
    -- if none of these identify a known reader, all built-in readers are tried in turn.
    --
    -- A CSV conversion rules file (@mrulesfiles@) can be specified to help convert CSV data.
    --
    -- Optionally, any balance assertions in the journal can be checked (@assrt@).
    --
    readJournalFile :: Maybe StorageFormat -> Maybe FilePath -> Bool -> PrefixedFilePath -> IO (Either String Journal)
    readJournalFile mformat mrulesfile assrt prefixedfile = do
      let
        (mprefixformat, f) = splitReaderPrefix prefixedfile
        mfmt = mformat <|> mprefixformat
      requireJournalFileExists f
      readFileOrStdinAnyLineEnding f >>= readJournal mfmt mrulesfile assrt (Just f)

    -- | If a filepath is prefixed by one of the reader names and a colon,
    -- split that off. Eg "csv:-" -> (Just "csv", "-").
    splitReaderPrefix :: PrefixedFilePath -> (Maybe String, FilePath)
    splitReaderPrefix f =
      headDef (Nothing, f)
      [(Just r, drop (length r + 1) f) | r <- readerNames, (r++":") `isPrefixOf` f]

    -- | If the specified journal file does not exist (and is not "-"),
    -- give a helpful error and quit.
    requireJournalFileExists :: FilePath -> IO ()
    requireJournalFileExists "-" = return ()
    requireJournalFileExists f = do
      exists <- doesFileExist f
      when (not exists) $ do  -- XXX might not be a journal file
        hPrintf stderr "The hledger journal file \"%s\" was not found.\n" f
        hPrintf stderr "Please create it first, eg with \"hledger add\" or a text editor.\n"
        hPrintf stderr "Or, specify an existing journal file with -f or LEDGER_FILE.\n"
        exitFailure

    -- | Ensure there is a journal file at the given path, creating an empty one if needed.
    ensureJournalFileExists :: FilePath -> IO ()
    ensureJournalFileExists f = do
      exists <- doesFileExist f
      when (not exists) $ do
        hPrintf stderr "Creating hledger journal file %s.\n" f
        -- note Hledger.Utils.UTF8.* do no line ending conversion on windows,
        -- we currently require unix line endings on all platforms.
        newJournalContent >>= writeFile f

    -- | Give the content for a new auto-created journal file.
    newJournalContent :: IO String
    newJournalContent = do
      d <- getCurrentDay
      return $ printf "; journal created %s by hledger\n" (show d)

    -- | Read a Journal from the given text trying all readers in turn, or throw an error.
    readJournal' :: Text -> IO Journal
    readJournal' t = readJournal Nothing Nothing True Nothing t >>= either error' return

    tests_readJournal' = [
      "readJournal' parses sample journal" ~: do
         _ <- samplejournal
         assertBool "" True
     ]

    -- | @readJournal mformat mrulesfile assrt mfile txt@
    --
    -- Read a Journal from some text, or return an error message.
    --
    -- The reader (data format) is chosen based on (in priority order):
    -- the @mformat@ argument;
    -- a recognised file name extension in @mfile@ (if provided).
    -- If none of these identify a known reader, all built-in readers are tried in turn
    -- (returning the first one's error message if none of them succeed).
    --
    -- A CSV conversion rules file (@mrulesfiles@) can be specified to help convert CSV data.
    --
    -- Optionally, any balance assertions in the journal can be checked (@assrt@).
    --
    readJournal :: Maybe StorageFormat -> Maybe FilePath -> Bool -> Maybe FilePath -> Text -> IO (Either String Journal)
    readJournal mformat mrulesfile assrt mfile txt =
      let
        stablereaders = filter (not.rExperimental) readers
        rs = maybe stablereaders (:[]) $ findReader mformat mfile
      in
        tryReaders rs mrulesfile assrt mfile txt

    -- | @findReader mformat mpath@
    --
    -- Find the reader named by @mformat@, if provided.
    -- Or, if a file path is provided, find the first reader that handles
    -- its file extension, if any.
    findReader :: Maybe StorageFormat -> Maybe FilePath -> Maybe Reader
    findReader Nothing Nothing     = Nothing
    findReader (Just fmt) _        = headMay [r | r <- readers, rFormat r == fmt]
    findReader Nothing (Just path) =
      case prefix of
        Just fmt -> headMay [r | r <- readers, rFormat r == fmt]
        Nothing  -> headMay [r | r <- readers, ext `elem` rExtensions r]
      where
        (prefix,path') = splitReaderPrefix path
        ext            = drop 1 $ takeExtension path'

    -- | @tryReaders readers mrulesfile assrt path t@
    --
    -- Try to parse the given text to a Journal using each reader in turn,
    -- returning the first success, or if all of them fail, the first error message.
    tryReaders :: [Reader] -> Maybe FilePath -> Bool -> Maybe FilePath -> Text -> IO (Either String Journal)
    tryReaders readers mrulesfile assrt path t = firstSuccessOrFirstError [] readers
      where
        firstSuccessOrFirstError :: [String] -> [Reader] -> IO (Either String Journal)
        firstSuccessOrFirstError [] []        = return $ Left "no readers found"
        firstSuccessOrFirstError errs (r:rs) = do
          dbg1IO "trying reader" (rFormat r)
          result <- (runExceptT . (rParser r) mrulesfile assrt path') t
          dbg1IO "reader result" $ either id show result
          case result of Right j -> return $ Right j                        -- success!
                         Left e  -> firstSuccessOrFirstError (errs++[e]) rs -- keep trying
        firstSuccessOrFirstError (e:_) []    = return $ Left e              -- none left, return first error
        path' = fromMaybe "(string)" path

    -- tests

    samplejournal = readJournal' $ T.unlines
     ["2008/01/01 income"
     ,"    assets:bank:checking  $1"
     ,"    income:salary"
     ,""
     ,"comment"
     ,"multi line comment here"
     ,"for testing purposes"
     ,"end comment"
     ,""
     ,"2008/06/01 gift"
     ,"    assets:bank:checking  $1"
     ,"    income:gifts"
     ,""
     ,"2008/06/02 save"
     ,"    assets:bank:saving  $1"
     ,"    assets:bank:checking"
     ,""
     ,"2008/06/03 * eat & shop"
     ,"    expenses:food      $1"
     ,"    expenses:supplies  $1"
     ,"    assets:cash"
     ,""
     ,"2008/12/31 * pay off"
     ,"    liabilities:debts  $1"
     ,"    assets:bank:checking"
     ]

    tests_Hledger_Read = TestList $
      tests_readJournal'
      ++ [
       JournalReader.tests_Hledger_Read_JournalReader,
    --    LedgerReader.tests_Hledger_Read_LedgerReader,
       TimeclockReader.tests_Hledger_Read_TimeclockReader,
       TimedotReader.tests_Hledger_Read_TimedotReader,
       CsvReader.tests_Hledger_Read_CsvReader,

       "journal" ~: do
        r <- runExceptT $ parseWithState mempty JournalReader.journalp ""
        assertBool "journalp should parse an empty file" (isRight $ r)
        jE <- readJournal Nothing Nothing True Nothing "" -- don't know how to get it from journal
        either error' (assertBool "journalp parsing an empty file should give an empty journal" . null . jtxns) jE

      ]