{-# LANGUAGE FlexibleContexts, TypeFamilies #-}
{- | 

Helpers for debug output and pretty-printing 
(using pretty-simple, with which there may be some overlap).
This module also exports Debug.Trace.

@dbg0@-@dbg9@ will pretty-print values to stderr
if the program was run with a sufficiently high @--debug=N@ argument. 
(@--debug@ with no argument means @--debug=1@; @dbg0@ always prints).

The @debugLevel@ global is set once at startup using unsafePerformIO. 
In GHCI, this happens only on the first run of :main, so if you want
to change the debug level without restarting GHCI,
save a dummy change in Debug.hs and do a :reload.
(Sometimes it's more convenient to temporarily add dbg0's and :reload.)

-}

-- more:
-- http://hackage.haskell.org/packages/archive/TraceUtils/0.1.0.2/doc/html/Debug-TraceUtils.html
-- http://hackage.haskell.org/packages/archive/trace-call/0.1/doc/html/Debug-TraceCall.html
-- http://hackage.haskell.org/packages/archive/htrace/0.1/doc/html/Debug-HTrace.html
-- http://hackage.haskell.org/packages/archive/traced/2009.7.20/doc/html/Debug-Traced.html

module Hledger.Utils.Debug (
  -- * Pretty printing
   pprint
  ,pshow
  -- * Tracing
  ,traceWith
  -- * Pretty tracing
  ,ptrace
  -- ** Debug-level-aware tracing
  ,debugLevel
  ,traceAt
  ,traceAtWith
  ,ptraceAt
  ,ptraceAtWith
  -- ** Easiest form (recommended)
  ,dbg0
  ,dbg1
  ,dbg2
  ,dbg3
  ,dbg4
  ,dbg5
  ,dbg6
  ,dbg7
  ,dbg8
  ,dbg9
  ,dbgExit
  -- ** More control
  ,dbg0With
  ,dbg1With
  ,dbg2With
  ,dbg3With
  ,dbg4With
  ,dbg5With
  ,dbg6With
  ,dbg7With
  ,dbg8With
  ,dbg9With
  -- ** For standalone lines in IO blocks
  ,ptraceAtIO
  ,dbg0IO
  ,dbg1IO
  ,dbg2IO
  ,dbg3IO
  ,dbg4IO
  ,dbg5IO
  ,dbg6IO
  ,dbg7IO
  ,dbg8IO
  ,dbg9IO
  -- ** Trace to a file
  ,plog
  ,plogAt
  -- ** Trace the state of hledger parsers
  ,traceParse
  ,dbgparse
  ,module Debug.Trace
)
where

import           Control.Monad (when)
import           Control.Monad.IO.Class
import           Data.List hiding (uncons)
import qualified Data.Text as T
import qualified Data.Text.Lazy as TL
import           Debug.Trace
import           Hledger.Utils.Parse
import           Safe (readDef)
import           System.Environment (getArgs)
import           System.Exit
import           System.IO.Unsafe (unsafePerformIO)
import           Text.Megaparsec
import           Text.Printf
import           Text.Pretty.Simple  -- (defaultOutputOptionsDarkBg, OutputOptions(..), pShowOpt, pPrintOpt)

prettyopts = 
    defaultOutputOptionsDarkBg
    -- defaultOutputOptionsLightBg
    -- defaultOutputOptionsNoColor
    { outputOptionsIndentAmount=2
    , outputOptionsCompact=True
    }

-- | Pretty print. Generic alias for pretty-simple's pPrint.
pprint :: Show a => a -> IO ()
pprint = pPrintOpt CheckColorTty prettyopts

-- | Pretty show. Generic alias for pretty-simple's pShow.
pshow :: Show a => a -> String
pshow = TL.unpack . pShowOpt prettyopts

-- XXX some of the below can be improved with pretty-simple, https://github.com/cdepillabout/pretty-simple#readme

-- | Pretty trace. Easier alias for traceShowId + pShow.
ptrace :: Show a => a -> a
ptrace = traceWith pshow

-- | Like traceShowId, but uses a custom show function to render the value.
-- traceShowIdWith was too much of a mouthful.
traceWith :: Show a => (a -> String) -> a -> a
traceWith f a = trace (f a) a

-- | Global debug level, which controls the verbosity of debug output
-- on the console. The default is 0 meaning no debug output. The
-- @--debug@ command line flag sets it to 1, or @--debug=N@ sets it to
-- a higher value (note: not @--debug N@ for some reason).  This uses
-- unsafePerformIO and can be accessed from anywhere and before normal
-- command-line processing. When running with :main in GHCI, you must
-- touch and reload this module to see the effect of a new --debug option.
-- {-# OPTIONS_GHC -fno-cse #-}
-- {-# NOINLINE debugLevel #-}
debugLevel :: Int
debugLevel = case snd $ break (=="--debug") args of
               "--debug":[]  -> 1
               "--debug":n:_ -> readDef 1 n
               _             ->
                 case take 1 $ filter ("--debug" `isPrefixOf`) args of
                   ['-':'-':'d':'e':'b':'u':'g':'=':v] -> readDef 1 v
                   _                                   -> 0

    where
      args = unsafePerformIO getArgs

-- | Trace (print to stderr) a string if the global debug level is at
-- or above the specified level. At level 0, always prints. Otherwise,
-- uses unsafePerformIO.
traceAt :: Int -> String -> a -> a
traceAt level
    | level > 0 && debugLevel < level = flip const
    | otherwise = trace

-- | Trace (print to stderr) a showable value using a custom show function.
traceAtWith :: (a -> String) -> a -> a
traceAtWith f a = trace (f a) a

-- | Pretty-print a label and a showable value to the console
-- if the global debug level is at or above the specified level.
-- At level 0, always prints. Otherwise, uses unsafePerformIO.
ptraceAt :: Show a => Int -> String -> a -> a
ptraceAt level
    | level > 0 && debugLevel < level = flip const
    | otherwise = \s a -> let p = pshow a
                              ls = lines p
                              nlorspace | length ls > 1 = "\n"
                                        | otherwise     = " " ++ take (10 - length s) (repeat ' ')
                              ls' | length ls > 1 = map (" "++) ls
                                  | otherwise     = ls
                          in trace (s++":"++nlorspace++intercalate "\n" ls') a

-- | Like ptraceAt, but takes a custom show function instead of a label.
ptraceAtWith :: Show a => Int -> (a -> String) -> a -> a
ptraceAtWith level f
    | level > 0 && debugLevel < level = id
    | otherwise = \a -> let p = f a
                            -- ls = lines p
                            -- nlorspace | length ls > 1 = "\n"
                            --           | otherwise     = " " ++ take (10 - length s) (repeat ' ')
                            -- ls' | length ls > 1 = map (" "++) ls
                            --     | otherwise     = ls
                        -- in trace (s++":"++nlorspace++intercalate "\n" ls') a
                        in trace p a

-- "dbg" would clash with megaparsec.
-- | Pretty-print a label and the showable value to the console, then return it.
dbg0 :: Show a => String -> a -> a
dbg0 = ptraceAt 0

-- | Pretty-print a label and the showable value to the console when the global debug level is >= 1, then return it.
-- Uses unsafePerformIO.
dbg1 :: Show a => String -> a -> a
dbg1 = ptraceAt 1

dbg2 :: Show a => String -> a -> a
dbg2 = ptraceAt 2

dbg3 :: Show a => String -> a -> a
dbg3 = ptraceAt 3

dbg4 :: Show a => String -> a -> a
dbg4 = ptraceAt 4

dbg5 :: Show a => String -> a -> a
dbg5 = ptraceAt 5

dbg6 :: Show a => String -> a -> a
dbg6 = ptraceAt 6

dbg7 :: Show a => String -> a -> a
dbg7 = ptraceAt 7

dbg8 :: Show a => String -> a -> a
dbg8 = ptraceAt 8

dbg9 :: Show a => String -> a -> a
dbg9 = ptraceAt 9

-- | Like dbg0, but also exit the program. Uses unsafePerformIO.
dbgExit :: Show a => String -> a -> a
dbgExit msg = const (unsafePerformIO exitFailure) . dbg0 msg

-- | Like dbg0, but takes a custom show function instead of a label.
dbg0With :: Show a => (a -> String) -> a -> a
dbg0With = ptraceAtWith 0

dbg1With :: Show a => (a -> String) -> a -> a
dbg1With = ptraceAtWith 1

dbg2With :: Show a => (a -> String) -> a -> a
dbg2With = ptraceAtWith 2

dbg3With :: Show a => (a -> String) -> a -> a
dbg3With = ptraceAtWith 3

dbg4With :: Show a => (a -> String) -> a -> a
dbg4With = ptraceAtWith 4

dbg5With :: Show a => (a -> String) -> a -> a
dbg5With = ptraceAtWith 5

dbg6With :: Show a => (a -> String) -> a -> a
dbg6With = ptraceAtWith 6

dbg7With :: Show a => (a -> String) -> a -> a
dbg7With = ptraceAtWith 7

dbg8With :: Show a => (a -> String) -> a -> a
dbg8With = ptraceAtWith 8

dbg9With :: Show a => (a -> String) -> a -> a
dbg9With = ptraceAtWith 9

-- | Like ptraceAt, but convenient to insert in an IO monad and
-- enforces monadic sequencing (plus convenience aliases).
-- XXX These have a bug; they should use
-- traceIO, not trace, otherwise GHC can occasionally over-optimise
-- (cf lpaste a few days ago where it killed/blocked a child thread).
ptraceAtIO :: (MonadIO m, Show a) => Int -> String -> a -> m ()
ptraceAtIO lvl lbl x = liftIO $ ptraceAt lvl lbl x `seq` return ()

-- XXX Could not deduce (a ~ ())
-- ptraceAtM :: (Monad m, Show a) => Int -> String -> a -> m a
-- ptraceAtM lvl lbl x = ptraceAt lvl lbl x `seq` return x

dbg0IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg0IO = ptraceAtIO 0

dbg1IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg1IO = ptraceAtIO 1

dbg2IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg2IO = ptraceAtIO 2

dbg3IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg3IO = ptraceAtIO 3

dbg4IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg4IO = ptraceAtIO 4

dbg5IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg5IO = ptraceAtIO 5

dbg6IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg6IO = ptraceAtIO 6

dbg7IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg7IO = ptraceAtIO 7

dbg8IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg8IO = ptraceAtIO 8

dbg9IO :: (MonadIO m, Show a) => String -> a -> m ()
dbg9IO = ptraceAtIO 9

-- | Log a label and a pretty-printed showable value to ./debug.log, then return it.
-- Can fail, see plogAt.
plog :: Show a => String -> a -> a
plog = plogAt 0

-- | Log a label and a pretty-printed showable value to ./debug.log,
-- if the global debug level is at or above the specified level.
-- At level 0, always logs. Otherwise, uses unsafePerformIO.
-- Tends to fail if called more than once too quickly, at least when built with -threaded
-- ("Exception: debug.log: openFile: resource busy (file is locked)").
plogAt :: Show a => Int -> String -> a -> a
plogAt lvl
    | lvl > 0 && debugLevel < lvl = flip const
    | otherwise = \s a ->
        let p = pshow a
            ls = lines p
            nlorspace | length ls > 1 = "\n"
                      | otherwise     = " " ++ take (10 - length s) (repeat ' ')
            ls' | length ls > 1 = map (" "++) ls
                | otherwise     = ls
            output = s++":"++nlorspace++intercalate "\n" ls'++"\n"
        in unsafePerformIO $ appendFile "debug.log" output >> return a

-- XXX redundant ? More/less robust than plogAt ?
-- -- | Like dbg, but writes the output to "debug.log" in the current directory.
-- dbglog :: Show a => String -> a -> a
-- dbglog label a =
--   (unsafePerformIO $
--     appendFile "debug.log" $ label ++ ": " ++ ppShow a ++ "\n")
--   `seq` a

-- | Print the provided label (if non-null) and current parser state
-- (position and next input) to the console. See also megaparsec's dbg.
traceParse :: String -> TextParser m ()
traceParse msg = do
  pos <- getSourcePos
  next <- (T.take peeklength) `fmap` getInput
  let (l,c) = (sourceLine pos, sourceColumn pos)
      s  = printf "at line %2d col %2d: %s" (unPos l) (unPos c) (show next) :: String
      s' = printf ("%-"++show (peeklength+30)++"s") s ++ " " ++ msg
  trace s' $ return ()
  where
    peeklength = 30

-- | Print the provided label (if non-null) and current parser state
-- (position and next input) to the console if the global debug level
-- is at or above the specified level. Uses unsafePerformIO.
-- (See also megaparsec's dbg.)
traceParseAt :: Int -> String -> TextParser m ()
traceParseAt level msg = when (level <= debugLevel) $ traceParse msg

-- | Convenience alias for traceParseAt
dbgparse :: Int -> String -> TextParser m ()
dbgparse level msg = traceParseAt level msg