{-# LANGUAGE MultiWayIf, LambdaCase, OverloadedStrings, RankNTypes #-}
module System.Pager where
import Control.Monad (forM)
import Control.Monad.IO.Class
import Control.Monad.Trans.Resource
import Data.ByteString (ByteString)
import qualified Data.ByteString as B
import Data.ByteString.Char8 (unpack)
import qualified Data.ByteString.Lazy as Bl
import Data.Conduit
import Data.Conduit.Binary
import Data.List
import qualified Data.Monoid (mconcat, mempty)
import Data.Text (Text)
import qualified Data.Text as T
import qualified Data.Text.Encoding as TE
import qualified Data.Text.IO as TIO
import Safe
import System.Directory
import System.Exit
import System.IO
import System.Posix.ByteString
import System.Process
import System.Console.Terminfo
printOrPage :: Text -> IO ()
printOrPage :: Text -> IO ()
printOrPage Text
text =
do Terminal
terminal <- IO Terminal
setupTermFromEnv
let linesInTerminal :: Maybe Int
linesInTerminal =
Terminal -> Capability Int -> Maybe Int
forall a. Terminal -> Capability a -> Maybe a
getCapability Terminal
terminal Capability Int
termLines
columnsInTerminal :: Maybe Int
columnsInTerminal =
Terminal -> Capability Int -> Maybe Int
forall a. Terminal -> Capability a -> Maybe a
getCapability Terminal
terminal Capability Int
termColumns
linesInText :: Int
linesInText = [Text] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length (Text -> [Text]
T.lines Text
text)
columnsInText :: Int
columnsInText =
[Int] -> Int
forall a. [a] -> a
last ([Int] -> [Int]
forall a. Ord a => [a] -> [a]
sort ((Text -> Int) -> [Text] -> [Int]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Text -> Int
T.length (Text -> [Text]
T.lines Text
text)))
usePager :: Bool
usePager =
case (Maybe Int
columnsInTerminal,Maybe Int
linesInTerminal) of
(Maybe Int
Nothing,Maybe Int
_) -> Bool
True
(Maybe Int
_,Maybe Int
Nothing) -> Bool
True
(Just Int
x,Just Int
y)
| [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [Int
x Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
columnsInText,Int
y Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
<= Int
linesInText] -> Bool
True
| Bool
otherwise -> Bool
False
if Bool
usePager
then ByteString -> IO ()
sendToPagerStrict (Text -> ByteString
TE.encodeUtf8 Text
text)
else Text -> IO ()
TIO.putStr Text
text
sendToPager :: Bl.ByteString -> IO ()
ByteString
bytes =
Producer (ResourceT IO) ByteString -> IO ()
sendToPagerConduit (ByteString -> ConduitT i ByteString (ResourceT IO) ()
forall (m :: * -> *) i.
Monad m =>
ByteString -> ConduitT i ByteString m ()
sourceLbs ByteString
bytes)
sendToPagerStrict :: B.ByteString -> IO ()
ByteString
bytes =
Producer (ResourceT IO) ByteString -> IO ()
sendToPagerConduit (ByteString -> ConduitT i ByteString (ResourceT IO) ()
forall (m :: * -> *) i.
Monad m =>
ByteString -> ConduitT i ByteString m ()
sourceLbs (ByteString -> ByteString
Bl.fromStrict ByteString
bytes))
findPager :: IO ByteString
=
ByteString -> IO (Maybe ByteString)
getEnv ByteString
"PAGER" IO (Maybe ByteString)
-> (Maybe ByteString -> IO ByteString) -> IO ByteString
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>=
\case
Just ByteString
x -> ByteString -> IO ByteString
forall (m :: * -> *) a. Monad m => a -> m a
return ByteString
x
Maybe ByteString
Nothing ->
ByteString -> IO (Maybe ByteString)
getEnv ByteString
"PATH" IO (Maybe ByteString)
-> (Maybe ByteString -> IO ByteString) -> IO ByteString
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>=
\case
Maybe ByteString
Nothing ->
String -> IO ByteString
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"There is no $PATH, so I can't see if 'less' or 'more' is installed."
Just ByteString
p ->
do let pathText :: Text
pathText = ByteString -> Text
TE.decodeUtf8 ByteString
p
pathPieces :: [Text]
pathPieces =
Text -> Text -> [Text]
T.splitOn Text
":" Text
pathText
[String]
searchForLess <-
([[String]] -> [String]) -> IO [[String]] -> IO [String]
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap [[String]] -> [String]
forall a. Monoid a => [a] -> a
mconcat
([Text] -> (Text -> IO [String]) -> IO [[String]]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
t a -> (a -> m b) -> m (t b)
forM [Text]
pathPieces
(\Text
pathPiece ->
do Bool
dirExists <-
String -> IO Bool
doesDirectoryExist (Text -> String
T.unpack Text
pathPiece)
[String]
filesInDir <-
if | Bool
dirExists ->
String -> IO [String]
getDirectoryContents (Text -> String
T.unpack Text
pathPiece)
| Bool
otherwise -> [String] -> IO [String]
forall (m :: * -> *) a. Monad m => a -> m a
return [String]
forall a. Monoid a => a
mempty
[String] -> IO [String]
forall (m :: * -> *) a. Monad m => a -> m a
return ((String -> Bool) -> [String] -> [String]
forall a. (a -> Bool) -> [a] -> [a]
filter (\String
x ->
(String
x String -> String -> Bool
forall a. Eq a => a -> a -> Bool
== String
"less") Bool -> Bool -> Bool
||
(String
x String -> String -> Bool
forall a. Eq a => a -> a -> Bool
== String
"more"))
[String]
filesInDir)))
if | [String]
searchForLess [String] -> [String] -> Bool
forall a. Eq a => a -> a -> Bool
== [String]
forall a. Monoid a => a
mempty ->
String -> IO ByteString
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
"There doesn't appear to be any pager installed."
| String -> [String] -> Bool
forall (t :: * -> *) a. (Foldable t, Eq a) => a -> t a -> Bool
elem String
"less" [String]
searchForLess ->
ByteString -> IO ByteString
forall (m :: * -> *) a. Monad m => a -> m a
return ByteString
"less"
| Bool
otherwise -> ByteString -> IO ByteString
forall (m :: * -> *) a. Monad m => a -> m a
return ByteString
"more"
sendToPagerConduit :: Producer (ResourceT IO) ByteString -> IO ()
Producer (ResourceT IO) ByteString
producer =
do String
pager <- (ByteString -> String) -> IO ByteString -> IO String
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap ByteString -> String
unpack IO ByteString
findPager
((Just Handle
stdinH),Maybe Handle
_,(Just Handle
stderrH),ProcessHandle
ph) <-
CreateProcess
-> IO (Maybe Handle, Maybe Handle, Maybe Handle, ProcessHandle)
createProcess
((String -> CreateProcess
shell String
pager) {std_in :: StdStream
std_in = StdStream
CreatePipe
,std_err :: StdStream
std_err = StdStream
CreatePipe})
ResourceT IO () -> IO ()
forall (m :: * -> *) a. MonadUnliftIO m => ResourceT m a -> m a
runResourceT (ConduitT () ByteString (ResourceT IO) ()
-> ConduitT ByteString Void (ResourceT IO) () -> ResourceT IO ()
forall (m :: * -> *) a r.
Monad m =>
ConduitT () a m () -> ConduitT a Void m r -> m r
connect ConduitT () ByteString (ResourceT IO) ()
Producer (ResourceT IO) ByteString
producer (Handle -> ConduitT ByteString Void (ResourceT IO) ()
forall (m :: * -> *) o.
MonadIO m =>
Handle -> ConduitT ByteString o m ()
sinkHandle Handle
stdinH))
Handle -> IO ()
hClose Handle
stdinH
ExitCode
exitCode <- ProcessHandle -> IO ExitCode
waitForProcess ProcessHandle
ph
case ExitCode
exitCode of
ExitFailure Int
i ->
do String
errContents <- Handle -> IO String
hGetContents Handle
stderrH
String -> IO ()
forall (m :: * -> *) a. MonadFail m => String -> m a
fail ([String] -> String
unlines [String -> String -> String
forall a. Monoid a => a -> a -> a
mappend String
"Pager exited with exit code " (Int -> String
forall a. Show a => a -> String
show Int
i)
,String
errContents])
ExitCode
ExitSuccess -> () -> IO ()
forall (m :: * -> *) a. Monad m => a -> m a
return ()