{- |
Copyright:  (c) 2018-2019 Kowainik
SPDX-License-Identifier: MIT
Maintainer: Kowainik <xrom.xkov@gmail.com>

Contains useful functions to work with GHC callstack.
-}

module Relude.Extra.CallStack
       ( ownName
       , callerName
       ) where

import Relude

{- | This function returns the name of its caller function, but it requires
that the caller function has 'HasCallStack' constraint. Otherwise, it returns
@"<unknown>"@.

>>> foo :: HasCallStack => String; foo = ownName
>>> foo
"foo"
>>> bar :: HasCallStack => String; bar = foo
>>> bar
"foo"
-}
ownName :: HasCallStack => String
ownName :: String
ownName = case CallStack -> [(String, SrcLoc)]
getCallStack CallStack
HasCallStack => CallStack
callStack of
    _:caller :: (String, SrcLoc)
caller:_ -> (String, SrcLoc) -> String
forall a b. (a, b) -> a
fst (String, SrcLoc)
caller
    _          -> "<unknown>"

{- | This function returns the name of its caller of the caller function, but it
requires that the caller function and caller of the caller function have
'HasCallStack' constraint. Otherwise, it returns @"<unkown>"@. It's useful for
logging:

>>> log :: HasCallStack => String -> IO (); log s = putStrLn $ callerName ++ ":" ++ s
>>> greeting :: HasCallStack => IO (); greeting = log "Starting..." >> putStrLn "Hello!" >> log "Ending..."
>>> greeting
greeting:Starting...
Hello!
greeting:Ending...
-}
callerName :: HasCallStack => String
callerName :: String
callerName = case CallStack -> [(String, SrcLoc)]
getCallStack CallStack
HasCallStack => CallStack
callStack of
    _:_:caller :: (String, SrcLoc)
caller:_ -> (String, SrcLoc) -> String
forall a b. (a, b) -> a
fst (String, SrcLoc)
caller
    _            -> "<unknown>"