ghc-mod and ghc-modi are based on the ["ghc-mod library" http://hackage.haskell.org/packages/archive/ghc-mod/latest/doc/html/Language-Haskell-GhcMod.html]
which is a wrapper of ["GHC API" http://www.haskell.org/ghc/docs/latest/html/libraries/ghc/] and [Cabal http://hackage.haskell.org/package/Cabal].
The ["ghc-mod package" http://hackage.haskell.org/package/ghc-mod] on Hackage
includes
the ghc-mod command, the ghc-modi command, the ghc-mod library, and
The ["source repository of ghc-mod" https://github.com/kazu-yamamoto/ghc-mod] is on github.
**Emacs
["Emacs front-end" emacs.html] is an extension of ["Haskell mode" https://github.com/haskell/haskell-mode]. They enable to complete Haskell symbols and to browse documents of modules. Syntax error highlighting with GHC/Hlint is also integrated. Moreover, you are free from "import hell".