default.nix

{ haskellNix ? import (builtins.fetchTarball "https://github.com/input-output-hk/haskell.nix/archive/master.tar.gz") {}
, nixpkgsSrc ? haskellNix.sources.nixpkgs-2003
, nixpkgsArgs ? haskellNix.nixpkgsArgs
, pkgs ? import nixpkgsSrc nixpkgsArgs
}:

let
  compiler = "ghc884";

  githubTarball = owner: repo: rev:
    builtins.fetchTarball { url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz"; };

  pkgsUnstable = import (githubTarball "NixOS" "nixpkgs" "502845c3e31ef3de0e424f3fcb09217df2ce6df6") {};  
  
  project = pkgs.haskell-nix.project {
    compiler-nix-name = compiler;
    src = pkgs.haskell-nix.haskellLib.cleanGit {
      name = "realworld";
      src = ./.;
    };
  };
in {
  shell = project.shellFor {
    packages = ps: [ ps.realworld ];
    exactDeps = true;
    buildInputs = with pkgs.haskellPackages;
      with pkgsUnstable.haskell.packages.${compiler}; [
        cabal-install
        haskell-language-server
      ];
  };
}