#!/bin/sh

set -ex

cabal --version
echo "$(ghc --version) [$(ghc --print-project-git-commit-id 2> /dev/null || echo '?')]"
stack --version

case $BUILD in
  stack)
    stack --no-terminal --skip-ghc-check setup
    stack --no-terminal --skip-ghc-check test --only-snapshot
    ;;
  cabal)
    if [ -f $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz ]
    then
      zcat $HOME/.cabal/packages/hackage.haskell.org/00-index.tar.gz > $HOME/.cabal/packages/hackage.haskell.org/00-index.tar
    fi
    cabal update -v || cabal update -v
    sed -i 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config
    cabal install --only-dependencies --enable-tests --enable-benchmarks --dry -v > installplan.txt
    sed -i -e '1,/^Resolving /d' installplan.txt; cat installplan.txt

    # check whether current requested install-plan matches cached package-db snapshot
    if diff -u installplan.txt $HOME/.cabsnap/installplan.txt;
    then
      echo "cabal build-cache HIT";
      rm -rfv .ghc;
      cp -a $HOME/.cabsnap/ghc $HOME/.ghc;
      cp -a $HOME/.cabsnap/lib $HOME/.cabsnap/share $HOME/.cabsnap/bin $HOME/.cabal/;
    else
      echo "cabal build-cache MISS";
      rm -rf $HOME/.cabsnap;
      mkdir -p $HOME/.ghc $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin;
      cabal install --only-dependencies --enable-tests --enable-benchmarks;
    fi

    # snapshot package-db on cache miss
    if [ ! -d $HOME/.cabsnap ];
    then
      echo "snapshotting package-db to build-cache";
      mkdir $HOME/.cabsnap;
      cp -a $HOME/.ghc $HOME/.cabsnap/ghc;
      cp -a $HOME/.cabal/lib $HOME/.cabal/share $HOME/.cabal/bin installplan.txt $HOME/.cabsnap/;
    fi
    ;;
esac