sudo: false              # Use the container-based infrastructure.

addons:
  apt:
    packages:
      - libgmp-dev       # Stack's GHC depends on this.

cache:
  directories:
    - $HOME/.stack       # Global stack's cache.
    - $HOME/.foldercache # Per exercise `.stack-work` cache.

env:
 - RESOLVER="nightly-2016-07-17" CURRENT="YES" # Equal to each stack.yaml.
 - RESOLVER="nightly"                          # Latest nightly snapshot.

matrix:
  allow_failures:             # The snapshot `nightly` is just an aliases to
    - env: RESOLVER="nightly" # the newest version released. We don't want
  fast_finish: true           # Travis to fail on new incompatible releases.

before_install:
 - mkdir -p ${HOME}/bin                        # Create folder for stack.
 - export PATH="${HOME}/bin:$PATH"             # For stack
 - export PATH="${TRAVIS_BUILD_DIR}/bin:$PATH" # For {,fetch-}configlet.

install:
 - travis_retry fetch-configlet
 - travis_retry curl -L https://www.stackage.org/stack/linux-x86_64 -o pack.tgz
 - tar xzf pack.tgz --wildcards --strip-components=1 -C ${HOME}/bin '*/stack'
 - stack --resolver ${RESOLVER} --install-ghc install hlint

script:
 - |
    set -e

    configlet .               # Check basic track configuration.
    hlint ${TRAVIS_BUILD_DIR} # Run `hlint` on the entire repository.

    # Explicit set exercises' resolver only if it's not the current one.
    if [ "${CURRENT}" != "YES" ]; then
        SET_RESOLVER="--resolver ${RESOLVER}"
    fi

    for exercise in ${TRAVIS_BUILD_DIR}/exercises/* ; do
        pushd ${exercise}

        # `stack --work-dir` fails if not targeting a subdirectory, so we just
        # symbolic-link `.stack-work` to a subfolder in the cache directory.
        mkdir -p "${HOME}/.foldercache/${exercise}/.stack-work"
        ln -f -s "${HOME}/.foldercache/${exercise}/.stack-work"

        # Here we prepare the exercise to be tested by Stack.
        MODULE=`sed -n 's/ *module \+\([a-zA-Z0-9]\+\).*/\1/p' src/Example.hs`
        mv src/Example.hs "src/${MODULE}.hs"

        stack test ${SET_RESOLVER} `# Select the correct resolver. `\
                   --install-ghc   `# Download GHC if not in cache.`\
                   --no-terminal   `# Terminal detection is broken.`\
                   --pedantic      `# Enable -Wall and -Werror.    `
        popd
    done