name: CI

on:
  push:
    branches:
    - master
  pull_request:
    types:
    - opened
    - synchronize

jobs:
  build-test-ubuntu-stack:
    runs-on: ubuntu-latest
    name: Ubuntu / Stack
    steps:
    - uses: actions/checkout@v2

    # relative paths are relative to the project directory
    - name: Cache Stack build artifacts (user + project)
      uses: actions/cache@v4
      with:
        path: |
          ~/.stack
          .stack-work
        # best effort for cache: tie it to Stack resolver and package config
        key: ${{ runner.os }}-stack-${{ hashFiles('stack.yaml.lock', 'package.yaml') }}
        restore-keys: |
          ${{ runner.os }}-stack

    - name: Install project dependencies
      run: stack --no-terminal test --only-dependencies

    - name: Build and run tests
      run: stack --no-terminal haddock --test --no-haddock-deps

  build-test-ubuntu-cabal:
    runs-on: ubuntu-latest
    name: Ubuntu / GHC ${{ matrix.ghc }}, Cabal ${{ matrix.cabal }}
    strategy:
      fail-fast: false      # don't stop if one job (= GHC version) fails
      matrix:
        cabal: ["3.4"]      # latest as of 2021-06-16
        ghc:
        - "8.6.5"
        - "9.2.4"
        - "9.4.2"
    env:
      # note that all flags must be passed to every command even when
      # irrelevant, else Cabal will trigger arbitrary rebuilds
      CABAL_FLAGS: --enable-tests --enable-benchmarks --test-show-details=streaming
    steps:

    # TODO: GHC decides to recompile based on timestamp, so cache isn't used
    # Preferably GHC would work via hashes instead. Stack had this feature
    # merged in Aug 2020.
    # Upstream GHC issue: https://gitlab.haskell.org/ghc/ghc/-/issues/16495
    # My issue on haskell/actions: https://github.com/haskell/actions/issues/41
    # This also requires us to do a deep fetch, else we don't get the Git commit
    # history we need to rewrite mod times.
    - uses: actions/checkout@v2
      with:
        fetch-depth: 0
    - name: Set all tracked file modification times to the time of their last commit
      run: |
        rev=HEAD
        for f in $(git ls-tree -r -t --full-name --name-only "$rev") ; do
            touch -d $(git log --pretty=format:%cI -1 "$rev" -- "$f") "$f";
        done

    - name: Setup Haskell build environment
      id: setup-haskell-build-env
      uses: haskell/actions/setup@v1
      with:
        ghc-version: ${{ matrix.ghc }}
        cabal-version: ${{ matrix.cabal }}

    - name: Freeze Cabal plan
      run: cabal freeze

    - name: Cache Cabal build artifacts
      uses: actions/cache@v4
      with:
        path: |
          ${{ steps.setup-haskell-build-env.outputs.cabal-store }}
          dist-newstyle
        key: ${{ runner.os }}-cabal-${{ matrix.ghc }}-${{ hashFiles('cabal.project.freeze') }}
        restore-keys: |
          ${{ runner.os }}-cabal-${{ matrix.ghc }}

    - name: Build
      run: cabal build

    - name: Test
      run: cabal test --test-show-details=streaming
      env:
        HSPEC_OPTIONS: --color