name: Lintcheck

on: pull_request

env:
  RUST_BACKTRACE: 1
  CARGO_INCREMENTAL: 0

concurrency:
  # For a given workflow, if we push to the same PR, cancel all previous builds on that PR.
  group: "${{ github.workflow }}-${{ github.event.pull_request.number}}"
  cancel-in-progress: true

jobs:
  # Generates `lintcheck-logs/base.json` and stores it in a cache
  base:
    runs-on: ubuntu-latest

    outputs:
      key: ${{ steps.key.outputs.key }}

    steps:
    - name: Checkout
      uses: actions/checkout@v4
      with:
        fetch-depth: 2

    # HEAD is the generated merge commit `refs/pull/N/merge` between the PR and `master`, `HEAD^`
    # being the commit from `master` that is the base of the merge
    - name: Checkout base
      run: git checkout HEAD^

    # Use the lintcheck from the PR to generate the JSON in case the PR modifies lintcheck in some
    # way
    - name: Checkout current lintcheck
      run: |
        rm -rf lintcheck
        git checkout ${{ github.sha }} -- lintcheck

    - name: Create cache key
      id: key
      run: echo "key=lintcheck-base-${{ hashfiles('lintcheck/**') }}-$(git rev-parse HEAD)" >> "$GITHUB_OUTPUT"

    - name: Cache results
      id: cache
      uses: actions/cache@v4
      with:
        path: lintcheck-logs/base.json
        key: ${{ steps.key.outputs.key }}

    - name: Run lintcheck
      if: steps.cache.outputs.cache-hit != 'true'
      run: cargo lintcheck --format json

    - name: Rename JSON file
      if: steps.cache.outputs.cache-hit != 'true'
      run: mv lintcheck-logs/lintcheck_crates_logs.json lintcheck-logs/base.json

  # Generates `lintcheck-logs/head.json` and stores it in a cache
  head:
    runs-on: ubuntu-latest

    outputs:
      key: ${{ steps.key.outputs.key }}

    steps:
    - name: Checkout
      uses: actions/checkout@v4

    - name: Create cache key
      id: key
      run: echo "key=lintcheck-head-${{ github.sha }}" >> "$GITHUB_OUTPUT"

    - name: Cache results
      id: cache
      uses: actions/cache@v4
      with:
        path: lintcheck-logs/head.json
        key: ${{ steps.key.outputs.key }}

    - name: Run lintcheck
      if: steps.cache.outputs.cache-hit != 'true'
      run: cargo lintcheck --format json

    - name: Rename JSON file
      if: steps.cache.outputs.cache-hit != 'true'
      run: mv lintcheck-logs/lintcheck_crates_logs.json lintcheck-logs/head.json

  # Retrieves `lintcheck-logs/base.json` and `lintcheck-logs/head.json` from the cache and prints
  # the diff to the GH actions step summary
  diff:
    runs-on: ubuntu-latest

    needs: [base, head]

    steps:
    - name: Checkout
      uses: actions/checkout@v4

    - name: Restore base JSON
      uses: actions/cache/restore@v4
      with:
        key: ${{ needs.base.outputs.key }}
        path: lintcheck-logs/base.json
        fail-on-cache-miss: true

    - name: Restore head JSON
      uses: actions/cache/restore@v4
      with:
        key: ${{ needs.head.outputs.key }}
        path: lintcheck-logs/head.json
        fail-on-cache-miss: true

    - name: Diff results
      run: cargo lintcheck diff lintcheck-logs/base.json lintcheck-logs/head.json >> $GITHUB_STEP_SUMMARY