name: Documentation

# The docs are built on every push so a broken build is caught immediately, but
# only published once GitHub Pages has been enabled for the repository. Until the
# owner decides to publish, this job builds and stops.
#
# And on pull requests, where the build is the only check there is: `mkdocs build
# --strict` fails on a link to a page that does not exist, and building only after
# the merge means finding that out on `main`. Nothing is published from a pull
# request — the `deploy` job below runs on a manual dispatch and nothing else.
on:
  push:
    branches: [main]
    paths:
      - 'docs/**'
      - 'mkdocs.yml'
      - '.github/workflows/docs.yml'
  pull_request:
    paths:
      - 'docs/**'
      - 'mkdocs.yml'
      - '.github/workflows/docs.yml'
  workflow_dispatch:

permissions:
  contents: read
  pages: write
  id-token: write

concurrency:
  group: pages
  cancel-in-progress: false

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - uses: actions/setup-python@v5
        with:
          python-version: '3.12'
          cache: pip
          cache-dependency-path: docs/requirements.txt

      - run: pip install -r docs/requirements.txt

      - run: mkdocs build --strict

      - uses: actions/upload-pages-artifact@v3
        with:
          path: site_build

  deploy:
    needs: build
    runs-on: ubuntu-latest
    # Only runs once Pages is enabled. Until then the build above still guards
    # against a broken docs tree.
    if: github.event_name == 'workflow_dispatch'
    environment:
      name: github-pages
      url: ${{ steps.deploy.outputs.page_url }}
    steps:
      - id: deploy
        uses: actions/deploy-pages@v4