# Custom Pages build: compiles Thor from source via the Nix flake, uses it to
# generate thor/site/, and publishes the result. Replaces the default Jekyll build.
name: Deploy site to GitHub Pages

on:
  push:
    branches: [main]
    # Only rebuild when something that affects the output changes.
    paths:
      - "site/**"
      - "**/*.odin"
      - "defaults/**"
      - "flake.nix"
      - "flake.lock"
      - ".github/workflows/pages.yml"
  workflow_dispatch:

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

# Allow one concurrent deployment; don't cancel an in-progress publish.
concurrency:
  group: pages
  cancel-in-progress: false

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

      - name: Install Nix
        uses: cachix/install-nix-action@v30
        with:
          extra_nix_config: |
            experimental-features = nix-command flakes

      # Free cache: snapshots /nix/store into GitHub's Actions cache. The key is
      # hashed over the inputs that change Thor's output, so a site-content-only
      # change is a full hit (Thor not recompiled), while an Odin source change
      # restores the nearest store and rebuilds just the delta.
      - name: Cache /nix/store
        uses: nix-community/cache-nix-action@v6
        with:
          primary-key: nix-${{ runner.os }}-${{ hashFiles('flake.lock', '**/*.nix', '**/*.odin') }}
          restore-prefixes-first-match: nix-${{ runner.os }}-
          gc-max-store-size-linux: 2G
          purge: true
          purge-prefixes: nix-${{ runner.os }}-
          purge-created: 604800 # drop entries older than 7 days

      # First run compiles Thor + the tree-sitter grammar libs; later runs
      # restore them from the cache above and skip the compile.
      - name: Build Thor
        run: nix build .#default --print-build-logs

      - name: Generate site
        working-directory: site
        run: ../result/bin/thor -base-url=https://sbrow.github.io/thor -minify

      - name: Upload Pages artifact
        uses: actions/upload-pages-artifact@v3
        with:
          path: site/public

  deploy:
    needs: build
    runs-on: ubuntu-latest
    environment:
      name: github-pages
      url: ${{ steps.deployment.outputs.page_url }}
    steps:
      - name: Deploy to GitHub Pages
        id: deployment
        uses: actions/deploy-pages@v4