name: Build CI Image
on:
  # Rebuild weekly (Monday 4am UTC) to pick up CLI updates — deliberately 2h
  # BEFORE evals-periodic's 6am cron so the weekly eval run finds a fresh
  # image instead of racing a half-pushed tag or duplicating the build.
  schedule:
    - cron: '0 4 * * 1'
  # Rebuild on Dockerfile or lockfile changes. package.json is deliberately
  # NOT a trigger: the tag hash below excludes it (its version field bumps on
  # every ship), so a package.json-triggered run rebuilt and re-pushed the
  # IDENTICAL tag on every merge to main (~2m26s each for zero content change).
  push:
    branches: [main]
    paths:
      - '.github/docker/Dockerfile.ci'
      - 'bun.lock'
      - 'patches/**'
  # Manual trigger
  workflow_dispatch:

# Two rapid main pushes must not race pushing the same :latest/:buildcache
# tags; newest wins.
concurrency:
  group: ci-image-${{ github.ref }}
  cancel-in-progress: true

jobs:
  build:
    runs-on: ubicloud-standard-8
    timeout-minutes: 30
    permissions:
      contents: read
      packages: write
    steps:
      - uses: actions/checkout@v7

      # Copy lockfile + package.json into Docker build context
      - run: cp package.json bun.lock .github/docker/ && cp -R patches .github/docker/patches

      # Same content-hash tag expression as evals.yml / evals-periodic.yml
      # (byte-identity pinned by test/ci-image-tag-binding.test.ts). This is
      # the tag the eval matrix looks up first — without pushing it here, the
      # weekly/main prebuild never warms the cache that matters.
      - id: meta
        run: echo "tag=ghcr.io/${{ github.repository }}/ci:${{ hashFiles('.github/docker/Dockerfile.ci', 'bun.lock', 'patches/**') }}" >> "$GITHUB_OUTPUT"

      - uses: docker/login-action@v4
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      # Skip the ~2.5min build when the content-hash tag already exists
      # (mirrors evals.yml's check). The weekly cron still refreshes :latest
      # via a full run when the tag is genuinely new.
      - name: Check if image exists
        id: check
        run: |
          if docker manifest inspect ${{ steps.meta.outputs.tag }} > /dev/null 2>&1; then
            echo "exists=true" >> "$GITHUB_OUTPUT"
          else
            echo "exists=false" >> "$GITHUB_OUTPUT"
          fi

      # Registry cache export needs a docker-container builder — the default
      # `docker` driver hard-errors on cache-to.
      - if: steps.check.outputs.exists == 'false'
        uses: docker/setup-buildx-action@v4

      - if: steps.check.outputs.exists == 'false'
        uses: docker/build-push-action@v7
        with:
          context: .github/docker
          file: .github/docker/Dockerfile.ci
          push: true
          cache-from: type=registry,ref=ghcr.io/${{ github.repository }}/ci:buildcache
          cache-to: type=registry,ref=ghcr.io/${{ github.repository }}/ci:buildcache,mode=max
          tags: |
            ${{ steps.meta.outputs.tag }}
            ghcr.io/${{ github.repository }}/ci:latest
            ghcr.io/${{ github.repository }}/ci:${{ github.sha }}