Base docker image (#5958)

Co-authored-by: Claude Haiku 4.5 <[email protected]>

.github/workflows/build.yml

@@ -30,6 +30,7 @@ jobs:
       project: ${{ steps.changes.outputs.project }}
       openapi: ${{ steps.changes.outputs.openapi }}
       frontend: ${{ steps.changes.outputs.frontend }}
+      docker-base: ${{ steps.changes.outputs.docker-base }}
     steps:
       - name: Harden the runner (Audit all outbound calls)
         uses: step-security/harden-runner@58077d3c7e43986b6b15fba718e8ea69e387dfcc # v2.15.1
@@ -402,6 +403,17 @@ jobs:
       - name: Checkout Repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9 # v3.7.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ github.token }}
+
+      - name: Convert repository owner to lowercase
+        id: repoowner
+        run: echo "lowercase=$(echo ${{ github.repository_owner }} | awk '{print tolower($0)}')" >> $GITHUB_OUTPUT
+
       - name: Free disk space on runner
         run: |
           echo "Disk space before cleanup:" && df -h
@@ -446,6 +458,22 @@ jobs:
         id: buildx
         uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3.12.0
 
+      - name: Build base image locally (PR base change only)
+        if: github.event_name == 'pull_request' && needs.files-changed.outputs.docker-base == 'true'
+        run: |
+          docker build -t stirling-pdf-base:pr-test -f docker/base/Dockerfile docker/base
+
+      - name: Set base image and platform for this build
+        id: build-params
+        run: |
+          if [ "${{ github.event_name }}" == "pull_request" ] && [ "${{ needs.files-changed.outputs.docker-base }}" == "true" ]; then
+            echo "base_image=stirling-pdf-base:pr-test" >> $GITHUB_OUTPUT
+            echo "platforms=linux/amd64" >> $GITHUB_OUTPUT
+          else
+            echo "base_image=ghcr.io/${{ steps.repoowner.outputs.lowercase }}/stirling-pdf-base:latest" >> $GITHUB_OUTPUT
+            echo "platforms=linux/amd64,linux/arm64/v8" >> $GITHUB_OUTPUT
+          fi
+
       - name: Build ${{ matrix.docker-rev }}
         uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0
         with:
@@ -455,7 +483,9 @@ jobs:
           push: false
           cache-from: type=gha,scope=${{ matrix.cache-scope }}
           cache-to: type=gha,mode=max,scope=${{ matrix.cache-scope }}
-          platforms: linux/amd64,linux/arm64/v8
+          platforms: ${{ steps.build-params.outputs.platforms }}
+          build-args: |
+            BASE_IMAGE=${{ steps.build-params.outputs.base_image }}
           provenance: true
           sbom: true