# ci-images/flutter-node/.gitea/workflows/build.yaml
#
# Daily check, build ONLY when an input actually changed.
#
# Inputs that define an image:  upstream base digests + the Dockerfile itself.
# Their combined hash is published as a marker tag `src-<hash>` next to the image.
# If that tag already exists in the registry, this exact image was already built
# and the run stops before doing any work.
#
# Tags pushed on a real build:
#   :stable      moving, what runners pull by default
#   :YYYYMMDD    immutable, for pinning / rollback
#   :src-<hash>  marker, 856 bytes, makes the next check a single registry lookup

name: build

on:
  schedule:
    - cron: "0 3 * * *"          # daily instead of weekly - costs nothing when nothing changed
  push:
    branches: [main]
  workflow_dispatch:
    inputs:
      force:
        description: "Build even if no upstream change was detected"
        type: boolean
        default: false

env:
  IMAGE: ${{ vars.REGISTRY_HOST }}/ci-images/flutter-node
  FLUTTER_IMAGE: ghcr.io/cirruslabs/flutter:stable
  NODE_IMAGE: node:20-bookworm-slim

jobs:
  check:
    runs-on: ubuntu-docker
    outputs:
      changed:  ${{ steps.cmp.outputs.changed }}
      hash:     ${{ steps.hash.outputs.hash }}
      flutter:  ${{ steps.up.outputs.flutter }}
      node:     ${{ steps.up.outputs.node }}
      date:     ${{ steps.date.outputs.date }}
    steps:
      - name: Validate registry token
        run: test -n "${{ secrets.REGISTRY_TOKEN }}" || { echo "REGISTRY_TOKEN missing"; exit 1; }

      - name: Checkout
        uses: actions/checkout@v4

      - name: Set up Buildx
        uses: docker/setup-buildx-action@v3

      - name: Log in to Gitea registry
        uses: docker/login-action@v3
        with:
          registry: ${{ vars.REGISTRY_HOST }}
          username: ${{ github.actor }}
          password: ${{ secrets.REGISTRY_TOKEN }}

      # Resolve the mutable upstream tags to immutable digests, right now.
      - name: Resolve upstream digests
        id: up
        run: |
          set -euo pipefail
          f=$(docker buildx imagetools inspect "$FLUTTER_IMAGE" --format '{{.Manifest.Digest}}')
          n=$(docker buildx imagetools inspect "$NODE_IMAGE"    --format '{{.Manifest.Digest}}')
          echo "flutter=$f" >> "$GITHUB_OUTPUT"
          echo "node=$n"    >> "$GITHUB_OUTPUT"
          echo "flutter: $f"
          echo "node:    $n"

      - name: Compute input hash
        id: hash
        run: |
          set -euo pipefail
          h=$(printf '%s\n' \
                "${{ steps.up.outputs.flutter }}" \
                "${{ steps.up.outputs.node }}" \
                "$(sha256sum Dockerfile | cut -d' ' -f1)" \
              | sha256sum | cut -c1-12)
          echo "hash=$h" >> "$GITHUB_OUTPUT"
          echo "input hash: $h"

      # The whole gate: does a marker tag for this exact input set already exist?
      - name: Compare against what is already published
        id: cmp
        run: |
          set -euo pipefail
          if [ "${{ github.event_name }}" = "push" ] || [ "${{ github.event.inputs.force }}" = "true" ]; then          
            echo "changed=true" >> "$GITHUB_OUTPUT"
            echo "non-scheduled or forced run - building"
            exit 0
          fi
          if docker buildx imagetools inspect "$IMAGE:src-${{ steps.hash.outputs.hash }}" >/dev/null 2>&1; then
            echo "changed=false" >> "$GITHUB_OUTPUT"
            echo "no change since last build - skipping"
          else
            echo "changed=true" >> "$GITHUB_OUTPUT"
            echo "upstream or Dockerfile changed - building"
          fi

      - name: Compute date tag
        id: date
        run: echo "date=$(date -u +%Y%m%d)" >> "$GITHUB_OUTPUT"

  build:
    needs: check
    if: needs.check.outputs.changed == 'true'
    runs-on: ubuntu-docker
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Set up Buildx
        uses: docker/setup-buildx-action@v3

      - name: Log in to Gitea registry
        uses: docker/login-action@v3
        with:
          registry: ${{ vars.REGISTRY_HOST }}
          username: ${{ github.actor }}
          password: ${{ secrets.REGISTRY_TOKEN }}

      - name: Build and push
        uses: docker/build-push-action@v5
        with:
          context: .
          push: true
          pull: true                      # re-resolve bases; without this the cron is a no-op
          provenance: false               # no attestation manifest -> half the package versions
          cache-from: type=registry,ref=${{ env.IMAGE }}:stable
          cache-to: type=inline
          build-args: |
            IMAGE_SOURCE=https://${{ vars.REGISTRY_HOST }}/ci-images/flutter-node
            FLUTTER_IMAGE=${{ env.FLUTTER_IMAGE }}@${{ needs.check.outputs.flutter }}
            NODE_IMAGE=${{ env.NODE_IMAGE }}@${{ needs.check.outputs.node }}
          labels: |
            org.opencontainers.image.base.name=${{ env.FLUTTER_IMAGE }}
            org.opencontainers.image.base.digest=${{ needs.check.outputs.flutter }}
            org.opencontainers.image.revision=${{ github.sha }}
          tags: |
            ${{ env.IMAGE }}:stable
            ${{ env.IMAGE }}:${{ needs.check.outputs.date }}
            ${{ env.IMAGE }}:src-${{ needs.check.outputs.hash }}