name: Build image when workload image tag changes

on:
  push:
    # Uncomment/adjust once it's working:
    # branches: [ main ]
    paths:
      - "argocd/deployment.yaml"
      - "Dockerfile"
      - ".gitea/workflows/build-on-demand.yml"

jobs:
  build-if-image-changed:
    runs-on: ubuntu-latest

    env:
      DEPLOY_FILE: "argocd/deployment.yaml"
      CONTAINER_NAME: "web"                       # we only consider this container
      EXPECTED_REPO: "git.baumann.gr/adebaumann/vui"  # sanity-check the repo

    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 2

      - name: Determine base commit
        id: base
        shell: bash
        run: |
          set -euo pipefail
          if git rev-parse --verify -q HEAD~1 >/dev/null; then
            echo "base=$(git rev-parse HEAD~1)" >> "$GITHUB_OUTPUT"
          else
            echo "base=$(git hash-object -t tree /dev/null)" >> "$GITHUB_OUTPUT"
          fi

      - name: Install yq
        shell: bash
        run: |
          set -euo pipefail
          YQ_VER=v4.44.3
          curl -sL "https://github.com/mikefarah/yq/releases/download/${YQ_VER}/yq_linux_amd64" -o /usr/local/bin/yq
          chmod +x /usr/local/bin/yq
          yq --version
      
      - name: Read workload image from deployment (old vs new)
        id: img
        shell: bash
        run: |
          set -euo pipefail
          file="${DEPLOY_FILE:-argocd/deployment.yaml}"
          cname="${CONTAINER_NAME:-web}"
          expected_repo="${EXPECTED_REPO:-git.baumann.gr/adebaumann/vui}"

          # --- functions ------------------------------------------------------
          have_yq() { command -v yq >/dev/null 2>&1; }

          # yq-based extractor (multi-doc aware; Deployment only; container name match)
          yq_extract() {
            yq -r '
              select(.kind == "Deployment") |
              .spec.template.spec.containers // [] |
              map(select(.name == env(cname))) |
              .[]?.image
            ' "$1" 2>/dev/null | tail -n 1
          }

          # ultra-tolerant fallback: grep around containers: block and pick name==web image
          # (still ignores initContainers by staying within the "containers:" block)
          fallback_extract() {
            # print the containers block, then associate names with images
            awk -v cname="$cname" '
              BEGIN{ in_cont=0; name=""; image="" }
              /^containers:/ {in_cont=1; next}
              in_cont {
                # end of containers block when dedented to less than two spaces or new top-level key
                if ($0 ~ /^[[:alpha:]][[:alnum:]_:-]*:/ || $0 ~ /^ *initContainers:/) { in_cont=0 }
                # capture name and image lines
                if ($0 ~ /^[[:space:]]*-?[[:space:]]*name:[[:space:]]*/) {
                  name=$0; sub(/^.*name:[[:space:]]*/,"",name); gsub(/^[ "\047]+|[ "\047]+$/,"",name)
                }
                if ($0 ~ /^[[:space:]]*image:[[:space:]]*/) {
                  image=$0; sub(/^.*image:[[:space:]]*/,"",image); gsub(/^[ "\047]+|[ "\047]+$/,"",image)
                  if (name==cname) { print image; exit }
                }
              }
            ' "$1"
          }

          list_workload_images() {
            echo "== workload containers in $1 ==" >&2
            if have_yq; then
              yq -r '
                select(.kind == "Deployment") |
                .spec.template.spec.containers // [] |
                .[] | "\(.name): \(.image)"
              ' "$1" 2>/dev/null | nl -ba >&2 || true
            else
              # coarse list for visibility
              awk '
                /^ *containers:/, /^[^ ]/ { if ($0 ~ /name:|image:/) print }
              ' "$1" | nl -ba >&2 || true
            fi
          }
          # --------------------------------------------------------------------

          # Ensure yq is present; if install failed earlier, try once more
          if ! have_yq; then
            echo "yq missing; attempting quick install..." >&2
            curl -fsSL https://github.com/mikefarah/yq/releases/latest/download/yq_linux_amd64 -o /usr/local/bin/yq || true
            chmod +x /usr/local/bin/yq || true
          fi

          # Prepare old file (previous commit) if exists
          if git cat-file -e "${{ steps.base.outputs.base }}":"$file" 2>/dev/null; then
            git show "${{ steps.base.outputs.base }}:$file" > /tmp/old.yaml
          else
            : > /tmp/old.yaml
          fi

          list_workload_images /tmp/old.yaml || true
          list_workload_images "$file" || true

          if have_yq; then
            old_image="$(yq_extract /tmp/old.yaml || true)"
            new_image="$(yq_extract "$file" || true)"
          else
            old_image="$(fallback_extract /tmp/old.yaml || true)"
            new_image="$(fallback_extract "$file" || true)"
          fi

          # If yq path failed to find it, try fallback once more as safety
          if [ -z "${new_image:-}" ]; then
            new_image="$(fallback_extract "$file" || true)"
          fi
          if [ -z "${old_image:-}" ]; then
            old_image="$(fallback_extract /tmp/old.yaml || true)"
          fi

          echo "Old workload image: ${old_image:-<none>}"
          echo "New workload image: ${new_image:-<none>}"

          if [ -z "${new_image:-}" ]; then
            echo "ERROR: Could not find containers[].name == \"$cname\" image in $file"
            exit 1
          fi

          # Split repo and tag
          new_repo="${new_image%:*}"
          new_tag="${new_image##*:}"
          if [[ "$new_repo" != "$expected_repo" ]]; then
            echo "ERROR: Found container \"$cname\" image repo is \"$new_repo\" but expected \"$expected_repo\""
            exit 1
          fi
          if [ -n "${old_image:-}" ]; then
            old_tag="${old_image##*:}"
          else
            old_tag=""
          fi

          registry="$(echo "$new_repo" | awk -F/ '{print $1}')"

          {
            echo "changed=$([ "$old_tag" != "$new_tag" ] && echo true || echo false)"
            echo "new_image=$new_image"
            echo "new_repo=$new_repo"
            echo "new_tag=$new_tag"
            echo "registry=$registry"
          } >> "$GITHUB_OUTPUT"
      
      - name: Skip if tag unchanged
        if: steps.img.outputs.changed != 'true'
        run: echo "Workload image tag unchanged; skipping build."

      - name: Set up Buildx
        if: steps.img.outputs.changed == 'true'
        uses: docker/setup-buildx-action@v3

      - name: Log in to registry
        if: steps.img.outputs.changed == 'true'
        uses: docker/login-action@v3
        with:
          registry: ${{ steps.img.outputs.registry }}
          username: ${{ secrets.REGISTRY_USER }}
          password: ${{ secrets.REGISTRY_PASSWORD }}

      - name: Build and push (exact tag from deployment)
        if: steps.img.outputs.changed == 'true'
        uses: docker/build-push-action@v6
        with:
          context: .
          push: true
          tags: |
            ${{ steps.img.outputs.new_image }}
            ${{ steps.img.outputs.new_repo }}:latest
          labels: |
            org.opencontainers.image.source=${{ gitea.repository }}
            org.opencontainers.image.revision=${{ gitea.sha }}
          cache-from: type=gha
          cache-to: type=gha,mode=max