name: Cascade FROM bump
description: |
  Bump a `FROM <image>:<tag>` line in a target repo's Dockerfile to trigger that
  repo's CI. Used when a base image rebuild needs to cascade rebuilds in
  downstream image repos.
inputs:
  target-repo:
    description: Target repo to edit (e.g. fritzlab/runner)
    required: true
  image:
    description: Image referenced in the target file's FROM line (e.g. code.fritzlab.net/fritzlab/base)
    required: true
  tag:
    description: New tag. Defaults to github.run_number when empty.
    required: false
    default: ''
  file:
    description: File path inside target-repo to edit
    required: false
    default: Dockerfile
  token:
    description: CI_BOT_TOKEN with write access to target-repo
    required: true
  host:
    description: Gitea host (without protocol)
    required: false
    default: code.fritzlab.net
  message:
    description: Commit message override. Defaults to "bump <image> to #<tag>".
    required: false
    default: ''
runs:
  using: composite
  steps:
    - name: Clone, edit, push
      shell: bash
      env:
        TARGET_REPO: ${{ inputs.target-repo }}
        IMAGE: ${{ inputs.image }}
        TAG_INPUT: ${{ inputs.tag }}
        FILE: ${{ inputs.file }}
        TOKEN: ${{ inputs.token }}
        HOST: ${{ inputs.host }}
        MESSAGE: ${{ inputs.message }}
        RUN_NUMBER: ${{ github.run_number }}
      run: |
        set -euo pipefail

        TAG="${TAG_INPUT:-$RUN_NUMBER}"
        NAME="$(basename "$IMAGE")"
        MSG="${MESSAGE:-bump ${NAME} to #${TAG}}"

        WORK="$(mktemp -d)"
        trap 'rm -rf "$WORK"' EXIT

        git clone --depth 1 "https://ci-bot:${TOKEN}@${HOST}/${TARGET_REPO}.git" "$WORK"
        cd "$WORK"
        git config user.name ci-bot
        git config user.email ci-bot@fritzlab.net

        if [ ! -f "$FILE" ]; then
          echo "FATAL: ${FILE} not found in ${TARGET_REPO}"
          exit 1
        fi

        # Escape forward slashes for sed pattern
        ESC_IMAGE="${IMAGE//\//\\/}"
        sed -i "s|^FROM ${IMAGE}:.*|FROM ${IMAGE}:${TAG}|" "$FILE"

        if ! grep -q "^FROM ${IMAGE}:${TAG}\b" "$FILE"; then
          echo "FATAL: sed did not match a FROM line for ${IMAGE} in ${FILE}"
          grep "^FROM" "$FILE" || true
          exit 1
        fi

        if git diff --quiet; then
          echo "${TARGET_REPO} already on ${NAME}:${TAG}, skipping"
          exit 0
        fi

        git add "$FILE"
        git commit -m "$MSG"

        ATTEMPTS=0
        until git push origin main; do
          ATTEMPTS=$((ATTEMPTS + 1))
          if [ "$ATTEMPTS" -ge 3 ]; then
            echo "FATAL: push to ${TARGET_REPO} failed after ${ATTEMPTS} attempts"
            exit 1
          fi
          echo "push rejected, attempt ${ATTEMPTS}; rebasing and retrying"
          git pull --rebase origin main
          sleep $((ATTEMPTS * 2))
        done

        echo "cascaded ${NAME}:${TAG} → ${TARGET_REPO}"