name: diff-js-api-changes
description: Check for breaking changes in the public React Native JS API
outputs:
  message:
    description: Formatted markdown message describing API changes, or empty if no changes
    value: ${{ steps.format_output.outputs.message }}
runs:
  using: composite
  steps:
    - name: Fetch PR and main, compute merge base
      id: merge_base
      shell: bash
      env:
        PR_SHA: ${{ github.event.pull_request.head.sha }}
      run: |
        git fetch origin main
        git fetch origin "$PR_SHA" --depth=500
        echo "merge_base=$(git merge-base "$PR_SHA" origin/main)" >> $GITHUB_OUTPUT

    - name: Extract before and after API snapshots
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
        MERGE_BASE: ${{ steps.merge_base.outputs.merge_base }}
        PR_SHA: ${{ github.event.pull_request.head.sha }}
      run: |
        mkdir -p $SCRATCH_DIR
        git show "$MERGE_BASE":packages/react-native/ReactNativeApi.d.ts > $SCRATCH_DIR/ReactNativeApi-before.d.ts \
          || echo "" > $SCRATCH_DIR/ReactNativeApi-before.d.ts
        git show "$PR_SHA":packages/react-native/ReactNativeApi.d.ts > $SCRATCH_DIR/ReactNativeApi-after.d.ts \
          || echo "" > $SCRATCH_DIR/ReactNativeApi-after.d.ts

    - name: Run breaking change detection
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
      run: |
        node ./scripts/js-api/diff-api-snapshot \
          $SCRATCH_DIR/ReactNativeApi-before.d.ts \
          $SCRATCH_DIR/ReactNativeApi-after.d.ts \
          > $SCRATCH_DIR/output.json

    - name: Format output message
      id: format_output
      shell: bash
      env:
        SCRATCH_DIR: ${{ runner.temp }}/diff-js-api-changes
      run: |
        if [ ! -f "$SCRATCH_DIR/output.json" ]; then
          echo "message=" >> $GITHUB_OUTPUT
          exit 0
        fi

        RESULT=$(cat $SCRATCH_DIR/output.json | jq -r '.result // empty')
        if [ -z "$RESULT" ] || [ "$RESULT" = "NON_BREAKING" ]; then
          echo "message=" >> $GITHUB_OUTPUT
          exit 0
        fi

        # Use delimiter for multiline output
        {
          echo "message<<EOF"
          echo "> [!WARNING]"
          echo "> **JavaScript API change detected**"
          echo ">"
          echo "> This PR commits an update to \`ReactNativeApi.d.ts\`, indicating a change to React Native's public JavaScript API."
          echo ">"
          echo "> - Please include a **clear changelog message**."
          echo "> - This change will be subject to additional review."
          echo ">"
          echo "> This change was flagged as: \`${RESULT}\`"
          echo "EOF"
        } >> $GITHUB_OUTPUT