diff.yml

on:
  workflow_dispatch:
  repository_dispatch:
    types: [release_event]

name: Diff Data

concurrency:
  group: diff-data
  cancel-in-progress: false

permissions:
  contents: read

jobs:
  diff_data:
    name: Diff and Release
    runs-on: ubuntu-latest
    # ncipollo/release-action creates a release + tag via GITHUB_TOKEN,
    # which requires contents: write (top-level default is contents: read).
    permissions:
      contents: write
    env:
      TZ: Europe/London
    steps:
      - uses: clusterflick/.github/setup@main

      - name: Get release tags
        id: tags
        run: |
          set -euo pipefail
          RELEASES=$(gh api repos/clusterflick/data-transformed/releases?per_page=10 \
            --jq 'sort_by(.published_at) | reverse')
          CURRENT=$(echo "$RELEASES" | jq -r '.[0].tag_name')
          PREVIOUS=$(echo "$RELEASES" | jq -r '.[1].tag_name')
          # The diff is anchored to when the current release was published rather
          # than to the wall clock, so a re-run — or a run repeated months later —
          # reproduces the same blob instead of quietly reclassifying everything
          # that has happened since as past
          CURRENT_PUBLISHED_AT=$(echo "$RELEASES" | jq -r '.[0].published_at')
          echo "Current: $CURRENT ($CURRENT_PUBLISHED_AT), Previous: $PREVIOUS"

          # data-transformed has published daily for years, so anything short of
          # two releases means the API answered wrong rather than that there is
          # nothing to diff. Treating that as "nothing to do" would make a blip
          # indistinguishable from a quiet day; failing lets rerun-on-failure trigger
          for value in "$CURRENT" "$PREVIOUS" "$CURRENT_PUBLISHED_AT"; do
            if [ -z "$value" ] || [ "$value" = "null" ]; then
              echo "::error::Expected two data-transformed releases to compare"
              exit 1
            fi
          done

          echo "current=$CURRENT" >> "$GITHUB_OUTPUT"
          echo "previous=$PREVIOUS" >> "$GITHUB_OUTPUT"
          echo "current_published_at=$CURRENT_PUBLISHED_AT" >> "$GITHUB_OUTPUT"
        env:
          GH_TOKEN: ${{ secrets.PAT }}

      - name: Download current release
        uses: clusterflick/release-downloader@v3
        with:
          token: ${{ secrets.PAT }}
          repository: "clusterflick/data-transformed"
          tag: ${{ steps.tags.outputs.current }}
          fileName: "*"
          out-file-path: "transformed-data/current"

      - name: Download previous release
        uses: clusterflick/release-downloader@v3
        with:
          token: ${{ secrets.PAT }}
          repository: "clusterflick/data-transformed"
          tag: ${{ steps.tags.outputs.previous }}
          fileName: "*"
          out-file-path: "transformed-data/previous"

      - name: Diff Data
        run: npm run diff -- ${{ steps.tags.outputs.current }} ${{ steps.tags.outputs.previous }} ${{ steps.tags.outputs.current_published_at }}

      # The registry carries forward from its own last publication, not from
      # the previous transformed release. Absent on the first run, and whenever
      # the latest release predates the registry - both leave it starting from
      # whatever is showing today, which is correct rather than merely tolerable.
      - name: Download previous seen registry
        uses: clusterflick/release-downloader@v3
        with:
          token: ${{ secrets.PAT }}
          repository: "clusterflick/data-diffed"
          latest: true
          fileName: "seen-registry.json"
          out-file-path: "previous-registry"

      # Downloaded separately from the seen registry: the two have different
      # retention rules and different consumers, and only this one is safe for a
      # backfill to rewrite.
      - name: Download previous venue registry
        uses: clusterflick/release-downloader@v3
        with:
          token: ${{ secrets.PAT }}
          repository: "clusterflick/data-diffed"
          latest: true
          fileName: "venue-registry.json"
          out-file-path: "previous-registry"

      - name: Build seen registry
        run: npm run registry -- ${{ steps.tags.outputs.current }}

      # The diff only writes its output when something actually changed, so its
      # absence is how a no-op run reports itself. The seen registry is written
      # either way but rides along in the same release: a run with no changes
      # has nothing departing, so the previous registry is still current and
      # the next run carries forward from it.
      - name: Check for changes
        id: changes
        run: |
          if [ -f diffed-data/diffed-data.json ]; then
            echo "has_changes=true" >> "$GITHUB_OUTPUT"
          else
            echo "No changes between releases; skipping release."
            echo "has_changes=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Generate Tag
        if: steps.changes.outputs.has_changes == 'true'
        run: echo "TAG=$(TZ=Europe/London date +'%Y%m%d.%H%M%S')" >> $GITHUB_ENV
      - uses: ncipollo/release-action@v1
        if: steps.changes.outputs.has_changes == 'true'
        id: release
        with:
          allowUpdates: false
          artifactErrorsFailBuild: true
          artifacts: "diffed-data/*"
          makeLatest: true
          tag: ${{ env.TAG }}
          commit: main
          body: |
            Changes between data-transformed ${{ steps.tags.outputs.previous }} and ${{ steps.tags.outputs.current }}

            ⚠️ **Internal build artifact — not licensed.** This exists so the website can render its New Listings feed and RSS without recomputing the diff, and it inherits the third-party metadata the transformed releases carry. No schema guarantees; changes without notice. For data you can use, see https://clusterflick.com/data-licence

            Created by job ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
      - name: Output summary
        if: steps.changes.outputs.has_changes == 'true'
        run: |
          echo "🔖 New release - ${{ steps.release.outputs.html_url }}" >> $GITHUB_STEP_SUMMARY

  trigger_downstream:
    name: Trigger downstream
    runs-on: ubuntu-latest
    needs: diff_data
    if: ${{ always() && !failure() && !cancelled() }}
    steps:
      - name: Repository Dispatch for data-cached
        uses: peter-evans/repository-dispatch@v4
        with:
          token: ${{ secrets.PAT }}
          repository: clusterflick/data-cached
          event-type: release_event