name: Rebuild video release assets

on:
  workflow_dispatch:
    inputs:
      release_tag:
        description: "Release tag holding the master video"
        required: true
        default: video-assets-v1
      source_asset:
        description: "Filename of the master asset to transcode from"
        required: true
        default: video4k.mkv

permissions:
  contents: write

jobs:
  transcode:
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        resolution: [480, 720, 1080, 2160]
    steps:
      - name: Install ffmpeg
        run: sudo apt-get update && sudo apt-get install -y ffmpeg

      - name: Download master asset
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          gh release download "${{ inputs.release_tag }}" \
            --repo "${{ github.repository }}" \
            --pattern "${{ inputs.source_asset }}" \
            --output source.input

      - name: Transcode
        run: |
          ffmpeg -y -i source.input -vf "scale=-2:${{ matrix.resolution }}" \
            -c:v libx264 -preset medium -crf 18 \
            -c:a aac -b:a 192k \
            -movflags +faststart \
            "video-${{ matrix.resolution }}p.mp4"

      - name: Verify output resolution
        run: |
          set -eu
          height=$(ffprobe -v error -select_streams v:0 \
            -show_entries stream=height -of csv=p=0 "video-${{ matrix.resolution }}p.mp4")
          echo "video-${{ matrix.resolution }}p.mp4 -> height=${height}"
          [ "$height" = "${{ matrix.resolution }}" ] || { echo "::error::expected height ${{ matrix.resolution }}, got $height"; exit 1; }

      - name: Upload transcoded asset
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          gh release upload "${{ inputs.release_tag }}" \
            "video-${{ matrix.resolution }}p.mp4" \
            --repo "${{ github.repository }}" --clobber

  # Video content can change (a re-transcode uploaded to the same asset
  # URLs) without any git diff at all, so there's nothing for Drone's own
  # push-triggered webhook (Settings > Webhooks in this repo) to detect.
  # Rather than talking to Drone directly (a separate token/API to
  # manage), just bump the marker comment at the top of .drone.yml and
  # push it - .drone.yml is already in every pipeline's paths filter, so
  # this is a normal push that flows through the exact same webhook the
  # Dockerfile/scripts-triggered builds already use.
  trigger-drone:
    needs: transcode
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7
        with:
          ref: master

      - name: Bump video refresh marker and push
        run: |
          sed -i "s/# Last video refresh:.*/# Last video refresh: $(date -u +%Y-%m-%dT%H:%M:%SZ)/" .drone.yml
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"
          git add .drone.yml
          git commit -m "Bump video refresh marker to trigger a Drone rebuild"
          git push origin master