name: Build Docker Image

# Release builds (master / v* tags) plus a build-only check on pull requests
# that touch anything the image depends on — the Dockerfile's stub-source
# machinery, the ffmpeg download and the entrypoint are exactly the parts that
# would otherwise break only at release time.
#
# Actions are pinned to commit SHAs (Dependabot keeps the pins current).

on:
  push:
    tags:
      - v*
    branches:
      - master
  pull_request:
    paths:
      - Dockerfile
      - docker-entrypoint.sh
      - .dockerignore
      - Cargo.toml
      - Cargo.lock
      - .github/workflows/docker.yml
      - 'crates/**/Cargo.toml'

env:
  APP_NAME: telegram-twitter-media-bot
  DOCKERHUB_REPO: yoursfunny/telegram-twitter-media-bot

permissions:
  contents: read

# Serialize runs per ref. Never cancel in progress: a killed run would drop a
# half-finished image push.
concurrency:
  group: docker-${{ github.ref }}
  cancel-in-progress: false

jobs:
  # A tag push and a branch push to the same commit fire two workflow runs;
  # build only once. Tag runs always build; master runs build only when the
  # pushed commit is not already tagged (the tag run covers it).
  should-build:
    runs-on: ubuntu-latest
    timeout-minutes: 10
    outputs:
      build: ${{ steps.check.outputs.build }}
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
        with:
          fetch-depth: 0
      # A release tag is the version claim: the manifests are bumped by hand,
      # so `v1.5.1` with `Cargo.toml` still at 1.5.0 would publish an image
      # whose tag lies about what is inside it (the binary carries no version).
      - name: Verify the tag matches both crate versions
        if: startsWith(github.ref, 'refs/tags/v')
        shell: bash
        run: |
          tag="${GITHUB_REF_NAME#v}"
          status=0
          for manifest in crates/x-media/Cargo.toml crates/xmedia-bot/Cargo.toml; do
            # tr -d '\r': a CRLF checkout (core.autocrlf on Windows) would
            # otherwise yield "1.5.0\r" and false-fail every tag.
            version="$(sed -n 's/^version = "\(.*\)"/\1/p' "$manifest" | head -1 | tr -d '\r')"
            if [ "$version" != "$tag" ]; then
              echo "::error file=$manifest::$manifest is at $version but the tag is v$tag"
              status=1
            else
              echo "$manifest: $version matches v$tag"
            fi
          done
          exit "$status"
      - id: check
        shell: bash
        run: |
          if [ "$GITHUB_REF_TYPE" = "branch" ] && git tag --points-at "$GITHUB_SHA" | grep -q .; then
            echo "commit already tagged; the tag run builds the image"
            echo "build=false" >> "$GITHUB_OUTPUT"
          else
            echo "build=true" >> "$GITHUB_OUTPUT"
          fi

  # No `actions/checkout` here on purpose: `docker/build-push-action` defaults
  # to the Git context (`https://github.com/<owner>/<repo>.git#<ref>`), so
  # BuildKit clones the repo itself and authenticates with the automatic
  # github.token. Adding `context: .` below without a checkout step would hand
  # BuildKit an empty workspace.
  docker:
    needs: should-build
    if: needs.should-build.outputs.build == 'true'
    runs-on: ubuntu-latest
    timeout-minutes: 60
    steps:
      - name: Docker meta
        id: meta
        uses: docker/metadata-action@dc802804100637a589fabce1cb79ff13a1411302 # v6
        with:
          images: ${{ env.DOCKERHUB_REPO }}
          tags: |
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}.{{patch}}
            type=semver,pattern={{major}}.{{minor}}
            type=semver,pattern={{major}}
            type=sha
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@f87e5991a6d7451dcb8d9637bfbc97413f497069 # v4
      # Pull requests build the image to prove the Dockerfile still works, but
      # must not read registry credentials (fork PRs have none).
      -
        name: Login to Docker Hub
        if: github.event_name != 'pull_request'
        uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      # Buildkit cache via the GitHub Actions cache backend (uses the
      # automatic GITHUB_TOKEN, no extra secrets). mode=max keeps every
      # stage's layers so the cargo-deps and ffmpeg layers are restored
      # instead of re-downloaded/recompiled. The scope must be pinned to a
      # fixed string: the gha backend defaults to the current git ref, which
      # would give every new tag a cold cache on release builds. PR runs only
      # read it (cache-to is empty) so they cannot evict the release cache.
      #
      # FFMPEG_URL/FFMPEG_SHA256 come from repository variables when set, so a
      # release can pin an exact ffmpeg build (the Dockerfile default follows
      # the project's `/redirect/latest/` URL, which has no sha256 sidecar).
      #
      # Single-arch (amd64) on purpose: adding arm64 means re-adding
      # `docker/setup-qemu-action`, `platforms: linux/amd64,linux/arm64`, and
      # parameterizing FFMPEG_URL by $TARGETARCH in the Dockerfile.
      -
        name: Build and push
        uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7
        with:
          push: ${{ github.event_name != 'pull_request' }}
          build-args: |
            APP_NAME=${{ env.APP_NAME }}
            FFMPEG_URL=${{ vars.FFMPEG_URL || 'https://ffmpeg.martin-riedl.de/redirect/latest/linux/amd64/release/ffmpeg.zip' }}
            FFMPEG_SHA256=${{ vars.FFMPEG_SHA256 }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha,scope=tgxmb-build
          cache-to: ${{ github.event_name != 'pull_request' && 'type=gha,mode=max,scope=tgxmb-build' || '' }}