name: Build + push image (Forgejo registry)

# Builds THIS repo's image (backend/Dockerfile) and pushes it to Forgejo's
# built-in container registry, tagged by git SHA (every push) and semver
# (version tags) -- build-once, deploy-everywhere.
#
# Repo-split "finish separating" (was Stage 6/7): the frontend and backend no
# longer share the single `emi/thermograph/app` image the old monorepo
# build-push.yml produced. Each app repo now publishes its OWN image from its
# OWN Dockerfile -- this one is emi/thermograph-backend/app -- and
# thermograph-infra's compose references the two paths independently
# (BACKEND_IMAGE_PATH / FRONTEND_IMAGE_PATH). IMAGE_PATH is derived from
# github.repository, so this file is byte-identical in the frontend repo; the
# repo it lives in is what makes the image distinct.
#
# Runs on the `docker` label -- the LAN runner's job containers get the host's
# docker.sock automounted in (forgejo-runner config: container.docker_host:
# automount; see thermograph-infra/deploy/forgejo/register-lan-runner.sh),
# Docker-outside-of-Docker rather than DinD -- no privileged mode needed.
# The job image itself (node:20-bookworm) has no docker CLI, hence the
# "Install Docker CLI" step.
#
# The registry is deliberately mesh-only: git.thermograph.org's public DNS
# resolves to beta's public IP, which Caddy's ACL rejects for /v2/ paths, so
# any runner host that pushes/pulls needs a /etc/hosts entry pointing
# git.thermograph.org at beta's WireGuard IP (10.10.0.2). The docker
# build/push commands run against the automounted HOST daemon, so it's the
# runner HOST's own resolver that has to route over the mesh, not anything
# settable from inside the job container.
#
# REGISTRY is the vars.REGISTRY_HOST Actions variable (git.thermograph.org),
# NOT github.server_url -- that context resolves to the bare mesh IP:port
# (http://10.10.0.2:3080, no TLS), which docker CLI refuses ("server gave HTTP
# response to HTTPS client"). git.thermograph.org gets real TLS via Caddy and
# routes over the mesh once /etc/hosts is set, so it's the only correct value.
# deploy.sh resolves the SHA tag at deploy time and `docker compose pull`s it.

on:
  push:
    branches: [dev, main, release]
    tags: ['v*.*.*']
  workflow_dispatch: {}

# The runner has capacity: 1 (one physical LAN box) -- a burst of pushes to the
# same ref would otherwise queue whole builds back to back even though only the
# last one still matters. Keying on github.ref means dev/main/release/each tag
# get their own group, so this only cancels a superseded build of the SAME ref.
concurrency:
  group: build-push-${{ github.ref }}
  cancel-in-progress: true

jobs:
  build-push:
    runs-on: docker
    env:
      REGISTRY: https://${{ vars.REGISTRY_HOST }}
      IMAGE_PATH: ${{ github.repository }}/app
    steps:
      - uses: actions/checkout@v4

      - name: Install Docker CLI
        run: |
          apt-get update -qq
          apt-get install -y -qq docker.io

      - name: Compute image ref + tags
        id: image
        run: |
          host="${REGISTRY#https://}"; host="${host#http://}"
          path="$(printf '%s' "$IMAGE_PATH" | tr '[:upper:]' '[:lower:]')"
          ref="$host/$path"
          sha_tag="$ref:sha-${GITHUB_SHA:0:12}"
          echo "host=$host" >> "$GITHUB_OUTPUT"
          echo "sha_tag=$sha_tag" >> "$GITHUB_OUTPUT"
          if [[ "$GITHUB_REF" == refs/tags/v* ]]; then
            echo "semver_tag=$ref:${GITHUB_REF#refs/tags/}" >> "$GITHUB_OUTPUT"
          fi

      - name: Log in to the Forgejo registry
        run: |
          # NOT secrets.GITHUB_TOKEN -- Forgejo's per-job auto-injected token
          # can never push to the container registry (a known Forgejo
          # limitation independent of any permission setting). Needs a
          # manually provisioned PAT with write:package scope, stored as the
          # REGISTRY_TOKEN secret.
          echo "${{ secrets.REGISTRY_TOKEN }}" | docker login "${{ steps.image.outputs.host }}" \
            --username emi --password-stdin

      - name: Build
        run: |
          # One build, both tags -- the semver tag (tag pushes only) rides
          # along with the SHA tag instead of a second tag+push round trip.
          tag_args=(-t "${{ steps.image.outputs.sha_tag }}")
          if [[ -n "${{ steps.image.outputs.semver_tag }}" ]]; then
            tag_args+=(-t "${{ steps.image.outputs.semver_tag }}")
          fi
          docker build "${tag_args[@]}" -f Dockerfile .

      - name: Push (SHA tag, every push)
        run: docker push "${{ steps.image.outputs.sha_tag }}"

      - name: Push (semver tag, tag pushes only)
        if: startsWith(github.ref, 'refs/tags/v')
        run: docker push "${{ steps.image.outputs.semver_tag }}"