name: Build & Push Docker Image (Prerelease)

on:
  workflow_dispatch:
    inputs:
      bump:
        description: 'Bump line for next prerelease (auto detects in-flight major)'
        type: choice
        options: [auto, minor, major]
        default: auto

permissions:
  contents: write

concurrency:
  group: prerelease-build
  cancel-in-progress: false

jobs:
  version-bump:
    runs-on: ubuntu-latest
    outputs:
      version: ${{ steps.bump.outputs.VERSION }}
      sha: ${{ steps.bump.outputs.SHA }}
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Determine prerelease version
        id: bump
        run: |
          git fetch --tags

          # Capture the exact commit we're building so build/merge jobs are pinned to it
          echo "SHA=$(git rev-parse HEAD)" >> $GITHUB_OUTPUT

          # Get latest stable tag (exclude prerelease tags)
          STABLE_TAG=$(git tag -l 'v[0-9]*.[0-9]*.[0-9]*' | grep -v '\-pre\.' | sort -V | tail -1)
          STABLE="${STABLE_TAG#v}"
          STABLE="${STABLE:-0.0.0}"
          echo "Latest stable: $STABLE"

          IFS='.' read -r MAJOR MINOR PATCH <<< "$STABLE"

          # Detect any in-flight major prerelease (v(MAJOR+1).0.0-pre.*). Stay on that line if found.
          NEXT_MAJOR="$((MAJOR + 1)).0.0"
          MAJOR_PRE_EXISTS=$(git tag -l "v${NEXT_MAJOR}-pre.*" | head -1)

          BUMP_INPUT="${{ github.event.inputs.bump || 'auto' }}"

          if [ "$BUMP_INPUT" = "major" ] || { [ "$BUMP_INPUT" = "auto" ] && [ -n "$MAJOR_PRE_EXISTS" ]; }; then
            TARGET="$NEXT_MAJOR"
          else
            TARGET="${MAJOR}.$((MINOR + 1)).0"
          fi
          echo "Target: $TARGET"

          # Find the highest existing prerelease N for this target and increment
          LAST_N=$(git tag -l "v${TARGET}-pre.*" | sed 's/.*-pre\.//' | sort -n | tail -1)
          N=$(( ${LAST_N:-0} + 1 ))

          NEW_VERSION="${TARGET}-pre.${N}"
          echo "VERSION=$NEW_VERSION" >> $GITHUB_OUTPUT
          echo "$STABLE → $NEW_VERSION"

  build:
    runs-on: ${{ matrix.runner }}
    needs: version-bump
    strategy:
      fail-fast: false
      matrix:
        include:
          - platform: linux/amd64
            runner: ubuntu-latest
          - platform: linux/arm64
            runner: ubuntu-24.04-arm
    steps:
      - name: Prepare platform tag-safe name
        run: echo "PLATFORM_PAIR=$(echo ${{ matrix.platform }} | sed 's|/|-|g')" >> $GITHUB_ENV

      - uses: actions/checkout@v4
        with:
          ref: ${{ needs.version-bump.outputs.sha }}

      - uses: docker/setup-buildx-action@v3

      - uses: docker/login-action@v3
        if: ${{ !env.ACT }}
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Build and push by digest
        id: build
        uses: docker/build-push-action@v6
        with:
          context: .
          platforms: ${{ matrix.platform }}
          outputs: ${{ env.ACT == 'true' && 'type=docker' || 'type=image,name=mauriceboe/trek,push-by-digest=true,name-canonical=true,push=true' }}
          no-cache: true
          build-args: |
            APP_VERSION=${{ needs.version-bump.outputs.version }}

      - name: Export digest
        if: ${{ !env.ACT }}
        run: |
          mkdir -p /tmp/digests
          digest="${{ steps.build.outputs.digest }}"
          touch "/tmp/digests/${digest#sha256:}"

      - name: Upload digest artifact
        if: ${{ !env.ACT }}
        uses: actions/upload-artifact@v4
        with:
          name: digests-${{ env.PLATFORM_PAIR }}
          path: /tmp/digests/*
          if-no-files-found: error
          retention-days: 1

  merge:
    runs-on: ubuntu-latest
    needs: [version-bump, build]
    steps:
      - uses: actions/checkout@v4
        if: ${{ !env.ACT }}
        with:
          ref: ${{ needs.version-bump.outputs.sha }}
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Download build digests
        if: ${{ !env.ACT }}
        uses: actions/download-artifact@v4
        with:
          path: /tmp/digests
          pattern: digests-*
          merge-multiple: true

      - uses: docker/setup-buildx-action@v3
        if: ${{ !env.ACT }}

      - uses: docker/login-action@v3
        if: ${{ !env.ACT }}
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

      - name: Create and push multi-arch manifest
        if: ${{ !env.ACT }}
        working-directory: /tmp/digests
        run: |
          VERSION="${{ needs.version-bump.outputs.version }}"
          mapfile -t digests < <(printf 'mauriceboe/trek@sha256:%s\n' *)
          MAJOR_TAG="$(echo "$VERSION" | cut -d. -f1)-pre"
          docker buildx imagetools create \
            -t "mauriceboe/trek:latest-pre" \
            -t "mauriceboe/trek:$MAJOR_TAG" \
            -t "mauriceboe/trek:$VERSION" \
            "${digests[@]}"

      - name: Inspect manifest
        if: ${{ !env.ACT }}
        run: docker buildx imagetools inspect mauriceboe/trek:latest-pre

      - name: Push git tag
        if: ${{ !env.ACT }}
        run: |
          VERSION="${{ needs.version-bump.outputs.version }}"
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"
          git tag "v$VERSION"
          git push origin "v$VERSION"

      - name: Clean up old prerelease tags
        if: ${{ !env.ACT }}
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          KEEP=20
          VERSION="${{ needs.version-bump.outputs.version }}"
          BASE_VERSION="$(echo "$VERSION" | sed 's/-pre\..*//')"
          git fetch --tags
          # Sort by numeric prerelease N (field after -pre.) to get correct ascending order
          mapfile -t ALL_TAGS < <(git tag -l "v${BASE_VERSION}-pre.*" | awk -F'-pre\\.' '{print $2" "$0}' | sort -n | awk '{print $2}')
          TOTAL=${#ALL_TAGS[@]}
          DELETE_COUNT=$((TOTAL - KEEP))
          if [ "$DELETE_COUNT" -gt 0 ]; then
            for TAG in "${ALL_TAGS[@]:0:$DELETE_COUNT}"; do
              echo "Deleting old prerelease tag: $TAG"
              git push origin --delete "$TAG"
            done
          fi