name: main 回灌 dev

on:
  push:
    branches:
      - main
  workflow_dispatch:

permissions:
  contents: write
  pull-requests: write

concurrency:
  group: sync-main-to-dev
  cancel-in-progress: true

jobs:
  sync-main-to-dev:
    name: 执行回灌同步
    runs-on: ubuntu-latest
    steps:
      - name: 检出代码
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: 检查是否需要同步
        id: diff_check
        shell: bash
        run: |
          set -euo pipefail
          echo "开始检查 main 与 dev 的分支差异..."
          git fetch origin main dev
          ahead_count="$(git rev-list --count origin/dev..origin/main)"
          echo "ahead_count=${ahead_count}" >> "$GITHUB_OUTPUT"
          if [ "${ahead_count}" -eq 0 ]; then
            echo "无需同步，dev 已包含 main 的最新提交。"
            echo "has_changes=false" >> "$GITHUB_OUTPUT"
          else
            echo "检测到 ${ahead_count} 个待同步提交，准备创建或复用同步 PR。"
            echo "has_changes=true" >> "$GITHUB_OUTPUT"
          fi

      - name: 创建或复用同步 PR
        id: sync_pr
        if: steps.diff_check.outputs.has_changes == 'true'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        shell: bash
        run: |
          set -euo pipefail
          existing_number="$(gh pr list --base dev --head main --state open --json number --jq '.[0].number // empty')"

          if [ -n "${existing_number}" ]; then
            pr_number="${existing_number}"
            pr_url="$(gh pr view "${pr_number}" --json url --jq '.url')"
            echo "复用已有同步 PR：#${pr_number}"
            echo "created=false" >> "$GITHUB_OUTPUT"
          else
            body_file="$(mktemp)"
            {
              echo "## 自动回灌：\`main -> dev\`"
              echo
              echo "- 触发条件：\`main\` 分支出现新提交（含贡献者直接合并到 \`main\` 的 PR）"
              echo "- 目标：让 \`dev\` 持续吸收 \`main\` 的更新，避免发布前集中冲突"
              echo
              echo "### 合并建议"
              echo "- 无冲突：直接合并该 PR（建议 \`Merge commit\`）"
              echo "- 有冲突：在该 PR 内解决冲突后再合并"
            } > "${body_file}"
            pr_url="$(gh pr create \
              --base dev \
              --head main \
              --title "🔁 chore(sync): 回灌 main 到 dev" \
              --body-file "${body_file}")"
            pr_number="${pr_url##*/}"
            echo "已创建同步 PR：#${pr_number}"
            echo "created=true" >> "$GITHUB_OUTPUT"
          fi

          echo "pr_number=${pr_number}" >> "$GITHUB_OUTPUT"
          echo "pr_url=${pr_url}" >> "$GITHUB_OUTPUT"

      - name: 检查合并状态
        id: merge_state
        if: steps.diff_check.outputs.has_changes == 'true'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        shell: bash
        run: |
          set -euo pipefail
          pr_number="${{ steps.sync_pr.outputs.pr_number }}"
          mergeable="$(gh pr view "${pr_number}" --json mergeable --jq '.mergeable')"
          merge_state_status="$(gh pr view "${pr_number}" --json mergeStateStatus --jq '.mergeStateStatus')"
          echo "PR #${pr_number} 合并状态：mergeable=${mergeable}, mergeStateStatus=${merge_state_status}"
          echo "mergeable=${mergeable}" >> "$GITHUB_OUTPUT"
          echo "merge_state_status=${merge_state_status}" >> "$GITHUB_OUTPUT"

      - name: 可合并时开启自动合并
        id: auto_merge
        if: steps.diff_check.outputs.has_changes == 'true' && steps.merge_state.outputs.mergeable == 'MERGEABLE'
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        shell: bash
        run: |
          set -euo pipefail
          pr_number="${{ steps.sync_pr.outputs.pr_number }}"
          if gh pr merge "${pr_number}" --merge --auto; then
            echo "已为 PR #${pr_number} 开启自动合并。"
            echo "result=enabled" >> "$GITHUB_OUTPUT"
          else
            echo "::warning::自动合并开启失败，请手动处理并合并该 PR。"
            echo "result=failed" >> "$GITHUB_OUTPUT"
          fi

      - name: 写入执行摘要
        if: always()
        shell: bash
        run: |
          {
            echo "## main 回灌 dev 执行结果"
            if [ "${{ steps.diff_check.outputs.has_changes }}" != "true" ]; then
              echo "- 状态：无需同步（dev 已包含 main 最新提交）"
              exit 0
            fi
            echo "- PR：${{ steps.sync_pr.outputs.pr_url }}"
            echo "- 可合并状态：${{ steps.merge_state.outputs.mergeable }}"
            echo "- 合并状态详情：${{ steps.merge_state.outputs.merge_state_status }}"
            if [ "${{ steps.merge_state.outputs.mergeable }}" = "CONFLICTING" ]; then
              echo "- 结论：检测到冲突，需要手动处理后合并"
            elif [ "${{ steps.auto_merge.outputs.result }}" = "enabled" ]; then
              echo "- 结论：已启用自动合并（满足保护规则后将自动入 dev）"
            else
              echo "- 结论：PR 已创建/复用，请按分支策略人工合并"
            fi
          } >> "$GITHUB_STEP_SUMMARY"