name: Pull request size limit

on:
  pull_request_target:
    branches:
      - master
    types:
      - opened
      - synchronize
      - reopened
      - ready_for_review

permissions:
  contents: read
  pull-requests: write
  issues: write

concurrency:
  group: pr-size-limit-${{ github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  enforce-size-limit:
    # 保持这个名字不变，这样你 Ruleset 里的 Required Check 不需要修改
    name: Enforce 5,000-line limit
    runs-on: ubuntu-latest
    timeout-minutes: 5

    env:
      MAX_CHANGED_LINES: "5000"
      PR_NUMBER: ${{ github.event.pull_request.number }}
      GH_TOKEN: ${{ github.token }}

    steps:
      - name: Check conflicts and pull request size via GitHub API
        shell: bash
        run: |
          set -euo pipefail

          echo "Checking PR #${PR_NUMBER}"

          ############################################################
          # Helper: comment on and close rejected PR
          ############################################################

          reject_pr() {
            local message="$1"

            echo "::error::${message}"

            COMMENT_PAYLOAD="$(
              jq -nc \
                --arg body "${message}" \
                '{body: $body}'
            )"

            echo "Posting rejection comment..."

            curl \
              --fail-with-body \
              --silent \
              --show-error \
              --request POST \
              --header "Accept: application/vnd.github+json" \
              --header "Authorization: Bearer ${GH_TOKEN}" \
              --header "X-GitHub-Api-Version: 2022-11-28" \
              "${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}/issues/${PR_NUMBER}/comments" \
              --data "${COMMENT_PAYLOAD}" \
              >/dev/null

            echo "Closing PR #${PR_NUMBER}..."

            curl \
              --fail-with-body \
              --silent \
              --show-error \
              --request PATCH \
              --header "Accept: application/vnd.github+json" \
              --header "Authorization: Bearer ${GH_TOKEN}" \
              --header "X-GitHub-Api-Version: 2022-11-28" \
              "${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}/pulls/${PR_NUMBER}" \
              --data '{"state":"closed"}' \
              >/dev/null

            exit 1
          }

          ############################################################
          # Fetch PR metadata from GitHub REST API
          ############################################################

          echo "Fetching pull request metadata from GitHub API..."

          PR_JSON=""
          for attempt in {1..10}; do
            PR_JSON="$(
              curl \
                --fail-with-body \
                --silent \
                --show-error \
                --request GET \
                --header "Accept: application/vnd.github+json" \
                --header "Authorization: Bearer ${GH_TOKEN}" \
                --header "X-GitHub-Api-Version: 2022-11-28" \
                "${GITHUB_API_URL}/repos/${GITHUB_REPOSITORY}/pulls/${PR_NUMBER}"
            )"

            MERGEABLE="$(echo "${PR_JSON}" | jq -r '.mergeable')"
            if [[ "${MERGEABLE}" != "null" ]]; then
              break
            fi

            echo "Mergeable state is calculating, waiting 2s (attempt ${attempt}/10)..."
            sleep 2
          done

          MERGEABLE="$(echo "${PR_JSON}" | jq -r '.mergeable')"
          ADDITIONS="$(echo "${PR_JSON}" | jq -r '.additions // 0')"
          DELETIONS="$(echo "${PR_JSON}" | jq -r '.deletions // 0')"
          CHANGED_FILES="$(echo "${PR_JSON}" | jq -r '.changed_files // 0')"

          CHANGED_LINES=$((ADDITIONS + DELETIONS))

          ############################################################
          # STEP 1: Reject PRs with merge conflicts
          ############################################################

          echo
          echo "Checking for merge conflicts..."

          if [[ "${MERGEABLE}" == "false" ]]; then

            {
              echo "### Pull request policy"
              echo
              echo "- Merge conflicts: ❌ Detected"
              echo "- Result: Rejected"
            } >> "${GITHUB_STEP_SUMMARY}"

            reject_pr "This pull request has merge conflicts with the current master branch and cannot be accepted. Please update your branch with the latest master, resolve all merge conflicts locally, and submit a conflict-free pull request."

          fi

          echo "No merge conflicts detected (mergeable: ${MERGEABLE})."

          ############################################################
          # Action summary
          ############################################################

          {
            echo "### Pull request policy"
            echo
            echo "- Merge conflicts: ✅ None"
            echo "- Changed files: ${CHANGED_FILES}"
            echo "- Additions: ${ADDITIONS}"
            echo "- Deletions: ${DELETIONS}"
            echo "- Total changed lines: ${CHANGED_LINES}"
            echo "- Maximum allowed: ${MAX_CHANGED_LINES}"
          } >> "${GITHUB_STEP_SUMMARY}"

          echo
          echo "Changed files: ${CHANGED_FILES}"
          echo "Additions: ${ADDITIONS}"
          echo "Deletions: ${DELETIONS}"
          echo "Total changed lines: ${CHANGED_LINES}"
          echo "Limit: ${MAX_CHANGED_LINES}"

          ############################################################
          # STEP 2: Reject oversized PRs
          ############################################################

          if (( CHANGED_LINES > MAX_CHANGED_LINES )); then

            reject_pr "This pull request changes ${CHANGED_LINES} lines (${ADDITIONS} additions + ${DELETIONS} deletions) across ${CHANGED_FILES} files, exceeding the repository limit of ${MAX_CHANGED_LINES} changed lines. It has been closed automatically. Please split the changes into smaller pull requests."

          fi

          ############################################################
          # PASS
          ############################################################

          echo
          echo "Pull request passed all policy checks."
          echo "No merge conflicts."
          echo "Changed lines: ${CHANGED_LINES}/${MAX_CHANGED_LINES}."

          {
            echo
            echo "### Result"
            echo
            echo "✅ Pull request passed."
          } >> "${GITHUB_STEP_SUMMARY}"