name: Sync CHANGELOG to README

on:
  push:
    branches: [master]
    paths: [CHANGELOG.md]
  workflow_dispatch:

permissions:
  contents: write

jobs:
  sync:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Extract recent changelog highlights and update README
        run: |
          node - <<'JSEOF'
          const fs = require("fs");

          const changelog = fs.readFileSync("CHANGELOG.md", "utf-8").replace(/\r\n/g, "\n");
          const readme = fs.readFileSync("README.md", "utf-8").replace(/\r\n/g, "\n");

          const MAX_VERSIONS = 3;
          const MAX_ITEMS = 5;

          // Split into version sections by "## " headings
          const sections = changelog.split(/(?=^## )/m).filter(s => s.startsWith("## "));

          let output = [];
          let count = 0;

          for (const section of sections) {
            if (count >= MAX_VERSIONS) break;

            // Extract version title line (first line)
            const titleLine = section.split("\n")[0];

            // Extract "### Added" block
            const addedMatch = section.match(/### Added\n([\s\S]*?)(?=\n### |\n## |$)/);
            if (!addedMatch) continue; // skip versions without Added

            // Parse items (lines starting with "- ")
            const items = addedMatch[1].trim().split("\n").filter(l => l.startsWith("- "));
            if (items.length === 0) continue;

            // Demote "## " to "### " for README context
            const demotedTitle = titleLine.replace(/^## /, "### ");
            output.push(demotedTitle);
            output.push("");

            const shown = items.slice(0, MAX_ITEMS);
            // Shorten each item to first sentence (up to first Chinese period or newline)
            for (const item of shown) {
              output.push(item);
            }

            if (items.length > MAX_ITEMS) {
              output.push(`- ...（[查看全部更新](./CHANGELOG.md)）`);
            }

            output.push("");
            count++;
          }

          if (output.length === 0) {
            console.log("No Added sections found in CHANGELOG.md");
            process.exit(0);
          }

          const content = output.join("\n").trim();
          const pattern = /(<!-- CHANGELOG:START -->)[\s\S]*?(<!-- CHANGELOG:END -->)/;
          const replacement = `<!-- CHANGELOG:START -->\n${content}\n<!-- CHANGELOG:END -->`;
          const newReadme = readme.replace(pattern, replacement);

          if (newReadme === readme) {
            console.log("README unchanged");
            process.exit(0);
          }

          fs.writeFileSync("README.md", newReadme, "utf-8");
          console.log(`Updated README with ${count} changelog section(s)`);
          JSEOF

      - name: Commit if changed
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "github-actions[bot]@users.noreply.github.com"
          git diff --quiet README.md && echo "No changes" && exit 0
          git add README.md
          git commit -m "docs: auto-sync changelog to README [skip ci]"
          for i in 1 2 3; do
            git push && exit 0
            echo "Push failed (attempt $i/3), rebasing and retrying..."
            git pull --rebase origin master
            sleep 2
          done
          echo "::error::Push failed after 3 attempts"
          exit 1