bundle-size.yml

name: Bundle Size Tracking

on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  bundle-size:
    runs-on: ubuntu-latest
    
    env:
      EXPO_PUBLIC_API_BASE_URL: https://api.teachlink.com
      EXPO_PUBLIC_SOCKET_URL: wss://api.teachlink.com
      EXPO_PUBLIC_APP_ENV: production
      EXPO_PUBLIC_ENABLE_PUSH_NOTIFICATIONS: true
      
    steps:
      - uses: actions/checkout@v4

      - uses: actions/setup-node@v4
        with:
          node-version: 20
          cache: npm

      - name: Install dependencies
        run: npm install

      - name: Build web bundle with stats
        run: npx expo export --platform web --output-dir ./dist --stats-output ./dist/stats.json

      - name: Upload bundle stats artifact
        if: github.ref == 'refs/heads/main'
        uses: actions/upload-artifact@v4
        with:
          name: bundle-stats-${{ github.sha }}
          path: ./dist/stats.json
          retention-days: 7

      - name: Store bundle size history
        if: github.ref == 'refs/heads/main'
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const path = require('path');
            const { Octokit } = require("@octokit/rest");
            const octokit = new Octokit({ auth: process.env.GITHUB_TOKEN });

            const owner = context.repo.owner;
            const repo = context.repo.repo;
            const historyFile = 'bundle-size-history.json';

            let history = [];
            try {
              const { data: artifact } = await octokit.actions.listArtifactsForRepo({
                owner,
                repo,
                name: 'bundle-size-history',
              }).then(res => res.data.artifacts[0]);

              if (artifact) {
                const download = await octokit.actions.downloadArtifact({
                  owner,
                  repo,
                  artifact_id: artifact.id,
                  archive_format: 'zip',
                });
                const AdmZip = require('adm-zip');
                const zip = new AdmZip(Buffer.from(download.data));
                history = JSON.parse(zip.readAsText(historyFile));
              }
            } catch (error) {
              console.log('No existing history artifact found, creating a new one.');
            }

            const stats = JSON.parse(fs.readFileSync('./dist/stats.json', 'utf8'));
            const totalSize = stats.assets.reduce((sum, a) => sum + a.size, 0);

            history.push({
              sha: context.sha,
              date: new Date().toISOString(),
              totalSize,
              assets: stats.assets.map(a => ({ name: a.name, size: a.size })),
            });

            fs.writeFileSync(historyFile, JSON.stringify(history, null, 2));

      - name: Upload bundle size history
        if: github.ref == 'refs/heads/main'
        uses: actions/upload-artifact@v4
        with:
          name: bundle-size-history
          path: bundle-size-history.json
          retention-days: 90

      - name: Download base branch bundle size
        if: github.event_name == 'pull_request'
        uses: actions/download-artifact@v4
        with:
          name: bundle-stats-${{ github.event.pull_request.base.sha }}
          path: ./base-bundle
          github-token: ${{ secrets.GITHUB_TOKEN }}
          run-id: ${{ github.event.pull_request.base.repo.id }}-${{ github.event.pull_request.base.sha }}


      - name: Compare bundle sizes and comment
        if: github.event_name == 'pull_request'
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const path = require('path');

            function parseStats(filePath) {
              if (!fs.existsSync(filePath)) return null;
              const stats = JSON.parse(fs.readFileSync(filePath, 'utf8'));
              const mainBundle = stats.assets.find(a => a.name === 'main.js');
              return {
                totalSize: stats.assets.reduce((sum, a) => sum + a.size, 0),
                mainBundleSize: mainBundle ? mainBundle.size : 0,
                assets: stats.assets,
              };
            }

            const baseStats = parseStats('./base-bundle/stats.json');
            const headStats = parseStats('./dist/stats.json');

            if (!headStats) {
              console.log('Could not find head bundle stats. Skipping comparison.');
              return;
            }

            let body = `## 📦 Bundle Size Report\n\n`;
            body += `| Asset | Size (KB) |\n`;
            body += `|---|---|\n`;
            headStats.assets.forEach(asset => {
              body += `| ${asset.name} | ${(asset.size / 1024).toFixed(2)} |\n`;
            });
            body += `| **Total** | **${(headStats.totalSize / 1024).toFixed(2)}** |\n`;

            if (baseStats) {
              const totalDiff = headStats.totalSize - baseStats.totalSize;
              const mainDiff = headStats.mainBundleSize - baseStats.mainBundleSize;
              const totalDiffPercent = (totalDiff / baseStats.totalSize * 100).toFixed(2);
              const mainDiffPercent = (mainDiff / baseStats.mainBundleSize * 100).toFixed(2);

              const emoji = totalDiff > 0 ? '📈' : '📉';

              body += `\n### ${emoji} Comparison with base branch\n\n`;
              body += `| Asset | Base (KB) | Head (KB) | Diff (KB) | Diff (%) |\n`;
              body += `|---|---|---|---|---|\n`;
              body += `| main.js | ${(baseStats.mainBundleSize / 1024).toFixed(2)} | ${(headStats.mainBundleSize / 1024).toFixed(2)} | ${(mainDiff / 1024).toFixed(2)} | ${mainDiffPercent}% |\n`;
              body += `| **Total** | **${(baseStats.totalSize / 1024).toFixed(2)}** | **${(headStats.totalSize / 1024).toFixed(2)}** | **${(totalDiff / 1024).toFixed(2)}** | **${totalDiffPercent}%** |\n`;

              if (Math.abs(mainDiff) > 50 * 1024) {
                core.setFailed(`Main bundle size changed by more than 50KB.`);
                body += `\n\n**Error:** Main bundle size changed by more than 50KB.`;
              }
              if (Math.abs(totalDiff) > 100 * 1024) {
                core.setFailed(`Total bundle size changed by more than 100KB.`);
                body += `\n\n**Error:** Total bundle size changed by more than 100KB.`;
              }
            }

            await github.rest.issues.createComment({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              body: body
            });