pre-commit Hook

Linting: run ESLint, Pylint, or equivalent on staged files. Block if errors.

Formatting: run Prettier, Black, or equivalent. Auto-format and re-stage.

Debug statements: check for console.log, debugger, print statements.

Large files: prevent committing files over a size limit (use Git LFS instead).

Secrets: check for API keys, passwords, tokens using tools like detect-secrets or gitleaks.

Trailing whitespace: prevent committing files with trailing spaces or missing newline.

Broken JSON/YAML: validate configuration files before they break your deployment.

For each check, decide: should it BLOCK (exit 1) or WARN (echo message but exit 0)?

cat > .git/hooks/pre-commit << 'EOF'
#!/bin/bash
set -e  # Exit on any error

# 1. Check for debug statements (BLOCK)
if git diff --cached --name-only | grep -qE '\.(js|ts)$'; then
  if git diff --cached -- '*.js' '*.ts' | grep -qE 'console\.(log|debug)|debugger'; then
    echo "❌ Debug statements found. Remove them."
    exit 1
  fi
fi

# 2. Check for secrets (BLOCK)
if git diff --cached | grep -qE "api_key|api_secret|password"; then
  echo "❌ Potential secret detected. Use environment variables!"
  exit 1
fi

# 3. Check for large files (BLOCK)
large_files=$(git diff --cached --name-only | xargs -I{} du -b {} 2>/dev/null | awk '$1 > 1048576 {print $2}')
if [ -n "$large_files" ]; then
  echo "❌ Large files detected (>1MB): $large_files"
  echo "Use Git LFS for large files."
  exit 1
fi

# 4. Auto-format with Prettier (FIX, don't block)
if command -v npx &> /dev/null; then
  npx prettier --write $(git diff --cached --name-only -- '*.js' '*.ts' '*.css' 2>/dev/null) 2>/dev/null || true
  git add -u  # Re-stage formatted files
fi

echo "✅ Pre-commit checks passed!"
exit 0
EOF
chmod +x .git/hooks/pre-commit