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CONTRIBUTING.md

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+# Contributing to PHP MJML Renderer
+
+Thank you for your interest in contributing to the PHP MJML Renderer! This document provides guidelines and instructions for contributing.
+
+## Getting Started
+
+1. Fork the repository
+2. Clone your fork locally
+3. Create a feature branch from `main`
+4. Make your changes
+5. Submit a pull request
+
+## Development Setup
+
+### Requirements
+
+- PHP 8.1 or higher
+- Composer
+
+### Installation
+
+```bash
+git clone https://github.com/YOUR_USERNAME/php-mjml-renderer.git
+cd php-mjml-renderer
+composer install
+```
+
+### Running Tests
+
+```bash
+# Run all tests
+composer test
+
+# Run only unit tests
+composer test:unit
+
+# Run with coverage
+composer test:coverage
+
+# Code style check
+composer test:style
+
+# Static analysis
+composer test:types
+```
+
+## Coding Standards
+
+### PSR-12 Compliance
+
+All code must follow PSR-12 coding standards. We enforce this using PHP_CodeSniffer.
+
+```bash
+# Check code style
+composer test:style
+
+# Auto-fix code style issues
+vendor/bin/phpcbf
+```
+
+### Type Safety
+
+- Use strict types: `declare(strict_types=1);` at the top of every PHP file
+- Add type hints to all method parameters and return types
+- Aim for PHPStan level 9 compliance
+
+### Documentation
+
+- Write PHPDoc blocks for all public methods
+- Include parameter descriptions and return types
+- Add `@throws` tags for exceptions
+- Document complex logic with inline comments
+
+Example:
+```php
+/**
+ * Render MJML content to HTML
+ *
+ * @param string $mjml The MJML markup to render
+ * @return string The rendered HTML output
+ * @throws \RuntimeException If MJML parsing fails
+ */
+public function render(string $mjml): string
+{
+    // Implementation
+}
+```
+
+## Testing Requirements
+
+### Write Tests for New Features
+
+All new features must include comprehensive tests:
+
+- Unit tests for individual methods and classes
+- Integration tests for component interactions
+- E2E tests for complete email rendering (if applicable)
+
+### Test Structure
+
+We use Pest PHP for testing. Follow the existing test patterns:
+
+```php
+describe('ComponentName', function () {
+    it('does something specific', function () {
+        $component = new ComponentName();
+
+        expect($component->someMethod())->toBe('expected result');
+    });
+});
+```
+
+### Coverage Requirements
+
+- Maintain high test coverage for new code
+- Critical rendering paths should have 100% coverage
+- Edge cases and error conditions must be tested
+
+## Pull Request Process
+
+### Before Submitting
+
+1. **Run all tests**: Ensure `composer test` passes
+2. **Check code style**: Ensure `composer test:style` passes
+3. **Run static analysis**: Ensure `composer test:types` passes
+4. **Update documentation**: If you've changed public APIs
+5. **Add tests**: Ensure your changes are tested
+
+### PR Guidelines
+
+1. **Branch naming**: Use descriptive names like `feature/element-name` or `fix/bug-description`
+2. **Commit messages**: Write clear, atomic commits with descriptive messages
+3. **PR description**: Explain what changes were made and why
+4. **Link issues**: Reference related issues in your PR description
+5. **Keep focused**: One feature/fix per PR when possible
+
+### Commit Message Format
+
+Use imperative mood and focus on why changes were made:
+
+```
+Add support for mj-social element
+
+Implement the mj-social component with support for major social
+platforms. Includes built-in icons and customization options.
+```
+
+## Pre-commit Hooks
+
+The project uses CaptainHook for pre-commit hooks. These run automatically:
+
+- Tests must pass
+- Code style must be compliant
+- PHPStan analysis must pass
+
+Install hooks after cloning:
+```bash
+vendor/bin/captainhook install
+```
+
+## Code Review Process
+
+1. All PRs require review before merging
+2. Address feedback promptly and professionally
+3. Be open to suggestions and improvements
+4. Maintainers may request changes or additional tests
+
+## Implementing New MJML Elements
+
+When adding a new MJML element:
+
+1. **Create element class** in `src/Elements/BodyComponents/` (or appropriate directory)
+2. **Extend AbstractElement** and implement required methods
+3. **Define attributes** in `$allowedAttributes` array
+4. **Implement render()** method to generate HTML output
+5. **Implement getStyles()** method for CSS styling
+6. **Write comprehensive tests** covering all attributes and edge cases
+7. **Update documentation** with usage examples
+
+Example element structure:
+```php
+<?php
+
+declare(strict_types=1);
+
+namespace MadeByDenis\PhpMjmlRenderer\Elements\BodyComponents;
+
+use MadeByDenis\PhpMjmlRenderer\Elements\AbstractElement;
+
+class MjNewElement extends AbstractElement
+{
+    public const string TAG_NAME = 'mj-new-element';
+    public const bool ENDING_TAG = false;
+
+    protected array $allowedAttributes = [
+        'attribute-name' => [
+            'unit' => 'string',
+            'type' => 'string',
+            'default_value' => 'default',
+        ],
+    ];
+
+    protected array $defaultAttributes = [
+        'attribute-name' => 'default',
+    ];
+
+    public function render(): string
+    {
+        // Implementation
+    }
+
+    public function getStyles(): array
+    {
+        return [];
+    }
+}
+```
+
+## Questions?
+
+If you have questions about contributing:
+
+- Open a [Discussion](https://github.com/dingo-d/php-mjml-renderer/discussions)
+- Check existing [Issues](https://github.com/dingo-d/php-mjml-renderer/issues)
+- Review the [MJML documentation](https://documentation.mjml.io/)
+
+## License
+
+By contributing to this project, you agree that your contributions will be licensed under the MIT License.