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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Common Commands
+
+### Testing and Quality Assurance
+- `composer tests` - Run PHPUnit tests
+- `composer phpstan` - Run PHPStan static analysis
+- `composer cs` - Run PHP CodeSniffer for code style checks
+- `composer csfix` - Fix code style issues automatically with PHP Code Beautifier and Fixer
+- `composer checks` - Run all quality checks (cs, phpstan, tests)
+
+### Development Workflow
+After making changes, always run `composer checks` to ensure code quality standards are met.
+
+## Architecture Overview
+
+### Core Components
+The DigiSign SDK is a PHP library that provides communication with the DigiSign API using PSR-18 HTTP Client, PSR-17 HTTP Factories, and PSR-16 SimpleCache.
+
+#### Main Classes
+- **DigiSign** (src/DigiSign.php) - Main entry point and service container
+- **DigiSignClient** (src/DigiSignClient.php) - HTTP client wrapper with PSR standard implementations
+- **ResourceEndpoint** (src/Endpoint/ResourceEndpoint.php) - Abstract base class for API endpoints
+- **BaseResource** (src/Resource/BaseResource.php) - Base class for API response resources
+
+#### Authentication
+- **ApiKeyCredentials** - API key-based authentication
+- **TokenCredentials** - Token-based authentication  
+- **CachedCredentials** - Decorator for caching credentials
+
+#### Endpoint Pattern
+All API endpoints extend ResourceEndpoint and use traits for common CRUD operations:
+- `CRUDEndpointTrait` - Full CRUD operations
+- `CreateEndpointTrait` - Create operations
+- `GetEndpointTrait` - Get operations
+- `ListEndpointTrait` - List operations
+- `UpdateEndpointTrait` - Update operations
+- `DeleteEndpointTrait` - Delete operations
+
+#### Resource System
+- Resources are automatically hydrated from API responses
+- Support for nested resources and collections
+- Type mapping through PHP DocBlocks for complex types
+- Dynamic property access for API fields not explicitly defined
+
+### Key Features
+- **Webhook Signature Validation** - Built-in signature validation for webhook security
+- **File Upload Support** - Handles file uploads via multipart streams
+- **Testing/Production API** - Configurable API base URLs
+- **PSR Compliance** - Uses PSR-18 (HTTP Client), PSR-17 (HTTP Factories), PSR-16 (SimpleCache)
+- **Exception Handling** - Comprehensive exception hierarchy for different HTTP error codes
+
+### Code Conventions
+- PHP 8.0+ with strict typing (`declare(strict_types=1)`)
+- Uses phpdoc for type hints, especially for collections and complex types
+- Follows PSR-12 coding standards
+- Extensive use of final classes and protected methods
+- Template-based type annotations for generic collections
+
+### Testing Structure
+- Unit tests mirror the src/ directory structure
+- Uses PHPUnit with extensive mocking
+- Separate test classes for each endpoint and resource
+- Test utilities in tests/bootstrap.php
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