Add rate limiting support

[ejsmith]

This pull request introduces rate limiting functionality to the FetchClient library, allowing developers to control the number of requests made within a specific time window. The changes include the addition of global and per-domain rate limiting, automatic updates from response headers, and enhanced error handling for rate limit violations. It also updates the documentation and tests to reflect these new features.

New Features: Rate Limiting

• Rate limiting middleware added:

  • Introduced the RateLimitMiddleware class to support rate limiting with configurable options such as maxRequests, windowSeconds, and automatic updates from headers. It also provides IETF-compliant rate limit headers and error handling when limits are exceeded. (src/RateLimitMiddleware.ts)
  • Added methods useRateLimit, usePerDomainRateLimit, and removeRateLimit to the FetchClientProvider class for enabling and managing rate limiting. (src/FetchClientProvider.ts)

• Per-domain rate limiting:

  • Implemented per-domain rate limiting with support for auto-updating limits based on headers and domain-specific configurations. (src/FetchClientProvider.ts)

Documentation Updates

• Updated readme.md:
  • Added sections for rate limiting, including examples for global and per-domain configurations, to guide developers on using the new feature. (readme.md) [1] [2]

Code Enhancements

• Type additions:
  • Added RateLimitMiddlewareOptions type for configuring rate limiting options. (src/DefaultHelpers.ts, src/FetchClientProvider.ts) [1] [2]

Testing Improvements

• New test cases:
  • Added tests to validate per-domain rate limiting functionality, including auto-updating limits based on headers and verifying the correct application of rate limit policies. (src/FetchClient.test.ts)

These changes provide robust support for rate limiting, making the FetchClient library more suitable for applications requiring controlled API usage.

[Copilot]

Pull Request Overview

This PR adds comprehensive rate limiting functionality to the FetchClient library, allowing developers to control request frequency with configurable limits and automatic header-based updates. The implementation includes support for both global and per-domain rate limiting with IETF standard compliance.

Key changes include:

• Implementation of core rate limiting logic with RateLimiter class and RateLimitMiddleware
• Integration with FetchClientProvider through new methods for enabling/managing rate limits
• Support for automatic rate limit updates from response headers with fallback to legacy formats

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/RateLimiter.ts	Core rate limiting implementation with group-based buckets, IETF header parsing, and per-domain support
src/RateLimitMiddleware.ts	Middleware integration that handles rate limit enforcement and error responses
src/RateLimit.test.ts	Comprehensive test suite covering rate limiting functionality and header parsing
src/FetchClientProvider.ts	Provider integration with useRateLimit and usePerDomainRateLimit methods
src/FetchClient.test.ts	Integration tests for per-domain rate limiting with header auto-updates
src/DefaultHelpers.ts	Helper functions for global rate limiting configuration
readme.md	Documentation updates with rate limiting usage examples