Summary

Major quality and reliability overhaul for the Bitkub PHP SDK — enforces strict typing across all files, fixes several API and data-handling bugs, refactors the WebSocket client with a builder pattern, and significantly expands test coverage.

Breaking Changes

• Message class is now immutable — offsetSet, offsetUnset, __set, and __unset throw BadMethodCallException
• PendingRequest properties changed from public to private — use accessor methods instead
• WebSocketClient constructor signature changed — accepts engine and optional HTTP client; use WebSocketClientBuilder for configuration
• LiveOrderBookEndpoint symbol map is now an instance property instead of static

Bug Fixes

• Fix array_filter usage with explicit callbacks to prevent filtering out valid falsy values (e.g., 0)
• Fix my-open-orders endpoint to send sym as query param instead of request body (matches Bitkub API v3 spec)
• Fix BitkubResponseErrorCodeException to handle missing error codes gracefully instead of throwing raw exceptions
• Replace @json_decode with proper validation (is_array checks)
• Fix README typos and incorrect API path for wallet endpoint (GET → POST /api/v3/market/wallet)

Improvements

• Add declare(strict_types=1) and return type declarations across all PHP files
• Cache endpoint instances, server timestamp drift, and symbol map to reduce redundant HTTP calls
• Add WebSocketClientBuilder for fluent WebSocket client configuration
• Add reconnection logic with configurable attempts to WebSocket Engine
• Improve WebSocket stream name validation with regex
• Improve type hints and PHPDoc annotations across WebSocket components

CI/CD

• Restrict code style workflow to main branch only
• Fix dependabot auto-merge workflow trigger (pull_request_target → pull_request)
• Set minimum-stability to stable in composer.json

Documentation

• Fix WebSocket examples to use WebSocketClientBuilder
• Add LiveOrderBook endpoint documentation
• Add PHP 8.2+ requirement badge to README

Tests

• Add tests for GenerateSignatureV3 (header attachment, timestamp caching, HMAC computation)
• Add tests for market order endpoints (openOrders, myOrderHistory, myOrderInfo)
• Add tests for immutable Message behavior and ResponseWithValidateErrorCode custom callbacks
• Add MockHttpClient request recording for better test assertions
• Add MockWebSocketEngine and tests for Engine, endpoints, and builder
• Refactor existing WebSocket tests to use mock engine

Test Plan

• Run composer test — all existing and new tests pass
• Verify GenerateSignatureV3 timestamp caching reduces server time API calls
• Verify Message immutability throws BadMethodCallException on mutation
• Verify array_filter fix preserves valid falsy values (e.g., 0)
• Verify my-open-orders sends sym as query param (not body)
• Verify WebSocketClientBuilder produces correctly configured clients