Architecture Improvements

Decoupled Command Architecture

• Decoupled commands from Client: Commands now only require their minimum dependencies (writer, store, args)
• Commands can be invoked from non-client contexts (e.g., AOF replay)
• Introduced three ClientHandler types: Default, Client, and Store
• Commands no longer require network stream, only a generic writer

Centralized Error Handling

• Moved error-to-RESP message mapping from individual commands to registry
• Expanded CommandError with specific error types (WrongType, ValueNotInteger, InvalidFloat, etc.)
• Added handleCommandError() function in registry for consistent error responses
• Commands now return typed errors instead of writing RESP errors directly

Modular RESP Protocol Layer

• Created dedicated src/commands/resp.zig module for RESP protocol writing
• Decoupled RESP writing from client/network layer
• Generic writer interface allows RESP output to any destination
• Improved writeInt() to accept any integer type via compile-time generics

Parser Improvements

• Decoupled parser from network streams - now only requires a generic reader
• Parser can consume from any source (network, file, buffer)
• Fixed memory leak in parser
• More flexible command parsing for AOF and testing scenarios

Performance Optimizations

Short String Optimization (SSO)

• Implemented inline storage for strings ≤23 bytes (no heap allocation)
• Added ShortString type with efficient fromSlice() and asSlice() methods
• Automatic type selection in Store.set() based on string length
• Significant memory savings for small strings (keys, common values)

Safe Memory Pool

• Added src/safe_memory_pool.zig for optimized allocations
• Pre-allocated pools for common string lengths
• Reduced allocation overhead for frequently-used sizes
• Integrated with store operations for better memory management

Testing Improvements

Refactored Test Architecture

• Removed MockClient dependency: Tests now call command functions directly
• Implemented fixed buffer writer pattern (std.Io.Writer.fixed(&buffer))
• More idiomatic Zig testing with stack-allocated buffers
• Cleaner test implementation without heap allocations
• Refactored all 31 string tests to use direct command calls
• Refactored all 30 list tests to use direct command calls

Enhanced Test Coverage

• Added comprehensive tests for 10 new string commands
• Expanded edge case testing (error conditions, boundary cases)
• Added AOF read/write tests
• Improved test utilities in src/test_utils.zig

Bug Fixes

• Fixed short_string handling in incrDecr() function - now properly parses integers from SSO strings
• Fixed parser memory leak
• Improved error handling for out-of-range operations
• Better type checking in store operations

Code Quality

• Simplified RESP command responses throughout codebase
• More consistent error handling patterns
• Reduced code duplication in command implementations
• Better separation of concerns (commands, parsing, protocol, persistence)
• Improved code documentation and inline comments

Refactoring

• Consolidated command argument handling
• Streamlined store interface
• Reduced client.zig complexity (103 lines removed)
• Reorganized command registry with better type safety
• Cleaned up pubsub and RDB integration points

Statistics

• Redis Command Coverage: 23% → 36% (string commands)

Breaking Changes

• Command function signatures changed to require writer and store instead of Client
• Error handling now returns typed errors instead of writing RESP directly
• Test utilities restructured (MockClient usage patterns changed)

Deprecations

• Removed benchmark results until async I/O work is complete