feed-mcp: Instructions file for GitHub Copilot

Copilot Instructions for MCP Feed Server

Codebase Structure & Architecture

• Entry Point: main.go sets up the CLI and launches the MCP server.
• CLI: Uses the kong library for command parsing (Run command is the main entry).
• Feed Logic: Handled in model (data structures, conversion) and store (fetching, caching, error handling) packages.
• Caching: Uses gocache and ristretto for in-memory feed caching.
• Feed Parsing: gofeed parses RSS/Atom/JSON feeds.
• Protocol Layer: mcpserver handles the MCP protocol with the official MCP Go SDK.
• Tests: All core logic is tested, with test files named *_test.go (see main_test.go, store/store_test.go, etc).

Go Conventions & Patterns

• Package Layout
  • model: Data structures (Feed, Globals, transports) and adapters (e.g., FromGoFeed()).
  • store: Feed fetching, caching, management (Store type, NewStore constructor, error handling).
• Error Handling
  • Returns error as the last return in all constructors and core methods.
  • Uses Go idioms: if error, return early (if err != nil { return ... }).
  • Custom errors for validation (e.g., ErrInvalidTransport).
• Concurrency
  • Uses goroutines and sync.WaitGroup for parallel feed fetching at startup.
• Config Struct Pattern
  • store.NewStore(Config) accepts a config struct, validates, and applies sensible defaults (Timeout, ExpireAfter).
• Test Patterns
  • Use Go’s testing package.
  • Test helpers (e.g., mockFeedServer) for HTTP mocking.
  • t.Fatalf/t.Errorf for error assertions and value checks.

Design Decisions

• Extensibility: Adding new transports, feed sources, or output formats requires minimal changes—extend the relevant package.
• Caching Layer: Abstracted for efficiency and to support pluggable backends.
• Decoupling: Strong separation between CLI, business logic, and protocol/server code.
• Strong Typing: All major entities (feeds, transports, config) are typed for clarity and type safety.