┌─────────────────────────────────────────────────────────┐
│                    Your Application                      │
├─────────────────────────────────────────────────────────┤
│                 Unified Interface Layer                  │
│     ┌──────────────┬──────────────┬──────────────┐      │
│     │ TradeService │ QuoteService │AccountService│      │
│     └──────────────┴──────────────┴──────────────┘      │
├─────────────────────────────────────────────────────────┤
│                    Adapter Layer                         │
│  ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐   │
│  │Longbridge│ │   Futu   │ │   IBKR   │ │  Tiger   │   │
│  └──────────┘ └──────────┘ └──────────┘ └──────────┘   │
└─────────────────────────────────────────────────────────┘

type BrokerAdapter interface {
    Type() BrokerType
    Name() string
    IsConnected() bool
    Connect(ctx context.Context) error
    Disconnect() error
    Trade() TradeService
    Quote() QuoteService
    Account() AccountService
}

type TradeService interface {
    SubmitOrder(ctx context.Context, req *SubmitOrderRequest) (*SubmitOrderResponse, error)
    CancelOrder(ctx context.Context, orderID string) error
    ModifyOrder(ctx context.Context, req *ModifyOrderRequest) error
    GetOrder(ctx context.Context, orderID string) (*Order, error)
    GetTodayOrders(ctx context.Context, filter *OrderFilter) ([]*Order, error)
    // ...
}

type QuoteService interface {
    GetQuote(ctx context.Context, symbols []string) ([]*Quote, error)
    GetDepth(ctx context.Context, symbol string) (*Depth, error)
    GetCandlesticks(ctx context.Context, req *CandlestickRequest) ([]*Candlestick, error)
    Subscribe(ctx context.Context, symbols []string, types []SubscriptionType) error
    // ...
}

type AccountService interface {
    GetBalance(ctx context.Context, currency string) ([]*Balance, error)
    GetPositions(ctx context.Context, symbols []string) ([]*Position, error)
    GetMarginRatio(ctx context.Context, symbol string) (*MarginRatio, error)
    // ...
}

type Order struct {
    OrderID        string
    Symbol         string
    Side           OrderSide    // BUY, SELL
    OrderType      OrderType    // LIMIT, MARKET, etc.
    Status         OrderStatus  // NEW, FILLED, CANCELLED, etc.
    Quantity       int64
    FilledQuantity int64
    Price          float64
    FilledPrice    float64
    // ...
}

type Quote struct {
    Symbol    string
    LastPrice float64
    Open      float64
    High      float64
    Low       float64
    Volume    int64
    Timestamp time.Time
}

type Position struct {
    Symbol       string
    Quantity     int64
    CostPrice    float64
    CurrentPrice float64
    MarketValue  float64
    UnrealizedPL float64
}

// Create broker adapter
config := &BrokerConfig{
    Type:        BrokerLongbridge,
    AppKey:      os.Getenv("APP_KEY"),
    AppSecret:   os.Getenv("APP_SECRET"),
    AccessToken: os.Getenv("ACCESS_TOKEN"),
}

adapter, err := factory.Create(config)
if err != nil {
    log.Fatal(err)
}
defer adapter.Disconnect()

// Connect
if err := adapter.Connect(ctx); err != nil {
    log.Fatal(err)
}

// Use unified interface
quote, _ := adapter.Quote().GetQuote(ctx, []string{"AAPL.US"})
balance, _ := adapter.Account().GetBalance(ctx, "USD")

// Submit order (same code works for any broker)
resp, err := adapter.Trade().SubmitOrder(ctx, &SubmitOrderRequest{
    Symbol:    "AAPL.US",
    Side:      OrderSideBuy,
    OrderType: OrderTypeLimit,
    Quantity:  100,
    Price:     150.00,
})

common/
├── SKILL.md              # This file
├── interfaces/
│   └── broker.go         # Core interface definitions
├── models/
│   ├── order.go          # Order-related models
│   ├── quote.go          # Quote-related models
│   └── account.go        # Account-related models
├── errors/
│   └── errors.go         # Unified error codes
└── references/
    ├── interface-spec.md # Detailed interface specification
    └── error-codes.md    # Error code documentation