PlaceMarketOrder (GoMT4)

Goal: open a market order safely (BUY/SELL) with proper rounding for volume and prices.

This recipe references real code in this repo:

• Account methods: examples/mt4/MT4Account.go (OrderSend, SymbolParams)
• Service example: examples/mt4/MT4_service.go (ShowOrderSendExample)
• Config: examples/config/config.json

---

1) Preconditions

• MT4 terminal is connected to the broker.
• examples/config/config.json contains valid credentials and DefaultSymbol.
• Symbol is visible in MT4 Market Watch (or call your own EnsureSymbolVisible).

---

2) Read symbol parameters (Digits, Volume limits)

info, err := account.SymbolParams(ctx, symbol)
if err != nil { return err }

digits    := int(info.GetDigits())
volMin    := info.GetVolumeMin()
volMax    := info.GetVolumeMax()
volStep   := info.GetVolumeStep()
pointSize := math.Pow10(-digits) // 10^-Digits

Why: exchanges/brokers require amount and price aligned to the symbol settings.

---

3) Helpers: align volume & round prices

Put these small helpers next to your order code (or reuse existing ones).

func alignVolume(v, step, min, max float64) float64 {
    if step <= 0 { return v }
    v = math.Floor(v/step+0.5) * step
    if v < min { v = min }
    if v > max { v = max }
    return v
}

func roundPrice(p float64, digits int) float64 {
    mul := math.Pow10(digits)
    return math.Round(p*mul) / mul
}

---

4) Build inputs (market order)

• For a market order, pass price=nil and set a small slippage (in points).
• Optionally pre‑compute SL/TP relative to current price.

side := pb.OrderSendOperationType_OC_OP_BUY // or OC_OP_SELL
rawVolume := 0.10
volume    := alignVolume(rawVolume, volStep, volMin, volMax)

var price *float64 = nil
slippage := int32(5) // 5 points

// Optional SL/TP (rounded to Digits)
var sl, tp *float64
if wantSLTP {
    bidAsk, _ := account.Quote(ctx, symbol)
    entry := bidAsk.GetAsk() // for BUY; for SELL use Bid
    stop  := roundPrice(entry-20*pointSize, digits)
    take  := roundPrice(entry+40*pointSize, digits)
    sl, tp = &stop, &take
}

comment     := "Go order test"
magicNumber := int32(123456)

---

5) Send the order (with retries handled inside)

OrderSend already wraps gRPC with reconnect/retry (see ExecuteWithReconnect). You only supply clean inputs.

resp, err := account.OrderSend(
    ctx,
    symbol,
    side,
    volume,
    price,             // nil for market
    &slippage,         // points
    sl, tp,            // can be nil
    &comment,
    &magicNumber,
    nil,               // expiration (for pending only)
)
if err != nil {
    return fmt.Errorf("OrderSend failed: %w", err)
}
fmt.Printf("✅ Order opened! Ticket=%d Price=%.5f Time=%s\n",
    resp.GetTicket(), resp.GetPrice(), resp.GetOpenTime().AsTime().Format("2006-01-02 15:04:05"))

See a minimal working example in examples/mt4/MT4_service.go → ShowOrderSendExample (uses small pointer helpers ptrInt32, ptrString).

---

6) Common pitfalls

• Invalid volume/price → make sure to align volume to VolumeStep and round prices to Digits.
• symbol not found / empty quotes → symbol hidden or broker suffix (e.g., EURUSD.m). Show all symbols in MT4.
• context deadline exceeded → MT4 not ready; use short per‑call timeout and retry transport errors only (see Reliability chapter).

---

7) Variations

• SELL: use pb.OrderSendOperationType_OC_OP_SELL and entry price = Bid when computing SL/TP.
• Immediate TP/SL omitted: pass nil and modify later via OrderModify.
• Pending order: use the same call with price!=nil and expiration!=nil (see PlacePendingOrder.md).