📚 GetMultipleQuotes (GoMT4)

Goal: fetch quotes for many symbols efficiently.

Real code refs:

• Single quote: examples/mt4/MT4Account.go (Quote)
• Demo: examples/mt4/MT4_service.go (see ShowQuotesMany flow)

---

✅ 1) Preconditions

• All symbols exist and are visible in MT4 (Market Watch → Show All).
• config.json has at least one known symbol to start with.

---

🚀 2) Fast path A — Batch RPC (if available in your build)

Some builds expose a batch RPC (e.g., QuotesMany(ctx, symbols)), mirroring the ShowQuotesMany example. If you have it, use it:

symbols := []string{"EURUSD", "GBPUSD", "USDJPY"}
qs, err := account.QuotesMany(ctx, symbols)
if err != nil { return err }
for _, q := range qs.GetQuotes() {
    fmt.Printf("%s Bid=%.5f Ask=%.5f Spread=%.1f pips\n",
        q.GetSymbol(), q.GetBid(), q.GetAsk(), (q.GetAsk()-q.GetBid())/q.GetPoint())
}

If your current API does not expose this convenience call, use fan‑out concurrency (next section).

---

🧵 3) Fast path B — Fan‑out with goroutines (always works)

Run Quote requests in parallel and collect results.

func GetQuotesParallel(ctx context.Context, a *MT4Account, syms []string) ([]*pb.Quote, error) {
    type item struct { q *pb.Quote; err error }
    out := make([]*pb.Quote, 0, len(syms))
    ch  := make(chan item, len(syms))
    var wg sync.WaitGroup

    // limit concurrency to avoid hammering the terminal
    sem := make(chan struct{}, 8) // 8 concurrent calls

    for _, s := range syms {
        s := s
        wg.Add(1)
        go func() {
            defer wg.Done()
            sem <- struct{}{}
            defer func(){ <-sem }()

            q, err := a.Quote(ctx, s)
            ch <- item{q, err}
        }()
    }
    wg.Wait()
    close(ch)

    for it := range ch {
        if it.err != nil { return nil, it.err }
        out = append(out, it.q)
    }
    return out, nil
}

Usage:

qs, err := GetQuotesParallel(ctx, account, []string{"EURUSD","GBPUSD","USDJPY"})
if err != nil { log.Fatal(err) }
for _, q := range qs {
    fmt.Printf("%s %.5f/%.5f @ %s\n", q.GetSymbol(), q.GetBid(), q.GetAsk(), q.GetTime().AsTime().Format(time.RFC3339))
}

---

🧪 4) Validation & fallbacks

• If a symbol fails (hidden or has a suffix), log it and continue.
• Optionally, map missing symbols to their broker‑specific names (EURUSD → EURUSD.m).

for _, s := range syms {
    q, err := a.Quote(ctx, s)
    if err != nil {
        log.Printf("skip %s: %v", s, err)
        continue
    }
    // ...
}

---

⚠️ Pitfalls

• Storming MT4: keep concurrency reasonable (4–8) to avoid timeouts.
• Suffixes: EURUSD vs EURUSD.m — normalize names or take from Market Watch.
• Timeouts: wrap each call with a short timeout (2–3s) and retry only transport errors.

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🔗 See also

• GetQuote.md — single symbol quote.
• StreamQuotes.md — live stream for continuous updates.
• SymbolParams.md — get Digits, Point, LotStep for rounding & display.