feat: add module and decimal wire helpers

internal/wire/wire.go

@@ -0,0 +1,69 @@
+package wire
+
+import (
+	"encoding/json"
+	"fmt"
+
+	decimal "github.com/alpacahq/alpacadecimal"
+)
+
+// Unwrap returns the inner JSON of an optional {"data": ...} envelope.
+func Unwrap(raw json.RawMessage) json.RawMessage {
+	if len(raw) == 0 {
+		return raw
+	}
+	var wrap struct {
+		Data json.RawMessage `json:"data"`
+	}
+	if json.Unmarshal(raw, &wrap) == nil && len(wrap.Data) > 0 {
+		return wrap.Data
+	}
+	return raw
+}
+
+// Dec parses a required money/size/price value.
+func Dec(v any) (decimal.Decimal, error) {
+	switch x := v.(type) {
+	case nil:
+		return decimal.Zero, nil
+	case float64:
+		return decimal.NewFromFloat(x), nil
+	case json.Number:
+		d, err := decimal.NewFromString(string(x))
+		if err != nil {
+			return decimal.Zero, fmt.Errorf("parse decimal: %v", v)
+		}
+		return d, nil
+	case string:
+		if x == "" {
+			return decimal.Zero, nil
+		}
+		d, err := decimal.NewFromString(x)
+		if err != nil {
+			return decimal.Zero, fmt.Errorf("parse decimal: %v", v)
+		}
+		return d, nil
+	default:
+		return decimal.Zero, fmt.Errorf("parse decimal: %v", v)
+	}
+}
+
+// DecOpt parses an optional money/size/price value.
+func DecOpt(v any) (*decimal.Decimal, error) {
+	if v == nil {
+		return nil, nil
+	}
+	if s, ok := v.(string); ok && s == "" {
+		return nil, nil
+	}
+	d, err := Dec(v)
+	if err != nil {
+		return nil, err
+	}
+	return &d, nil
+}
+
+// Encode is Decimal.String for Robinhood string wire fields.
+func Encode(d decimal.Decimal) string {
+	return d.String()
+}