add metar request/response to protocol

protocol/metar_request.go

@@ -0,0 +1,43 @@
+package protocol
+
+import (
+	"fmt"
+	"strings"
+)
+
+type MetarRequestPDU struct {
+	From    string `validate:"required,alphanum,max=7"`
+	To      string `validate:"required,alphanum,max=7"`
+	Station string `validate:"required,alphanum,max=4"`
+}
+
+func (p *MetarRequestPDU) Serialize() string {
+	return fmt.Sprintf("$AX%s:%s:METAR:%s%s", p.From, p.To, p.Station, PacketDelimeter)
+}
+
+func ParseMetarRequestPDU(rawPacket string) (*MetarRequestPDU, error) {
+	rawPacket = strings.TrimSuffix(rawPacket, PacketDelimeter)
+	rawPacket = strings.TrimPrefix(rawPacket, "$AX")
+	fields := strings.Split(rawPacket, Delimeter)
+
+	if len(fields) != 4 {
+		return nil, NewGenericFSDError(SyntaxError)
+	}
+
+	if fields[2] != "METAR" {
+		return nil, NewGenericFSDError(SyntaxError)
+	}
+
+	pdu := MetarRequestPDU{
+		From:    fields[0],
+		To:      fields[1],
+		Station: fields[3],
+	}
+
+	err := V.Struct(pdu)
+	if err != nil {
+		return nil, NewGenericFSDError(SyntaxError)
+	}
+
+	return &pdu, nil
+}