protocol/aprs: refactored

protocol/aprs/query.go

@@ -0,0 +1,50 @@
+package aprs
+
+import (
+	"strconv"
+	"strings"
+)
+
+type Query struct {
+	Type      string `json:"type"`
+	Latitude  float64
+	Longitude float64
+	Radius    float64 // radius in meters
+}
+
+func (q Query) String() string {
+	return q.Type
+}
+
+type queryDecoder struct{}
+
+func (queryDecoder) CanDecode(frame *Frame) bool {
+	return len(frame.Raw) >= 3 && frame.Raw.Type() == '?'
+}
+
+func (queryDecoder) Decode(frame *Frame) (data Data, err error) {
+	var (
+		kind = string(frame.Raw[1:])
+		args string
+		i    int
+	)
+	if i = strings.IndexByte(kind, '?'); i == -1 {
+		return &Query{
+			Type: kind,
+		}, nil
+	} else {
+		kind, args = kind[:i], kind[i+1:]
+	}
+
+	query := &Query{Type: kind}
+
+	if part := strings.SplitN(strings.TrimSpace(args), ",", 3); len(part) == 3 {
+		var radius int
+		query.Latitude, _ = strconv.ParseFloat(part[0], 64)
+		query.Longitude, _ = strconv.ParseFloat(part[1], 64)
+		radius, _ = strconv.Atoi(part[2])
+		query.Radius = milesToMeters(float64(radius))
+	}
+
+	return query, nil
+}