protocol/aprs: refactored

protocol/aprs/frame.go

@@ -0,0 +1,58 @@
+package aprs
+
+import (
+	"errors"
+	"strings"
+)
+
+var (
+	ErrPayloadMarker     = errors.New("aprs: can't find payload marker")
+	ErrDestinationMarker = errors.New("aprs: can't find destination marker")
+	ErrPathLength        = errors.New("aprs: invalid path length")
+)
+
+// Frame represents a single APRS frame.
+type Frame struct {
+	Source      Address `json:"source"`
+	Destination Address `json:"destination"`
+	Path        Path    `json:"path"`
+	Raw         Raw     `json:"raw"`
+	Data        Data    `json:"data,omitempty"`
+}
+
+func Parse(s string) (*Frame, error) {
+	i := strings.IndexByte(s, ':')
+	if i == -1 {
+		return nil, ErrPayloadMarker
+	}
+
+	var (
+		route = s[:i]
+		frame = &Frame{Raw: Raw(s[i+1:])}
+	)
+	if i = strings.IndexByte(route, '>'); i == -1 {
+		return nil, ErrDestinationMarker
+	}
+	frame.Source, route = ParseAddress(route[:i]), route[i+1:]
+
+	path := strings.Split(route, ",")
+	if len(path) == 0 || len(path) > 9 {
+		return nil, ErrPathLength
+	}
+	frame.Destination = ParseAddress(path[0])
+	for i, l := 1, len(path); i < l; i++ {
+		addr := ParseAddress(path[i])
+		frame.Path = append(frame.Path, addr)
+	}
+
+	var err error
+	for _, d := range decoders {
+		if d.CanDecode(frame) {
+			if frame.Data, err = d.Decode(frame); err == nil {
+				break
+			}
+		}
+	}
+
+	return frame, nil
+}