sync

internal/fit/decoder.go

@@ -0,0 +1,111 @@
+package fit
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+	"os"
+)
+
+const (
+	headerSize    = 12
+	protocolMajor = 2
+)
+
+// FileHeader represents the header of a FIT file
+type FileHeader struct {
+	Size      uint8
+	Protocol  uint8
+	Profile   [4]byte
+	DataSize  uint32
+	Signature [4]byte
+}
+
+// Activity represents activity data from a FIT file
+type Activity struct {
+	Type          string
+	StartTime     int64
+	TotalDistance float64
+	Duration      float64
+}
+
+// Decoder parses FIT files
+type Decoder struct {
+	r io.Reader
+}
+
+// NewDecoder creates a new FIT decoder
+func NewDecoder(r io.Reader) *Decoder {
+	return &Decoder{r: r}
+}
+
+// Parse decodes the FIT file and returns the activity data
+func (d *Decoder) Parse() (*Activity, error) {
+	var header FileHeader
+	if err := binary.Read(d.r, binary.LittleEndian, &header); err != nil {
+		return nil, err
+	}
+
+	// Validate header
+	if header.Protocol != protocolMajor {
+		return nil, errors.New("unsupported FIT protocol version")
+	}
+
+	// For simplicity, we'll just extract basic activity data
+	activity := &Activity{}
+
+	// Skip to activity record (simplified for example)
+	// In a real implementation, we would parse the file structure properly
+	for {
+		var recordHeader uint8
+		if err := binary.Read(d.r, binary.LittleEndian, &recordHeader); err == io.EOF {
+			break
+		} else if err != nil {
+			return nil, err
+		}
+
+		if recordHeader == 0x21 { // Activity record header (example value)
+			var record struct {
+				Type          uint8
+				StartTime     int64
+				TotalDistance float32
+				Duration      uint32
+			}
+			if err := binary.Read(d.r, binary.LittleEndian, &record); err != nil {
+				return nil, err
+			}
+
+			activity.Type = activityType(record.Type)
+			activity.StartTime = record.StartTime
+			activity.TotalDistance = float64(record.TotalDistance)
+			activity.Duration = float64(record.Duration)
+			break
+		}
+	}
+
+	return activity, nil
+}
+
+func activityType(t uint8) string {
+	switch t {
+	case 1:
+		return "Running"
+	case 2:
+		return "Cycling"
+	case 3:
+		return "Swimming"
+	default:
+		return "Unknown"
+	}
+}
+
+// ReadFile reads and parses a FIT file
+func ReadFile(path string) (*Activity, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	return NewDecoder(file).Parse()
+}