Merge pull request #876 from wader/fit-date-time

fit: Formatted date/time description for timestamp fields

doc/formats.md

@@ -591,6 +591,7 @@ $ fq '[.data_records[] | select(.record_header.message_type == "data").data_mess
 
 ### References
 - https://developer.garmin.com/fit/protocol/
+- https://developer.garmin.com/fit/cookbook/decoding-activity-files/
 
 ## flac_frame
 

format/fit/fit.go

@@ -1,5 +1,8 @@
 package fit
 
+// https://developer.garmin.com/fit/protocol/
+// https://developer.garmin.com/fit/cookbook/decoding-activity-files/
+
 import (
 	"embed"
 	"fmt"

format/fit/fit.md

@@ -16,3 +16,4 @@ $ fq '[.data_records[] | select(.record_header.message_type == "data").data_mess
 
 ### References
 - https://developer.garmin.com/fit/protocol/
+- https://developer.garmin.com/fit/cookbook/decoding-activity-files/

format/fit/mappers/values.go

@@ -2,10 +2,13 @@ package mappers
 
 import (
 	"math"
+	"time"
 
 	"github.com/wader/fq/pkg/scalar"
 )
 
+var epochDate = time.Date(1989, time.December, 31, 0, 0, 0, 0, time.UTC)
+
 // Used for conversion from semicircles to decimal longitude latitude
 var scConst = 180 / math.Pow(2, 31)
 
@@ -51,12 +54,20 @@ func GetUintFormatter(fDef LocalFieldDef) scalar.UintFn {
 			}
 		}
 
-		s.Description = fDef.Unit
 		if t, ok := TypeDefMap[fDef.Format]; ok {
 			if u, innerOk := t[s.Actual]; innerOk {
 				s.Sym = u.Name
 			}
 		}
+
+		switch fDef.Format {
+		case "date_time",
+			"local_date_time":
+			s.Description = epochDate.Add(time.Duration(s.Actual) * time.Second).Format(time.RFC3339)
+		default:
+			s.Description = fDef.Unit
+		}
+
 		return s, nil
 	})
 }