Work in Progress: Implement Go backend features

apps/api/.env.example

@@ -1 +1,2 @@
 PORT=8080
+METRA_API_KEY=

apps/api/go.mod

@@ -1,3 +1,12 @@
-module github.com/rnielsen/tracky/api
+module github.com/Tracky-Trains/tracky/api
 
 go 1.26
+
+require (
+	github.com/MobilityData/gtfs-realtime-bindings/golang/gtfs v1.0.0
+	google.golang.org/protobuf v1.36.11
+)
+
+require golang.org/x/crypto v0.49.0
+
+require github.com/joho/godotenv v1.5.1

apps/api/go.sum

@@ -0,0 +1,10 @@
+github.com/MobilityData/gtfs-realtime-bindings/golang/gtfs v1.0.0 h1:f4P+fVYmSIWj4b/jvbMdmrmsx/Xb+5xCpYYtVXOdKoc=
+github.com/MobilityData/gtfs-realtime-bindings/golang/gtfs v1.0.0/go.mod h1:nSmbVVQSM4lp9gYvVaaTotnRxSwZXEdFnJARofg5V4g=
+github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
+github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
+github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+golang.org/x/crypto v0.49.0 h1:+Ng2ULVvLHnJ/ZFEq4KdcDd/cfjrrjjNSXNzxg0Y4U4=
+golang.org/x/crypto v0.49.0/go.mod h1:ErX4dUh2UM+CFYiXZRTcMpEcN8b/1gxEuv3nODoYtCA=
+google.golang.org/protobuf v1.36.11 h1:fV6ZwhNocDyBLK0dj+fg8ektcVegBBuEolpbTQyBNVE=
+google.golang.org/protobuf v1.36.11/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=

apps/api/gtfs/realtime.go

@@ -0,0 +1,203 @@
+package gtfs
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	gtfsrt "github.com/MobilityData/gtfs-realtime-bindings/golang/gtfs"
+	"google.golang.org/protobuf/proto"
+
+	"github.com/Tracky-Trains/tracky/api/spec"
+)
+
+// FetchAndParsePositions downloads a GTFS-RT vehicle positions feed and returns
+// parsed TrainPositions stamped with providerID.
+func FetchAndParsePositions(
+	ctx context.Context,
+	url string,
+	providerID string,
+	apiKey string,
+) ([]spec.TrainPosition, error) {
+	feed, err := fetchFeed(ctx, url, apiKey)
+	if err != nil {
+		return nil, fmt.Errorf("gtfs-rt positions: %w", err)
+	}
+
+	now := time.Now()
+	var positions []spec.TrainPosition
+
+	if b, err := json.MarshalIndent(feed.Entity, "", "  "); err == nil {
+		filename := fmt.Sprintf("debug_%s_positions.json", providerID)
+		if err := os.WriteFile(filename, b, 0644); err != nil {
+			log.Printf("[DEBUG] failed to write %s: %v", filename, err)
+		} else {
+			log.Printf("[DEBUG] %s realtime positions (%d) saved to %s", providerID, len(feed.Entity), filename)
+		}
+	}
+
+	for _, entity := range feed.Entity {
+		vp := entity.Vehicle
+		if vp == nil || vp.Trip == nil {
+			continue
+		}
+
+		pos := spec.TrainPosition{
+			Provider:    providerID,
+			LastUpdated: now,
+		}
+
+		if trip := vp.Trip; trip != nil {
+			pos.TripID = providerID + ":" + trip.GetTripId()
+			pos.RouteID = providerID + ":" + trip.GetRouteId()
+			pos.RunDate = parseStartDate(trip.GetStartDate())
+		}
+
+		if vehicle := vp.Vehicle; vehicle != nil {
+			pos.TrainNumber = vehicle.GetLabel()
+			pos.VehicleID = vehicle.GetId()
+		}
+
+		if p := vp.Position; p != nil {
+			lat := float64(p.GetLatitude())
+			lon := float64(p.GetLongitude())
+			pos.Lat = &lat
+			pos.Lon = &lon
+
+			if p.Bearing != nil {
+				h := fmt.Sprintf("%.0f", float64(p.GetBearing()))
+				pos.Heading = &h
+			}
+
+			if p.Speed != nil {
+				// GTFS-RT speed is m/s — convert to mph
+				mph := float64(p.GetSpeed()) * 2.23694
+				pos.SpeedMPH = &mph
+			}
+		}
+
+		if vp.StopId != nil {
+			stopID := providerID + ":" + vp.GetStopId()
+			pos.CurrentStopCode = &stopID
+		}
+
+		if vp.Timestamp != nil {
+			pos.LastUpdated = time.Unix(int64(vp.GetTimestamp()), 0)
+		}
+
+		positions = append(positions, pos)
+	}
+
+	return positions, nil
+}
+
+// FetchAndParseTripUpdates downloads a GTFS-RT trip updates feed and returns
+// parsed TrainStopTimes stamped with providerID.
+func FetchAndParseTripUpdates(
+	ctx context.Context,
+	url string,
+	providerID string,
+	apiKey string,
+) ([]spec.TrainStopTime, error) {
+	feed, err := fetchFeed(ctx, url, apiKey)
+	if err != nil {
+		return nil, fmt.Errorf("gtfs-rt trip updates: %w", err)
+	}
+
+	now := time.Now()
+	var stopTimes []spec.TrainStopTime
+
+	if b, err := json.MarshalIndent(feed.Entity, "", "  "); err == nil {
+		filename := fmt.Sprintf("debug_%s_stoptimes.json", providerID)
+		if err := os.WriteFile(filename, b, 0644); err != nil {
+			log.Printf("[DEBUG] failed to write %s: %v", filename, err)
+		} else {
+			log.Printf("[DEBUG] %s trip updates (%d entities) saved to %s", providerID, len(feed.Entity), filename)
+		}
+	}
+
+	for _, entity := range feed.Entity {
+		tu := entity.TripUpdate
+		if tu == nil {
+			continue
+		}
+
+		tripID := ""
+		runDate := time.Time{}
+
+		if trip := tu.Trip; trip != nil {
+			tripID = providerID + ":" + trip.GetTripId()
+			runDate = parseStartDate(trip.GetStartDate())
+		}
+
+		for _, stu := range tu.StopTimeUpdate {
+			st := spec.TrainStopTime{
+				Provider:     providerID,
+				TripID:       tripID,
+				RunDate:      runDate,
+				StopCode:     providerID + ":" + stu.GetStopId(),
+				StopSequence: int(stu.GetStopSequence()),
+				LastUpdated:  now,
+			}
+
+			if arr := stu.Arrival; arr != nil && arr.Time != nil {
+				t := time.Unix(arr.GetTime(), 0)
+				st.EstimatedArr = &t
+			}
+
+			if dep := stu.Departure; dep != nil && dep.Time != nil {
+				t := time.Unix(dep.GetTime(), 0)
+				st.EstimatedDep = &t
+			}
+
+			stopTimes = append(stopTimes, st)
+		}
+	}
+
+	return stopTimes, nil
+}
+
+// fetchFeed downloads and unmarshals a GTFS-RT protobuf feed.
+func fetchFeed(ctx context.Context, url string, apiKey string) (*gtfsrt.FeedMessage, error) {
+	data, err := fetchBytes(ctx, url, apiKey)
+	if err != nil {
+		return nil, fmt.Errorf("fetch %s: %w", url, err)
+	}
+	var feed gtfsrt.FeedMessage
+	if err := proto.Unmarshal(data, &feed); err != nil {
+		return nil, fmt.Errorf("fetch %s: unmarshal: %w", url, err)
+	}
+	return &feed, nil
+}
+
+// fetchBytes performs a GET request and returns the response body.
+// If apiKey is non-empty, it's sent as a Bearer token in the Authorization header.
+func fetchBytes(ctx context.Context, url string, apiKey string) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	if apiKey != "" {
+		req.Header.Set("Authorization", "Bearer "+apiKey)
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
+	}
+	return io.ReadAll(resp.Body)
+}
+
+// parseStartDate parses a GTFS-RT start_date string (YYYYMMDD) into a time.Time.
+func parseStartDate(s string) time.Time {
+	t, _ := time.Parse("20060102", s)
+	return t
+}