feat: prototyping a concurrent location service

drone-black-box/go.mod

@@ -0,0 +1,3 @@
+module drone-black-box
+
+go 1.25.3

drone-black-box/main.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"sync"
+)
+
+// Define the DroneEvent struct as JSON
+type DroneEvent struct {
+	DroneID   string  `json:"drone_id"`
+	Latitude  float64 `json:"latitude"`
+	Longitude float64 `json:"longitude"`
+	Timestamp string  `json:"timestamp"`
+}
+
+// Shared state type alias
+type Server struct {
+	// This is a shared state between handlers
+	// It is protected by a mutex to prevent concurrent access
+	mu      sync.RWMutex
+	history []DroneEvent
+}
+
+// Ingest handler
+func (s *Server) ingestHandler(w http.ResponseWriter, r *http.Request) {
+	var event DroneEvent
+	if err := json.NewDecoder(r.Body).Decode(&event); err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	fmt.Printf("Data ingested: %+v\n", event)
+
+	s.mu.Lock()
+	s.history = append(s.history, event)
+	s.mu.Unlock()
+
+	w.WriteHeader(http.StatusCreated)
+}
+
+// Snapshot handler
+func (s *Server) snapshotHandler(w http.ResponseWriter, r *http.Request) {
+	timeParam := r.URL.Query().Get("time")
+	if timeParam == "" {
+		http.Error(w, "Missing 'time' query parameter", http.StatusBadRequest)
+		return
+	}
+
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	latestStates := make(map[string]DroneEvent)
+
+	for _, event := range s.history {
+		if event.Timestamp <= timeParam {
+			latestStates[event.DroneID] = event
+		}
+	}
+
+	result := make([]DroneEvent, 0, len(latestStates))
+	for _, event := range latestStates {
+		result = append(result, event)
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	if err := json.NewEncoder(w).Encode(result); err != nil {
+		log.Printf("Error encoding response: %v", err)
+	}
+}
+
+func main() {
+	// By default, listen on port 3000
+	port := os.Getenv("BLACKBOX_PORT")
+	if port == "" {
+		port = "3000"
+	}
+
+	server := &Server{
+		history: make([]DroneEvent, 0),
+	}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /ingest", server.ingestHandler)
+	mux.HandleFunc("GET /snapshot", server.snapshotHandler)
+
+	fmt.Printf("Black Box Service is running on port %s...\n", port)
+	if err := http.ListenAndServe(":"+port, mux); err != nil {
+		log.Fatal(err)
+		os.Exit(1)	
+	}
+}