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)	
	}
}