// tera-sessiond owns Direct Mode WebSocket attachments and bounded fan-out.
package main

import (
	"context"
	"encoding/json"
	"log"
	"net/http"
	"os"
	"os/signal"
	"strings"
	"sync"
	"syscall"
	"time"

	"tera-clone/services/tera-api/internal/directstream"
	"tera-clone/services/tera-api/internal/serial"
)

func main() {
	listenAddress := sessiondGetenv("TERA_SESSIOND_LISTEN_ADDR", "127.0.0.1:8081")
	ticketSockets := sessiondGetenvList("TERA_SESSIOND_TICKET_SOCKETS")
	if len(ticketSockets) == 0 {
		ticketSockets = []string{sessiondGetenv("TERA_SESSIOND_TICKET_SOCKET", directstream.DefaultTicketSocketPath)}
	}
	serialSocket := sessiondGetenv("TERA_SESSIOND_SERIAL_STREAM_SOCKET", serial.DefaultStreamSocketPath)
	ticketClient := directstream.NewTicketSocketPool(ticketSockets)
	transportFactory := serial.NewStreamSocketClient(serialSocket, "tera-sessiond")
	broker, err := directstream.NewBroker(transportFactory, directstream.BrokerOptions{})
	if err != nil {
		log.Fatalf("tera-sessiond broker setup failed: %v", err)
	}
	defer broker.Close()

	webSocketMetrics := &directstream.WebSocketMetrics{}
	streamHandler := directstream.NewWebSocketHandler(broker, ticketClient, ticketClient, directstream.WebSocketOptions{
		AllowedOrigins: sessiondGetenvList("TERA_SESSIOND_ALLOWED_ORIGINS"),
		Metrics:        webSocketMetrics,
	})
	mux := http.NewServeMux()
	mux.Handle("/api/v1/direct/", streamHandler)
	statusHandler := newSessiondStatusHandler(broker, webSocketMetrics, ticketClient, transportFactory)
	mux.Handle("/healthz", statusHandler(false))
	mux.Handle("/readyz", statusHandler(true))
	server := &http.Server{
		Addr:              listenAddress,
		Handler:           mux,
		ReadHeaderTimeout: 5 * time.Second,
		IdleTimeout:       60 * time.Second,
	}
	log.Printf("tera-sessiond listening on http://%s", listenAddress)
	serverErrors := make(chan error, 1)
	go func() { serverErrors <- server.ListenAndServe() }()
	signalContext, stopSignals := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stopSignals()
	select {
	case <-signalContext.Done():
		log.Printf("tera-sessiond stopping")
		_ = broker.Close()
		shutdownContext, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()
		if err := server.Shutdown(shutdownContext); err != nil {
			log.Printf("tera-sessiond HTTP shutdown failed: %v", err)
		}
	case err := <-serverErrors:
		if err != nil && err != http.ErrServerClosed {
			log.Fatalf("tera-sessiond failed: %v", err)
		}
	}
}

type ticketStatusProvider interface {
	Status(context.Context) (directstream.TicketServiceSnapshot, error)
}

type serialStatusProvider interface {
	Status(context.Context) (serial.StreamSnapshot, error)
}

type sessiondStatus struct {
	Status      string                             `json:"status"`
	Broker      directstream.BrokerSnapshot        `json:"broker"`
	WebSocket   directstream.WebSocketSnapshot     `json:"websocket"`
	Tickets     directstream.TicketServiceSnapshot `json:"tickets"`
	Serial      serial.StreamSnapshot              `json:"serial"`
	TicketError string                             `json:"ticket_error,omitempty"`
	SerialError string                             `json:"serial_error,omitempty"`
}

func newSessiondStatusHandler(broker *directstream.Broker, metrics *directstream.WebSocketMetrics, tickets ticketStatusProvider, seriald serialStatusProvider) func(bool) http.Handler {
	return func(readiness bool) http.Handler {
		return http.HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
			if request.Method != http.MethodGet {
				response.Header().Set("Allow", http.MethodGet)
				response.WriteHeader(http.StatusMethodNotAllowed)
				return
			}
			ctx, cancel := context.WithTimeout(request.Context(), time.Second)
			defer cancel()
			status := sessiondStatus{Status: "ok", Broker: broker.Snapshot(), WebSocket: metrics.Snapshot()}
			var wait sync.WaitGroup
			wait.Add(2)
			go func() {
				defer wait.Done()
				value, err := tickets.Status(ctx)
				status.Tickets = value
				if err != nil {
					status.TicketError = err.Error()
				}
			}()
			go func() {
				defer wait.Done()
				value, err := seriald.Status(ctx)
				status.Serial = value
				if err != nil {
					status.SerialError = err.Error()
				}
			}()
			wait.Wait()
			if status.TicketError != "" || status.SerialError != "" {
				status.Status = "degraded"
			}
			response.Header().Set("Content-Type", "application/json")
			if readiness && status.Status != "ok" {
				response.WriteHeader(http.StatusServiceUnavailable)
			}
			_ = json.NewEncoder(response).Encode(status)
		})
	}
}

func sessiondGetenv(key, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		return value
	}
	return fallback
}

func sessiondGetenvList(key string) []string {
	value := os.Getenv(key)
	result := make([]string, 0)
	for _, item := range strings.Split(value, ",") {
		item = strings.TrimSpace(item)
		if item != "" {
			result = append(result, item)
		}
	}
	return result
}