package main

import (
	"database/sql"
	"log"
	"net/http"
	"os"
	"strconv"
	"sync"
	"time"

	"agentmon/internal/httpx"
	"agentmon/internal/store/postgres"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
	"github.com/gorilla/websocket"
	"github.com/nats-io/nats.go"
)

var (
	wsUpgrader = websocket.Upgrader{
		CheckOrigin: func(r *http.Request) bool { return true },
	}
	wsClients = make(map[*websocket.Conn]bool)
	wsMu      sync.RWMutex
	natsConn  *nats.Conn
)

func subscribeToNATS(nc *nats.Conn) {
	topic := envDefault("NATS_TOPIC", "agentmon.events.v1")
	sub, err := nc.Subscribe(topic, func(msg *nats.Msg) {
		wsMu.RLock()
		var stale []*websocket.Conn
		for conn := range wsClients {
			err := conn.WriteMessage(websocket.TextMessage, msg.Data)
			if err != nil {
				conn.Close()
				stale = append(stale, conn)
			}
		}
		wsMu.RUnlock()

		if len(stale) > 0 {
			wsMu.Lock()
			for _, conn := range stale {
				delete(wsClients, conn)
			}
			wsMu.Unlock()
		}
	})
	if err != nil {
		log.Printf("failed to subscribe to NATS: %v", err)
		return
	}
	log.Printf("subscribed to NATS topic: %s", topic)
	_ = sub
}

func wsHandler(w http.ResponseWriter, r *http.Request) {
	conn, err := wsUpgrader.Upgrade(w, r, nil)
	if err != nil {
		return
	}
	defer conn.Close()

	wsMu.Lock()
	wsClients[conn] = true
	wsMu.Unlock()

	log.Printf("WebSocket client connected")

	for {
		_, _, err := conn.ReadMessage()
		if err != nil {
			break
		}
	}

	wsMu.Lock()
	delete(wsClients, conn)
	wsMu.Unlock()
	log.Printf("WebSocket client disconnected")
}

func main() {
	addr := envDefault("AGENTMON_QUERY_ADDR", ":8081")
	dsn := os.Getenv("DATABASE_URL")
	natsURL := envDefault("NATS_URL", "nats://localhost:4222")

	if dsn == "" {
		log.Fatalf("DATABASE_URL is required")
	}

	db, err := postgres.Open(dsn)
	if err != nil {
		log.Fatalf("failed to open DB: %v", err)
	}
	defer func() { _ = db.Close() }()

	nc, err := nats.Connect(natsURL)
	if err != nil {
		log.Printf("warning: failed to connect to NATS: %v", err)
	} else {
		natsConn = nc
		go subscribeToNATS(nc)
	}

	r := chi.NewRouter()
	r.Use(middleware.RequestID)
	r.Use(middleware.RealIP)
	r.Use(middleware.Logger)
	r.Use(middleware.Recoverer)

	r.Get("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("ok"))
	})

	r.Get("/v1/ws", wsHandler)

	r.Get("/v1/events", func(w http.ResponseWriter, r *http.Request) {
		limit, _ := strconv.Atoi(r.URL.Query().Get("limit"))
		f := postgres.EventsFilter{
			Limit:     limit,
			EventType: r.URL.Query().Get("event_type"),
			Framework: r.URL.Query().Get("framework"),
		}
		events, err := db.ListRecentEvents(r.Context(), f)
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}
		httpx.WriteJSON(w, http.StatusOK, map[string]any{"events": events})
	})

	r.Get("/v1/sessions", func(w http.ResponseWriter, r *http.Request) {
		q := r.URL.Query()
		f := postgres.SessionsFilter{
			Framework: q.Get("framework"),
			Host:      q.Get("host"),
		}

		if v := q.Get("limit"); v != "" {
			f.Limit, _ = strconv.Atoi(v)
		}

		if v := q.Get("from"); v != "" {
			if t, err := time.Parse(time.RFC3339, v); err == nil {
				f.From = &t
			} else if t, err := time.Parse("2006-01-02", v); err == nil {
				f.From = &t
			}
		}

		if v := q.Get("to"); v != "" {
			if t, err := time.Parse(time.RFC3339, v); err == nil {
				f.To = &t
			} else if t, err := time.Parse("2006-01-02", v); err == nil {
				end := t.Add(24*time.Hour - time.Nanosecond)
				f.To = &end
			}
		}

		if v := q.Get("cursor"); v != "" {
			if t, err := time.Parse(time.RFC3339Nano, v); err == nil {
				f.Cursor = &t
			}
		}

		sessions, nextCursor, err := db.ListSessions(r.Context(), f)
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}

		resp := map[string]any{"sessions": sessions}
		if nextCursor != nil {
			resp["next_cursor"] = nextCursor.Format(time.RFC3339Nano)
		}
		httpx.WriteJSON(w, http.StatusOK, resp)
	})

	r.Get("/v1/sessions/{sessionID}", func(w http.ResponseWriter, r *http.Request) {
		sessionID := chi.URLParam(r, "sessionID")
		session, runs, err := db.GetSessionWithRuns(r.Context(), sessionID)
		if err == sql.ErrNoRows {
			httpx.WriteJSON(w, http.StatusNotFound, map[string]any{"error": "not_found"})
			return
		}
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}
		httpx.WriteJSON(w, http.StatusOK, map[string]any{"session": session, "runs": runs})
	})

	r.Get("/v1/runs/{runID}", func(w http.ResponseWriter, r *http.Request) {
		runID := chi.URLParam(r, "runID")
		run, spans, err := db.GetRunWithSpans(r.Context(), runID)
		if err == sql.ErrNoRows {
			httpx.WriteJSON(w, http.StatusNotFound, map[string]any{"error": "not_found"})
			return
		}
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}
		httpx.WriteJSON(w, http.StatusOK, map[string]any{"run": run, "spans": spans})
	})

	r.Get("/v1/stats/summary", func(w http.ResponseWriter, r *http.Request) {
		summary, err := db.GetSummary(r.Context())
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}
		httpx.WriteJSON(w, http.StatusOK, summary)
	})

	r.Get("/v1/stats/timeseries", func(w http.ResponseWriter, r *http.Request) {
		window := r.URL.Query().Get("window")
		switch window {
		case "1h", "6h", "24h", "7d":
		case "":
			window = "1h"
		default:
			httpx.WriteJSON(w, http.StatusBadRequest, map[string]any{"error": "invalid_window"})
			return
		}
		timeseries, err := db.GetTimeseries(r.Context(), window)
		if err != nil {
			httpx.WriteJSON(w, http.StatusInternalServerError, map[string]any{"error": "db_error"})
			return
		}
		httpx.WriteJSON(w, http.StatusOK, timeseries)
	})

	log.Printf("query-api listening on %s", addr)
	log.Fatal(http.ListenAndServe(addr, r))
}

func envDefault(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}