package main

import (
	"context"
	"errors"
	"fmt"
	"io"
	"log"
	"log/slog"
	"net/http"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/bluesky-social/indigo/api/atproto"
	"github.com/bluesky-social/indigo/xrpc"
	"github.com/gorilla/websocket"
	"github.com/joho/godotenv"
)

func main() {
	envLocation := os.Getenv("ENV_LOCATION")
	if envLocation == "" {
		envLocation = ".env"
	}

	err := godotenv.Load(envLocation)
	if err != nil {
		if !os.IsNotExist(err) {
			log.Fatal("Error loading .env file")
		}
	}

	hostname := os.Getenv("PDS_HOST")
	slog.Info("hostname", "is", hostname)

	relays := strings.Split(os.Getenv("RELAYS"), ",")

	srv := Server{
		upgrader: websocket.Upgrader{},
		conns:    make(map[string]*websocket.Conn),
		relays:   relays,
		hostname: hostname,
	}

	go srv.requestCrawl(context.Background())

	mux := http.NewServeMux()
	mux.HandleFunc("/xrpc/com.atproto.sync.subscribeRepos", srv.handleSyncSubscribeRepos)
	mux.HandleFunc("POST /events", srv.handleNewEvent)
	mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("hello"))
	})

	port := os.Getenv("PORT")
	if port == "" {
		port = "3000"
		slog.Info("PORT env not set - using default 3000")
	}

	if err := http.ListenAndServe(fmt.Sprintf(":%s", port), mux); err != nil {
		slog.Error("http listen and serve", "error", err)
	}
}

type Server struct {
	upgrader         websocket.Upgrader
	mu               sync.Mutex
	conns            map[string]*websocket.Conn
	lastRequestCrawl time.Time
	relays           []string
	hostname         string
}

func (s *Server) handleSyncSubscribeRepos(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithCancel(r.Context())
	defer cancel()

	conn, err := s.upgrader.Upgrade(w, r, w.Header())
	if err != nil {
		slog.Error("unable to establish websocket with relay", "err", err)
		w.Write([]byte("fail to upgrade to websocket"))
		return
	}

	ident := r.RemoteAddr + "-" + r.UserAgent()
	slog.Info("new connection established", "ident", ident)

	s.mu.Lock()
	s.conns[ident] = conn
	s.mu.Unlock()

	defer func() {
		// we should tell the relay to request a new crawl at this point if we got disconnected
		// use a new context since the old one might be cancelled at this point
		go func() {
			retryCtx, retryCancel := context.WithTimeout(context.Background(), 10*time.Second)
			defer retryCancel()
			if err := s.requestCrawl(retryCtx); err != nil {
				slog.Error("error requesting crawls", "err", err)
			}
		}()
	}()

	for {
		select {
		case <-ctx.Done():
			return
		default:
			if _, _, err := conn.ReadMessage(); err != nil {
				slog.Warn("websocket error", "err", err)
				cancel()
				return
			}
		}
	}
}

func (s *Server) handleNewEvent(w http.ResponseWriter, r *http.Request) {
	b, err := io.ReadAll(r.Body)
	if err != nil {
		slog.Error("read event body", "error", err)
		w.Write([]byte("read event body"))
		return
	}

	slog.Info("got event")
	s.mu.Lock()
	conns := s.conns
	s.mu.Unlock()

	for ident, conn := range conns {
		wc, err := conn.NextWriter(websocket.BinaryMessage)
		if err != nil {
			slog.Error("error writing message to relay", "err", err)
			if errors.Is(err, websocket.ErrCloseSent) {
				s.mu.Lock()
				delete(s.conns, ident)
				s.mu.Unlock()
			}
			continue
		}

		_, err = wc.Write(b)
		if err != nil {
			slog.Error("writing data to conn", "error", err, "ident", ident)
			continue
		}

		if err := wc.Close(); err != nil {
			slog.Error("failed to flush-close our event write", "err", err, "ident", ident)
			continue
		}
	}
	w.WriteHeader(http.StatusAccepted)
}

func (s *Server) requestCrawl(ctx context.Context) error {
	if time.Since(s.lastRequestCrawl) <= 1*time.Minute {
		return fmt.Errorf("a crawl request has already been made within the last minute")
	}

	for _, relay := range s.relays {
		slog.Info("requesting crawl from relay", "relay", relay)
		cli := xrpc.Client{Host: relay}
		err := atproto.SyncRequestCrawl(ctx, &cli, &atproto.SyncRequestCrawl_Input{
			Hostname: s.hostname,
		})
		if err != nil {
			slog.Error("error requesting crawl", "err", err)
			continue
		}
		slog.Info("crawl requested successfully")
	}

	s.lastRequestCrawl = time.Now()

	return nil
}