// kaiyan-ingest receives chat messages as webhooks and emplaces them to Kafka.
package main

import (
	"context"
	"flag"
	"fmt"
	"log/slog"
	"net"
	"net/http"
	"os"
	"os/signal"
	"sync"
	"time"

	"github.com/go-json-experiment/json"
	"github.com/twmb/franz-go/pkg/kgo"

	"git.sunturtle.xyz/zephyr/kaiyan/ingest"
	"git.sunturtle.xyz/zephyr/kaiyan/queue"
	"git.sunturtle.xyz/zephyr/kaiyan/twitch"
)

func main() {
	var (
		listen     string
		secretFile string
	)
	flag.StringVar(&listen, "listen", ":80", "address to bind for webhooks")
	flag.StringVar(&secretFile, "secret", "", "path to file containing the system secret")
	flag.Parse()
	if flag.NArg() == 0 {
		fail("provide broker addresses as args")
	}
	if secretFile == "" {
		fail("-secret is required")
	}

	secret, err := os.ReadFile(secretFile)
	if err != nil {
		fail(err.Error())
	}
	// TODO(branden): derive secrets for twitch webhook and users?
	q, err := kgo.NewClient(
		kgo.SeedBrokers(flag.Args()...),
		kgo.ProducerBatchCompression(kgo.ZstdCompression()),
	)
	if err != nil {
		fail(err.Error())
	}
	errs := make(chan error, 1)
	go func() {
		for err := range errs {
			slog.Error("enqueue", slog.Any("err", err))
		}
	}()
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	mux := http.NewServeMux()
	mux.Handle("POST /twitch", webhook(q, secret, errs))
	// TODO(branden): GET /metrics
	l, err := net.Listen("tcp", listen)
	if err != nil {
		fail(err.Error())
	}
	srv := http.Server{
		Addr:         listen,
		Handler:      mux,
		ReadTimeout:  3 * time.Second,
		WriteTimeout: 3 * time.Second,
		IdleTimeout:  1 * time.Minute,
		BaseContext:  func(l net.Listener) context.Context { return ctx },
	}
	go func() {
		slog.InfoContext(ctx, "HTTP API", slog.Any("addr", l.Addr()))
		// TODO(branden): tls? or do we just use caddy/nginx after all?
		err := srv.Serve(l)
		if err == http.ErrServerClosed {
			return
		}
		slog.ErrorContext(ctx, "HTTP API closed", slog.Any("err", err))
	}()
	// TODO(branden): tell eventsub we're listening
	<-ctx.Done()
	stop()
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()
	if err := srv.Shutdown(ctx); err != nil {
		slog.ErrorContext(ctx, "HTTP API shutdown", slog.Any("err", err))
	}
}

var byteptrPool sync.Pool

func webhook(q *kgo.Client, secret []byte, errs chan<- error) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		ctx := r.Context()
		log := slog.With(slog.Group("request",
			slog.String("host", r.Host),
			slog.String("remote", r.RemoteAddr),
			slog.String("id", r.Header.Get("Twitch-Eventsub-Message-Id")),
		))
		p, _ := byteptrPool.Get().(*[]byte)
		if p == nil {
			p = new([]byte)
		}
		b, err := twitch.Receive(*p, secret, r)
		defer func() {
			*p = b[:0]
			byteptrPool.Put(p)
		}()
		if err != nil {
			log.ErrorContext(ctx, "webhook receive", slog.Any("err", err))
			http.Error(w, "bad request", http.StatusBadRequest)
			return
		}
		var ev twitch.EventSub[ingest.Twitch]
		if err := json.Unmarshal(b, &ev); err != nil {
			log.ErrorContext(ctx, "webhook decode", slog.Any("err", err))
			http.Error(w, "bad request", http.StatusBadRequest)
			return
		}
		switch evtype := r.Header.Get("Twitch-Eventsub-Message-Type"); evtype {
		case twitch.Notification:
			log.LogAttrs(ctx, slog.LevelInfo, "webhook receive",
				slog.String("broadcaster", ev.Event.Broadcaster),
				slog.String("id", ev.Event.ID),
			)
			msg := queue.Message{
				ID:      ev.Event.ID,
				Channel: ev.Event.Broadcaster,
				Sender:  queue.Sender(secret, ev.Event.Broadcaster, ev.Event.Chatter),
				Text:    ev.Event.Message.Text,
			}
			// TODO(branden): the context in the http request cancels once this
			// handler returns, which means the producer doesn't relay it.
			// what's a good context to use, then?
			queue.Send(context.TODO(), q, msg, errs)
			w.WriteHeader(http.StatusNoContent)
			log.LogAttrs(ctx, slog.LevelInfo, "received",
				slog.String("broadcaster", ev.Event.Broadcaster),
				slog.String("id", ev.Event.ID),
			)

		case twitch.Revocation:
			log.LogAttrs(ctx, slog.LevelInfo, "webhook revoke")
			// TODO(branden): this
			w.WriteHeader(http.StatusNoContent)

		case twitch.Verification:
			log.LogAttrs(ctx, slog.LevelInfo, "verification challenge")
			twitch.HandleChallenge(w, b)

		default:
			log.ErrorContext(ctx, "invalid EventSub message type", slog.String("type", evtype))
			w.WriteHeader(http.StatusBadRequest)
		}
	}
}

func fail(format string, args ...any) {
	fmt.Fprintf(os.Stderr, format+"\n", args...)
	os.Exit(1)
}