package httpserver

import (
	"context"
	"crypto/ed25519"
	"encoding/hex"
	"encoding/json"
	"io"
	"net/http"
	"slices"
	"strconv"
	"time"

	"github.com/example/notify-gateway/internal/model"
)

func (s *Server) discord(w http.ResponseWriter, r *http.Request) {
	c := s.store.Get().Ingress.Discord
	if !c.Enabled {
		http.NotFound(w, r)
		return
	}
	body, err := io.ReadAll(io.LimitReader(r.Body, (1<<20)+1))
	if err != nil || len(body) > 1<<20 {
		http.Error(w, "invalid request", 400)
		return
	}
	stamp := r.Header.Get("X-Signature-Timestamp")
	ts, err := strconv.ParseInt(stamp, 10, 64)
	key, e1 := hex.DecodeString(c.PublicKey)
	sig, e2 := hex.DecodeString(r.Header.Get("X-Signature-Ed25519"))
	if err != nil || e1 != nil || e2 != nil || len(key) != ed25519.PublicKeySize || ts < time.Now().Add(-5*time.Minute).Unix() || ts > time.Now().Add(5*time.Minute).Unix() || !ed25519.Verify(key, append([]byte(stamp), body...), sig) {
		http.Error(w, "invalid signature", 401)
		return
	}
	var in struct {
		ID            string `json:"id"`
		ApplicationID string `json:"application_id"`
		Type          int    `json:"type"`
		GuildID       string `json:"guild_id"`
		ChannelID     string `json:"channel_id"`
		Data          struct {
			Name    string `json:"name"`
			Type    int    `json:"type"`
			Options []struct {
				Name  string          `json:"name"`
				Type  int             `json:"type"`
				Value json.RawMessage `json:"value"`
			} `json:"options"`
		} `json:"data"`
	}
	if json.Unmarshal(body, &in) != nil || in.ApplicationID != c.ApplicationID {
		http.Error(w, "invalid interaction", 400)
		return
	}
	if in.Type == 1 {
		writeJSON(w, 200, map[string]int{"type": 1})
		return
	}
	if in.Type != 2 || in.Data.Type != 1 || in.Data.Name != c.Command || in.ID == "" || !slices.Contains(c.GuildIDs, in.GuildID) || !slices.Contains(c.ChannelIDs, in.ChannelID) {
		http.Error(w, "interaction not allowed", 403)
		return
	}
	msg := model.InboundMessage{Source: "discord", Channel: in.ChannelID, ReceivedAt: time.Now().UTC()}
	for _, o := range in.Data.Options {
		switch o.Name {
		case "title":
			err = json.Unmarshal(o.Value, &msg.Title)
		case "message":
			err = json.Unmarshal(o.Value, &msg.Message)
		case "priority":
			err = json.Unmarshal(o.Value, &msg.Priority)
		default:
			http.Error(w, "unsupported option", 400)
			return
		}
		if err != nil {
			http.Error(w, "invalid option", 400)
			return
		}
	}
	if msg.Message == "" {
		http.Error(w, "message required", 400)
		return
	}
	if s.queue == nil {
		http.Error(w, "outbox unavailable", 503)
		return
	}
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()
	receipt, err := s.queue.Accept(ctx, msg, "discord:"+in.ID)
	if err != nil {
		http.Error(w, "interaction could not be queued; check routing", 503)
		return
	}
	writeJSON(w, 200, map[string]any{"type": 4, "data": map[string]any{"content": "Meldung angenommen. Referenz: " + receipt.ID, "flags": 64, "allowed_mentions": map[string]any{"parse": []string{}}}})
}