package main

import (
	"context"
	"encoding/json"
	"net/http"

	"fiatjaf.com/nostr"
	"fiatjaf.com/nostr/eventstore"
	"fiatjaf.com/nostr/khatru"

	"github.com/nosterm/relay/internal/federation"
	"github.com/nosterm/relay/internal/group"
	"github.com/nosterm/relay/internal/relayinfo"
)

// relayConfig holds everything buildRelay needs to assemble a relay. It is the
// seam between env/flag parsing (main) and the wiring (buildRelay), so tests can
// construct a relay with an in-memory store and explicit config.
type relayConfig struct {
	secretKey   nostr.SecretKey
	store       eventstore.Store
	name        string
	description string
	contact     string
	motd        string
	fedCfg      federation.Config
}

// relayApp is a fully-wired relay: the khatru relay, its HTTP handler, the group
// state authority, and (when configured) the federator. main starts/stops these;
// tests assert against them.
type relayApp struct {
	relay     *khatru.Relay
	handler   http.Handler
	groups    *group.State
	federator *federation.Federator
	pubKey    nostr.PubKey
}

// buildRelay assembles the relay from its internal packages and wires khatru's
// hooks: NIP-29 enforcement on ingress, addressable-list (re)publishing on
// group mutations, federation ingress/egress, and NIP-11 serving with the
// Nosterm capability handshake. It does NOT rebuild state, start retention,
// or start federation — the caller owns lifecycle so tests can drive it.
func buildRelay(cfg relayConfig) *relayApp {
	pk := nostr.GetPublicKey(cfg.secretKey)

	groups := group.NewState(cfg.secretKey)
	if cfg.fedCfg.Enabled() {
		// Chat on a federated channel is accepted regardless of local membership.
		groups.IsFederated = cfg.fedCfg.FederatesChannel
	}

	relay := khatru.NewRelay()
	relay.Info.Name = cfg.name
	relay.Info.Description = cfg.description
	relay.Info.Contact = cfg.contact
	relay.Info.PubKey = &pk
	relay.Info.SupportedNIPs = []any{1, 11, 29, 42}
	relay.UseEventstore(cfg.store, 500)

	// Enforce NIP-29 group rules on every write.
	relay.OnEvent = func(ctx context.Context, evt nostr.Event) (reject bool, msg string) {
		return groups.Evaluate(evt)
	}

	// Federator: connects to peers, pulls their chat (injecting it through the
	// relay's own add pipeline — whose eventstore dedup breaks forwarding loops),
	// and forwards locally-saved chat to mirror peers via the OnEventSaved hook.
	var fed *federation.Federator
	if cfg.fedCfg.Enabled() {
		fed = federation.NewFederator(cfg.fedCfg, func(ctx context.Context, evt nostr.Event) bool {
			// Ensure the channel exists locally so federated chat has a home, then
			// run it through the normal pipeline (OnEvent → store → OnEventSaved).
			// AddEvent returns skipBroadcast=true on a duplicate: that is our loop
			// guard — a re-seen event never reaches the egress hook again.
			groups.EnsureFederatedGroup(group.GroupIDFromEvent(evt))
			skip, err := relay.AddEvent(ctx, evt)
			if err != nil || skip {
				return false
			}
			// AddEvent stores but does not broadcast; deliver to local subscribers.
			relay.BroadcastEvent(evt)
			return true
		})
	}

	// After a group-mutating event is stored, (re)publish the affected NIP-29
	// addressable lists (39000 metadata, 39001 admins, 39002 members) so clients
	// can discover the channel and track who may moderate it.
	publish := func(evt nostr.Event, ok bool) {
		if ok {
			relay.BroadcastEvent(evt)
			_ = cfg.store.SaveEvent(evt)
		}
	}
	relay.OnEventSaved = func(ctx context.Context, evt nostr.Event) {
		id := group.GroupIDFromEvent(evt)
		if id == "" {
			return
		}
		switch evt.Kind {
		case nostr.KindSimpleGroupCreateGroup:
			publish(groups.MetadataEvent(ctx, id))
			publish(groups.AdminsEvent(id))
			publish(groups.MembersEvent(id))
		case nostr.KindSimpleGroupEditMetadata:
			publish(groups.MetadataEvent(ctx, id))
		case nostr.KindSimpleGroupJoinRequest,
			nostr.KindSimpleGroupLeaveRequest,
			nostr.KindSimpleGroupPutUser,
			nostr.KindSimpleGroupRemoveUser:
			// Membership (and possibly admin) changed → refresh both lists.
			publish(groups.AdminsEvent(id))
			publish(groups.MembersEvent(id))
		case nostr.KindSimpleGroupChatMessage, nostr.KindSimpleGroupThreadedReply:
			// Egress: forward newly-saved chat to mirror peers. A chat event
			// re-injected from a peer is a store duplicate and never reaches here
			// (AddEvent stops on dedup before OnEventSaved), so this can't loop.
			if fed != nil {
				fed.Forward(evt)
			}
		}
	}

	// Serve NIP-11 ourselves so we can add the nostermd `features` array
	// (the upstream document type has no field for it), then dispatch the real
	// protocol traffic to khatru's specific handlers. We must NOT call
	// relay.ServeHTTP here: khatru's ServeHTTP dispatches through this same mux,
	// so routing "/" back into it recurses infinitely (stack overflow on the
	// first non-NIP-11 request). Call the concrete handlers directly instead.
	mux := relay.Router()
	federated := cfg.fedCfg.Enabled()
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		switch {
		case r.Header.Get("Accept") == "application/nostr+json":
			serveNIP11(w, cfg.name, cfg.description, cfg.contact, cfg.motd, pk, federated)
		case r.Header.Get("Upgrade") == "websocket":
			relay.HandleWebsocket(w, r)
		case r.Header.Get("Content-Type") == "application/nostr+json+rpc":
			relay.HandleNIP86(w, r)
		default:
			http.Error(w, "expected a nostr relay connection (WebSocket) or NIP-11 request", http.StatusUpgradeRequired)
		}
	})

	return &relayApp{
		relay:     relay,
		handler:   mux,
		groups:    groups,
		federator: fed,
		pubKey:    pk,
	}
}

// serveNIP11 emits a standard NIP-11 document merged with the Nosterm handshake
// keys (software/version/features), plus an optional `motd` the client shows in
// the relay's server window.
func serveNIP11(w http.ResponseWriter, name, description, contact, motd string, pk nostr.PubKey, federated bool) {
	doc := map[string]any{
		"name":           name,
		"description":    description,
		"contact":        contact,
		"pubkey":         pk.Hex(),
		"supported_nips": []int{1, 11, 29, 42},
	}
	if motd != "" {
		doc["motd"] = motd
	}
	for k, v := range relayinfo.Extras(federated) {
		doc[k] = v
	}
	w.Header().Set("Content-Type", "application/nostr+json")
	w.Header().Set("Access-Control-Allow-Origin", "*")
	_ = json.NewEncoder(w).Encode(doc)
}