package gameserver

import (
	"fmt"
	"os"
	"sync"
	"sync/atomic"
	"time"

	"google.golang.org/protobuf/proto"

	"gac-hkrpg-go/internal/common"
	kcplib "gac-hkrpg-go/pkg/kcp"
	goproto "gac-hkrpg-go/protocol/proto"
)

const maxPacketSize = 1400

// PropEntry mirrors PlayerSession.prop_entities: entity_id -> (prop_id, inst_id, state).
type PropEntry struct {
	GroupID uint32
	PropID  uint32
	InstID  uint32
	State   uint32
}

// Session is the Go port of PlayerSession.
type Session struct {
	Token        uint32
	ConvID       uint32
	Addr         string
	publicSDKURL string

	jsonMu  sync.RWMutex
	stateMu sync.Mutex // serializes packet handlers and hot reload mutations
	json    *common.FreesrData

	kcpMu sync.Mutex
	kcp   *kcplib.KCP

	startTime         time.Time
	nextSceneSave     int64
	battleProbeMu     sync.Mutex
	battleProbe       []byte
	PropEntities      map[uint32]PropEntry
	CurrentSceneFloor uint32
	// MonsterEntities tracks real overworld monster entities (entity_id -> event_id)
	// spawned in the current scene. Used by SceneCastSkill to decide whether an
	// attack actually hit a monster (the camera-detach bug fix).
	MonsterEntities        map[uint32]uint32
	SceneMonsterIdentities map[uint32]sceneMonsterIdentity
	partyActorSlots        map[uint32]bool
	// Set by the challenge scene loader, cleared when loading an overworld scene.
	ChallengeStageID      uint32
	ChallengeBattleConfig *common.BattleConfig
	ChallengeRun          *challengeRun
	PeakHardModes         map[uint32]bool
	TierceTeams           map[uint32][][]uint32
	TierceBuffs           map[uint32][]uint32
	currencyWarsRevision  uint64
	currencyWarsOpen      bool
	pendingExRankSync     map[uint32]bool
	techniqueMP           *uint32
	leaderSlot            uint32
	paidTechniqueCasts    map[uint32]bool

	closed    atomic.Bool
	closeOnce sync.Once
	closeCh   chan struct{}
}

// NewSession builds a session bound to one UDP endpoint.
func NewSession(sendTo func(data []byte) error, conv, token uint32) *Session {
	s := &Session{
		Token:           token,
		ConvID:          conv,
		kcp:             kcplib.New(conv, token, false, sendTo),
		startTime:       time.Now(),
		PropEntities:    map[uint32]PropEntry{},
		MonsterEntities: map[uint32]uint32{},
		closeCh:         make(chan struct{}),
	}
	return s
}

// Close marks the session as shut down (idempotent).
func (s *Session) Close() {
	s.closeOnce.Do(func() {
		s.closed.Store(true)
		close(s.closeCh)
	})
}

// Done returns a channel closed when the session shuts down.
func (s *Session) Done() <-chan struct{} { return s.closeCh }

// JSON returns the player data snapshot (read-mostly).
func (s *Session) JSON() *common.FreesrData {
	s.jsonMu.RLock()
	defer s.jsonMu.RUnlock()
	return s.json
}

// SetJSON installs (or reloads) the player data.
func (s *Session) SetJSON(d *common.FreesrData) {
	s.jsonMu.Lock()
	if s.json == nil && d != nil {
		s.leaderSlot = d.TeamPreset(d.ActiveTeamPreset).LeaderSlot
	}
	s.json = d
	s.jsonMu.Unlock()
}

// sessionTimeMs is the KCP clock (milliseconds since session start).
// The Rust server fed KCP seconds, which broke RTT math; ms matches the
// protocol's design and the client's clock domain.
func (s *Session) sessionTimeMs() uint32 {
	return uint32(time.Since(s.startTime).Milliseconds())
}

// Consume feeds a raw UDP payload into KCP and processes completed packets.
func (s *Session) Consume(data []byte) error {
	if s.closed.Load() {
		return nil
	}

	s.kcpMu.Lock()
	if err := s.kcp.Input(data); err != nil {
		s.kcpMu.Unlock()
		return err
	}
	if err := s.kcp.Update(s.sessionTimeMs()); err != nil {
		s.kcpMu.Unlock()
		return err
	}

	var packets []*NetPacket
	buf := make([]byte, 65536)
	for {
		n, err := s.kcp.Recv(buf)
		if err != nil {
			break
		}
		pkt, err := DecodeNetPacket(buf[:n])
		if err != nil {
			PacketLog(fmt.Sprintf("[ERROR] bad packet: %v", err))
			continue
		}
		packets = append(packets, pkt)
	}
	s.kcpMu.Unlock()

	for _, pkt := range packets {
		if pkt.CmdType == goproto.CmdIDByName["PlayerLogoutCsReq"] {
			Log("[PACKET] Player logged out")
			s.Close()
			return nil
		}
		DispatchMessage(s, pkt.CmdType, pkt.Body)
	}

	s.kcpMu.Lock()
	err := s.kcp.Update(s.sessionTimeMs())
	s.kcpMu.Unlock()
	return err
}

// Send marshals a proto response and pushes it through KCP.
func (s *Session) Send(msg proto.Message) error {
	name := string(msg.ProtoReflect().Descriptor().Name())
	switch name {
	case "GridFightGetDataScRsp", "GridFightStartGamePlayScRsp", "GridFightSyncUpdateResultScNotify", "GridFightSettleNotify",
		"GridFightEnterBattleStageScRsp", "GridFightEndBattleStageNotify", "GridFightGetArchiveScRsp":
		catalog, err := common.LoadCurrencyWarsCatalog()
		if err != nil {
			return err
		}
		cwProjectRoleIDs(msg, catalog)
	}
	cmdID, ok := goproto.CmdIDByName[name]
	if !ok {
		return fmt.Errorf("no cmd id registered for %s", name)
	}

	body, err := protoMarshal(msg)
	if err != nil {
		return err
	}
	PacketLog(fmt.Sprintf("[PACKET SEND] cmd_id: %d %s (len: %d)", cmdID, name, len(body)))
	Log(fmt.Sprintf("sent packet with CmdID: %d (%s)", cmdID, name))

	if err := s.SendRaw(&NetPacket{CmdType: cmdID, Body: body}); err != nil {
		return err
	}
	s.captureBattleResponse(msg, cmdID, body)
	return nil
}

// SendRaw writes an already-framed packet into the KCP stream.
func (s *Session) SendRaw(pkt *NetPacket) error {
	if s.closed.Load() {
		return nil
	}
	PacketLog(fmt.Sprintf("[PACKET SEND RAW] cmd_id: %d %s (len: %d)", pkt.CmdType, goproto.NameByCmdID[pkt.CmdType], len(pkt.Body)))

	payload := pkt.Encode()

	s.kcpMu.Lock()
	defer s.kcpMu.Unlock()
	if _, err := s.kcp.Send(payload); err != nil {
		return err
	}
	return s.kcp.Flush()
}

// DriveUpdate is called by the gateway ticker to run retransmissions.
func (s *Session) DriveUpdate() {
	if s.closed.Load() {
		return
	}
	s.kcpMu.Lock()
	defer s.kcpMu.Unlock()
	_ = s.kcp.Update(s.sessionTimeMs())
}

// SyncPlayer is the Go port of PlayerSession::sync_player — re-pushes the
// whole inventory + avatar set after freesr-data.json changes.
func (s *Session) SyncPlayer() error {
	player := s.JSON()
	if player == nil {
		Log("data is not init!")
		return nil
	}
	materials, err := bagMaterials(player)
	if err != nil {
		return err
	}
	supportedRelics, err := supportedRelicIDs()
	if err != nil {
		return err
	}

	// clear relics & lightcones
	del := &goproto.PlayerSyncScNotify{
		DelRelicList:     uint32Range(1, 3000),
		DelEquipmentList: uint32Range(3001, 3500),
	}
	if err := s.Send(del); err != nil {
		return err
	}

	// clear all avatar equip items
	avatarSync := &goproto.AvatarSync{}
	for _, id := range BaseAvatarIDs {
		if av, ok := player.Avatars[id]; ok {
			avatarSync.AvatarList = append(avatarSync.AvatarList, av.ToAvatarProto(nil, player.MainCharacter.ID(), player.MarchType.ID()))
		}
	}
	for _, av := range player.Avatars {
		avatarSync.AvatarPathDataInfoList = append(avatarSync.AvatarPathDataInfoList,
			av.ToAvatarPathDataProto(nil, nil, player.DressedSkins[av.AvatarID]))
	}
	if err := s.Send(&goproto.PlayerSyncScNotify{AvatarSync: avatarSync}); err != nil {
		return err
	}

	// sync new relics & lightcones
	sync := &goproto.PlayerSyncScNotify{}
	for i := range player.Relics {
		if _, supported := supportedRelics[player.Relics[i].RelicID]; supported {
			sync.RelicList = append(sync.RelicList, player.Relics[i].ToProtoRelic())
		}
	}
	for i := range player.Lightcones {
		sync.EquipmentList = append(sync.EquipmentList, player.Lightcones[i].ToProtoEquipment())
	}
	if err := s.Send(sync); err != nil {
		return err
	}

	// sync avatars with equip items attached
	avatarSync2 := &goproto.AvatarSync{}
	for _, id := range BaseAvatarIDs {
		if av, ok := player.Avatars[id]; ok {
			avatarSync2.AvatarList = append(avatarSync2.AvatarList,
				av.ToAvatarProto(player.FindLightconeFor(id), player.MainCharacter.ID(), player.MarchType.ID()))
		}
	}
	for _, av := range player.Avatars {
		avatarSync2.AvatarPathDataInfoList = append(avatarSync2.AvatarPathDataInfoList,
			av.ToAvatarPathDataProto(player.FindLightconeFor(av.AvatarID), filterSupportedRelics(player.FindRelicsFor(av.AvatarID), supportedRelics), player.DressedSkins[av.AvatarID]))
	}
	// FreeSR imports can change ranks as well as equipment. Publish the same
	// material quantities as GetBag, without deleting/recreating materials.
	return s.Send(&goproto.PlayerSyncScNotify{AvatarSync: avatarSync2, MaterialList: materials})
}

func uint32Range(from, to uint32) []uint32 {
	out := make([]uint32, 0, to-from+1)
	for i := from; i <= to; i++ {
		out = append(out, i)
	}
	return out
}

// ---------------------------------------------------------------------------
// logging helpers (Rust: tracing + util::packet_log)
// ---------------------------------------------------------------------------

var logMu sync.Mutex

func Log(msg string) {
	logMu.Lock()
	defer logMu.Unlock()
	common.LogInfo("%s", msg)
}

func PacketLog(msg string) {
	logMu.Lock()
	defer logMu.Unlock()
	f, err := os.OpenFile("gameserver.log", os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		return
	}
	defer f.Close()
	fmt.Fprintf(f, "[%d] %s\n", time.Now().UnixMilli(), msg)
}

// SceneDebugLog appends to server_debug.log (Rust: handlers::scene_debug_log).
func SceneDebugLog(format string, args ...any) {
	logMu.Lock()
	defer logMu.Unlock()
	f, err := os.OpenFile("server_debug.log", os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o644)
	if err != nil {
		return
	}
	defer f.Close()
	fmt.Fprintf(f, "[%d] %s\n", time.Now().UnixMilli(), fmt.Sprintf(format, args...))
}