package gameserver

import (
	"fmt"

	"google.golang.org/protobuf/proto"

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

// Challenge flows use the generated request and response layouts. Command
// numbers are resolved through the current protocol table at registration/send.

type decodedChallengeStart struct {
	challengeID   uint32
	stageIndex    uint32
	isSingleStage bool
	firstAvatars  []uint32
	secondAvatars []uint32
	thirdAvatars  []uint32
	stageInfoList [][]uint32
	buffID        uint32
	buffIDs       []uint32
}

// ---------------------------------------------------------------------------
// protobuf wire helpers (mirroring the Rust prost decoding loops)
// ---------------------------------------------------------------------------

func skipWireField(wireType uint32, buf *[]byte) {
	b := *buf
	switch wireType {
	case 0:
		_, n := readUvarint(b)
		if n == 0 {
			*buf = nil
		} else {
			*buf = b[n:]
		}
	case 1:
		if len(b) >= 8 {
			*buf = b[8:]
		} else {
			*buf = nil
		}
	case 2:
		l, n := readUvarint(b)
		if n == 0 || int(l) > len(b[n:]) {
			*buf = nil
		} else {
			*buf = b[n+int(l):]
		}
	case 5:
		if len(b) >= 4 {
			*buf = b[4:]
		} else {
			*buf = nil
		}
	default:
		*buf = nil
	}
}

func decodeStartChallengeReq(payload []byte) decodedChallengeStart {
	var pbReq goproto.StartChallengeCsReq
	if err := proto.Unmarshal(payload, &pbReq); err != nil {
		return decodedChallengeStart{}
	}
	req := decodedChallengeStart{challengeID: pbReq.ChallengeId,
		firstAvatars: pbReq.FirstLineup, secondAvatars: pbReq.SecondLineup}
	if len(req.firstAvatars) == 0 {
		for _, avatar := range pbReq.AvatarLineupFirst {
			if avatar.Id != 0 {
				req.firstAvatars = append(req.firstAvatars, avatar.Id)
			}
		}
	}
	if len(req.secondAvatars) == 0 {
		for _, avatar := range pbReq.AvatarLineupSecond {
			if avatar.Id != 0 {
				req.secondAvatars = append(req.secondAvatars, avatar.Id)
			}
		}
	}
	if pbReq.StageInfo != nil {
		if info := pbReq.StageInfo.BossInfo; info != nil {
			req.buffID = info.BuffOne
			req.buffIDs = []uint32{info.BuffOne, info.BuffTwo}
		}
		if info := pbReq.StageInfo.StoryInfo; info != nil && req.buffID == 0 {
			req.buffID = info.BuffOne
			req.buffIDs = []uint32{info.BuffOne, info.BuffTwo}
		}
	}
	return req
}

func decodeStartChallengeTierceReq(payload []byte) decodedChallengeStart {
	var pbReq goproto.StartChallengeTierceCsReq
	if err := proto.Unmarshal(payload, &pbReq); err != nil {
		return decodedChallengeStart{}
	}
	req := decodedChallengeStart{challengeID: pbReq.ChallengeId,
		stageIndex: pbReq.FINOCEGDBDI, isSingleStage: pbReq.MPKMIKBFEHG}
	for index, stage := range pbReq.LineupTierceList {
		req.buffIDs = append(req.buffIDs, stage.BuffId)
		var avatars []uint32
		for _, avatar := range stage.TierceAvatarIdList {
			if avatar.Id != 0 {
				avatars = append(avatars, avatar.Id)
			}
		}
		req.stageInfoList = append(req.stageInfoList, avatars)
		if uint32(index) == req.stageIndex {
			req.buffID = stage.BuffId
		}
	}
	if len(req.stageInfoList) > 0 {
		req.firstAvatars = req.stageInfoList[0]
	}
	if len(req.stageInfoList) > 1 {
		req.secondAvatars = req.stageInfoList[1]
	}
	if len(req.stageInfoList) > 2 {
		req.thirdAvatars = req.stageInfoList[2]
	}
	return req
}

func decodeSetChallengeTierceLineupReq(payload []byte) (uint32, [][]uint32, []uint32) {
	var req goproto.SetChallengeTierceLineupCsReq
	if err := proto.Unmarshal(payload, &req); err != nil {
		return 0, nil, nil
	}
	var stages [][]uint32
	var buffs []uint32
	for _, stage := range req.StageInfoList {
		buffs = append(buffs, stage.BuffId)
		var avatars []uint32
		for _, avatar := range stage.TierceAvatarIdList {
			if avatar.Id != 0 {
				avatars = append(avatars, avatar.Id)
			}
		}
		stages = append(stages, avatars)
	}
	return req.ChallengeId, stages, buffs
}

// ---------------------------------------------------------------------------
// config setup shared by start handlers
// ---------------------------------------------------------------------------

// Build challenge configuration from the selected resource stage, never from
// Freesr custom monsters. Only the current session owns this configuration.
func setChallengeBattleConfig(s *Session, avatars []uint32, challengeID, eventID uint32, buffs []uint32) error {
	stage, ok := getChallengeData().Stages[eventID]
	if !ok || len(stage.Monsters) == 0 {
		return fmt.Errorf("challenge stage %d has no resource waves", eventID)
	}
	config := common.BattleConfig{StageID: eventID, CustomBattleLineup: map[uint32]uint32{}}
	for i, id := range avatars {
		config.CustomBattleLineup[uint32(i)] = id
	}
	switch {
	case challengeID >= 20000 && challengeID < 30000:
		config.BattleType = common.BattleTypePF
	case challengeID >= 30000:
		config.BattleType = common.BattleTypeAS
	default:
		config.BattleType = common.BattleTypeDefault
	}
	// ChallengeCountDown is supplied by the installed challenge table.
	configID := challengeID
	if tierce, ok := getChallengeData().Tierce[challengeID]; ok {
		configID = tierce.PreChallengeID
	}
	config.CycleCount = getChallengeData().Countdowns[configID]
	if config.CycleCount == 0 {
		// AS/PF rows omit ChallengeCountDown. Their limits come from the
		// sourced challenge rules, not the user's custom battle configuration.
		rules, err := loadBattleRules()
		if err != nil {
			return err
		}
		config.CycleCount = rules.ChallengeRoundLimits[config.BattleType]
		if config.CycleCount == 0 {
			return fmt.Errorf("missing challenge round limit for %s", config.BattleType)
		}
	}
	for _, wave := range stage.Monsters {
		if len(wave) == 0 {
			return fmt.Errorf("challenge stage %d has an empty wave", eventID)
		}
		monsters := make([]common.Monster, 0, len(wave))
		for _, id := range wave {
			monsters = append(monsters, common.Monster{Level: stage.Level, MonsterID: id})
		}
		config.Monsters = append(config.Monsters, monsters)
	}
	seen := map[uint32]bool{}
	for _, id := range buffs {
		if id != 0 && !seen[id] {
			config.Blessings = append(config.Blessings, common.BattleBuffJson{ID: id, Level: 1})
			seen[id] = true
		}
	}
	s.ChallengeBattleConfig = &config
	SceneDebugLog("[CHALLENGE] battle source=resource challenge=%d stage=%d waves=%v buffs=%v", challengeID, eventID, stage.Monsters, buffs)
	return nil
}

func lineupInfoFromAvatars(avatars []uint32, planeID uint32, extraType goproto.ExtraLineupType, index uint32) *goproto.LineupInfo {
	custom := map[uint32]uint32{}
	for i, aid := range avatars {
		custom[uint32(i)] = aid
	}
	lineup := common.ToLineupInfo(custom)
	lineup.PlaneId = planeID
	lineup.ExtraLineupType = extraType
	lineup.Index = index
	return lineup
}

func challengeAvatarsFallback(s *Session) []uint32 {
	if player := s.JSON(); player != nil {
		var out []uint32
		for _, slot := range player.SortedLineupKeys() {
			if v := player.Lineups[slot]; v != 0 {
				out = append(out, v)
			}
		}
		return out
	}
	return nil
}

func dedupeTruncate4(in []uint32) []uint32 {
	seen := map[uint32]bool{}
	var out []uint32
	for _, v := range in {
		if !seen[v] {
			seen[v] = true
			out = append(out, v)
		}
		if len(out) == 4 {
			break
		}
	}
	return out
}

// handleStartChallenge ports handle_start_challenge: respond cmd 1787 with
// retcode(3) + cur_challenge(5) + lineup_list(6) + scene(10) + stage_info(13).
func handleStartChallenge(s *Session, payload []byte) error {
	req := decodeStartChallengeReq(payload)
	if req.challengeID == 0 {
		return s.Send(&goproto.StartChallengeScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	Log("handle_start_challenge: challenge_id=" + itoa(int(req.challengeID)))

	chosenAvatars := req.firstAvatars
	if len(chosenAvatars) == 0 {
		chosenAvatars = challengeAvatarsFallback(s)
	}
	// cap team at 4 (client TeamManager IndexOutOfRange otherwise)
	chosenAvatars = dedupeTruncate4(chosenAvatars)

	baseID := req.challengeID
	cd := getChallengeData()
	stage, ok := cd.Challenges[baseID]
	if !ok {
		return s.Send(&goproto.StartChallengeScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	entrance, group, monster, event := stage.Entrance, stage.Group1, stage.Monster1, stage.Event1
	buff := req.buffID
	if buff == 0 {
		buff = stage.Buff
	}

	Log("[CHALLENGE] Start: challenge_id=" + itoa(int(req.challengeID)) + " (mapped " + itoa(int(baseID)) + ")")
	Log("[CHALLENGE] Arena: entrance=" + itoa(int(entrance)) + " group=" + itoa(int(group)) + " monster=" + itoa(int(monster)) + " event=" + itoa(int(event)))

	previousConfig := s.ChallengeBattleConfig
	if err := setChallengeBattleConfig(s, chosenAvatars, req.challengeID, event, []uint32{buff, cd.Challenges[baseID].Buff}); err != nil {
		SceneDebugLog("[CHALLENGE] start rejected: %v", err)
		return s.Send(&goproto.StartChallengeScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}

	sceneInfo, _, err := loadChallengeScene(s, entrance, group, monster, event, chosenAvatars)
	if err != nil {
		s.ChallengeBattleConfig = previousConfig
		SceneDebugLog("[CHALLENGE] scene rejected: %v", err)
		return s.Send(&goproto.StartChallengeScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}

	var lineups []*goproto.LineupInfo
	lineups = append(lineups, lineupInfoFromAvatars(chosenAvatars, sceneInfo.PlaneId, goproto.ExtraLineupType(1), 0))

	secondAvatars := req.secondAvatars
	if len(secondAvatars) == 0 {
		secondAvatars = chosenAvatars
	}
	secondAvatars = dedupeTruncate4(secondAvatars)
	lineups = append(lineups, lineupInfoFromAvatars(secondAvatars, sceneInfo.PlaneId, goproto.ExtraLineupType_ExtraLineupType_LineupChallenge2, 0))

	curChallenge := &goproto.CurChallenge{
		ChallengeId:     req.challengeID,
		Status:          goproto.ChallengeStatus_CHALLENGE_DOING,
		RoundCount:      0,
		ScoreId:         0,
		ScoreTwo:        0,
		ExtraLineupType: goproto.ExtraLineupType(1),
	}
	// PearlSR 005d2c12 challenge_mgr.zig creates this mode-specific state
	// before the Client recovers its challenge instance. Omitting it causes
	// ChallengeBossInstance._SyncExtraInfo to dereference a missing message.
	mazeBuff := cd.Challenges[baseID].Buff
	buffs := make([]uint32, 0, 2)
	for _, id := range []uint32{req.buffID, mazeBuff} {
		if id != 0 {
			buffs = append(buffs, id)
		}
	}
	switch {
	case req.challengeID > 20000 && req.challengeID < 30000:
		curChallenge.StageInfo = &goproto.ChallengeCurBuffInfo{
			CurStoryBuffs: &goproto.ChallengeStoryBuffList{BuffList: buffs},
		}
	case req.challengeID > 30000:
		curChallenge.StageInfo = &goproto.ChallengeCurBuffInfo{
			CurBossBuffs: &goproto.ChallengeBossBuffList{BuffList: buffs, ChallengeBossConst: 1},
		}
	}
	rooms := []challengeRoom{resourceRoom(stage, false, chosenAvatars, req.buffID)}
	if stage.Entrance2 != 0 && stage.Event2 != 0 {
		var secondBuff uint32
		if len(req.buffIDs) > 1 {
			secondBuff = req.buffIDs[1]
		}
		rooms = append(rooms, resourceRoom(stage, true, secondAvatars, secondBuff))
	}
	s.ChallengeRun = &challengeRun{ID: req.challengeID, Rooms: rooms, Scores: make([]uint32, len(rooms)), Cur: curChallenge}

	rsp := &goproto.StartChallengeScRsp{
		Retcode:      0,
		CurChallenge: curChallenge,
		LineupList:   lineups,
		Scene:        sceneInfo,
	}
	SceneDebugLog("[CHALLENGE] start id=%d mapped=%d entry=%d floor=%d world=%d mode=%d buff=%v storyState=%t bossState=%t", req.challengeID, baseID, sceneInfo.EntryId, sceneInfo.FloorId, sceneInfo.WorldId, sceneInfo.GameModeType, buffs, curChallenge.GetStageInfo().GetCurStoryBuffs() != nil, curChallenge.GetStageInfo().GetCurBossBuffs() != nil)
	return s.Send(rsp)
}

// handleStartChallengeTierce uses the current Tierce request schema.
func handleStartChallengeTierce(s *Session, payload []byte) error {
	req := decodeStartChallengeTierceReq(payload)
	if req.challengeID == 0 {
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	baseID := req.challengeID
	Log("handle_start_challenge_tierce: challenge_id=" + itoa(int(req.challengeID)) + " (mapped " + itoa(int(baseID)) + ")")

	if err := rememberTierceTeams(s, req.challengeID, req.stageInfoList, req.buffIDs, req.isSingleStage, req.stageIndex); err != nil {
		return err
	}
	req.stageInfoList = s.TierceTeams[req.challengeID]
	req.buffIDs = s.TierceBuffs[req.challengeID]
	if int(req.stageIndex) < len(req.buffIDs) {
		req.buffID = req.buffIDs[req.stageIndex]
	}

	if req.stageIndex >= tierceNodeCount {
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	chosenAvatars := req.stageInfoList[req.stageIndex]
	if len(chosenAvatars) == 0 {
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_LINEUP_IS_EMPTY)})
	}

	cd := getChallengeData()
	// PearlSR challenge_mgr.zig: Tierce nodes 0/1 use the preceding
	// ChallengeMazeConfig's first/second node; node 2 uses Tierce config.
	tierce, tierceOK := cd.Tierce[req.challengeID]
	base, baseOK := cd.Challenges[tierce.PreChallengeID]
	if !tierceOK || !baseOK || req.stageIndex > 2 {
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	entrance, group, monster, event := base.Entrance, base.Group1, base.Monster1, base.Event1
	switch req.stageIndex {
	case 1:
		entrance, group, monster, event = base.Entrance2, base.Group2, base.Monster2, base.Event2
	case 2:
		entrance, group, monster, event = tierce.Entrance, tierce.Group, tierce.Monster, tierce.Event
	}
	previousConfig := s.ChallengeBattleConfig
	if err := setChallengeBattleConfig(s, chosenAvatars, req.challengeID, event, []uint32{req.buffID, base.Buff}); err != nil {
		SceneDebugLog("[CHALLENGE] tierce start rejected: %v", err)
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}

	sceneInfo, _, err := loadChallengeScene(s, entrance, group, monster, event, chosenAvatars)
	if err != nil {
		s.ChallengeBattleConfig = previousConfig
		SceneDebugLog("[CHALLENGE] tierce scene rejected: %v", err)
		return s.Send(&goproto.StartChallengeTierceScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}

	// The response carries the active node's lineup, as upstream does.
	// Other nodes are cached for subsequent requests, not installed as active teams.
	tierceLineupList := []*goproto.LineupInfo{lineupInfoFromAvatars(chosenAvatars, sceneInfo.PlaneId, goproto.ExtraLineupType(1), 0)}
	SceneDebugLog("[CHALLENGE] tierce id=%d node=%d entry=%d floor=%d group=%d event=%d avatars=%v", req.challengeID, req.stageIndex, entrance, sceneInfo.FloorId, group, event, chosenAvatars)

	// Generated response resolves its command ID through Session.Send.
	rsp := &goproto.StartChallengeTierceScRsp{
		Retcode: 0,
		Scene:   sceneInfo,
		CurTierceChallenge: &goproto.CurTierceChallenge{
			LineupList:  tierceLineupList,
			ChallengeId: req.challengeID,
			FINOCEGDBDI: req.stageIndex,
			MPKMIKBFEHG: req.isSingleStage,
		},
	}
	teams := req.stageInfoList
	if len(teams) == 0 {
		teams = s.TierceTeams[req.challengeID]
	}
	rooms := make([]challengeRoom, tierceNodeCount)
	for node := range rooms {
		var team []uint32
		if node < len(teams) {
			team = teams[node]
		}
		if uint32(node) == req.stageIndex {
			team = chosenAvatars
		}
		var selectedBuff uint32
		if node < len(req.buffIDs) {
			selectedBuff = req.buffIDs[node]
		}
		rooms[node] = resourceRoom(base, node == 1, team, selectedBuff)
		if node == 2 {
			rooms[node].Entrance, rooms[node].Group, rooms[node].Monster, rooms[node].Event = tierce.Entrance, tierce.Group, tierce.Monster, tierce.Event
		}
	}
	s.ChallengeRun = &challengeRun{ID: req.challengeID, Tierce: true, Single: req.isSingleStage, Node: req.stageIndex, Rooms: rooms, Scores: make([]uint32, len(rooms)), TierceCur: rsp.CurTierceChallenge}
	// A single-node retry keeps the other nodes' measured best results.
	if req.isSingleStage {
		if saved := s.JSON().TierceProgress[req.challengeID]; saved != nil {
			for node, result := range saved.Nodes {
				if node < tierceNodeCount && node != req.stageIndex {
					s.ChallengeRun.Scores[node] = result.Score
					s.ChallengeRun.Results = append(s.ChallengeRun.Results, tierceNodeResult(node, result, s.TierceTeams[req.challengeID][node]))
				}
			}
		}
	}

	rsp.CurTierceChallenge.LineupList = []*goproto.LineupInfo{s.ChallengeRun.activeLineup(sceneInfo.PlaneId)}
	return s.Send(rsp)
}

func handleSetChallengeTierceLineup(s *Session, payload []byte) error {
	challengeID, stages, buffs := decodeSetChallengeTierceLineupReq(payload)
	if challengeID == 0 {
		return s.Send(&goproto.SetChallengeTierceLineupScRsp{Retcode: uint32(goproto.Retcode_RET_CHALLENGE_NOT_EXIST)})
	}
	if err := rememberTierceTeams(s, challengeID, stages, buffs, false, 0); err != nil {
		return err
	}
	return s.Send(&goproto.SetChallengeTierceLineupScRsp{})
}

func handleLeaveChallenge(s *Session, _ []byte) error {
	return leaveChallengeScene(s, &goproto.LeaveChallengeScRsp{})
}

func handleLeaveChallengeTierce(s *Session, _ []byte) error {
	return leaveChallengeScene(s, &goproto.LeaveChallengeTierceScRsp{})
}

func leaveChallengeScene(s *Session, response proto.Message) error {
	player := s.JSON()
	if player == nil || player.Scene.EntryID == 0 {
		return fmt.Errorf("challenge return scene is unavailable")
	}
	// loadChallengeScene preserves the player's saved overworld scene.
	entryID := player.Scene.EntryID
	CURRENT_BATTLE.Delete(s.Token)
	if err := s.Send(&goproto.QuitBattleScNotify{}); err != nil {
		return err
	}
	if _, err := loadScene(s, entryID, true, true, nil, nil); err != nil {
		return err
	}
	if err := refreshLineup(s); err != nil {
		return err
	}
	return s.Send(response)
}

func handleTakeChallengeReward(s *Session, payload []byte) error {
	var req goproto.TakeChallengeRewardCsReq
	if err := proto.Unmarshal(payload, &req); err != nil {
		return err
	}
	return s.Send(&goproto.TakeChallengeRewardScRsp{GroupId: req.GroupId})
}

// Return saved teams and measured scores, including genuinely unplayed stages.
func buildGetChallengeTierceDataScRspReal(s *Session) *goproto.GetChallengeTierceDataScRsp {
	rsp := &goproto.GetChallengeTierceDataScRsp{}
	for _, id := range sortedU32Keys2(getChallengeData().Tierce) {
		var saved *common.TierceProgress
		if p := s.JSON(); p != nil {
			saved = p.TierceProgress[id]
		}
		rsp.ChallengeTierceGroups = append(rsp.ChallengeTierceGroups, buildTierceGroup(id, saved))
	}
	return rsp
}