package modules

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"math/rand"
	"time"

	"github.com/heroiclabs/nakama-common/runtime"
	"github.com/jackc/pgx/v5"

	"github.com/honghuang-game/server/internal/battle"
	hhdb "github.com/honghuang-game/server/internal/db"
)

// RegisterBattle 注册战斗相关 RPC。
func RegisterBattle(initializer runtime.Initializer) error {
	if err := initializer.RegisterRpc("BattleService/StartCombat", startCombat); err != nil {
		return err
	}
	if err := initializer.RegisterRpc("BattleService/GetBattleReport", getBattleReport); err != nil {
		return err
	}
	if err := initializer.RegisterRpc("BattleService/PvpChallenge", pvpChallenge); err != nil {
		return err
	}
	return nil
}

type startCombatReq struct {
	BattleType      string   `json:"battle_type"`
	ContextID       string   `json:"context_id"`
	PartyMembers    []string `json:"party_members"`
	PreferredSkills []string `json:"preferred_skills"`
}

type pvpChallengeReq struct {
	TargetCharacterID string `json:"target_character_id"`
	BountyID          string `json:"bounty_id"`
	UsePaidChance     bool   `json:"use_paid_chance"`
}

type battleReportReq struct {
	BattleID string `json:"battle_id"`
}

type combatData struct {
	BattleID            string      `json:"battle_id"`
	Status              string      `json:"status"`
	ResultSummary       interface{} `json:"result_summary"`
	Drops               interface{} `json:"drops"`
	DeathPenaltyApplied bool        `json:"death_penalty_applied"`
	HonorPoints         int32       `json:"honor_points"`
	DailyPvpCount       int32       `json:"daily_pvp_count"`
	DailyPvpLimit       int32       `json:"daily_pvp_limit"`
}

type battleReportData struct {
	BattleID      string `json:"battle_id"`
	Type          string `json:"type"`
	RealmTier     int32  `json:"realm_tier"`
	GameTimestamp string `json:"game_timestamp"`
	Attacker      interface{} `json:"attacker"`
	Defender      interface{} `json:"defender"`
	Rounds        interface{} `json:"rounds"`
	Result        interface{} `json:"result"`
	SpecialEvents interface{} `json:"special_events"`
	Drops         interface{} `json:"drops"`
}

const (
	battleTypeExpedition = "expedition_pve"
	battleTypeDungeon    = "dungeon_pve"
	battleTypeRuin       = "ruin_pve"
)

// startCombat 触发一场 PVE 战斗，服务端完整计算并返回战报摘要。
func startCombat(ctx context.Context, logger runtime.Logger, _ *sql.DB, nk runtime.NakamaModule, payload string) (string, error) {
	traceID := newTraceID()
	uid := userIDFromCtx(ctx)
	if uid == "" {
		return errResp(1001, "missing token", traceID)
	}

	var req startCombatReq
	if err := json.Unmarshal([]byte(payload), &req); err != nil {
		return errResp(4001, "invalid payload", traceID)
	}

	if req.BattleType != battleTypeExpedition && req.BattleType != battleTypeDungeon && req.BattleType != battleTypeRuin {
		return errResp(4001, "invalid battle type", traceID)
	}
	if req.ContextID == "" {
		return errResp(4002, "missing context_id", traceID)
	}

	// 取当前玩家激活角色（若多角色则取最近创建）
	char, err := loadCharacterForBattle(ctx, uid)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return errResp(4002, "character not found", traceID)
		}
		logger.Error("load character failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}

	skills, err := loadCharacterSkills(ctx, char.ID)
	if err != nil {
		logger.Error("load skills failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}

	player := battle.NewFighterFromJSON(
		char.ID, char.Name, char.RaceID, "attacker",
		int(char.WorldTier), int(char.RealmTier),
		char.BaseStats, "neutral", "none", true,
	)
	for _, s := range skills {
		player.AddSkill(s)
	}

	monster := battle.GenerateMonster(int(char.RealmTier), int(char.WorldTier), player, rand.New(rand.NewSource(time.Now().UnixNano())))

	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	eng := battle.NewEngine(player, monster, rng, req.BattleType, int(char.RealmTier))
	report := eng.Run()

	battleID, err := persistBattle(ctx, char.ID, req.BattleType, char.WorldTier, char.RealmTier, report)
	if err != nil {
		logger.Error("persist battle failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}
	report.BattleID = battleID

	if err := applyBattleRewards(ctx, char.ID, char.WorldTier, char.RealmTier, report); err != nil {
		logger.Error("apply battle rewards failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}

	return okResp(combatData{
		BattleID:            battleID,
		Status:              "completed",
		ResultSummary:       report.Result,
		Drops:               report.Drops,
		DeathPenaltyApplied: false,
		HonorPoints:         0,
	}, traceID)
}

// getBattleReport 查询完整文字战报。
func getBattleReport(ctx context.Context, logger runtime.Logger, _ *sql.DB, nk runtime.NakamaModule, payload string) (string, error) {
	traceID := newTraceID()
	uid := userIDFromCtx(ctx)
	if uid == "" {
		return errResp(1001, "missing token", traceID)
	}

	var req battleReportReq
	if err := json.Unmarshal([]byte(payload), &req); err != nil {
		return errResp(4005, "invalid payload", traceID)
	}

	var raw []byte
	err := hhdb.Pool.QueryRow(ctx, `
		SELECT bl.report
		FROM battle_logs bl
		JOIN battles b ON bl.battle_id = b.id
		WHERE bl.battle_id = $1 AND (b.attacker_id = (SELECT id FROM characters WHERE player_id = $2 LIMIT 1) OR b.defender_id = (SELECT id FROM characters WHERE player_id = $2 LIMIT 1))
	`, req.BattleID, uid).Scan(&raw)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return errResp(4005, "battle report not found", traceID)
		}
		logger.Error("get battle report failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}

	var data interface{}
	_ = json.Unmarshal(raw, &data)

	return okResp(data, traceID)
}

// pvpChallenge 向同 realm_tier 玩家发起战书（当前版本保留桩，待 PVP 完整规则接入）。
func pvpChallenge(ctx context.Context, logger runtime.Logger, _ *sql.DB, nk runtime.NakamaModule, payload string) (string, error) {
	traceID := newTraceID()
	uid := userIDFromCtx(ctx)
	if uid == "" {
		return errResp(1001, "missing token", traceID)
	}
	var req pvpChallengeReq
	if err := json.Unmarshal([]byte(payload), &req); err != nil {
		return errResp(4007, "invalid payload", traceID)
	}

	// 获取挑战者信息
	attacker, err := loadCharacterForBattle(ctx, uid)
	if err != nil {
		return errResp(4002, "character not found", traceID)
	}

	// 查询目标玩家
	var defender characterBattleInfo
	err = hhdbPool.QueryRow(ctx, `
		SELECT id, name, race_id, world_tier, realm_tier, minor_realm, base_stats
		FROM characters WHERE id = $1 AND status = 'active'
	`, req.TargetCharacterID).Scan(&defender.ID, &defender.Name, &defender.RaceID,
		&defender.WorldTier, &defender.RealmTier, &defender.MinorRealm, &defender.BaseStats)
	if err != nil {
		return errResp(4008, "target not found", traceID)
	}

	// 检查同 realm_tier
	if attacker.RealmTier != defender.RealmTier {
		return errResp(4009, "realm tier mismatch", traceID)
	}

	// 检查每日次数
	var dailyCount int32
	err = hhdbPool.QueryRow(ctx, `
		SELECT COUNT(*) FROM battles
		WHERE attacker_id = $1 AND battle_type = 'pvp'
		AND created_at >= CURRENT_DATE
	`, attacker.ID).Scan(&dailyCount)
	if err != nil {
		dailyCount = 0
	}
	if dailyCount >= 20 {
		return errResp(4010, "daily pvp limit reached", traceID)
	}

	// 加载技能
	skills, err := loadCharacterSkills(ctx, attacker.ID)
	if err != nil {
		skills = []*battle.SkillInstance{}
	}

	// 创建战斗实体
	player := battle.NewFighterFromJSON(
		attacker.ID, attacker.Name, attacker.RaceID, "attacker",
		int(attacker.WorldTier), int(attacker.RealmTier),
		attacker.BaseStats, "neutral", "none", true,
	)
	for _, s := range skills {
		player.AddSkill(s)
	}

	// 创建怪物作为PVP对手（简化版）
	monster := battle.NewFighterFromJSON(
		defender.ID, defender.Name, defender.RaceID, "defender",
		int(defender.WorldTier), int(defender.RealmTier),
		defender.BaseStats, "neutral", "none", false,
	)

	// 运行战斗
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	eng := battle.NewEngine(player, monster, rng, "pvp", int(attacker.RealmTier))
	report := eng.Run()

	// 持久化战斗记录
	battleID, err := persistBattle(ctx, attacker.ID, "pvp", attacker.WorldTier, attacker.RealmTier, report)
	if err != nil {
		logger.Error("persist pvp battle failed: %v", err)
		return errResp(9002, "internal error", traceID)
	}
	report.BattleID = battleID

	// 应用战斗奖励
	if err := applyBattleRewards(ctx, attacker.ID, attacker.WorldTier, attacker.RealmTier, report); err != nil {
		logger.Error("apply pvp rewards failed: %v", err)
	}

	logger.Info("BattleService/PvpChallenge success: battle_id=%s winner=%s", battleID, report.Result.Winner)
	return okResp(combatData{
		BattleID:      battleID,
		Status:        "completed",
		ResultSummary: report.Result,
		Drops:         report.Drops,
		DailyPvpCount: dailyCount + 1,
		DailyPvpLimit: 20,
	}, traceID)
}

// ---------------------------------------------------------------------------
// 数据加载与持久化
// ---------------------------------------------------------------------------

type characterBattleInfo struct {
	ID        string
	Name      string
	RaceID    string
	WorldTier int32
	RealmTier int32
	MinorRealm int32
	BaseStats []byte
}

func loadCharacterForBattle(ctx context.Context, playerID string) (*characterBattleInfo, error) {
	var c characterBattleInfo
	err := hhdb.Pool.QueryRow(ctx, `
		SELECT id, name, race_id, world_tier, realm_tier, minor_realm, base_stats
		FROM characters
		WHERE player_id = $1 AND status = 'active'
		ORDER BY created_at DESC
		LIMIT 1
	`, playerID).Scan(&c.ID, &c.Name, &c.RaceID, &c.WorldTier, &c.RealmTier, &c.MinorRealm, &c.BaseStats)
	if err != nil {
		return nil, err
	}
	return &c, nil
}

type skillTemplateData struct {
	BaseCoef    float64 `json:"base_coef"`
	CD          int     `json:"cd"`
	Cost        float64 `json:"cost"`
	TriggerRate float64 `json:"trigger_rate"`
	TargetType  string  `json:"target_type"`
}

func loadCharacterSkills(ctx context.Context, characterID string) ([]*battle.SkillInstance, error) {
	rows, err := hhdb.Pool.Query(ctx, `
		SELECT cs.id, cs.custom_name, cs.instance_data,
		       s.id, s.name, s.element, s.alignment, s.damage_type, s.scaling_attr, s.base_template
		FROM character_skills cs
		JOIN skills s ON cs.skill_id = s.id
		WHERE cs.character_id = $1
	`, characterID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var skills []*battle.SkillInstance
	for rows.Next() {
		var instanceID, customName, instanceDataRaw, skillID, name, element, alignment, damageType, scalingAttr, baseTemplateRaw string
		if err := rows.Scan(&instanceID, &customName, &instanceDataRaw, &skillID, &name, &element, &alignment, &damageType, &scalingAttr, &baseTemplateRaw); err != nil {
			return nil, err
		}

		baseTmpl := parseSkillTemplate(baseTemplateRaw)
		instTmpl := parseSkillTemplate(instanceDataRaw)

		// 实例数据覆盖模板默认值
		skill := &battle.SkillInstance{
			InstanceID:  instanceID,
			SkillID:     skillID,
			Name:        firstNonEmpty(customName, name),
			DamageType:  battle.DamageType(damageType),
			Element:     element,
			Alignment:   alignment,
			ScalingAttr: scalingAttr,
			BaseCoef:    coalesceFloat(instTmpl.BaseCoef, baseTmpl.BaseCoef, 1.8),
			CD:          coalesceInt(instTmpl.CD, baseTmpl.CD, 225),
			Cost:        coalesceFloat(instTmpl.Cost, baseTmpl.Cost, 20),
			TriggerRate: coalesceFloat(instTmpl.TriggerRate, baseTmpl.TriggerRate, 1.25),
			TargetType:  battle.TargetSingle,
		}
		if instTmpl.TargetType != "" {
			skill.TargetType = battle.TargetType(instTmpl.TargetType)
		} else if baseTmpl.TargetType != "" {
			skill.TargetType = battle.TargetType(baseTmpl.TargetType)
		}
		if skill.DamageType == "" {
			skill.DamageType = battle.DamageTypePhysical
		}
		skills = append(skills, skill)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	// 没有任何技能时补一个默认小技能，确保战斗不至于只有普攻
	if len(skills) == 0 {
		skills = append(skills, &battle.SkillInstance{
			InstanceID:  "default_small",
			SkillID:     "default_small",
			Name:        "基础战技",
			DamageType:  battle.DamageTypePhysical,
			Element:     "none",
			Alignment:   "neutral",
			ScalingAttr: "str",
			BaseCoef:    1.8,
			CD:          225,
			Cost:        20,
			TriggerRate: 1.25,
			TargetType:  battle.TargetSingle,
		})
	}
	return skills, nil
}

func parseSkillTemplate(raw string) skillTemplateData {
	var t skillTemplateData
	if raw == "" || raw == "{}" {
		return t
	}
	_ = json.Unmarshal([]byte(raw), &t)
	return t
}

func firstNonEmpty(a, b string) string {
	if a != "" {
		return a
	}
	return b
}

func coalesceFloat(values ...float64) float64 {
	for _, v := range values {
		if v > 0 {
			return v
		}
	}
	return 0
}

func coalesceInt(values ...int) int {
	for _, v := range values {
		if v > 0 {
			return v
		}
	}
	return 0
}

// persistBattle 将战报写入 battles / battle_logs 表
func persistBattle(ctx context.Context, characterID, battleType string, worldTier, realmTier int32, report *battle.BattleReport) (string, error) {
	reportJSON, err := report.MarshalReport()
	if err != nil {
		return "", err
	}

	tx, err := hhdb.Pool.Begin(ctx)
	if err != nil {
		return "", err
	}
	defer tx.Rollback(ctx)

	var battleID string
	err = tx.QueryRow(ctx, `
		INSERT INTO battles (battle_type, world_tier, realm_tier, game_timestamp, attacker_id, defender_id, party_a, party_b, status, result_summary)
		VALUES ($1, $2, $3, NOW(), $4, NULL, '{}', '{}', 'completed', $5)
		RETURNING id::text
	`, battleType, worldTier, realmTier, characterID, report.Result).Scan(&battleID)
	if err != nil {
		return "", err
	}

	_, err = tx.Exec(ctx, `
		INSERT INTO battle_logs (battle_id, report, special_events, drops)
		VALUES ($1, $2, $3, $4)
	`, battleID, reportJSON, report.SpecialEvents, report.Drops)
	if err != nil {
		return "", err
	}

	if err := tx.Commit(ctx); err != nil {
		return "", err
	}
	return battleID, nil
}

// applyBattleRewards 发放战斗奖励：货币、经验、审计日志
func applyBattleRewards(ctx context.Context, characterID string, worldTier, realmTier int32, report *battle.BattleReport) error {
	if report.Result.Winner != "attacker" || len(report.Drops.Currency) == 0 {
		return nil
	}

	tx, err := hhdb.Pool.Begin(ctx)
	if err != nil {
		return err
	}
	defer tx.Rollback(ctx)

	for _, c := range report.Drops.Currency {
		if c.Amount <= 0 {
			continue
		}
		_, err = tx.Exec(ctx, `
			INSERT INTO currency_balances (character_id, currency_code, amount, total_earned, total_spent)
			VALUES ($1, $2, $3, $3, 0)
			ON CONFLICT (character_id, currency_code)
			DO UPDATE SET amount = currency_balances.amount + EXCLUDED.amount,
			              total_earned = currency_balances.total_earned + EXCLUDED.amount,
			              updated_at = NOW()
		`, characterID, c.Type, c.Amount)
		if err != nil {
			return err
		}

		_, err = tx.Exec(ctx, `
			INSERT INTO economy_audit_logs (character_id, entity_type, entity_id, currency_code, flow_type, reason_code, amount, related_id, world_tier)
			VALUES ($1, 'character', $1, $2, 'faucet', 'combat_drop', $3, $4, $5)
		`, characterID, c.Type, c.Amount, report.BattleID, worldTier)
		if err != nil {
			return err
		}
	}

	if report.Drops.Exp > 0 {
		_, err = tx.Exec(ctx, `
			UPDATE characters SET exp = exp + $1, updated_at = NOW() WHERE id = $2
		`, report.Drops.Exp, characterID)
		if err != nil {
			return err
		}
	}

	// 材料掉落仅记录到战报 drops，实际进背包需要物品模板存在，当前版本保留扩展点
	return tx.Commit(ctx)
}