package registerreward

import (
	"context"
	"strings"
	"time"

	"chatapp3-golang/internal/model"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// registerRewardGrantPlan 表示当前注册奖励日志最终命中的发奖决策。
type registerRewardGrantPlan struct {
	ClaimDate    string // 领取日期，按每日限额口径记录
	GrantMode    string // 发奖决策模式
	SkipDispatch bool   // 是否跳过真实发奖动作
}

// resolveGrantPlan 负责确定本次注册奖励是否还能占用当天名额。
func (s *RegisterRewardService) resolveGrantPlan(
	ctx context.Context,
	logRecord *model.ResidentRegisterRewardLog,
	event registerRewardEvent,
	resolved registerRewardResolvedConfig,
) (registerRewardGrantPlan, error) {
	// 已经有过发奖决策的日志，失败重试时必须沿用原始结果，避免重试把配额重新算乱。
	if strings.TrimSpace(logRecord.ClaimDate) != "" && strings.TrimSpace(logRecord.GrantMode) != "" {
		return registerRewardGrantPlan{
			ClaimDate:    logRecord.ClaimDate,
			GrantMode:    logRecord.GrantMode,
			SkipDispatch: strings.ToUpper(strings.TrimSpace(logRecord.GrantMode)) == registerRewardGrantModeQuotaExhausted,
		}, nil
	}

	claimDate := currentRegisterRewardClaimDate()
	if resolved.DailyLimit <= 0 {
		if err := updateRegisterRewardGrantDecision(
			s.repo.DB.WithContext(ctx),
			logRecord.ID,
			claimDate,
			registerRewardGrantModeIssueReward,
		); err != nil {
			return registerRewardGrantPlan{}, err
		}
		return registerRewardGrantPlan{
			ClaimDate: claimDate,
			GrantMode: registerRewardGrantModeIssueReward,
		}, nil
	}

	plan := registerRewardGrantPlan{
		ClaimDate: claimDate,
		GrantMode: registerRewardGrantModeIssueReward,
	}

	err := s.repo.DB.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
		// 通过锁定当前系统的配置行，串行化每日限额检查，避免并发用户同时穿透当天名额。
		var configRow model.ResidentRegisterRewardConfig
		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("sys_origin = ?", strings.ToUpper(strings.TrimSpace(event.SysOrigin))).
			First(&configRow).Error; err != nil {
			return err
		}

		dailyLimit := configRow.DailyLimit
		if dailyLimit <= 0 {
			plan.GrantMode = registerRewardGrantModeIssueReward
			return updateRegisterRewardGrantDecision(tx, logRecord.ID, claimDate, plan.GrantMode)
		}

		var occupiedCount int64
		if err := tx.Model(&model.ResidentRegisterRewardLog{}).
			Where("sys_origin = ? AND claim_date = ? AND grant_mode = ?", event.SysOrigin, claimDate, registerRewardGrantModeIssueReward).
			Count(&occupiedCount).Error; err != nil {
			return err
		}

		if occupiedCount >= dailyLimit {
			plan.GrantMode = registerRewardGrantModeQuotaExhausted
			plan.SkipDispatch = true
		}

		return updateRegisterRewardGrantDecision(tx, logRecord.ID, claimDate, plan.GrantMode)
	})
	if err != nil {
		return registerRewardGrantPlan{}, err
	}

	return plan, nil
}

// updateRegisterRewardGrantDecision 回写日志的领取日期和发奖决策结果。
func updateRegisterRewardGrantDecision(
	db *gorm.DB,
	logID int64,
	claimDate string,
	grantMode string,
) error {
	return db.Model(&model.ResidentRegisterRewardLog{}).
		Where("id = ?", logID).
		Updates(map[string]any{
			"claim_date":  strings.TrimSpace(claimDate),
			"grant_mode":  strings.ToUpper(strings.TrimSpace(grantMode)),
			"update_time": time.Now(),
		}).Error
}

// currentRegisterRewardClaimDate 返回“每日限额”口径下的当前日期。
func currentRegisterRewardClaimDate() string {
	location, err := time.LoadLocation(registerRewardDailyQuotaTimezone)
	if err != nil {
		return time.Now().Format("2006-01-02")
	}
	return time.Now().In(location).Format("2006-01-02")
}

// normalizeRegisterRewardClaimDate 规范后台查询传入的日期；未传时默认看今天。
func normalizeRegisterRewardClaimDate(raw string) string {
	trimmed := strings.TrimSpace(raw)
	if trimmed == "" {
		return currentRegisterRewardClaimDate()
	}
	if _, err := time.Parse("2006-01-02", trimmed); err == nil {
		return trimmed
	}
	return currentRegisterRewardClaimDate()
}