// Package handler contains real PrizeHandler implementations for lottery prize
// dispatch. Handlers live in the logic layer because they depend on UserModel,
// NodeModel, and commonLogic — importing those from the pure-model
// internal/model/lottery package would flip the layering.
//
// All Dispatch entry points are called inside the draw service's transaction
// and must remain tx-only: no cache invalidation, no goroutine fan-out. The
// draw service is responsible for post-commit side effects (node cache clear,
// user group recalculation) once the enclosing transaction commits.
package handler

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/perfect-panel/server/internal/model/lottery"
	usermodel "github.com/perfect-panel/server/internal/model/user"
	"gorm.io/gorm"
)

// VPNDurationHandler 发放"N 天订阅时长"。
//
// 幂等模型：DispatchRequest.IdempotencyKey → lottery_grant_ledger.external_ref。
// Reserve 命中即幂等，返回 payload 里之前记录的 message；未命中才走真实发放。
//
// 家庭组：走 ResolveEffectiveUser 归位到 owner；若 owner 无活跃订阅，日志
// "skipped" 并返回 auto_claimed（与 grantGiftDays 的行为一致，避免中奖后无处发
// 的场景导致抽奖事务回滚吞事件）。
type VPNDurationHandler struct {
	deps VPNDurationDeps
}

// VPNDurationDeps 是 VPNDurationHandler 需要的依赖。用 struct 显式收拢，避免
// 直接依赖庞大的 ServiceContext；测试时可注入实现了同接口的 mock。
type VPNDurationDeps struct {
	UserModel usermodel.Model
	Ledger    lottery.LedgerService
	DB        *gorm.DB
	// ResolveEffectiveUser 用于家庭组归位。为 nil 时不做归位（等价于身份函数）。
	// 生产接线用 DefaultResolveEffectiveUser(DB) 包出闭包。
	ResolveEffectiveUser func(ctx context.Context, userID int64) (int64, error)
}

// DefaultResolveEffectiveUser 是生产环境的家庭组归位实现。语义与
// internal/logic/common.ResolveEntitlementUser 一致（活跃家庭成员 → owner），
// 但直接在 handler 包内做 JOIN 查询以避免 internal/svc → internal/logic/common
// 的 import cycle（common 包里有别的文件反向 import 了 svc）。
func DefaultResolveEffectiveUser(db *gorm.DB) func(ctx context.Context, userID int64) (int64, error) {
	return func(ctx context.Context, userID int64) (int64, error) {
		if userID <= 0 {
			return userID, nil
		}
		var row struct {
			OwnerUserID int64 `gorm:"column:owner_user_id"`
		}
		q := db.WithContext(ctx).
			Table("user_family_member").
			Select("user_family.owner_user_id AS owner_user_id").
			Joins("JOIN user_family ON user_family.id = user_family_member.family_id AND user_family.deleted_at IS NULL").
			Where("user_family_member.user_id = ? AND user_family_member.deleted_at IS NULL AND user_family_member.status = ?", userID, usermodel.FamilyMemberActive).
			Order("user_family_member.role").
			Limit(1).
			Scan(&row)
		if q.Error != nil {
			return 0, q.Error
		}
		if q.RowsAffected == 0 || row.OwnerUserID <= 0 {
			return userID, nil
		}
		return row.OwnerUserID, nil
	}
}

// NewVPNDurationHandler 构造真实的 vpn_duration handler。
func NewVPNDurationHandler(deps VPNDurationDeps) *VPNDurationHandler {
	return &VPNDurationHandler{deps: deps}
}

// Type / IsAuto / ValidateClaim / ClaimSchema 实现 PrizeHandler 接口。
func (*VPNDurationHandler) Type() string                 { return lottery.PrizeTypeVPNDuration }
func (*VPNDurationHandler) IsAuto() bool                 { return true }
func (*VPNDurationHandler) ValidateClaim([]byte) error   { return nil }
func (*VPNDurationHandler) ClaimSchema() json.RawMessage { return nil }

// vpnDurationConfig 是奖品 Config JSON 的解码目标。
type vpnDurationConfig struct {
	DurationDays int `json:"duration_days"`
}

// vpnDurationPayload 落库到 lottery_grant_ledger.payload，用于幂等重放时返回同一
// message；同时便于对账（哪条 user_subscribe 被延长、延长了多少天）。
type vpnDurationPayload struct {
	EffectiveUserID int64  `json:"effective_user_id"`
	SubscribeID     int64  `json:"subscribe_id"`
	Days            int    `json:"days"`
	Message         string `json:"message"`
}

// Dispatch 在 caller 的事务内发放订阅时长。
func (h *VPNDurationHandler) Dispatch(ctx context.Context, tx *gorm.DB, req lottery.DispatchRequest) (lottery.DispatchResult, error) {
	if tx == nil {
		return lottery.DispatchResult{}, errors.New("vpn_duration handler requires a transaction")
	}
	if req.IdempotencyKey == "" {
		return lottery.DispatchResult{}, errors.New("vpn_duration handler requires DispatchRequest.IdempotencyKey")
	}

	var cfg vpnDurationConfig
	if err := json.Unmarshal([]byte(req.Prize.Config), &cfg); err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("decode vpn_duration config: %w", err)
	}
	if cfg.DurationDays <= 0 {
		return lottery.DispatchResult{}, fmt.Errorf("vpn_duration config duration_days must be > 0, got %d", cfg.DurationDays)
	}

	// 家庭组归位：注入的 ResolveEffectiveUser 决定是否穿透到 owner。
	effectiveUserID := req.UserId
	if h.deps.ResolveEffectiveUser != nil {
		if eid, err := h.deps.ResolveEffectiveUser(ctx, req.UserId); err == nil && eid > 0 {
			effectiveUserID = eid
		}
	}

	entry := lottery.GrantLedger{
		ExternalRef: req.IdempotencyKey,
		HandlerType: lottery.PrizeTypeVPNDuration,
		UserId:      effectiveUserID,
		ActivityId:  req.ActivityId,
		DrawId:      req.DrawId,
		Amount:      int64(cfg.DurationDays),
	}
	row, alreadyExisted, err := h.deps.Ledger.Reserve(ctx, tx, entry)
	if err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("reserve grant ledger: %w", err)
	}
	if alreadyExisted {
		// 幂等命中：直接返回之前记录的 payload.message。
		var payload vpnDurationPayload
		if row.Payload != "" {
			_ = json.Unmarshal([]byte(row.Payload), &payload)
		}
		if payload.Message == "" {
			payload.Message = "已加到订阅"
		}
		return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
	}

	// 未存在 → 真实发放。查用户的活跃订阅。
	activeSub, findErr := h.findActiveSubscribe(ctx, effectiveUserID)
	if errors.Is(findErr, gorm.ErrRecordNotFound) {
		// 与 grantGiftDays 一致：无活跃订阅时记录 skipped 但不失败。
		payload := vpnDurationPayload{
			EffectiveUserID: effectiveUserID,
			Days:            cfg.DurationDays,
			Message:         "跳过：用户无活跃订阅",
		}
		if err := h.writeBackPayload(ctx, tx, row.Id, payload); err != nil {
			return lottery.DispatchResult{}, err
		}
		return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
	}
	if findErr != nil {
		return lottery.DispatchResult{}, fmt.Errorf("find active subscribe for user %d: %w", effectiveUserID, findErr)
	}

	// 计算新 ExpireTime。样板见 activateOrderLogic.go:1336-1342：
	//  a) NoLimit 永久（time.UnixMilli(0)）→ 不延长
	//  b) 已过期 → 从 now 起加
	//  c) 未过期 → 从 ExpireTime 起加
	now := time.Now()
	if !activeSub.ExpireTime.Equal(time.UnixMilli(0)) {
		if activeSub.ExpireTime.Before(now) {
			activeSub.ExpireTime = now.Add(time.Duration(cfg.DurationDays) * 24 * time.Hour)
		} else {
			activeSub.ExpireTime = activeSub.ExpireTime.Add(time.Duration(cfg.DurationDays) * 24 * time.Hour)
		}
	}
	activeSub.Status = 1
	activeSub.FinishedAt = nil

	if err := h.deps.UserModel.UpdateSubscribe(ctx, activeSub, tx); err != nil {
		return lottery.DispatchResult{}, fmt.Errorf("update subscribe %d: %w", activeSub.Id, err)
	}

	payload := vpnDurationPayload{
		EffectiveUserID: effectiveUserID,
		SubscribeID:     activeSub.Id,
		Days:            cfg.DurationDays,
		Message:         fmt.Sprintf("已加 %d 天到订阅", cfg.DurationDays),
	}
	if err := h.writeBackPayload(ctx, tx, row.Id, payload); err != nil {
		return lottery.DispatchResult{}, err
	}
	return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
}

// findActiveSubscribe 优先走 UserModel.FindActiveSubscribe；未找到则回退到
// 最新 token 非空的历史订阅（样板 activateOrderLogic.go:1371-1393）。
func (h *VPNDurationHandler) findActiveSubscribe(ctx context.Context, userID int64) (*usermodel.Subscribe, error) {
	activeSub, err := h.deps.UserModel.FindActiveSubscribe(ctx, userID)
	if err == nil {
		return activeSub, nil
	}
	if !errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, err
	}
	if h.deps.DB == nil {
		return nil, gorm.ErrRecordNotFound
	}
	var fallback usermodel.Subscribe
	fallbackErr := h.deps.DB.WithContext(ctx).
		Model(&usermodel.Subscribe{}).
		Where("user_id = ? AND token != ''", userID).
		Where("status IN ?", []int64{0, 1, 2, 3}).
		Order("expire_time DESC").
		Order("updated_at DESC").
		Order("id DESC").
		First(&fallback).Error
	if fallbackErr != nil {
		return nil, fallbackErr
	}
	return &fallback, nil
}

func (h *VPNDurationHandler) writeBackPayload(ctx context.Context, tx *gorm.DB, ledgerID int64, payload vpnDurationPayload) error {
	raw, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("marshal ledger payload: %w", err)
	}
	if err := tx.WithContext(ctx).
		Model(&lottery.GrantLedger{}).
		Where("id = ?", ledgerID).
		UpdateColumn("payload", string(raw)).Error; err != nil {
		return fmt.Errorf("update ledger payload: %w", err)
	}
	return nil
}