package user

import (
	"context"
	"errors"
	"fmt"

	"bindbox-game/internal/repository/mysql/dao"
	"bindbox-game/internal/repository/mysql/model"

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

// BindInviterInput 绑定邀请人输入
type BindInviterInput struct {
	InviteCode string // 邀请人的邀请码
}

// BindInviterOutput 绑定邀请人输出
type BindInviterOutput struct {
	InviterID       int64  `json:"inviter_id"`
	InviterNickname string `json:"inviter_nickname"`
}

var (
	ErrAlreadyBound     = errors.New("already_bound")
	ErrInvalidCode      = errors.New("invalid_code")
	ErrCannotInviteSelf = errors.New("cannot_invite_self")
)

// BindInviter 用户主动绑定邀请人（仅限未绑定过的用户）
func (s *service) BindInviter(ctx context.Context, userID int64, in BindInviterInput) (*BindInviterOutput, error) {
	var result *BindInviterOutput

	err := s.writeDB.Transaction(func(tx *dao.Query) error {
		// 1. 获取当前用户，加行锁
		user, err := tx.Users.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).
			Where(tx.Users.ID.Eq(userID)).First()
		if err != nil {
			return err
		}

		// 2. 检查是否已绑定邀请人
		if user.InviterID != 0 {
			return ErrAlreadyBound
		}

		// 3. 查找邀请人
		inviter, err := tx.Users.WithContext(ctx).Where(tx.Users.InviteCode.Eq(in.InviteCode)).First()
		if err != nil {
			if errors.Is(err, gorm.ErrRecordNotFound) {
				return ErrInvalidCode
			}
			return err
		}

		// 4. 不能邀请自己
		if inviter.ID == userID {
			return ErrCannotInviteSelf
		}

		// 5. 创建邀请记录
		invite := &model.UserInvites{
			InviterID:  inviter.ID,
			InviteeID:  userID,
			InviteCode: in.InviteCode,
		}
		if err := tx.UserInvites.WithContext(ctx).Create(invite); err != nil {
			return err
		}

		// 6. 更新用户的邀请人ID
		if _, err := tx.Users.WithContext(ctx).Where(tx.Users.ID.Eq(userID)).
			UpdateColumn(tx.Users.InviterID, inviter.ID); err != nil {
			return err
		}

		result = &BindInviterOutput{
			InviterID:       inviter.ID,
			InviterNickname: inviter.Nickname,
		}

		return nil
	})

	if err != nil {
		return nil, err
	}

	return result, nil
}

// AdminBindInviterInput 管理端强制绑定/修改/解绑邀请人输入
type AdminBindInviterInput struct {
	TargetUserID  int64 // 被操作用户ID
	InviterUserID int64 // 新邀请人ID（0 表示解绑）
	OperatorID    int64 // 操作管理员ID
}

// AdminBindInviterOutput 管理端操作结果
type AdminBindInviterOutput struct {
	OldInviterID       int64  `json:"old_inviter_id"`
	OldInviterNickname string `json:"old_inviter_nickname"`
	NewInviterID       int64  `json:"new_inviter_id"`
	NewInviterNickname string `json:"new_inviter_nickname"`
}

// AdminBindInviter 管理端强制设置/修改/解绑用户的邀请人
func (s *service) AdminBindInviter(ctx context.Context, in AdminBindInviterInput) (*AdminBindInviterOutput, error) {
	var result *AdminBindInviterOutput

	err := s.writeDB.Transaction(func(tx *dao.Query) error {
		// 1. 加锁获取目标用户
		targetUser, err := tx.Users.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).
			Where(tx.Users.ID.Eq(in.TargetUserID)).First()
		if err != nil {
			return fmt.Errorf("target_user_not_found")
		}

		// 2. 不允许自己绑自己
		if in.InviterUserID > 0 && in.InviterUserID == in.TargetUserID {
			return ErrCannotInviteSelf
		}

		// 3. 查询旧邀请人昵称
		oldInviterNickname := ""
		if targetUser.InviterID > 0 {
			if oldInviter, e := tx.Users.WithContext(ctx).
				Where(tx.Users.ID.Eq(targetUser.InviterID)).First(); e == nil {
				oldInviterNickname = oldInviter.Nickname
			}
		}

		// 4. 查询新邀请人（解绑时跳过）
		newInviterNickname := ""
		if in.InviterUserID > 0 {
			newInviter, e := tx.Users.WithContext(ctx).
				Where(tx.Users.ID.Eq(in.InviterUserID)).First()
			if e != nil {
				return fmt.Errorf("inviter_user_not_found")
			}
			newInviterNickname = newInviter.Nickname
		}

		// 5. 更新 users.inviter_id
		if _, err := tx.Users.WithContext(ctx).
			Where(tx.Users.ID.Eq(in.TargetUserID)).
			Update(tx.Users.InviterID, in.InviterUserID); err != nil {
			return err
		}

		// 6. 同步 user_invites：先删旧记录，再插新记录
		if targetUser.InviterID > 0 {
			if _, err := tx.UserInvites.WithContext(ctx).
				Where(tx.UserInvites.InviteeID.Eq(in.TargetUserID)).
				Where(tx.UserInvites.InviterID.Eq(targetUser.InviterID)).
				Delete(); err != nil {
				return err
			}
		}
		if in.InviterUserID > 0 {
			newInvite := &model.UserInvites{
				InviterID:  in.InviterUserID,
				InviteeID:  in.TargetUserID,
				InviteCode: fmt.Sprintf("admin_op_by_%d", in.OperatorID),
			}
			if err := tx.UserInvites.WithContext(ctx).Create(newInvite); err != nil {
				return err
			}
		}

		result = &AdminBindInviterOutput{
			OldInviterID:       targetUser.InviterID,
			OldInviterNickname: oldInviterNickname,
			NewInviterID:       in.InviterUserID,
			NewInviterNickname: newInviterNickname,
		}
		return nil
	})

	if err != nil {
		return nil, err
	}
	return result, nil
}