package service

import (
	"context"
	"errors"
	"fmt"
	"sub2api/internal/config"
	"sub2api/internal/model"
	"sub2api/internal/repository"

	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
)

var (
	ErrUserNotFound       = errors.New("user not found")
	ErrPasswordIncorrect  = errors.New("current password is incorrect")
	ErrInsufficientPerms  = errors.New("insufficient permissions")
)

// UpdateProfileRequest 更新用户资料请求
type UpdateProfileRequest struct {
	Email       *string `json:"email"`
	Concurrency *int    `json:"concurrency"`
}

// ChangePasswordRequest 修改密码请求
type ChangePasswordRequest struct {
	CurrentPassword string `json:"current_password"`
	NewPassword     string `json:"new_password"`
}

// UserService 用户服务
type UserService struct {
	userRepo *repository.UserRepository
	cfg      *config.Config
}

// NewUserService 创建用户服务实例
func NewUserService(userRepo *repository.UserRepository, cfg *config.Config) *UserService {
	return &UserService{
		userRepo: userRepo,
		cfg:      cfg,
	}
}

// GetProfile 获取用户资料
func (s *UserService) GetProfile(ctx context.Context, userID int64) (*model.User, error) {
	user, err := s.userRepo.GetByID(ctx, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrUserNotFound
		}
		return nil, fmt.Errorf("get user: %w", err)
	}
	return user, nil
}

// UpdateProfile 更新用户资料
func (s *UserService) UpdateProfile(ctx context.Context, userID int64, req UpdateProfileRequest) (*model.User, error) {
	user, err := s.userRepo.GetByID(ctx, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrUserNotFound
		}
		return nil, fmt.Errorf("get user: %w", err)
	}

	// 更新字段
	if req.Email != nil {
		// 检查新邮箱是否已被使用
		exists, err := s.userRepo.ExistsByEmail(ctx, *req.Email)
		if err != nil {
			return nil, fmt.Errorf("check email exists: %w", err)
		}
		if exists && *req.Email != user.Email {
			return nil, ErrEmailExists
		}
		user.Email = *req.Email
	}

	if req.Concurrency != nil {
		user.Concurrency = *req.Concurrency
	}

	if err := s.userRepo.Update(ctx, user); err != nil {
		return nil, fmt.Errorf("update user: %w", err)
	}

	return user, nil
}

// ChangePassword 修改密码
func (s *UserService) ChangePassword(ctx context.Context, userID int64, req ChangePasswordRequest) error {
	user, err := s.userRepo.GetByID(ctx, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrUserNotFound
		}
		return fmt.Errorf("get user: %w", err)
	}

	// 验证当前密码
	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.CurrentPassword)); err != nil {
		return ErrPasswordIncorrect
	}

	// 生成新密码哈希
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("hash password: %w", err)
	}

	user.PasswordHash = string(hashedPassword)

	if err := s.userRepo.Update(ctx, user); err != nil {
		return fmt.Errorf("update user: %w", err)
	}

	return nil
}

// GetByID 根据ID获取用户（管理员功能）
func (s *UserService) GetByID(ctx context.Context, id int64) (*model.User, error) {
	user, err := s.userRepo.GetByID(ctx, id)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, ErrUserNotFound
		}
		return nil, fmt.Errorf("get user: %w", err)
	}
	return user, nil
}

// List 获取用户列表（管理员功能）
func (s *UserService) List(ctx context.Context, params repository.PaginationParams) ([]model.User, *repository.PaginationResult, error) {
	users, pagination, err := s.userRepo.List(ctx, params)
	if err != nil {
		return nil, nil, fmt.Errorf("list users: %w", err)
	}
	return users, pagination, nil
}

// UpdateBalance 更新用户余额（管理员功能）
func (s *UserService) UpdateBalance(ctx context.Context, userID int64, amount float64) error {
	if err := s.userRepo.UpdateBalance(ctx, userID, amount); err != nil {
		return fmt.Errorf("update balance: %w", err)
	}
	return nil
}

// UpdateStatus 更新用户状态（管理员功能）
func (s *UserService) UpdateStatus(ctx context.Context, userID int64, status string) error {
	user, err := s.userRepo.GetByID(ctx, userID)
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrUserNotFound
		}
		return fmt.Errorf("get user: %w", err)
	}

	user.Status = status

	if err := s.userRepo.Update(ctx, user); err != nil {
		return fmt.Errorf("update user: %w", err)
	}

	return nil
}

// Delete 删除用户（管理员功能）
func (s *UserService) Delete(ctx context.Context, userID int64) error {
	if err := s.userRepo.Delete(ctx, userID); err != nil {
		return fmt.Errorf("delete user: %w", err)
	}
	return nil
}