package service

import (
	"context"
	"errors"
	"fmt"
	"math/rand"
	"time"

	"golang.org/x/crypto/bcrypt"
	"gofaster/internal/auth/model"
	"gofaster/internal/auth/repository"
)

type PasswordService struct {
	userRepo           repository.UserRepository
	passwordPolicyRepo repository.PasswordPolicyRepository
	passwordHistoryRepo repository.PasswordHistoryRepository
	passwordResetRepo  repository.PasswordResetRepository
}

func NewPasswordService(
	userRepo repository.UserRepository,
	passwordPolicyRepo repository.PasswordPolicyRepository,
	passwordHistoryRepo repository.PasswordHistoryRepository,
	passwordResetRepo repository.PasswordResetRepository,
) *PasswordService {
	return &PasswordService{
		userRepo:           userRepo,
		passwordPolicyRepo: passwordPolicyRepo,
		passwordHistoryRepo: passwordHistoryRepo,
		passwordResetRepo:  passwordResetRepo,
	}
}

// GetPasswordPolicy 获取密码策略
func (ps *PasswordService) GetPasswordPolicy() (*model.PasswordPolicy, error) {
	return ps.passwordPolicyRepo.GetActivePolicy()
}

// ValidatePassword 验证密码强度
func (ps *PasswordService) ValidatePassword(password string) (*model.PasswordValidationResult, error) {
	// 获取密码策略
	policy, err := ps.GetPasswordPolicy()
	if err != nil {
		return nil, err
	}

	// 计算密码强度
	strength := ps.calculatePasswordStrength(password)
	level := ps.calculatePasswordLevel(password)

	// 检查密码长度
	if len(password) < policy.MinLength {
		return &model.PasswordValidationResult{
			IsValid: false,
			Strength: strength,
			Level:   level,
			Errors:  []string{fmt.Sprintf("密码长度不能少于%d位", policy.MinLength)},
		}, nil
	}

	// 检查字符类型要求
	charTypes := 0
	hasUppercase := false
	hasLowercase := false
	hasNumbers := false
	hasSpecial := false

	for _, char := range password {
		if char >= 'A' && char <= 'Z' {
			hasUppercase = true
		} else if char >= 'a' && char <= 'z' {
			hasLowercase = true
		} else if char >= '0' && char <= '9' {
			hasNumbers = true
		} else {
			hasSpecial = true
		}
	}

	if hasUppercase {
		charTypes++
	}
	if hasLowercase {
		charTypes++
	}
	if hasNumbers {
		charTypes++
	}
	if hasSpecial {
		charTypes++
	}

	// 检查字符类型数量要求
	if charTypes < policy.MinCharTypes {
		return &model.PasswordValidationResult{
			IsValid: false,
			Strength: strength,
			Level:   level,
			Errors:  []string{fmt.Sprintf("密码必须包含至少%d种字符类型", policy.MinCharTypes)},
		}, nil
	}

	// 检查密码等级要求
	if level < policy.MinRequiredLevel {
		return &model.PasswordValidationResult{
			IsValid: false,
			Strength: strength,
			Level:   level,
			Errors:  []string{fmt.Sprintf("密码强度等级不能低于%d级", policy.MinRequiredLevel)},
		}, nil
	}

	return &model.PasswordValidationResult{
		IsValid: true,
		Strength: strength,
		Level:   level,
		Errors:  []string{},
	}, nil
}

// calculatePasswordStrength 计算密码强度（0-100）
func (ps *PasswordService) calculatePasswordStrength(password string) int {
	strength := 0

	// 基础长度分数
	if len(password) >= 8 {
		strength += 20
	} else if len(password) >= 6 {
		strength += 15
	} else {
		strength += 10
	}

	// 字符类型分数
	charTypes := 0
	hasUppercase := false
	hasLowercase := false
	hasNumbers := false
	hasSpecial := false

	for _, char := range password {
		if char >= 'A' && char <= 'Z' {
			hasUppercase = true
		} else if char >= 'a' && char <= 'z' {
			hasLowercase = true
		} else if char >= '0' && char <= '9' {
			hasNumbers = true
		} else {
			hasSpecial = true
		}
	}

	if hasUppercase {
		charTypes++
		strength += 15
	}
	if hasLowercase {
		charTypes++
		strength += 15
	}
	if hasNumbers {
		charTypes++
		strength += 15
	}
	if hasSpecial {
		charTypes++
		strength += 20
	}

	// 复杂度奖励
	if charTypes >= 4 {
		strength += 20
	} else if charTypes >= 3 {
		strength += 15
	} else if charTypes >= 2 {
		strength += 10
	}

	// 确保分数在0-100范围内
	if strength > 100 {
		strength = 100
	}

	return strength
}

// calculatePasswordLevel 计算密码等级（0-5）
func (ps *PasswordService) calculatePasswordLevel(password string) int {
	if len(password) < 6 {
		return 0
	}

	charTypes := 0
	hasUppercase := false
	hasLowercase := false
	hasNumbers := false
	hasSpecial := false

	for _, char := range password {
		if char >= 'A' && char <= 'Z' {
			hasUppercase = true
		} else if char >= 'a' && char <= 'z' {
			hasLowercase = true
		} else if char >= '0' && char <= '9' {
			hasNumbers = true
		} else {
			hasSpecial = true
		}
	}

	if hasUppercase {
		charTypes++
	}
	if hasLowercase {
		charTypes++
	}
	if hasNumbers {
		charTypes++
	}
	if hasSpecial {
		charTypes++
	}

	// 根据长度和字符类型确定等级
	if len(password) >= 8 && charTypes >= 4 {
		return 5
	} else if len(password) >= 8 && charTypes >= 3 {
		return 4
	} else if len(password) >= 6 && charTypes >= 3 {
		return 3
	} else if len(password) >= 6 && charTypes >= 2 {
		return 2
	} else if len(password) >= 6 && charTypes >= 1 {
		return 1
	}

	return 0
}

// CheckPasswordReuse 检查密码是否重复使用
func (ps *PasswordService) CheckPasswordReuse(userID uint, newPassword string) error {
	policy, err := ps.GetPasswordPolicy()
	if err != nil {
		return err
	}

	if policy.PreventReuse <= 0 {
		return nil // 不检查重复使用
	}

	// 获取用户密码历史
	history, err := ps.passwordHistoryRepo.GetUserPasswordHistory(userID, policy.PreventReuse)
	if err != nil {
		return err
	}

	// 检查新密码是否与历史密码重复
	for _, record := range history {
		if ps.verifyPassword(newPassword, record.Password) {
			return errors.New(fmt.Sprintf("新密码不能与前%d次使用的密码重复", policy.PreventReuse))
		}
	}

	return nil
}

// ChangePassword 修改密码
func (ps *PasswordService) ChangePassword(ctx context.Context, userID uint, currentPassword, newPassword string) error {
	// 获取用户信息
	user, err := ps.userRepo.GetByID(userID)
	if err != nil {
		return err
	}

	// 验证当前密码
	if !ps.verifyPassword(currentPassword, user.Password) {
		return errors.New("当前密码不正确")
	}

	// 验证新密码
	validationResult, err := ps.ValidatePassword(newPassword)
	if err != nil {
		return err
	}

	if !validationResult.IsValid {
		return errors.New("新密码不符合要求")
	}

	// 检查密码重复使用
	if err := ps.CheckPasswordReuse(userID, newPassword); err != nil {
		return err
	}

	// 哈希新密码
	newPasswordHash, err := ps.hashPassword(newPassword)
	if err != nil {
		return err
	}

	// 更新用户密码
	user.Password = string(newPasswordHash)
	user.PasswordChangedAt = &time.Time{}
	user.ForceChangePassword = false

	if err := ps.userRepo.Update(user); err != nil {
		return err
	}

	// 记录密码历史
	passwordHistory := &model.PasswordHistory{
		UserID:    userID,
		Password:  string(newPasswordHash),
		ChangedAt: time.Now(),
	}

	return ps.passwordHistoryRepo.Create(passwordHistory)
}

// ResetPassword 重置密码
func (ps *PasswordService) ResetPassword(ctx context.Context, userID string) error {
	// 生成临时密码
	tempPassword := ps.generateTempPassword()

	// 哈希临时密码
	hashedPassword, err := ps.hashPassword(tempPassword)
	if err != nil {
		return err
	}

	// 更新用户密码
	user, err := ps.userRepo.GetByID(userID)
	if err != nil {
		return err
	}

	user.Password = string(hashedPassword)
	user.PasswordChangedAt = &time.Time{}
	user.ForceChangePassword = true

	return ps.userRepo.Update(user)
}

// CheckPasswordExpiration 检查密码是否过期
func (ps *PasswordService) CheckPasswordExpiration(user *model.User) (bool, error) {
	if user.PasswordChangedAt == nil {
		return false, nil
	}

	policy, err := ps.GetPasswordPolicy()
	if err != nil {
		return false, err
	}

	expirationDate := user.PasswordChangedAt.Add(time.Duration(policy.ExpirationDays) * 24 * time.Hour)
	return time.Now().After(expirationDate), nil
}

// CheckForceChangePassword 检查是否需要强制修改密码
func (ps *PasswordService) CheckForceChangePassword(user *model.User) bool {
	return user.ForceChangePassword
}

// generateTempPassword 生成临时密码
func (ps *PasswordService) generateTempPassword() string {
	const charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
	password := make([]byte, 8)
	for i := range password {
		password[i] = charset[rand.Intn(len(charset))]
	}
	return string(password)
}

// hashPassword 哈希密码
func (ps *PasswordService) hashPassword(password string) ([]byte, error) {
	return bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
}

// verifyPassword 验证密码
func (ps *PasswordService) verifyPassword(password, hashedPassword string) bool {
	return bcrypt.CompareHashAndPassword([]byte(hashedPassword), []byte(password)) == nil
}

// CheckPasswordStatus 检查密码状态
func (ps *PasswordService) CheckPasswordStatus(ctx context.Context, userID uint) (*model.PasswordStatus, error) {
	user, err := ps.userRepo.GetByID(userID)
	if err != nil {
		return nil, err
	}

	isExpired, err := ps.CheckPasswordExpiration(user)
	if err != nil {
		return nil, err
	}

	forceChange := ps.CheckForceChangePassword(user)

	return &model.PasswordStatus{
		ForceChangePassword: forceChange,
		PasswordExpired:     isExpired,
		PasswordChangedAt:   user.PasswordChangedAt,
	}, nil
}

// UpdatePasswordPolicy 更新密码策略
func (ps *PasswordService) UpdatePasswordPolicy(policy *model.PasswordPolicy) error {
	return ps.passwordPolicyRepo.Update(policy)
}