package validation

import (
	"net/mail"
	"regexp"
	"strings"
	"unicode"

	"git.techease.ru/Smart-search/smart-search-back/pkg/errors"
)

const (
	MinPasswordLength = 8
	MaxPasswordLength = 128
	MaxEmailLength    = 254
	MaxNameLength     = 100
	MaxPhoneLength    = 20
	MaxRequestTxtLen  = 50000
	MaxFileSizeBytes  = 10 * 1024 * 1024
)

var (
	phoneRegex = regexp.MustCompile(`^\+?[1-9]\d{6,14}$`)
)

func ValidateEmail(email string) error {
	if email == "" {
		return errors.NewBusinessError(errors.ValidationInvalidEmail, "email is required")
	}

	if len(email) > MaxEmailLength {
		return errors.NewBusinessError(errors.ValidationInvalidEmail, "email is too long")
	}

	_, err := mail.ParseAddress(email)
	if err != nil {
		return errors.NewBusinessError(errors.ValidationInvalidEmail, "invalid email format")
	}

	parts := strings.Split(email, "@")
	if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
		return errors.NewBusinessError(errors.ValidationInvalidEmail, "invalid email format")
	}

	if strings.Contains(parts[1], "..") {
		return errors.NewBusinessError(errors.ValidationInvalidEmail, "invalid email format")
	}

	return nil
}

func ValidatePassword(password string) error {
	if password == "" {
		return errors.NewBusinessError(errors.ValidationInvalidPassword, "password is required")
	}

	if len(password) < MinPasswordLength {
		return errors.NewBusinessError(errors.ValidationInvalidPassword, "password must be at least 8 characters")
	}

	if len(password) > MaxPasswordLength {
		return errors.NewBusinessError(errors.ValidationInvalidPassword, "password is too long")
	}

	var hasUpper, hasLower, hasDigit bool
	for _, c := range password {
		switch {
		case unicode.IsUpper(c):
			hasUpper = true
		case unicode.IsLower(c):
			hasLower = true
		case unicode.IsDigit(c):
			hasDigit = true
		}
	}

	if !hasUpper || !hasLower || !hasDigit {
		return errors.NewBusinessError(errors.ValidationInvalidPassword, "password must contain uppercase, lowercase and digit")
	}

	return nil
}

func ValidatePhone(phone string) error {
	if phone == "" {
		return nil
	}

	if len(phone) > MaxPhoneLength {
		return errors.NewBusinessError(errors.ValidationInvalidPhone, "phone is too long")
	}

	cleaned := strings.ReplaceAll(phone, " ", "")
	cleaned = strings.ReplaceAll(cleaned, "-", "")
	cleaned = strings.ReplaceAll(cleaned, "(", "")
	cleaned = strings.ReplaceAll(cleaned, ")", "")

	if !phoneRegex.MatchString(cleaned) {
		return errors.NewBusinessError(errors.ValidationInvalidPhone, "invalid phone format")
	}

	return nil
}

func ValidateName(name string) error {
	if name == "" {
		return errors.NewBusinessError(errors.ValidationInvalidName, "name is required")
	}

	if len(name) > MaxNameLength {
		return errors.NewBusinessError(errors.ValidationInvalidName, "name is too long")
	}

	trimmed := strings.TrimSpace(name)
	if trimmed == "" {
		return errors.NewBusinessError(errors.ValidationInvalidName, "name cannot be only whitespace")
	}

	return nil
}

func ValidateRequestTxt(txt string) error {
	if len(txt) > MaxRequestTxtLen {
		return errors.NewBusinessError(errors.ValidationRequestTooLong, "request text exceeds 50000 characters limit")
	}

	return nil
}

func ValidateFileSize(size int) error {
	if size > MaxFileSizeBytes {
		return errors.NewBusinessError(errors.ValidationFileTooLarge, "file size exceeds 10MB limit")
	}

	return nil
}

func ValidateRegistration(email, password, name, phone string) error {
	if err := ValidateEmail(email); err != nil {
		return err
	}

	if err := ValidatePassword(password); err != nil {
		return err
	}

	if err := ValidateName(name); err != nil {
		return err
	}

	if err := ValidatePhone(phone); err != nil {
		return err
	}

	return nil
}