package service

import (
	"context"
	"net/mail"
	"strings"
	"unicode/utf8"

	"git.yuntuo.hk/k2safe/go-omni/examples/reference/model"
)

// UserRepository describes the storage operations the business needs.
// Implementations must atomically enforce unique, normalized email addresses.
type UserRepository interface {
	Create(context.Context, model.UserInput) (model.User, error)
	Get(context.Context, int64) (model.User, error)
	List(context.Context, int, int) (model.UserPage, error)
	Update(context.Context, int64, model.UserInput) (model.User, error)
	Delete(context.Context, int64) error
}

type Users struct {
	repository UserRepository
}

func NewUsers(repository UserRepository) *Users {
	return &Users{repository: repository}
}

func (s *Users) Create(ctx context.Context, input model.UserInput) (model.User, error) {
	input, err := normalize(input)
	if err != nil {
		return model.User{}, err
	}
	return s.repository.Create(ctx, input)
}

func (s *Users) Get(ctx context.Context, id int64) (model.User, error) {
	return s.repository.Get(ctx, id)
}

func (s *Users) List(ctx context.Context, page, pageSize int) (model.UserPage, error) {
	if page < 1 || pageSize < 1 || pageSize > 100 {
		return model.UserPage{}, model.ErrInvalidPage
	}
	return s.repository.List(ctx, page, pageSize)
}

func (s *Users) Update(ctx context.Context, id int64, input model.UserInput) (model.User, error) {
	input, err := normalize(input)
	if err != nil {
		return model.User{}, err
	}
	return s.repository.Update(ctx, id, input)
}

func (s *Users) Delete(ctx context.Context, id int64) error {
	return s.repository.Delete(ctx, id)
}

func normalize(input model.UserInput) (model.UserInput, error) {
	input.Name = strings.TrimSpace(input.Name)
	// This example treats the entire email address as case-insensitive.
	input.Email = strings.ToLower(strings.TrimSpace(input.Email))
	address, err := mail.ParseAddress(input.Email)
	if input.Name == "" || utf8.RuneCountInString(input.Name) > 100 ||
		len(input.Email) > 254 || err != nil || address.Address != input.Email {
		return model.UserInput{}, model.ErrInvalidUser
	}
	return input, nil
}