package biz

import (
	"context"
	"encoding/json"
	"errors"
	"time"
)

type Announcement struct {
	ID          uint
	CreatedAt   time.Time
	UpdatedAt   time.Time
	Title       string
	Content     string
	UserID      *uint
	Attachments json.RawMessage
}

type AnnouncementFilter struct {
	Page, PageSize               int
	StartCreatedAt, EndCreatedAt *time.Time
}

type AnnouncementRepo interface {
	Create(context.Context, *Announcement) error
	Delete(context.Context, uint) error
	DeleteByIDs(context.Context, []uint) error
	Update(context.Context, *Announcement) error
	Find(context.Context, uint) (*Announcement, error)
	List(context.Context, AnnouncementFilter) ([]*Announcement, int64, error)
	UserOptions(context.Context) ([]UserOption, error)
}

type UserOption struct {
	Label string
	Value uint
}

type AnnouncementUsecase struct{ repo AnnouncementRepo }

func NewAnnouncementUsecase(repo AnnouncementRepo) *AnnouncementUsecase {
	return &AnnouncementUsecase{repo: repo}
}

func validateAnnouncement(item *Announcement) error {
	if item == nil || item.Title == "" {
		return errors.New("公告标题不能为空")
	}
	if len(item.Attachments) == 0 || !json.Valid(item.Attachments) {
		item.Attachments = json.RawMessage("[]")
	}
	return nil
}

func (uc *AnnouncementUsecase) Create(ctx context.Context, item *Announcement) error {
	if err := validateAnnouncement(item); err != nil {
		return err
	}
	return uc.repo.Create(ctx, item)
}

func (uc *AnnouncementUsecase) Update(ctx context.Context, item *Announcement) error {
	if item == nil || item.ID == 0 {
		return errors.New("公告ID不能为空")
	}
	if err := validateAnnouncement(item); err != nil {
		return err
	}
	return uc.repo.Update(ctx, item)
}

func (uc *AnnouncementUsecase) Delete(ctx context.Context, id uint) error {
	if id == 0 {
		return errors.New("公告ID不能为空")
	}
	return uc.repo.Delete(ctx, id)
}

func (uc *AnnouncementUsecase) DeleteByIDs(ctx context.Context, ids []uint) error {
	if len(ids) == 0 {
		return errors.New("公告ID不能为空")
	}
	return uc.repo.DeleteByIDs(ctx, ids)
}

func (uc *AnnouncementUsecase) Find(ctx context.Context, id uint) (*Announcement, error) {
	if id == 0 {
		return nil, errors.New("公告ID不能为空")
	}
	return uc.repo.Find(ctx, id)
}

func (uc *AnnouncementUsecase) List(ctx context.Context, filter AnnouncementFilter) ([]*Announcement, int64, error) {
	return uc.repo.List(ctx, filter)
}

func (uc *AnnouncementUsecase) UserOptions(ctx context.Context) ([]UserOption, error) {
	return uc.repo.UserOptions(ctx)
}