import { groupService } from '../services/groupService';
import { CursorPaginationResponse, GroupMemberResponse } from '../types/dto';

export const GROUP_MEMBER_LIST_PAGE_SIZE = 50;

export type GroupMemberListSourceKind = 'cursor' | 'offset';

export interface IGroupMemberListPagedSource {
  restart(): void;
  loadNext(): Promise<CursorPaginationResponse<GroupMemberResponse>>;
  readonly hasMore: boolean;
}

export class NetworkCursorGroupMemberListPagedSource implements IGroupMemberListPagedSource {
  private nextCursor: string | null = null;
  private hasMoreAfterLastLoad = false;
  private loadedOnce = false;
  private readonly groupId: string;
  private readonly pageSize: number;

  constructor(groupId: string, pageSize: number = GROUP_MEMBER_LIST_PAGE_SIZE) {
    this.groupId = groupId;
    this.pageSize = pageSize;
  }

  restart(): void {
    this.nextCursor = null;
    this.hasMoreAfterLastLoad = false;
    this.loadedOnce = false;
  }

  get hasMore(): boolean {
    return this.loadedOnce && this.hasMoreAfterLastLoad;
  }

  async loadNext(): Promise<CursorPaginationResponse<GroupMemberResponse>> {
    const response = await groupService.getGroupMembersCursor(
      this.groupId,
      this.nextCursor == null
        ? { page_size: this.pageSize }
        : { cursor: this.nextCursor, page_size: this.pageSize }
    );

    this.nextCursor = response.next_cursor ?? null;
    this.hasMoreAfterLastLoad = Boolean(response.has_more && response.next_cursor != null);
    this.loadedOnce = true;

    return {
      list: response.list || [],
      next_cursor: response.next_cursor ?? null,
      prev_cursor: response.prev_cursor ?? null,
      has_more: response.has_more ?? false,
    };
  }
}

export class NetworkOffsetGroupMemberListPagedSource implements IGroupMemberListPagedSource {
  private nextPage = 1;
  private hasMoreAfterLastLoad = false;
  private loadedOnce = false;
  private readonly groupId: string;
  private readonly pageSize: number;

  constructor(groupId: string, pageSize: number = GROUP_MEMBER_LIST_PAGE_SIZE) {
    this.groupId = groupId;
    this.pageSize = pageSize;
  }

  restart(): void {
    this.nextPage = 1;
    this.hasMoreAfterLastLoad = false;
    this.loadedOnce = false;
  }

  get hasMore(): boolean {
    return this.loadedOnce && this.hasMoreAfterLastLoad;
  }

  async loadNext(): Promise<CursorPaginationResponse<GroupMemberResponse>> {
    const response = await groupService.getMembers(this.groupId, this.nextPage, this.pageSize);
    const list = response.list || [];
    const currentPage = response.page ?? this.nextPage;
    const totalPages = response.total_pages ?? currentPage;
    const hasMore = currentPage < totalPages;
    const nextPageCursor = hasMore ? String(currentPage + 1) : null;
    const prevPageCursor = currentPage > 1 ? String(currentPage - 1) : null;

    this.nextPage = currentPage + 1;
    this.hasMoreAfterLastLoad = hasMore;
    this.loadedOnce = true;

    return {
      list,
      next_cursor: nextPageCursor,
      prev_cursor: prevPageCursor,
      has_more: hasMore,
    };
  }
}

export function createRemoteGroupMemberListSource(
  kind: GroupMemberListSourceKind,
  groupId: string,
  pageSize: number = GROUP_MEMBER_LIST_PAGE_SIZE
): IGroupMemberListPagedSource {
  return kind === 'offset'
    ? new NetworkOffsetGroupMemberListPagedSource(groupId, pageSize)
    : new NetworkCursorGroupMemberListPagedSource(groupId, pageSize);
}