103 lines
2.6 KiB
TypeScript
103 lines
2.6 KiB
TypeScript
export class Pagination {
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public static deserialize(str: string): Pagination {
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const data = JSON.parse(str);
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return new Pagination(data.page, data.perPage, data.totalCount);
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}
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public readonly page: number;
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public readonly perPage: number;
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public readonly totalCount: number;
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public constructor(page: number, perPage: number, totalCount: number) {
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if (perPage <= 0) throw new Error('perPage must be >= 1');
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if (totalCount < 0) throw new Error('totalCount must be >= 0');
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this.page = page;
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this.perPage = perPage;
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this.totalCount = totalCount;
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if (this.page < 1 || this.page > 1 && this.page > this.lastPage) {
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throw new PageNotFoundError(this.page);
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}
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}
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public hasPrevious(): boolean {
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return this.page > 1;
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}
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public hasNext(): boolean {
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return this.page < this.lastPage;
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}
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public get lastPage(): number {
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return Math.max(Math.ceil(this.totalCount / this.perPage), 1);
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}
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public previousPages(contextSize: number): number[] {
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if (typeof contextSize !== 'number') throw new Error('contextSize must be a number');
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const pages = [];
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let i = 1;
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// Leftmost context
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while (i < this.page && i <= contextSize) {
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pages.push(i);
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i++;
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}
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// Ellipsis
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if (i < this.page - contextSize) {
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pages.push(-1);
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}
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// Middle left context
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i = Math.max(i, this.page - contextSize);
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while (i < this.page) {
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pages.push(i);
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i++;
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}
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return pages;
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}
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public nextPages(contextSize: number): number[] {
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if (typeof contextSize !== 'number') throw new Error('contextSize must be a number');
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const pages = [];
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let i = this.page + 1;
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// Middle right context
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while (i <= this.lastPage && i <= this.page + contextSize) {
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pages.push(i);
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i++;
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}
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// Ellipsis
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if (this.page + contextSize + 1 < this.lastPage - contextSize + 1) {
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pages.push(-1);
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}
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// Rightmost context
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i = Math.max(i, this.lastPage - contextSize + 1);
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while (i <= this.lastPage) {
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pages.push(i);
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i++;
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}
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return pages;
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}
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public serialize(): string {
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return JSON.stringify(this);
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}
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}
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export class PageNotFoundError extends Error {
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public constructor(
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public readonly page: number,
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) {
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super(`Page ${page} not found.`);
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}
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}
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