114 lines
3 KiB
TypeScript
114 lines
3 KiB
TypeScript
export class ValidationError extends Error {
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status = 400;
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}
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export interface ValidatedScreenshotRequest {
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pagePath: string;
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qs: URLSearchParams;
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}
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const MAX_REPEATED_PARAMS = 40;
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const MAX_VALUE_LENGTH = 500;
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const NUMERIC_RE = /^-?(?:\d+|\d*\.\d+)$/;
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const PATH_RE = /^\/(?:invite\/[A-Za-z0-9]{1,20})?$/;
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const SAFE_VALUE_RE = /^[^\u0000-\u001f\u007f]+$/;
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const REPEATED_KEYS = ['filter', 'school', 'crime', 'ethnicity', 'poi', 'tt'] as const;
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type Query = Record<string, unknown>;
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function validationError(message: string): never {
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throw new ValidationError(message);
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}
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function firstString(query: Query, key: string): string | undefined {
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const value = query[key];
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if (value == null) return undefined;
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if (Array.isArray(value)) {
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validationError(`${key} must not be repeated`);
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}
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if (typeof value !== 'string') {
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validationError(`${key} must be a string`);
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}
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return value || undefined;
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}
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function repeatedStrings(query: Query, key: string): string[] {
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const value = query[key];
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if (value == null) return [];
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const values = Array.isArray(value) ? value : [value];
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if (values.length > MAX_REPEATED_PARAMS) {
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validationError(`${key} has too many values`);
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}
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return values.filter((item): item is string => {
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if (typeof item !== 'string') {
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validationError(`${key} values must be strings`);
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}
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return item.length > 0;
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});
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}
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function assertSafeValue(key: string, value: string): void {
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if (value.length > MAX_VALUE_LENGTH) {
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validationError(`${key} is too long`);
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}
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if (!SAFE_VALUE_RE.test(value)) {
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validationError(`${key} contains invalid characters`);
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}
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}
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function appendBoundedNumber(
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qs: URLSearchParams,
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query: Query,
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key: string,
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min: number,
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max: number,
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): void {
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const value = firstString(query, key);
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if (value == null) return;
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if (value.length > 40 || !NUMERIC_RE.test(value)) {
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validationError(`${key} must be a number`);
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}
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const numeric = Number(value);
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if (!Number.isFinite(numeric) || numeric < min || numeric > max) {
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validationError(`${key} is out of range`);
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}
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qs.set(key, value);
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}
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export function buildScreenshotRequest(query: Query): ValidatedScreenshotRequest {
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const qs = new URLSearchParams();
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appendBoundedNumber(qs, query, 'lat', -90, 90);
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appendBoundedNumber(qs, query, 'lon', -180, 180);
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appendBoundedNumber(qs, query, 'zoom', 0, 22);
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const tab = firstString(query, 'tab');
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if (tab != null) {
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if (tab !== 'area' && tab !== 'properties') {
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validationError('tab is invalid');
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}
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qs.set('tab', tab);
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}
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const og = firstString(query, 'og');
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if (og != null) {
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if (og !== '1') {
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validationError('og is invalid');
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}
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qs.set('og', og);
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}
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for (const key of REPEATED_KEYS) {
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for (const value of repeatedStrings(query, key)) {
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assertSafeValue(key, value);
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qs.append(key, value);
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}
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}
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const pagePath = firstString(query, 'path') ?? '/';
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if (!PATH_RE.test(pagePath)) {
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validationError('path is invalid');
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}
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return { pagePath, qs };
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}
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