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expectContext.ts
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expectContext.ts
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/*
* Copyright (C) 2022 PixieBrix, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import {
isBackground,
isContentScript,
isExtensionContext,
isWebPage,
} from "webext-detect-page";
/**
* Accepts 'This is my error' | new Error('This is my error') | Error;
* The constructor would be used to create a custom error with the default message
*/
type ErrorBaseType = string | Error | (new (message?: string) => Error);
function createError(
defaultMessage: string,
errorOrCtor: ErrorBaseType = Error
): Error {
if (typeof errorOrCtor === "string") {
return new Error(errorOrCtor);
}
if (errorOrCtor instanceof Error) {
return errorOrCtor;
}
// eslint-disable-next-line new-cap -- variable can be an value or constructor
return new errorOrCtor(defaultMessage);
}
const contexts = [
"web",
"extension",
"background",
"contentScript",
"devTools",
] as const;
const contextMap = new Map<typeof contexts[number], () => boolean>([
["web", isWebPage],
["extension", isExtensionContext],
["background", isBackground],
["contentScript", isContentScript],
["devTools", () => "devtools" in chrome],
]);
/**
* @example expectContext('extension')
* @example expectContext('extension', WrongContextError)
* @example expectContext('extension', 'Wrong context and this is my custom error')
* @example expectContext('extension', new Error('Wrong context and this is my custom error'))
*/
export function expectContext(
context: typeof contexts[number],
error?: ErrorBaseType
): void {
const isContext = contextMap.get(context);
if (!isContext) {
throw new TypeError(`Context "${context}" not found`);
}
if (!isContext()) {
throw createError(
`This code can only run in the "${context}" context`,
error
);
}
}
/**
* @example forbidContext('extension')
* @example forbidContext('extension', WrongContextError)
* @example forbidContext('extension', 'Wrong context and this is my custom error')
* @example forbidContext('extension', new Error('Wrong context and this is my custom error'))
*/
export function forbidContext(
context: typeof contexts[number],
error?: ErrorBaseType
): void {
const isContext = contextMap.get(context);
if (!isContext) {
throw new TypeError(`Context "${context}" not found`);
}
if (isContext()) {
throw createError(
`This code cannot run in the "${context}" context`,
error
);
}
}