ThreadNet-Web/src/utils/permalinks/ElementPermalinkConstructor.ts

/*
Copyright 2024 New Vector Ltd.
Copyright 2019-2021 The Matrix.org Foundation C.I.C.

SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
Please see LICENSE files in the repository root for full details.
*/

import PermalinkConstructor, { PermalinkParts } from "./PermalinkConstructor";

/**
 * Generates permalinks that self-reference the running webapp
 */
export default class ElementPermalinkConstructor extends PermalinkConstructor {
    private elementUrl: string;

    public constructor(elementUrl: string) {
        super();
        this.elementUrl = elementUrl;

        if (!this.elementUrl.startsWith("http:") && !this.elementUrl.startsWith("https:")) {
            throw new Error("Element prefix URL does not appear to be an HTTP(S) URL");
        }
    }

    public forEvent(roomId: string, eventId: string, serverCandidates: string[]): string {
        return `${this.elementUrl}/#/room/${roomId}/${eventId}${this.encodeServerCandidates(serverCandidates)}`;
    }

    public forRoom(roomIdOrAlias: string, serverCandidates?: string[]): string {
        return `${this.elementUrl}/#/room/${roomIdOrAlias}${this.encodeServerCandidates(serverCandidates)}`;
    }

    public forUser(userId: string): string {
        return `${this.elementUrl}/#/user/${userId}`;
    }

    public forEntity(entityId: string): string {
        if (entityId[0] === "!" || entityId[0] === "#") {
            return this.forRoom(entityId);
        } else if (entityId[0] === "@") {
            return this.forUser(entityId);
        } else throw new Error("Unrecognized entity");
    }

    public isPermalinkHost(testHost: string): boolean {
        const parsedUrl = new URL(this.elementUrl);
        return testHost === (parsedUrl.host || parsedUrl.hostname); // one of the hosts should match
    }

    public encodeServerCandidates(candidates?: string[]): string {
        if (!candidates || candidates.length === 0) return "";
        return `?via=${candidates.map((c) => encodeURIComponent(c)).join("&via=")}`;
    }

    // Heavily inspired by/borrowed from the matrix-bot-sdk (with permission):
    // https://github.com/turt2live/matrix-js-bot-sdk/blob/7c4665c9a25c2c8e0fe4e509f2616505b5b66a1c/src/Permalinks.ts#L33-L61
    // Adapted for Element's URL format
    public parsePermalink(fullUrl: string): PermalinkParts {
        if (!fullUrl || !fullUrl.startsWith(this.elementUrl)) {
            throw new Error("Does not appear to be a permalink");
        }

        const parts = fullUrl.substring(`${this.elementUrl}/#/`.length);
        return ElementPermalinkConstructor.parseAppRoute(parts);
    }

    /**
     * Parses an app route (`(user|room)/identifier`) to a Matrix entity
     * (room, user).
     * @param {string} route The app route
     * @returns {PermalinkParts}
     */
    public static parseAppRoute(route: string): PermalinkParts {
        const parts = route.split("/");

        if (parts.length < 2) {
            // we're expecting an entity and an ID of some kind at least
            throw new Error("URL is missing parts");
        }

        // Split optional query out of last part
        const [lastPartMaybeWithQuery] = parts.splice(-1, 1);
        const [lastPart, query = ""] = lastPartMaybeWithQuery.split("?");
        parts.push(lastPart);

        const entityType = parts[0];
        const entity = parts[1];
        if (entityType === "user") {
            // Probably a user, no further parsing needed.
            return PermalinkParts.forUser(entity);
        } else if (entityType === "room") {
            // Rejoin the rest because v3 events can have slashes (annoyingly)
            const eventId = parts.length > 2 ? parts.slice(2).join("/") : "";
            const via = query.split(/&?via=/).filter((p) => !!p);
            return PermalinkParts.forEvent(entity, eventId, via);
        } else {
            throw new Error("Unknown entity type in permalink");
        }
    }
}