matrix-js-sdk/src/rendezvous/transports/MSC3886SimpleHttpRendezvousTransport.ts

Matrix Client-Server SDK for Javascript

/*
Copyright 2022 The Matrix.org Foundation C.I.C.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import { UnstableValue } from "matrix-events-sdk";

import { logger } from "../../logger";
import { sleep } from "../../utils";
import {
    RendezvousFailureListener,
    RendezvousFailureReason,
    RendezvousTransport,
    RendezvousTransportDetails,
} from "..";
import { MatrixClient } from "../../matrix";
import { ClientPrefix } from "../../http-api";

const TYPE = new UnstableValue("http.v1", "org.matrix.msc3886.http.v1");

export interface MSC3886SimpleHttpRendezvousTransportDetails extends RendezvousTransportDetails {
    uri: string;
}

/**
 * Implementation of the unstable [MSC3886](https://github.com/matrix-org/matrix-spec-proposals/pull/3886)
 * simple HTTP rendezvous protocol.
 * Note that this is UNSTABLE and may have breaking changes without notice.
 */
export class MSC3886SimpleHttpRendezvousTransport<T extends {}> implements RendezvousTransport<T> {
    private uri?: string;
    private etag?: string;
    private expiresAt?: Date;
    private client: MatrixClient;
    private fallbackRzServer?: string;
    private fetchFn?: typeof global.fetch;
    private cancelled = false;
    private _ready = false;
    public onFailure?: RendezvousFailureListener;

    public constructor({
        onFailure,
        client,
        fallbackRzServer,
        fetchFn,
    }: {
        fetchFn?: typeof global.fetch;
        onFailure?: RendezvousFailureListener;
        client: MatrixClient;
        fallbackRzServer?: string;
    }) {
        this.fetchFn = fetchFn;
        this.onFailure = onFailure;
        this.client = client;
        this.fallbackRzServer = fallbackRzServer;
    }

    public get ready(): boolean {
        return this._ready;
    }

    public async details(): Promise<MSC3886SimpleHttpRendezvousTransportDetails> {
        if (!this.uri) {
            throw new Error("Rendezvous not set up");
        }

        return {
            type: TYPE.name,
            uri: this.uri,
        };
    }

    private fetch(resource: URL | string, options?: RequestInit): ReturnType<typeof global.fetch> {
        if (this.fetchFn) {
            return this.fetchFn(resource, options);
        }
        return global.fetch(resource, options);
    }

    private async getPostEndpoint(): Promise<string | undefined> {
        try {
            if (await this.client.doesServerSupportUnstableFeature("org.matrix.msc3886")) {
                return `${this.client.baseUrl}${ClientPrefix.Unstable}/org.matrix.msc3886/rendezvous`;
            }
        } catch (err) {
            logger.warn("Failed to get unstable features", err);
        }

        return this.fallbackRzServer;
    }

    public async send(data: T): Promise<void> {
        if (this.cancelled) {
            return;
        }
        const method = this.uri ? "PUT" : "POST";
        const uri = this.uri ?? (await this.getPostEndpoint());

        if (!uri) {
            throw new Error("Invalid rendezvous URI");
        }

        const headers: Record<string, string> = { "content-type": "application/json" };
        if (this.etag) {
            headers["if-match"] = this.etag;
        }

        const res = await this.fetch(uri, { method, headers, body: JSON.stringify(data) });
        if (res.status === 404) {
            return this.cancel(RendezvousFailureReason.Unknown);
        }
        this.etag = res.headers.get("etag") ?? undefined;

        if (method === "POST") {
            const location = res.headers.get("location");
            if (!location) {
                throw new Error("No rendezvous URI given");
            }
            const expires = res.headers.get("expires");
            if (expires) {
                this.expiresAt = new Date(expires);
            }
            // we would usually expect the final `url` to be set by a proper fetch implementation.
            // however, if a polyfill based on XHR is used it won't be set, we we use existing URI as fallback
            const baseUrl = res.url ?? uri;
            // resolve location header which could be relative or absolute
            this.uri = new URL(location, `${baseUrl}${baseUrl.endsWith("/") ? "" : "/"}`).href;
            this._ready = true;
        }
    }

    public async receive(): Promise<Partial<T> | undefined> {
        if (!this.uri) {
            throw new Error("Rendezvous not set up");
        }
        // eslint-disable-next-line no-constant-condition
        while (true) {
            if (this.cancelled) {
                return undefined;
            }

            const headers: Record<string, string> = {};
            if (this.etag) {
                headers["if-none-match"] = this.etag;
            }
            const poll = await this.fetch(this.uri, { method: "GET", headers });

            if (poll.status === 404) {
                this.cancel(RendezvousFailureReason.Unknown);
                return undefined;
            }

            // rely on server expiring the channel rather than checking ourselves

            if (poll.headers.get("content-type") !== "application/json") {
                this.etag = poll.headers.get("etag") ?? undefined;
            } else if (poll.status === 200) {
                this.etag = poll.headers.get("etag") ?? undefined;
                return poll.json();
            }
            await sleep(1000);
        }
    }

    public async cancel(reason: RendezvousFailureReason): Promise<void> {
        if (reason === RendezvousFailureReason.Unknown && this.expiresAt && this.expiresAt.getTime() < Date.now()) {
            reason = RendezvousFailureReason.Expired;
        }

        this.cancelled = true;
        this._ready = false;
        this.onFailure?.(reason);

        if (this.uri && reason === RendezvousFailureReason.UserDeclined) {
            try {
                await this.fetch(this.uri, { method: "DELETE" });
            } catch (e) {
                logger.warn(e);
            }
        }
    }
}