ethers.js/packages/web/src.ts/index.ts

"use strict";

import { XMLHttpRequest } from "xmlhttprequest";

import { encode as base64Encode } from "@ethersproject/base64";
import * as errors from "@ethersproject/errors";
import { shallowCopy } from "@ethersproject/properties";
import { toUtf8Bytes } from "@ethersproject/strings";


// Exported Types
export type ConnectionInfo = {
    url: string,
    user?: string,
    password?: string,
    allowInsecure?: boolean,
    timeout?: number,
    headers?: { [key: string]: string | number }
};

export interface OnceBlockable {
    once(eventName: "block", handler: () => void): void;
}

export type PollOptions = {
    timeout?: number,
    floor?: number,
    ceiling?: number,
    interval?: number,
    retryLimit?: number,
    onceBlock?: OnceBlockable
};



type Header = { key: string, value: string };

export function fetchJson(connection: string | ConnectionInfo, json?: string, processFunc?: (value: any) => any): Promise<any> {
    let headers: { [key: string]: Header } = { };

    let url: string = null;

    let timeout = 2 * 60 * 1000;

    if (typeof(connection) === "string") {
        url = connection;

    } else if (typeof(connection) === "object") {
        if (connection.url == null) {
            errors.throwError("missing URL", errors.MISSING_ARGUMENT, { arg: "url" });
        }

        url = connection.url;

        if (typeof(connection.timeout) === "number" && connection.timeout > 0) {
            timeout = connection.timeout;
        }

        if (connection.headers) {
            for (let key in connection.headers) {
                headers[key.toLowerCase()] = { key: key, value: String(connection.headers[key]) };
            }
        }

        if (connection.user != null && connection.password != null) {
            if (url.substring(0, 6) !== "https:" && connection.allowInsecure !== true) {
                errors.throwError(
                    "basic authentication requires a secure https url",
                    errors.INVALID_ARGUMENT,
                    { arg: "url", url: url, user: connection.user, password: "[REDACTED]" }
                );
            }

            let authorization = connection.user + ":" + connection.password;
            headers["authorization"] = {
                key: "Authorization",
                value: "Basic " + base64Encode(toUtf8Bytes(authorization))
            };
        }
    }

    return new Promise(function(resolve, reject) {
        let request = new XMLHttpRequest();

        let timer: any = null;
        timer = setTimeout(() => {
            if (timer == null) { return; }
            timer = null;

            reject(new Error("timeout"));
            setTimeout(() => {
                request.abort();
            }, 0);
        }, timeout);

        let cancelTimeout = () => {
            if (timer == null) { return; }
            clearTimeout(timer);
            timer = null;
        }

        if (json) {
            request.open("POST", url, true);
            headers["content-type"] = { key: "Content-Type", value: "application/json" };
        } else {
            request.open("GET", url, true);
        }

        Object.keys(headers).forEach((key) => {
            let header = headers[key];
            request.setRequestHeader(header.key, header.value);
        });

        request.onreadystatechange = function() {
            if (request.readyState !== 4) { return; }

            if (request.status != 200) {
                cancelTimeout();
                // @TODO: not any!
                let error: any = new Error("invalid response - " + request.status);
                error.statusCode = request.status;
                if (request.responseText) {
                    error.responseText = request.responseText;
                }
                reject(error);
                return;
            }

            let result: any = null;
            try {
                result = JSON.parse(request.responseText);
            } catch (error) {
                cancelTimeout();
                // @TODO: not any!
                let jsonError: any = new Error("invalid json response");
                jsonError.orginialError = error;
                jsonError.responseText = request.responseText;
                if (json != null) {
                    jsonError.requestBody = json;
                }
                jsonError.url = url;
                reject(jsonError);
                return;
            }

            if (processFunc) {
                try {
                    result = processFunc(result);
                } catch (error) {
                    cancelTimeout();
                    error.url = url;
                    error.body = json;
                    error.responseText = request.responseText;
                    reject(error);
                    return;
                }
            }

            cancelTimeout();
            resolve(result);
        };

        request.onerror = function(error) {
            cancelTimeout();
            reject(error);
        }

        try {
            if (json != null) {
                request.send(json);
            } else {
                request.send();
            }

        } catch (error) {
            cancelTimeout();
            // @TODO: not any!
            let connectionError: any = new Error("connection error");
            connectionError.error = error;
            reject(connectionError);
        }
    });
}

export function poll(func: () => Promise<any>, options?: PollOptions): Promise<any> {
    if (!options) { options = {}; }
    options = shallowCopy(options);
    if (options.floor == null) { options.floor = 0; }
    if (options.ceiling == null) { options.ceiling = 10000; }
    if (options.interval == null) { options.interval = 250; }

    return new Promise(function(resolve, reject) {

        let timer: any = null;
        let done: boolean = false;

        // Returns true if cancel was successful. Unsuccessful cancel means we're already done.
        let cancel = (): boolean => {
            if (done) { return false; }
            done = true;
            if (timer) { clearTimeout(timer); }
            return true;
        };

        if (options.timeout) {
            timer = setTimeout(() => {
                if (cancel()) { reject(new Error("timeout")); }
            }, options.timeout)
        }

        let retryLimit = options.retryLimit;

        let attempt = 0;
        function check() {
            return func().then(function(result) {

                // If we have a result, or are allowed null then we're done
                if (result !== undefined) {
                    if (cancel()) { resolve(result); }

                } else if (options.onceBlock) {
                    options.onceBlock.once("block", check);

                // Otherwise, exponential back-off (up to 10s) our next request
                } else if (!done) {
                    attempt++;
                    if (attempt > retryLimit) {
                        if (cancel()) { reject(new Error("retry limit reached")); }
                        return;
                    }

                    let timeout = options.interval * parseInt(String(Math.random() * Math.pow(2, attempt)));
                    if (timeout < options.floor) { timeout = options.floor; }
                    if (timeout > options.ceiling) { timeout = options.ceiling; }

                    setTimeout(check, timeout);
                }

                return null;
            }, function(error) {
                if (cancel()) { reject(error); }
            });
        }
        check();
    });
}