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diff --git a/packages/taler-util/src/http.ts b/packages/taler-util/src/http.ts
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+/*
+ This file is part of TALER
+ (C) 2016 GNUnet e.V.
+
+ TALER is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ TALER 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 General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+/**
+ * Helpers for doing XMLHttpRequest-s that are based on ES6 promises.
+ * Allows for easy mocking for test cases.
+ *
+ * The API is inspired by the HTML5 fetch API.
+ */
+
+/**
+ * Imports
+ */
+import {
+  Logger,
+  Duration,
+  AbsoluteTime,
+  TalerErrorDetail,
+  Codec,
+  j2s,
+  CancellationToken,
+} from "@gnu-taler/taler-util";
+import { TalerErrorCode } from "@gnu-taler/taler-util";
+import { makeErrorDetail, TalerError } from "./errors.js";
+import * as impl from "#http-impl";
+import { HttpLibArgs } from "./http-common.js";
+
+const logger = new Logger("http.ts");
+
+/**
+ * An HTTP response that is returned by all request methods of this library.
+ */
+export interface HttpResponse {
+  requestUrl: string;
+  requestMethod: string;
+  status: number;
+  headers: Headers;
+  json(): Promise<any>;
+  text(): Promise<string>;
+  bytes(): Promise<ArrayBuffer>;
+}
+
+export const DEFAULT_REQUEST_TIMEOUT_MS = 60000;
+
+export interface HttpRequestOptions {
+  method?: "POST" | "PUT" | "GET";
+  headers?: { [name: string]: string };
+
+  /**
+   * Timeout after which the request should be aborted.
+   */
+  timeout?: Duration;
+
+  /**
+   * Cancellation token that should abort the request when
+   * cancelled.
+   */
+  cancellationToken?: CancellationToken;
+
+  body?: string | ArrayBuffer | Record<string, unknown>;
+}
+
+/**
+ * Headers, roughly modeled after the fetch API's headers object.
+ */
+export class Headers {
+  private headerMap = new Map<string, string>();
+
+  get(name: string): string | null {
+    const r = this.headerMap.get(name.toLowerCase());
+    if (r) {
+      return r;
+    }
+    return null;
+  }
+
+  set(name: string, value: string): void {
+    const normalizedName = name.toLowerCase();
+    const existing = this.headerMap.get(normalizedName);
+    if (existing !== undefined) {
+      this.headerMap.set(normalizedName, existing + "," + value);
+    } else {
+      this.headerMap.set(normalizedName, value);
+    }
+  }
+
+  toJSON(): any {
+    const m: Record<string, string> = {};
+    this.headerMap.forEach((v, k) => (m[k] = v));
+    return m;
+  }
+}
+
+/**
+ * Interface for the HTTP request library used by the wallet.
+ *
+ * The request library is bundled into an interface to make mocking and
+ * request tunneling easy.
+ */
+export interface HttpRequestLibrary {
+  /**
+   * Make an HTTP GET request.
+   *
+   * FIXME: Get rid of this, we want the API surface to be minimal.
+   */
+  get(url: string, opt?: HttpRequestOptions): Promise<HttpResponse>;
+
+  /**
+   * Make an HTTP POST request with a JSON body.
+   *
+   * FIXME: Get rid of this, we want the API surface to be minimal.
+   */
+  postJson(
+    url: string,
+    body: any,
+    opt?: HttpRequestOptions,
+  ): Promise<HttpResponse>;
+
+  /**
+   * Make an HTTP POST request with a JSON body.
+   */
+  fetch(url: string, opt?: HttpRequestOptions): Promise<HttpResponse>;
+}
+
+type TalerErrorResponse = {
+  code: number;
+} & unknown;
+
+type ResponseOrError<T> =
+  | { isError: false; response: T }
+  | { isError: true; talerErrorResponse: TalerErrorResponse };
+
+export async function readTalerErrorResponse(
+  httpResponse: HttpResponse,
+): Promise<TalerErrorDetail> {
+  const errJson = await httpResponse.json();
+  const talerErrorCode = errJson.code;
+  if (typeof talerErrorCode !== "number") {
+    logger.warn(
+      `malformed error response (status ${httpResponse.status}): ${j2s(
+        errJson,
+      )}`,
+    );
+    throw TalerError.fromDetail(
+      TalerErrorCode.WALLET_RECEIVED_MALFORMED_RESPONSE,
+      {
+        requestUrl: httpResponse.requestUrl,
+        requestMethod: httpResponse.requestMethod,
+        httpStatusCode: httpResponse.status,
+      },
+      "Error response did not contain error code",
+    );
+  }
+  return errJson;
+}
+
+export async function readUnexpectedResponseDetails(
+  httpResponse: HttpResponse,
+): Promise<TalerErrorDetail> {
+  const errJson = await httpResponse.json();
+  const talerErrorCode = errJson.code;
+  if (typeof talerErrorCode !== "number") {
+    return makeErrorDetail(
+      TalerErrorCode.WALLET_RECEIVED_MALFORMED_RESPONSE,
+      {
+        requestUrl: httpResponse.requestUrl,
+        requestMethod: httpResponse.requestMethod,
+        httpStatusCode: httpResponse.status,
+      },
+      "Error response did not contain error code",
+    );
+  }
+  return makeErrorDetail(
+    TalerErrorCode.WALLET_UNEXPECTED_REQUEST_ERROR,
+    {
+      requestUrl: httpResponse.requestUrl,
+      requestMethod: httpResponse.requestMethod,
+      httpStatusCode: httpResponse.status,
+      errorResponse: errJson,
+    },
+    `Unexpected HTTP status (${httpResponse.status}) in response`,
+  );
+}
+
+export async function readSuccessResponseJsonOrErrorCode<T>(
+  httpResponse: HttpResponse,
+  codec: Codec<T>,
+): Promise<ResponseOrError<T>> {
+  if (!(httpResponse.status >= 200 && httpResponse.status < 300)) {
+    return {
+      isError: true,
+      talerErrorResponse: await readTalerErrorResponse(httpResponse),
+    };
+  }
+  const respJson = await httpResponse.json();
+  let parsedResponse: T;
+  try {
+    parsedResponse = codec.decode(respJson);
+  } catch (e: any) {
+    throw TalerError.fromDetail(
+      TalerErrorCode.WALLET_RECEIVED_MALFORMED_RESPONSE,
+      {
+        requestUrl: httpResponse.requestUrl,
+        requestMethod: httpResponse.requestMethod,
+        httpStatusCode: httpResponse.status,
+        validationError: e.toString(),
+      },
+      "Response invalid",
+    );
+  }
+  return {
+    isError: false,
+    response: parsedResponse,
+  };
+}
+
+type HttpErrorDetails = {
+  requestUrl: string;
+  requestMethod: string;
+  httpStatusCode: number;
+};
+
+export function getHttpResponseErrorDetails(
+  httpResponse: HttpResponse,
+): HttpErrorDetails {
+  return {
+    requestUrl: httpResponse.requestUrl,
+    requestMethod: httpResponse.requestMethod,
+    httpStatusCode: httpResponse.status,
+  };
+}
+
+export function throwUnexpectedRequestError(
+  httpResponse: HttpResponse,
+  talerErrorResponse: TalerErrorResponse,
+): never {
+  throw TalerError.fromDetail(
+    TalerErrorCode.WALLET_UNEXPECTED_REQUEST_ERROR,
+    {
+      requestUrl: httpResponse.requestUrl,
+      requestMethod: httpResponse.requestMethod,
+      httpStatusCode: httpResponse.status,
+      errorResponse: talerErrorResponse,
+    },
+    `Unexpected HTTP status ${httpResponse.status} in response`,
+  );
+}
+
+export async function readSuccessResponseJsonOrThrow<T>(
+  httpResponse: HttpResponse,
+  codec: Codec<T>,
+): Promise<T> {
+  const r = await readSuccessResponseJsonOrErrorCode(httpResponse, codec);
+  if (!r.isError) {
+    return r.response;
+  }
+  throwUnexpectedRequestError(httpResponse, r.talerErrorResponse);
+}
+
+export async function readSuccessResponseTextOrErrorCode<T>(
+  httpResponse: HttpResponse,
+): Promise<ResponseOrError<string>> {
+  if (!(httpResponse.status >= 200 && httpResponse.status < 300)) {
+    const errJson = await httpResponse.json();
+    const talerErrorCode = errJson.code;
+    if (typeof talerErrorCode !== "number") {
+      throw TalerError.fromDetail(
+        TalerErrorCode.WALLET_RECEIVED_MALFORMED_RESPONSE,
+        {
+          httpStatusCode: httpResponse.status,
+          requestUrl: httpResponse.requestUrl,
+          requestMethod: httpResponse.requestMethod,
+        },
+        "Error response did not contain error code",
+      );
+    }
+    return {
+      isError: true,
+      talerErrorResponse: errJson,
+    };
+  }
+  const respJson = await httpResponse.text();
+  return {
+    isError: false,
+    response: respJson,
+  };
+}
+
+export async function checkSuccessResponseOrThrow(
+  httpResponse: HttpResponse,
+): Promise<void> {
+  if (!(httpResponse.status >= 200 && httpResponse.status < 300)) {
+    const errJson = await httpResponse.json();
+    const talerErrorCode = errJson.code;
+    if (typeof talerErrorCode !== "number") {
+      throw TalerError.fromDetail(
+        TalerErrorCode.WALLET_RECEIVED_MALFORMED_RESPONSE,
+        {
+          httpStatusCode: httpResponse.status,
+          requestUrl: httpResponse.requestUrl,
+          requestMethod: httpResponse.requestMethod,
+        },
+        "Error response did not contain error code",
+      );
+    }
+    throwUnexpectedRequestError(httpResponse, errJson);
+  }
+}
+
+export async function readSuccessResponseTextOrThrow<T>(
+  httpResponse: HttpResponse,
+): Promise<string> {
+  const r = await readSuccessResponseTextOrErrorCode(httpResponse);
+  if (!r.isError) {
+    return r.response;
+  }
+  throwUnexpectedRequestError(httpResponse, r.talerErrorResponse);
+}
+
+/**
+ * Get the timestamp at which the response's content is considered expired.
+ */
+export function getExpiry(
+  httpResponse: HttpResponse,
+  opt: { minDuration?: Duration },
+): AbsoluteTime {
+  const expiryDateMs = new Date(
+    httpResponse.headers.get("expiry") ?? "",
+  ).getTime();
+  let t: AbsoluteTime;
+  if (Number.isNaN(expiryDateMs)) {
+    t = AbsoluteTime.now();
+  } else {
+    t = {
+      t_ms: expiryDateMs,
+    };
+  }
+  if (opt.minDuration) {
+    const t2 = AbsoluteTime.addDuration(AbsoluteTime.now(), opt.minDuration);
+    return AbsoluteTime.max(t, t2);
+  }
+  return t;
+}
+
+export function createPlatformHttpLib(args?: HttpLibArgs): HttpRequestLibrary {
+  return new impl.HttpLibImpl(args);
+}