Feat #1130 [WIP] Adding support for downloading and zipping files (#1501)

* Feat #1130 Adding support for downloading and zipping files

@ This is a combination of 12 commits.
 - Feat #1130 Initial Commit
 - Feat #1130 Adding support for hierachical lists
 - Feat #1130 [WIP] Adding support for downloading and zipping files
 - Feat #1130 Adding support for hierarchical folder structure study, series, instances on generated zip file
 - Feat #1130 Adding unit tests and addressing code review feedbacks
 - Feat #1130 POC (adding module to support on progress handling)
 - Feat #1130 Improving logic from progress tracking utils
 - Feat #1130 Renaming module with progress tracking utils
 - Feat #1130 Beta version of Progress Tracking utils
 - Feat #1130 Adding unit tests for Progress Tracking Utils
 - Feat #1130 Documenting public methods from progress tracking utils module
 - Feat #1130 Adding support for download and zip progress reporting

* Feat #1130 Addressing code review feedback

* Feat #1130 Preventing multiple downloads from executing at once

* Feat #1130 Improving error message for concurrent downloads

* Remove downloadAndZipSeriesOnViewports

Co-authored-by: James Petts <jamesapetts@gmail.com>

platform/core/src/utils/Queue.js

@@ -0,0 +1,66 @@
+
+export default class Queue {
+
+  constructor(limit) {
+    this.limit = limit;
+    this.size = 0;
+    this.awaiting = null;
+  }
+
+  /**
+   * Creates a new "proxy" function associated with the current execution queue
+   * instance. When the returned function is invoked, the queue limit is checked
+   * to make sure the limit of scheduled tasks is repected (throwing an
+   * exception when the limit has been reached and before calling the original
+   * function). The original function is only invoked after all the previously
+   * scheduled tasks have finished executing (their returned promises have
+   * resolved/rejected);
+   *
+   * @param {function} task The function whose execution will be associated
+   * with the current Queue instance;
+   * @returns {function} The "proxy" function bound to the current Queue
+   * instance;
+   */
+  bind(task) {
+    return bind(this, task);
+  }
+
+  bindSafe(task, onError) {
+    const boundTask = bind(this, task);
+    return async function safeTask(...args) {
+      try {
+        return await boundTask(...args);
+      } catch (e) {
+        onError(e);
+      }
+    };
+  }
+}
+
+/**
+ * Utils
+ */
+
+function bind(queue, task) {
+  const cleaner = clean.bind(null, queue);
+  return async function boundTask(...args) {
+    if (queue.size >= queue.limit) {
+      throw new Error('Queue limit reached');
+    }
+    const promise = chain(queue.awaiting, task, args);
+    queue.awaiting = promise.then(cleaner, cleaner);
+    queue.size++;
+    return promise;
+  };
+}
+
+function clean(queue) {
+  if (queue.size > 0 && --queue.size === 0) {
+    queue.awaiting = null;
+  }
+}
+
+async function chain(prev, task, args) {
+  await prev;
+  return task(...args);
+}

platform/core/src/utils/Queue.test.js

@@ -0,0 +1,66 @@
+import makeDeferred from './makeDeferred';
+import Queue from './Queue';
+
+/**
+ * Utils
+ */
+
+function timeout(delay) {
+  const { resolve, promise } = makeDeferred();
+  setTimeout(() => void resolve(Date.now()), delay);
+  return promise;
+}
+
+/**
+ * Tests
+ */
+
+describe('Queue', () => {
+  it('should bind functions to the queue', async () => {
+    const queue = new Queue(2);
+    const mockedTimeout = jest.fn(timeout);
+    const timer = queue.bind(mockedTimeout);
+    const start = Date.now();
+    timer(120).then(now => {
+      const elapsed = now - start;
+      expect(elapsed >= 120 && elapsed < 240).toBe(true);
+    });
+    const end = await timer(120);
+    expect(end - start > 240).toBe(true);
+    expect(mockedTimeout).toBeCalledTimes(2);
+  });
+  it('should prevent task execution when queue limit is reached', async () => {
+    const queue = new Queue(1);
+    const mockedTimeout = jest.fn(timeout);
+    const timer = queue.bind(mockedTimeout);
+    const start = Date.now();
+    const promise = timer(120).then(time => time - start);
+    try {
+      await timer(120);
+    } catch (e) {
+      expect(Date.now() - start < 120).toBe(true);
+      expect(e.message).toBe('Queue limit reached');
+    }
+    const elapsed = await promise;
+    expect(elapsed >= 120 && elapsed < 240).toBe(true);
+    expect(mockedTimeout).toBeCalledTimes(1);
+  });
+  it('should safely bind tasks to the queue', async () => {
+    const queue = new Queue(1);
+    const mockedErrorHandler = jest.fn();
+    const mockedTimeout = jest.fn(timeout);
+    const timer = queue.bindSafe(mockedTimeout, mockedErrorHandler);
+    const start = Date.now();
+    const promise = timer(120).then(time => time - start);
+    await timer(120);
+    expect(Date.now() - start < 120).toBe(true);
+    expect(mockedErrorHandler).toBeCalledTimes(1);
+    expect(mockedErrorHandler).nthCalledWith(
+      1,
+      expect.objectContaining({ message: 'Queue limit reached' })
+    );
+    const elapsed = await promise;
+    expect(elapsed >= 120 && elapsed < 240).toBe(true);
+    expect(mockedTimeout).toBeCalledTimes(1);
+  });
+});

platform/core/src/utils/hierarchicalListUtils.js

@@ -0,0 +1,193 @@
+/**
+ * Constants
+ */
+
+const SEPARATOR = '/';
+
+/**
+ * API
+ */
+
+/**
+ * Add values to a list hierarchically.
+ *  @ For example:
+ *    addToList([], 'a', 'b', 'c');
+ *  will add the following hierarchy to the list:
+ *    a > b > c
+ *  resulting in the following array:
+ *    [['a', [['b', ['c']]]]]
+ * @param {Array} list The target list;
+ * @param  {...string} values The values to be hierarchically added to the list;
+ * @returns {Array} Returns the provided list possibly updated with the given
+ *  values or null when a bad list (not an actual array) is provided
+ */
+function addToList(list, ...values) {
+  if (Array.isArray(list)) {
+    if (values.length > 0) {
+      addValuesToList(list, values);
+    }
+    return list;
+  }
+  return null;
+}
+
+/**
+ * Iterates through the provided hierarchical list executing the callback
+ * once for each leaf-node of the tree. The ancestors of the leaf-node being
+ * visited are passed to the callback function along with the leaf-node in
+ * the exact same order they appear on the tree (from root to leaf);
+ *  @ For example, if the hierachy `a > b > c` appears on the tree ("a" being
+ *    the root and "c" being the leaf) the callback function will be called as:
+ *  callback('a', 'b', 'c');
+ * @param {Array} list The hierarchical list to be iterated
+ * @param {function} callback The callback which will be exected once for
+ *  each leaf-node of the hierarchical list;
+ * @returns {Array} Returns the provided list or null for bad arguments;
+ */
+function forEach(list, callback) {
+  if (Array.isArray(list)) {
+    if (typeof callback === 'function') {
+      forEachValue(list, callback);
+    }
+    return list;
+  }
+  return null;
+}
+
+/**
+ * Retrieves an item from the given hierarchical list based on an index (number)
+ * or a path (string).
+ *  @ For example:
+ *    getItem(list, '1/0/4')
+ *  will retrieve the fourth grandchild, from the first child of the second
+ *  element of the list;
+ * @param {Array} list The source list;
+ * @param {string|number} indexOrPath The index of the element inside list
+ *  (number) or the path to reach the desired element (string). The slash "/"
+ *  character is cosidered the path separator;
+ */
+function getItem(list, indexOrPath) {
+  if (Array.isArray(list)) {
+    let subpath = null;
+    let index = typeof indexOrPath === 'number' ? indexOrPath : -1;
+    if (typeof indexOrPath === 'string') {
+      const separator = indexOrPath.indexOf(SEPARATOR);
+      if (separator > 0) {
+        index = parseInt(indexOrPath.slice(0, separator), 10);
+        if (separator + 1 < indexOrPath.length) {
+          subpath = indexOrPath.slice(separator + 1, indexOrPath.length);
+        }
+      } else {
+        index = parseInt(indexOrPath, 10);
+      }
+    }
+    if (index >= 0 && index < list.length) {
+      const item = list[index];
+      if (isSublist(item)) {
+        if (subpath !== null) {
+          return getItem(item[1], subpath);
+        }
+        return item[0];
+      }
+      return item;
+    }
+  }
+}
+
+/**
+ * Pretty-print the provided hierarchical list;
+ * @param {Array} list The source list;
+ * @returns {string} The textual representation of the hierarchical list;
+ */
+function print(list) {
+  let text = '';
+  if (Array.isArray(list)) {
+    let prev = [];
+    forEachValue(list, function(...args) {
+      let prevLen = prev.length;
+      for (let i = 0, l = args.length; i < l; ++i) {
+        if (i < prevLen && args[i] === prev[i]) {
+          continue;
+        }
+        text += '  '.repeat(i) + args[i] + '\n';
+      }
+      prev = args;
+    });
+  }
+  return text;
+}
+
+/**
+ * Utils
+ */
+
+function forEachValue(list, callback) {
+  for (let i = 0, l = list.length; i < l; ++i) {
+    let item = list[i];
+    if (isSublist(item)) {
+      if (item[1].length > 0) {
+        forEachValue(item[1], callback.bind(null, item[0]));
+        continue;
+      }
+      item = item[0];
+    }
+    callback(item);
+  }
+}
+
+function addValuesToList(list, values) {
+  let value = values.shift();
+  let index = add(list, value);
+  if (index >= 0) {
+    if (values.length > 0) {
+      let sublist = list[index];
+      if (!isSublist(sublist)) {
+        sublist = toSublist(value);
+        list[index] = sublist;
+      }
+      return addValuesToList(sublist[1], values);
+    }
+    return true;
+  }
+  return false;
+}
+
+function add(list, value) {
+  let index = find(list, value);
+  if (index === -2) {
+    index = list.push(value) - 1;
+  }
+  return index;
+}
+
+function find(list, value) {
+  if (typeof value === 'string') {
+    for (let i = 0, l = list.length; i < l; ++i) {
+      let item = list[i];
+      if (item === value || (isSublist(item) && item[0] === value)) {
+        return i;
+      }
+    }
+    return -2;
+  }
+  return -1;
+}
+
+function isSublist(subject) {
+  return (
+    Array.isArray(subject) &&
+    subject.length === 2 &&
+    typeof subject[0] === 'string' &&
+    Array.isArray(subject[1])
+  );
+}
+
+function toSublist(value) {
+  return [value + '', []];
+}
+
+/**
+ * Exports
+ */
+
+export { addToList, getItem, forEach, print };

platform/core/src/utils/hierarchicalListUtils.test.js

@@ -0,0 +1,96 @@
+import { addToList, forEach, getItem, print } from './hierarchicalListUtils';
+
+describe('hierarchicalListUtils', function() {
+  let sharedList;
+
+  beforeEach(function() {
+    sharedList = [
+      ['1.2.3.1', ['1.2.3.1.1', '1.2.3.1.2']],
+      '1.2.3.2',
+      ['1.2.3.3', ['1.2.3.3.1', ['1.2.3.3.2', ['1.2.3.3.2.1', '1.2.3.3.2.2']]]],
+    ];
+  });
+
+  describe('getItem', function() {
+    it('should retrieve elements from a list by index', function() {
+      expect(getItem(sharedList, 0)).toBe('1.2.3.1');
+      expect(getItem(sharedList, 1)).toBe('1.2.3.2');
+      expect(getItem(sharedList, 2)).toBe('1.2.3.3');
+      expect(getItem(sharedList, 3)).toBeUndefined();
+    });
+    it('should retrieve elements from a list by path', function() {
+      expect(getItem(sharedList, '0')).toBe('1.2.3.1');
+      expect(getItem(sharedList, '0/0')).toBe('1.2.3.1.1');
+      expect(getItem(sharedList, '0/1')).toBe('1.2.3.1.2');
+      expect(getItem(sharedList, '0/2')).toBeUndefined();
+      expect(getItem(sharedList, '1')).toBe('1.2.3.2');
+      expect(getItem(sharedList, '2')).toBe('1.2.3.3');
+      expect(getItem(sharedList, '2/0')).toBe('1.2.3.3.1');
+      expect(getItem(sharedList, '2/1')).toBe('1.2.3.3.2');
+      expect(getItem(sharedList, '2/2')).toBeUndefined();
+      expect(getItem(sharedList, '2/1/0')).toBe('1.2.3.3.2.1');
+      expect(getItem(sharedList, '2/1/1')).toBe('1.2.3.3.2.2');
+      expect(getItem(sharedList, '2/1/2')).toBeUndefined();
+      expect(getItem(sharedList, '3')).toBeUndefined();
+    });
+  });
+
+  describe('addToList', function() {
+    it('should support adding elements to a list hierarchically', function() {
+      const list = [];
+      addToList(list, '1.2.3.1', '1.2.3.1.1');
+      addToList(list, '1.2.3.1', '1.2.3.1.2');
+      addToList(list, '1.2.3.2');
+      addToList(list, '1.2.3.3', '1.2.3.3.1');
+      addToList(list, '1.2.3.3', '1.2.3.3.2', '1.2.3.3.2.1');
+      addToList(list, '1.2.3.3', '1.2.3.3.2', '1.2.3.3.2.2');
+      expect(list).toStrictEqual(sharedList);
+    });
+    it('should change leaf nodes into non-leaf nodes', function() {
+      const listw = [];
+      const listx = [['x.1', ['x.1.1', 'x.1.2']], 'x.2'];
+      const listy = [
+        ['x.1', [['x.1.1', ['x.1.1.1']], 'x.1.2']],
+        ['x.2', ['x.2.1']],
+      ];
+      addToList(listw, 'x.1');
+      addToList(listw, 'x.1', 'x.1.1');
+      addToList(listw, 'x.1', 'x.1.2');
+      addToList(listw, 'x.2');
+      expect(listw).toStrictEqual(listx);
+      addToList(listw, 'x.2', 'x.2.1');
+      addToList(listw, 'x.1', 'x.1.1', 'x.1.1.1');
+      expect(listw).toStrictEqual(listy);
+    });
+  });
+
+  describe('forEach', function() {
+    it('should iterate through all leaf nodes of the tree', function() {
+      const fn = jest.fn();
+      forEach(sharedList, fn);
+      expect(fn).toHaveBeenCalledTimes(6);
+      expect(fn).nthCalledWith(1, '1.2.3.1', '1.2.3.1.1');
+      expect(fn).nthCalledWith(2, '1.2.3.1', '1.2.3.1.2');
+      expect(fn).nthCalledWith(3, '1.2.3.2');
+      expect(fn).nthCalledWith(4, '1.2.3.3', '1.2.3.3.1');
+      expect(fn).nthCalledWith(5, '1.2.3.3', '1.2.3.3.2', '1.2.3.3.2.1');
+      expect(fn).nthCalledWith(6, '1.2.3.3', '1.2.3.3.2', '1.2.3.3.2.2');
+    });
+  });
+
+  describe('print', function() {
+    it('should pretty-print the hierarchical list', function() {
+      expect(print(sharedList)).toBe(
+        '1.2.3.1\n' +
+          '  1.2.3.1.1\n' +
+          '  1.2.3.1.2\n' +
+          '1.2.3.2\n' +
+          '1.2.3.3\n' +
+          '  1.2.3.3.1\n' +
+          '  1.2.3.3.2\n' +
+          '    1.2.3.3.2.1\n' +
+          '    1.2.3.3.2.2\n'
+      );
+    });
+  });
+});

platform/core/src/utils/index.js

@@ -10,8 +10,14 @@ import DicomLoaderService from './dicomLoaderService.js';
 import b64toBlob from './b64toBlob.js';
 import loadAndCacheDerivedDisplaySets from './loadAndCacheDerivedDisplaySets.js';
 import * as urlUtil from './urlUtil';
+import makeDeferred from './makeDeferred';
 import makeCancelable from './makeCancelable';
 import hotkeys from './hotkeys';
+import Queue from './Queue';
+import isDicomUid from './isDicomUid';
+import resolveObjectPath from './resolveObjectPath';
+import * as hierarchicalListUtils from './hierarchicalListUtils';
+import * as progressTrackingUtils from './progressTrackingUtils';
 
 const utils = {
   guid,
@@ -26,8 +32,14 @@ const utils = {
   DicomLoaderService,
   urlUtil,
   loadAndCacheDerivedDisplaySets,
+  makeDeferred,
   makeCancelable,
   hotkeys,
+  Queue,
+  isDicomUid,
+  resolveObjectPath,
+  hierarchicalListUtils,
+  progressTrackingUtils,
 };
 
 export {
@@ -43,8 +55,14 @@ export {
   DicomLoaderService,
   urlUtil,
   loadAndCacheDerivedDisplaySets,
+  makeDeferred,
   makeCancelable,
   hotkeys,
+  Queue,
+  isDicomUid,
+  resolveObjectPath,
+  hierarchicalListUtils,
+  progressTrackingUtils,
 };
 
 export default utils;

platform/core/src/utils/index.test.js

@@ -15,8 +15,14 @@ describe('Top level exports', () => {
       'loadAndCacheDerivedDisplaySets',
       'DicomLoaderService',
       'urlUtil',
+      'makeDeferred',
       'makeCancelable',
       'hotkeys',
+      'Queue',
+      'isDicomUid',
+      'resolveObjectPath',
+      'hierarchicalListUtils',
+      'progressTrackingUtils',
     ].sort();
 
     const exports = Object.keys(utils.default).sort();

platform/core/src/utils/isDicomUid.js

@@ -0,0 +1,4 @@
+export default function isDicomUid(subject) {
+  const regex = /^\d+(?:\.\d+)*$/;
+  return typeof subject === 'string' && regex.test(subject.trim());
+}

platform/core/src/utils/isDicomUid.test.js

@@ -0,0 +1,16 @@
+import isDicomUid from './isDicomUid';
+
+describe('isDicomUid', function() {
+  it('should return true for valid DICOM UIDs', function() {
+    expect(isDicomUid('1')).toBe(true);
+    expect(isDicomUid('1.2')).toBe(true);
+    expect(isDicomUid('1.2.3')).toBe(true);
+    expect(isDicomUid('1.2.3.4')).toBe(true);
+  });
+  it('should return false for invalid DICOM UIDs', function() {
+    expect(isDicomUid('x')).toBe(false);
+    expect(isDicomUid('1.')).toBe(false);
+    expect(isDicomUid('1. 2')).toBe(false);
+    expect(isDicomUid('1.2.n.4')).toBe(false);
+  });
+});

platform/core/src/utils/makeDeferred.js

@@ -0,0 +1,7 @@
+export default function makeDeferred() {
+  let reject, resolve, promise = new Promise(function (res, rej) {
+    resolve = res;
+    reject = rej;
+  });
+  return Object.freeze({ promise, resolve, reject });
+}

platform/core/src/utils/makeDeferred.test.js

@@ -0,0 +1,14 @@
+import makeDeferred from './makeDeferred';
+
+describe('makeDeferred', () => {
+  it('should provide a promise to be resolved externally', () => {
+    const deferred = makeDeferred();
+    setTimeout(() => void deferred.resolve('Yay!'));
+    return deferred.promise.then(result => void expect(result).toBe('Yay!'));
+  });
+  it('should provide a promise to be rejected externally', () => {
+    const deferred = makeDeferred();
+    setTimeout(() => void deferred.reject('Oops...'));
+    return deferred.promise.catch(error => void expect(error).toBe('Oops...'));
+  });
+});

platform/core/src/utils/progressTrackingUtils.js

@@ -0,0 +1,336 @@
+import makeDeferred from './makeDeferred';
+
+/**
+ * Constants
+ */
+
+const TYPE = Symbol('Type');
+const TASK = Symbol('Task');
+const LIST = Symbol('List');
+
+/**
+ * Public Methods
+ */
+
+/**
+ * Creates an instance of a task list
+ * @returns {Object} A task list object
+ */
+function createList() {
+  return objectWithType(LIST, {
+    head: null,
+    named: Object.create(null),
+    observers: [],
+  });
+}
+
+/**
+ * Checks if the given argument is a List instance
+ * @param {any} subject The value to be tested
+ * @returns {boolean} true if a valid List instance is given, false otherwise
+ */
+function isList(subject) {
+  return isOfType(LIST, subject);
+}
+
+/**
+ * Creates an instance of a task
+ * @param {Object} list The List instance related to this task
+ * @param {Object} next The next Task instance to link to
+ * @returns {Object} A task object
+ */
+function createTask(list, next) {
+  return objectWithType(TASK, {
+    list: isList(list) ? list : null,
+    next: isTask(next) ? next : null,
+    failed: false,
+    awaiting: null,
+    progress: 0.0,
+  });
+}
+
+/**
+ * Checks if the given argument is a Task instance
+ * @param {any} subject The value to be tested
+ * @returns {boolean} true if a valid Task instance is given, false otherwise
+ */
+function isTask(subject) {
+  return isOfType(TASK, subject);
+}
+
+/**
+ * Appends a new Task to the given List instance and notifies the list observers
+ * @param {Object} list A List instance
+ * @returns {Object} The new Task instance appended to the List or null if the
+ *  given List instanc is not valid
+ */
+function increaseList(list) {
+  if (isList(list)) {
+    const task = createTask(list, list.head);
+    list.head = task;
+    notify(list, getOverallProgress(list));
+    return task;
+  }
+  return null;
+}
+
+/**
+ * Updates the internal progress value of the given Task instance and notifies
+ * the observers of the associated list.
+ * @param {Object} task The Task instance to be updated
+ * @param {number} value A number between 0 (inclusive) and 1 (exclusive)
+ *  indicating the progress of the task;
+ * @returns {void} Nothing is returned
+ */
+function update(task, value) {
+  if (isTask(task) && isValidProgress(value) && value < 1.0) {
+    if (task.progress !== value) {
+      task.progress = value;
+      if (isList(task.list)) {
+        notify(task.list, getOverallProgress(task.list));
+      }
+    }
+  }
+}
+
+/**
+ * Sets a Task instance as finished (progress = 1.0), freezes it in order to
+ * prevent further modifications and notifies the observers of the associated
+ * list.
+ * @param {Object} task The Task instance to be finalized
+ * @returns {void} Nothing is returned
+ */
+function finish(task) {
+  if (isTask(task)) {
+    task.progress = 1.0;
+    task.awaiting = null;
+    Object.freeze(task);
+    if (isList(task.list)) {
+      notify(task.list, getOverallProgress(task.list));
+    }
+  }
+}
+
+/**
+ * Generate a summarized snapshot of the current status of the given task List
+ * @param {Object} list The List instance to be scanned
+ * @returns {Object} An obeject representing the summarized status of the list
+ */
+function getOverallProgress(list) {
+  const status = createStatus();
+  if (isList(list)) {
+    let task = list.head;
+    while (isTask(task)) {
+      status.total++;
+      if (isValidProgress(task.progress)) {
+        status.partial += task.progress;
+        if (task.progress === 1.0 && task.failed) status.failures++;
+      }
+      task = task.next;
+    }
+  }
+  if (status.total > 0) {
+    status.progress = status.partial / status.total;
+  }
+  return Object.freeze(status);
+}
+
+/**
+ * Adds a Task instance to the given list that waits on a given "thenable". When
+ * the thenable resolves the "finish" method is called on the newly created
+ * instance thus notifying the observers of the list.
+ * @param {Object} list The List instance to which the new task will be added
+ * @param {Object|Promise} thenable The thenable to be waited on
+ * @returns {Object} A reference to the newly created Task;
+ */
+function waitOn(list, thenable) {
+  const task = increaseList(list);
+  if (isTask(task)) {
+    task.awaiting = Promise.resolve(thenable).then(
+      function() {
+        finish(task);
+      },
+      function() {
+        task.failed = true;
+        finish(task);
+      }
+    );
+    return task;
+  }
+  return null;
+}
+
+/**
+ * Adds a Task instance to the given list using a deferred (a Promise that can
+ * be externally resolved) notifying the observers of the list.
+ * @param {Object} list The List instance to which the new task will be added
+ * @returns {Object} An object with references to the created deferred and task
+ */
+function addDeferred(list) {
+  const deferred = makeDeferred();
+  const task = waitOn(list, deferred.promise);
+  return Object.freeze({
+    deferred,
+    task,
+  });
+}
+
+/**
+ * Assigns a name to a specific task of the list
+ * @param {Object} list The List instance whose task will be named
+ * @param {Object} task The specified Task instance
+ * @param {string} name The name of the task
+ * @returns {boolean} Returns true on success, false otherwise
+ */
+function setTaskName(list, task, name) {
+  if (
+    contains(list, task) &&
+    list.named !== null &&
+    typeof list.named === 'object' &&
+    typeof name === 'string'
+  ) {
+    list.named[name] = task;
+    return true;
+  }
+  return false;
+}
+
+/**
+ * Retrieves a task by name
+ * @param {Object} list The List instance whose task will be retrieved
+ * @param {string} name The name of the task to be retrieved
+ * @returns {Object} The Task instance or null if not found
+ */
+function getTaskByName(list, name) {
+  if (
+    isList(list) &&
+    list.named !== null &&
+    typeof list.named === 'object' &&
+    typeof name === 'string'
+  ) {
+    const task = list.named[name];
+    if (isTask(task)) {
+      return task;
+    }
+  }
+  return null;
+}
+
+/**
+ * Adds an observer (callback function) to a given List instance
+ * @param {Object} list The List instance to which the observer will be appended
+ * @param {Function} observer The observer (function) that will be executed
+ *  every time a change happens within the list
+ * @returns {boolean} Returns true on success and false otherewise
+ */
+function addObserver(list, observer) {
+  if (
+    isList(list) &&
+    Array.isArray(list.observers) &&
+    typeof observer === 'function'
+  ) {
+    list.observers.push(observer);
+    return true;
+  }
+  return false;
+}
+
+/**
+ * Removes an observer (callback function) from a given List instance
+ * @param {Object} list The instance List from which the observer will removed
+ * @param {Function} observer The observer function to be removed
+ * @returns {boolean} Returns true on success and false otherewise
+ */
+function removeObserver(list, observer) {
+  if (
+    isList(list) &&
+    Array.isArray(list.observers) &&
+    list.observers.length > 0
+  ) {
+    const index = list.observers.indexOf(observer);
+    if (index >= 0) {
+      list.observers.splice(index, 1);
+      return true;
+    }
+  }
+  return false;
+}
+
+/**
+ * Utils
+ */
+
+function createStatus() {
+  return Object.seal({
+    total: 0,
+    partial: 0.0,
+    progress: 0.0,
+    failures: 0,
+  });
+}
+
+function objectWithType(type, object) {
+  return Object.seal(Object.defineProperty(object, TYPE, { value: type }));
+}
+
+function isOfType(type, subject) {
+  return (
+    subject !== null && typeof subject === 'object' && subject[TYPE] === type
+  );
+}
+
+function isValidProgress(value) {
+  return typeof value === 'number' && value >= 0.0 && value <= 1.0;
+}
+
+function contains(list, task) {
+  if (isList(list) && isTask(task)) {
+    let item = list.head;
+    while (isTask(item)) {
+      if (item === task) {
+        return true;
+      }
+      item = item.next;
+    }
+  }
+  return false;
+}
+
+function notify(list, data) {
+  if (
+    isList(list) &&
+    Array.isArray(list.observers) &&
+    list.observers.length > 0
+  ) {
+    list.observers.slice().forEach(function(observer) {
+      if (typeof observer === 'function') {
+        try {
+          observer(data, list);
+        } catch (e) {
+          /* Oops! */
+        }
+      }
+    });
+  }
+}
+
+/**
+ * Exports
+ */
+
+export {
+  createList,
+  isList,
+  createTask,
+  isTask,
+  increaseList,
+  update,
+  finish,
+  getOverallProgress,
+  waitOn,
+  addDeferred,
+  setTaskName,
+  getTaskByName,
+  addObserver,
+  removeObserver,
+};

platform/core/src/utils/progressTrackingUtils.test.js

@@ -0,0 +1,175 @@
+import * as utils from './progressTrackingUtils';
+
+describe('progressTrackingUtils', () => {
+  describe('Creation of lists of tasks to be tracked', () => {
+    it('should support creation of task lists', () => {
+      expect(utils.createList()).toBeInstanceOf(Object);
+    });
+    it('should support validation of task lists', () => {
+      const list = utils.createList();
+      expect(utils.isList(list)).toBe(true);
+      expect(utils.isList(JSON.parse(JSON.stringify(list)))).toBe(false);
+    });
+  });
+
+  describe('Usage of lists of tasks to be tracked', () => {
+    let context;
+
+    // Mock for download
+    function fakeRequest(callback) {
+      return new Promise(resolve => {
+        let progress = 0.0;
+        setTimeout(function step() {
+          if (progress < 1.0) {
+            progress += 1 / 4;
+            callback(progress);
+            setTimeout(step);
+            return;
+          }
+          resolve(true);
+        });
+      });
+    }
+
+    beforeEach(() => {
+      const list = utils.createList();
+      const observer = jest.fn();
+      utils.addObserver(list, observer);
+      context = { list, observer };
+    });
+
+    it('should call observer twice for each task', () => {
+      const { list, observer } = context;
+      const promises = [
+        Promise.resolve('A'),
+        Promise.resolve('B'),
+        Promise.resolve('C'),
+      ];
+      promises.forEach(promise => void utils.waitOn(list, promise));
+      return Promise.all(promises).then(() => {
+        expect(observer).toBeCalledTimes(6);
+        [
+          {
+            failures: 0,
+            partial: 0,
+            progress: 0,
+            total: 1,
+          },
+          {
+            failures: 0,
+            partial: 0,
+            progress: 0,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 0,
+            progress: 0,
+            total: 3,
+          },
+          {
+            failures: 0,
+            partial: 1.0,
+            progress: 1 / 3,
+            total: 3,
+          },
+          {
+            failures: 0,
+            partial: 2.0,
+            progress: 2 / 3,
+            total: 3,
+          },
+          {
+            failures: 0,
+            partial: 3.0,
+            progress: 1.0,
+            total: 3,
+          },
+        ].forEach((item, i) => {
+          const result = expect.objectContaining(item);
+          expect(observer).nthCalledWith(i + 1, result, list);
+        });
+        expect(utils.getOverallProgress(list)).toStrictEqual({
+          failures: 0,
+          partial: 3.0,
+          progress: 1.0,
+          total: 3,
+        });
+      });
+    });
+
+    it('should support tasks with internal progress updates', () => {
+      const { list, observer } = context;
+      const download = utils.addDeferred(list);
+      const processing = download.deferred.promise.then(result => result);
+      const update = jest.fn(p => void utils.update(download.task, p));
+      download.deferred.resolve(fakeRequest(update));
+      utils.waitOn(list, processing);
+      return processing.then(() => {
+        expect(update).toBeCalledTimes(4);
+        [0.25, 0.5, 0.75, 1.0].forEach(
+          (value, i) => void expect(update).nthCalledWith(i + 1, value)
+        );
+        expect(observer).toBeCalledTimes(7);
+        [
+          {
+            failures: 0,
+            partial: 0,
+            progress: 0,
+            total: 1,
+          },
+          {
+            failures: 0,
+            partial: 0,
+            progress: 0,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 0.25,
+            progress: 0.125,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 0.5,
+            progress: 0.25,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 0.75,
+            progress: 0.375,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 1.0,
+            progress: 0.5,
+            total: 2,
+          },
+          {
+            failures: 0,
+            partial: 2.0,
+            progress: 1.0,
+            total: 2,
+          },
+        ].forEach((item, i) => {
+          const result = expect.objectContaining(item);
+          expect(observer).nthCalledWith(i + 1, result, list);
+        });
+      });
+    });
+  });
+
+  describe('Naming of specific tasks', () => {
+    it('should support naming specific tasks', () => {
+      const list = utils.createList();
+      const tasks = [utils.increaseList(list), utils.increaseList(list)];
+      expect(utils.setTaskName(list, tasks[0], 'firstTask')).toBe(true);
+      expect(utils.setTaskName(list, tasks[1], 'secondTask')).toBe(true);
+      expect(utils.getTaskByName(list, 'secondTask')).toBe(tasks[1]);
+      expect(utils.getTaskByName(list, 'firstTask')).toBe(tasks[0]);
+    });
+  });
+});

platform/core/src/utils/resolveObjectPath.js

@@ -0,0 +1,17 @@
+export default function resolveObjectPath(root, path, defaultValue) {
+  if (root !== null && typeof root === 'object' && typeof path === 'string') {
+    let value,
+      separator = path.indexOf('.');
+    if (separator >= 0) {
+      return resolveObjectPath(
+        root[path.slice(0, separator)],
+        path.slice(separator + 1, path.length),
+        defaultValue
+      );
+    }
+    value = root[path];
+    return value === undefined && defaultValue !== undefined
+      ? defaultValue
+      : value;
+  }
+}

platform/core/src/utils/resolveObjectPath.test.js

@@ -0,0 +1,35 @@
+import resolveObjectPath from './resolveObjectPath';
+
+describe('resolveObjectPath', function() {
+  let config;
+
+  beforeEach(function() {
+    config = {
+      active: {
+        user: {
+          name: {
+            first: 'John',
+            last: 'Doe',
+          },
+        },
+        servers: [
+          {
+            ipv4: '10.0.0.1',
+          },
+        ],
+      },
+    };
+  });
+
+  it('should safely return deeply nested values from an object', function() {
+    expect(resolveObjectPath(config, 'active.user.name.first')).toBe('John');
+    expect(resolveObjectPath(config, 'active.user.name.last')).toBe('Doe');
+    expect(resolveObjectPath(config, 'active.servers.0.ipv4')).toBe('10.0.0.1');
+  });
+
+  it('should silently return undefined when intermediate values are not valid objects', function() {
+    expect(resolveObjectPath(config, 'active.usr.name.first')).toBeUndefined();
+    expect(resolveObjectPath(config, 'active.name.last')).toBeUndefined();
+    expect(resolveObjectPath(config, 'active.servers.7.ipv4')).toBeUndefined();
+  });
+});

platform/viewer/package.json

@@ -56,6 +56,7 @@
     "@ohif/extension-dicom-rt": "^0.0.2",
     "@ohif/extension-dicom-segmentation": "^0.1.2",
     "@ohif/extension-lesion-tracker": "^0.2.0",
+    "@ohif/extension-dicom-p10-downloader": "^0.0.1",
     "@ohif/extension-vtk": "^1.3.11",
     "@ohif/i18n": "^0.52.8",
     "@ohif/ui": "^1.4.3",

platform/viewer/src/index.js

@@ -29,6 +29,7 @@ import OHIFDicomSegmentationExtension from '@ohif/extension-dicom-segmentation';
 import OHIFDicomRtExtension from '@ohif/extension-dicom-rt';
 import OHIFDicomMicroscopyExtension from '@ohif/extension-dicom-microscopy';
 import OHIFDicomPDFExtension from '@ohif/extension-dicom-pdf';
+import OHIFDicomP10DownloaderExtension from '@ohif/extension-dicom-p10-downloader';
 
 /*
  * Default Settings
@@ -48,6 +49,7 @@ const appProps = {
     OHIFDicomPDFExtension,
     OHIFDicomSegmentationExtension,
     OHIFDicomRtExtension,
+    OHIFDicomP10DownloaderExtension,
   ],
 };