feat(StatusInput): add support for asynchronous validators

Allows asynchronous validation, with the ability to track the validated value for use in the StatusInput as a value that is separate from the entered text.

Async operations are debounced internally to the StatusAsyncValidator.

- `validate`: the input value to this function is the value sent to `asyncComplete`, which must be called by the validator. Return true when the value from the async operation is valid.
- `asyncComplete`: signal to be called by the validator after the async operation has completed. It should contain the value returned by the async operation that should be validated in `validate`.
- `validatedValue`: This is the valid value returned from the async operation. It it tracked separately so that the input text on the `StatusInput` can remain as entered by the user. Use this property and the `onValidatedValueChanged` signal handler for the “real” value to be used by other components.

Closes #395

ui/StatusQ/src/StatusQ/Controls/StatusBaseInput.qml

@@ -47,6 +47,7 @@ Item {
     property bool valid: true
     property bool pristine: true
     property bool dirty: false
+    property bool pending: false
     property bool leftIcon: true
 
     property StatusIconSettings icon: StatusIconSettings {

ui/StatusQ/src/StatusQ/Controls/StatusInput.qml

@@ -1,6 +1,7 @@
 import QtQuick 2.14
 
 import StatusQ.Core 0.1
+import StatusQ.Core.Backpressure 1.0
 import StatusQ.Core.Theme 0.1
 import StatusQ.Controls 0.1
 import StatusQ.Controls.Validators 0.1
@@ -24,6 +25,7 @@ Item {
 
     property alias input: statusBaseInput
     property alias valid: statusBaseInput.valid
+    property alias pending: statusBaseInput.pending
     property alias text: statusBaseInput.text
     property string label: ""
     property string secondaryLabel: ""
@@ -32,19 +34,25 @@ Item {
     property real leftPadding: 16
     property real rightPadding: 16
     property list<StatusValidator> validators
+    property list<StatusAsyncValidator> asyncValidators
     property int validationMode: StatusInput.ValidationMode.OnlyWhenDirty
+    property string validatedValue
+
+    property var pendingValidators: []
+
     enum ValidationMode {
         OnlyWhenDirty, // validates input only after it has become dirty
         Always // validates input even before it has become dirty
     }
 
     property var errors: ({})
+    property var asyncErrors: ({})
 
     function reset() {
         statusBaseInput.valid = false
         statusBaseInput.pristine = true
         statusBaseInput.text = ""
-        errorMessage = ""
+        root.errorMessage = ""
     }
 
     function validate() {
@@ -78,6 +86,43 @@ Item {
                 }
             }
         }
+
+        if (asyncValidators.length && !Object.values(errors).length) {
+            for (let idx in asyncValidators) {
+                let asyncValidator = asyncValidators[idx]
+                asyncValidator.validationComplete.connect(function (value, valid) {
+                    updateAsyncValidity(asyncValidator.name, value, valid)
+                })
+                root.pending = true
+                pendingValidators.push(asyncValidator.name)
+                asyncValidator.asyncOperationInternal(statusBaseInput.text)
+            }
+        } else if (!asyncValidators.length && !Object.values(errors).length) {
+            root.validatedValue = root.text
+        }
+    }
+
+    function updateAsyncValidity(validatorName, value, result) {
+        if (!asyncErrors) {
+            asyncErrors = {}
+        }
+
+        if (typeof result === "boolean" && result) {
+            if (asyncErrors[validatorName] !== undefined) {
+                delete asyncErrors[validatorName]
+            }
+            errorMessage.text = ""
+            root.validatedValue = value
+        } else {
+            asyncErrors[validatorName] = result
+            for (let idx in asyncValidators) {
+                errorMessage.text = asyncValidators[idx].errorMessage || root.errorMessage
+                break;
+            }
+        }
+        pendingValidators = pendingValidators.filter(v => v !== validatorName)
+        root.pending = pendingValidators.length > 0
+        root.valid = Object.values(asyncErrors).length == 0
     }
 
     Component.onCompleted: validate()

ui/StatusQ/src/StatusQ/Controls/Validators/StatusAsyncEnsValidator.qml

@@ -0,0 +1,15 @@
+import StatusQ.Controls 0.1
+import StatusQ.Core.Utils 0.1
+
+StatusAsyncValidator {
+    readonly property string uuid: Utils.uuid()
+
+    name: "asyncEns"
+
+    errorMessage: "ENS name could not be resolved in to an address"
+
+    validate: function (asyncResult) {
+        return Utils.isValidAddress(asyncResult)
+    }
+}
+

ui/StatusQ/src/StatusQ/Controls/Validators/StatusAsyncValidator.qml

@@ -0,0 +1,32 @@
+import QtQuick 2.13
+import StatusQ.Core.Backpressure 1.0
+
+Item {
+    id: statusAsyncValidator
+
+    property string name: ""
+    property string errorMessage: "invalid input"
+    signal asyncComplete(var result)
+    signal validationComplete(var value, bool valid)
+
+    // Prevents firing async operations before time has elapsed. If multiple
+    // calls are attempted, the timer resets each time.
+    property int debounceTime: 600
+
+    property var validate: function (value) {
+        return value === "async result"
+    }
+    property var asyncOperation: function(inputText) {
+        // Do something with the input text. Once completed, fire the
+        // `asyncComplete` signal
+        asyncComplete("async result")
+    }
+
+    readonly property var asyncOperationInternal: Backpressure.debounce(statusAsyncValidator, debounceTime, function(inputText) {
+        statusAsyncValidator.asyncOperation(inputText)
+    })
+
+    onAsyncComplete: function(result) {
+        validationComplete(result, validate(result))
+    }
+}

ui/StatusQ/src/StatusQ/Controls/Validators/StatusValidator.qml

@@ -1,4 +1,5 @@
 import QtQuick 2.13
+import StatusQ.Controls 0.1
 
 QtObject {
     id: statusValidator

ui/StatusQ/src/StatusQ/Controls/Validators/qmldir

@@ -2,6 +2,8 @@ module StatusQ.Controls.Validators
 
 StatusAddressValidator 0.1 StatusAddressValidator.qml
 StatusAddressOrEnsValidator 0.1 StatusAddressOrEnsValidator.qml
-StatusValidator 0.1 StatusValidator.qml
+StatusAsyncValidator 0.1 StatusAsyncValidator.qml
+StatusAsyncEnsValidator 0.1 StatusAsyncEnsValidator.qml
 StatusMinLengthValidator 0.1 StatusMinLengthValidator.qml
 StatusMaxLengthValidator 0.1 StatusMaxLengthValidator.qml
+StatusValidator 0.1 StatusValidator.qml

ui/StatusQ/src/StatusQ/Core/Backpressure/Backpressure.qml

@@ -0,0 +1,123 @@
+pragma Singleton
+import QtQuick 2.0
+
+Item {
+
+    id: backpressure
+
+    property var _timers: ({})
+    property int _nextId: 0
+
+    function setTimeout(owner, timeout, callback) {
+        var tid = ++_nextId;
+
+        var cleanup = function() {
+            if (tid !== null) {
+                clearTimeout(tid);
+            }
+        }
+
+        if (!owner) {
+            owner = backpressure;
+        }
+
+        owner.Component.destruction.connect(cleanup);
+
+        var obj = Qt.createQmlObject('import QtQuick 2.0; Timer {running: false; repeat: false; interval: ' + timeout + '}', backpressure, "setTimeout");
+        obj.triggered.connect(function() {
+            callback();
+            obj.destroy();
+            owner.Component.destruction.disconnect(cleanup);
+            delete _timers[tid];
+        });
+        obj.running = true;
+        _timers[tid] = obj;
+        return tid;
+    }
+
+    function clearTimeout(timerId) {
+        if (!_timers.hasOwnProperty(timerId)) {
+            return;
+        }
+        var timer = _timers[timerId];
+        timer.stop();
+        timer.destroy();
+        delete _timers[timerId];
+    }
+
+    function oneInTime(owner, duration, callback) {
+        var pending = false;
+        var timerId = null;
+
+        return function() {
+            if (pending) {
+                return;
+            }
+            pending = true;
+            var args = arguments;
+            callback.apply(null, args);
+            timerId = setTimeout(owner, duration , function() {
+                pending = false;
+            }, duration);
+        }
+    }
+
+    function promisedOneInTime(owner, callback) {
+        var q = priv.loadPromiseLib();
+        var promise = null;
+
+        return function() {
+            var args = arguments;
+            if (promise !== null) {
+                return q.rejected();
+            }
+
+            promise = q.promise(function(fulfill, reject) {
+                fulfill(callback.apply(null, args));
+            });
+
+            promise.then(function() {
+                promise = null;
+            }, function() {
+                promise = null;
+            });
+            return promise;
+        };
+    }
+
+    function debounce(owner, duration, callback) {
+        var timerId = null;
+
+        return function() {
+            var args = arguments;
+
+            if (timerId !== null) {
+                clearTimeout(timerId);
+            }
+
+            timerId = setTimeout(owner, duration, function() {
+                timerId = null;
+                callback.apply(null, args);
+            });
+        }
+    }    
+
+    QtObject {
+        id: priv
+        property var q: null
+
+        function loadPromiseLib() {
+            if (q !== null) {
+                return q.q;
+            }
+
+            q = Qt.createQmlObject('import QtQuick 2.0; import QuickPromise 1.0; Item { property var q: Q;}', backpressure);
+            if (q.hasOwnProperty("qmlErrors")) {
+                console.error("Backpressure: Failed to load QuickPromise. Please check your installation.");
+            }
+            return q.q;
+        }
+
+    }
+
+}

ui/StatusQ/src/StatusQ/Core/Backpressure/LICENSE

@@ -0,0 +1,201 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright {yyyy} {name of copyright owner}
+
+   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.

ui/StatusQ/src/StatusQ/Core/Backpressure/README.md

@@ -0,0 +1,80 @@
+[![Build Status](https://www.travis-ci.org/e-fever/backpressure.svg?branch=master)](https://www.travis-ci.org/e-fever/backpressure)
+[![Build status](https://ci.appveyor.com/api/projects/status/knt6r7gra9dm0oui?svg=true)](https://ci.appveyor.com/project/benlau/backpressure)
+
+Backpressure
+============
+
+Backpressure happens on a stream of data where you are not fast enough to process. 
+This library is designed to provide a few mechanism to handle it.
+
+Installation
+============
+
+    qpm install net.efever.backpressure
+    
+    
+API
+===
+
+```
+import Backpressure 1.0
+```
+
+
+**Backpressure.oneInTime(owner, duration, callback)**
+
+It will create a wrapper function of the callback. Whatever you have invoked the wrapper function, it will execute the callback immediately. Then it will be blocked within duration period. It could prevent to process the same event twice within the duration period.
+
+Example:
+```
+
+Item {
+  id : item
+  property var processClick : Backpressure.oneInTime(item, 500, function(value) { 
+    /* Callback */ 
+  });
+
+  MouseArea {
+    onClicked: {
+       processClick(value);
+    }
+  }
+
+}
+```
+
+If the owner is destroyed, the callback will no longer be able to access.
+
+**Backpressure.debounce(owner, duration, callback)**
+
+If will create a wrapper function of the callback. Whatever you have invoked the wrapper function, it won't execute the callback until the duration period finished. If user invoked the wrapper function again within the period, then the previous call will be dropped, and the timer is restarted.
+
+It will guarantee only the last function call and parameter will be passed to the callback.
+
+Reference: [ReactiveX - Debounce operator](http://reactivex.io/documentation/operators/debounce.html)
+
+**Backpressure.promisedOneInTime(owner, callback)**
+
+This function is similar to oneInTime that will create a wrapper of the callback. But it does not take a timeout value as an argument of the construction function.
+
+Instead, it will convert the return from the callback to a promise object. Then blocks successively calls until the promise is resolved/rejected.
+
+The wrapper function returns a promise represents the result of the callback. If that is blocked, it will simply a rejected promise.
+
+You must install QuickPromise in order to use this funciton.
+
+Example
+```
+
+var timeout = Backpressure.promisedOneInTime(anyItem, function(delay) {
+    return Q.promise(function(fulfill, reject) {
+        Q.setTimeout(function() {
+            fulfill();
+        }, delay);
+    });
+});
+
+var promise1 = timeout(1000); // Pending
+var promise2 = timeout(1000); // Rejected
+
+```

ui/StatusQ/src/StatusQ/Core/Backpressure/qmldir

@@ -0,0 +1,3 @@
+module StatusQ.Core.Backpressure
+
+singleton Backpressure 1.0 Backpressure.qml

ui/StatusQ/src/StatusQ/Core/Utils/Utils.qml

@@ -26,6 +26,10 @@ QtObject {
         const isDomain = /(?:(?:(?<thld>[\w\-]*)(?:\.))?(?<sld>[\w\-]*))\.(?<tld>[\w\-]*)/.test(inputValue)
         return isEmail || isDomain || (inputValue.startsWith("@") && inputValue.length > 1)
     }
+
+    function uuid() {
+        return Date.now().toString(36) + Math.random().toString(36).substr(2, 5)
+    }
 }