388 lines
16 KiB
JavaScript
388 lines
16 KiB
JavaScript
/* eslint-disable class-methods-use-this */
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import { dedupeMixin } from '@lion/core';
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import { Unparseable } from '@lion/validate';
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// For a future breaking release:
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// - do not allow the private `.formattedValue` as property that can be set to
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// trigger a computation loop.
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// - do not fire events for those private and protected concepts
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// - simplify _calculateValues: recursive trigger lock can be omitted, since need for connecting
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// the loop via sync observers is not needed anymore.
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// - consider `formatOn` as an overridable function, by default something like:
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// `(!__isHandlingUserInput || !hasError) && !focused`
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// This would allow for more advanced scenarios, like formatting an input whenever it becomes valid.
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// This would make formattedValue as a concept obsolete, since for maximum flexibility, the
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// formattedValue condition needs to be evaluated right before syncing back to the view
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/**
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* @desc Designed to be applied on top of a LionField.
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* To understand all concepts within the Mixin, please consult the flow diagram in the
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* documentation.
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*
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* ## Flows
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* FormatMixin supports these two main flows:
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* [1] Application Developer sets `.modelValue`:
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* Flow: `.modelValue` (formatter) -> `.formattedValue` -> `._inputNode.value`
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* (serializer) -> `.serializedValue`
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* [2] End user interacts with field:
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* Flow: `@user-input-changed` (parser) -> `.modelValue` (formatter) -> `.formattedValue` - (debounce till reflect condition (formatOn) is met) -> `._inputNode.value`
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* (serializer) -> `.serializedValue`
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*
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* For backwards compatibility with the platform, we also support `.value` as an api. In that case
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* the flow will be like [2], without the debounce.
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*
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* ## Difference between value, viewValue and formattedValue
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* A viewValue is a concept rather than a property. To be compatible with the platform api, the
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* property for the concept of viewValue is thus called `.value`.
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* When reading code and docs, one should be aware that the term viewValue is mostly used, but the
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* terms can be used interchangeably.
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* The `.formattedValue` should be seen as the 'scheduled' viewValue. It is computed realtime and
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* stores the output of formatter. It will replace viewValue. once condition `formatOn` is met.
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* Another difference is that formattedValue lives on `LionField`, whereas viewValue is shared
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* across `LionField` and `._inputNode`.
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*
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* For restoring serialized values fetched from a server, we could consider one extra flow:
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* [3] Application Developer sets `.serializedValue`:
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* Flow: serializedValue (deserializer) -> `.modelValue` (formatter) -> `.formattedValue` -> `._inputNode.value`
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*/
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export const FormatMixin = dedupeMixin(
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superclass =>
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// eslint-disable-next-line no-unused-vars, no-shadow
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class FormatMixin extends superclass {
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static get properties() {
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return {
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/**
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* The model value is the result of the parser function(when available).
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* It should be considered as the internal value used for validation and reasoning/logic.
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* The model value is 'ready for consumption' by the outside world (think of a Date
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* object or a float). The modelValue can(and is recommended to) be used as both input
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* value and output value of the `LionField`.
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*
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* Examples:
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* - For a date input: a String '20/01/1999' will be converted to new Date('1999/01/20')
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* - For a number input: a formatted String '1.234,56' will be converted to a Number:
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* 1234.56
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*/
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modelValue: {
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type: Object,
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},
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/**
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* The view value is the result of the formatter function (when available).
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* The result will be stored in the native _inputNode (usually an input[type=text]).
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*
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* Examples:
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* - For a date input, this would be '20/01/1999' (dependent on locale).
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* - For a number input, this could be '1,234.56' (a String representation of modelValue
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* 1234.56)
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*
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* @private
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*/
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formattedValue: {
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type: String,
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},
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/**
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* The serialized version of the model value.
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* This value exists for maximal compatibility with the platform API.
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* The serialized value can be an interface in context where data binding is not
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* supported and a serialized string needs to be set.
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*
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* Examples:
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* - For a date input, this would be the iso format of a date, e.g. '1999-01-20'.
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* - For a number input this would be the String representation of a float ('1234.56'
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* instead of 1234.56)
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*
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* When no parser is available, the value is usually the same as the formattedValue
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* (being _inputNode.value)
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*
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*/
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serializedValue: {
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type: String,
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},
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/**
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* Event that will trigger formatting (more precise, visual update of the view, so the
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* user sees the formatted value)
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* Default: 'change'
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*/
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formatOn: {
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type: String,
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},
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/**
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* Configuration object that will be available inside the formatter function
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*/
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formatOptions: {
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type: Object,
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},
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};
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}
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_requestUpdate(name, oldVal) {
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super._requestUpdate(name, oldVal);
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if (name === 'modelValue' && this.modelValue !== oldVal) {
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this._onModelValueChanged({ modelValue: this.modelValue }, { modelValue: oldVal });
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}
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if (name === 'serializedValue' && this.serializedValue !== oldVal) {
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this._calculateValues({ source: 'serialized' });
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}
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if (name === 'formattedValue' && this.formattedValue !== oldVal) {
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this._calculateValues({ source: 'formatted' });
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}
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}
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/**
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* Converts formattedValue to modelValue
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* For instance, a localized date to a Date Object
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* @param {String} value - formattedValue: the formatted value inside <input>
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* @returns {Object} modelValue
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*/
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parser(v) {
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return v;
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}
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/**
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* Converts modelValue to formattedValue (formattedValue will be synced with
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* `._inputNode.value`)
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* For instance, a Date object to a localized date.
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* @param {Object} value - modelValue: can be an Object, Number, String depending on the
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* input type(date, number, email etc)
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* @returns {String} formattedValue
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*/
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formatter(v) {
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return v;
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}
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/**
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* Converts `.modelValue` to `.serializedValue`
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* For instance, a Date object to an iso formatted date string
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* @param {Object} value - modelValue: can be an Object, Number, String depending on the
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* input type(date, number, email etc)
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* @returns {String} serializedValue
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*/
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serializer(v) {
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return v;
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}
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/**
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* Converts `LionField.value` to `.modelValue`
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* For instance, an iso formatted date string to a Date object
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* @param {Object} value - modelValue: can be an Object, Number, String depending on the
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* input type(date, number, email etc)
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* @returns {Object} modelValue
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*/
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deserializer(v) {
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return v;
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}
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/**
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* Responsible for storing all representations(modelValue, serializedValue, formattedValue
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* and value) of the input value. Prevents infinite loops, so all value observers can be
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* treated like they will only be called once, without indirectly calling other observers.
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* (in fact, some are called twice, but the __preventRecursiveTrigger lock prevents the
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* second call from having effect).
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*
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* @param {string} source - the type of value that triggered this method. It should not be
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* set again, so that its observer won't be triggered. Can be:
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* 'model'|'formatted'|'serialized'.
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*/
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_calculateValues({ source } = {}) {
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if (this.__preventRecursiveTrigger) return; // prevent infinite loops
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this.__preventRecursiveTrigger = true;
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if (source !== 'model') {
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if (source === 'serialized') {
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this.modelValue = this.deserializer(this.serializedValue);
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} else if (source === 'formatted') {
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this.modelValue = this.__callParser();
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}
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}
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if (source !== 'formatted') {
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this.formattedValue = this.__callFormatter();
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}
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if (source !== 'serialized') {
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this.serializedValue = this.serializer(this.modelValue);
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}
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this._reflectBackFormattedValueToUser();
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this.__preventRecursiveTrigger = false;
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}
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__callParser(value = this.formattedValue) {
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// A) check if we need to parse at all
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// A.1) The end user had no intention to parse
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if (value === '') {
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// Ideally, modelValue should be undefined for empty strings.
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// For backwards compatibility we return an empty string:
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// - it triggers validation for required validators (see ValidateMixin.validate())
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// - it can be expected by 3rd parties (for instance unit tests)
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// TODO: In a breaking refactor of the Validation System, this behavior can be corrected.
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return '';
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}
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// A.2) Handle edge cases We might have no view value yet, for instance because
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// _inputNode.value was not available yet
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if (typeof value !== 'string') {
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// This means there is nothing to find inside the view that can be of
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// interest to the Application Developer or needed to store for future
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// form state retrieval.
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return undefined;
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}
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// B) parse the view value
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// - if result:
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// return the successfully parsed viewValue
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// - if no result:
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// Apparently, the parser was not able to produce a satisfactory output for the desired
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// modelValue type, based on the current viewValue. Unparseable allows to restore all
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// states (for instance from a lost user session), since it saves the current viewValue.
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const result = this.parser(value, this.formatOptions);
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return result !== undefined ? result : new Unparseable(value);
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}
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__callFormatter() {
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// - Why check for this.hasError?
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// We only want to format values that are considered valid. For best UX,
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// we only 'reward' valid inputs.
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// - Why check for __isHandlingUserInput?
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// Downwards sync is prevented whenever we are in an `@user-input-changed` flow, [2].
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// If we are in a 'imperatively set `.modelValue`' flow, [1], we want to reflect back
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// the value, no matter what.
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// This means, whenever we are in hasError and modelValue is set
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// imperatively, we DO want to format a value (it is the only way to get meaningful
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// input into `._inputNode` with modelValue as input)
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if (
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this.__isHandlingUserInput &&
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this.hasFeedbackFor &&
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this.hasFeedbackFor.length &&
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this.hasFeedbackFor.includes('error') &&
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this._inputNode
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) {
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return this._inputNode ? this.value : undefined;
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}
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if (this.modelValue instanceof Unparseable) {
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// When the modelValue currently is unparseable, we need to sync back the supplied
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// viewValue. In flow [2], this should not be needed.
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// In flow [1] (we restore a previously stored modelValue) we should sync down, however.
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return this.modelValue.viewValue;
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}
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return this.formatter(this.modelValue, this.formatOptions);
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}
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/** Observer Handlers */
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_onModelValueChanged(...args) {
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this._calculateValues({ source: 'model' });
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this._dispatchModelValueChangedEvent(...args);
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}
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/**
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* This is wrapped in a distinct method, so that parents can control when the changed event
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* is fired. For objects, a deep comparison might be needed.
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*/
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_dispatchModelValueChangedEvent() {
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/** @event model-value-changed */
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this.dispatchEvent(
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new CustomEvent('model-value-changed', { bubbles: true, composed: true }),
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);
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}
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/**
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* Synchronization from `._inputNode.value` to `LionField` (flow [2])
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*/
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_syncValueUpwards() {
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// Downwards syncing should only happen for `LionField`.value changes from 'above'
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// This triggers _onModelValueChanged and connects user input to the
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// parsing/formatting/serializing loop
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this.modelValue = this.__callParser(this.value);
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}
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/**
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* Synchronization from `LionField.value` to `._inputNode.value`
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* - flow [1] will always be reflected back
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* - flow [2] will not be reflected back when this flow was triggered via
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* `@user-input-changed` (this will happen later, when `formatOn` condition is met)
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*/
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_reflectBackFormattedValueToUser() {
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if (this._reflectBackOn()) {
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// Text 'undefined' should not end up in <input>
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this.value = typeof this.formattedValue !== 'undefined' ? this.formattedValue : '';
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}
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}
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_reflectBackOn() {
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return !this.__isHandlingUserInput;
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}
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// This can be called whenever the view value should be updated. Dependent on component type
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// ("input" for <input> or "change" for <select>(mainly for IE)) a different event should be
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// used as source for the "user-input-changed" event (which can be seen as an abstraction
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// layer on top of other events (input, change, whatever))
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_proxyInputEvent() {
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this.dispatchEvent(
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new CustomEvent('user-input-changed', {
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bubbles: true,
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composed: true,
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}),
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);
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}
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_onUserInputChanged() {
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// Upwards syncing. Most properties are delegated right away, value is synced to
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// `LionField`, to be able to act on (imperatively set) value changes
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this.__isHandlingUserInput = true;
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this._syncValueUpwards();
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this.__isHandlingUserInput = false;
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}
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constructor() {
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super();
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this.formatOn = 'change';
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this.formatOptions = {};
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}
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connectedCallback() {
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super.connectedCallback();
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this._reflectBackFormattedValueToUser = this._reflectBackFormattedValueToUser.bind(this);
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this._reflectBackFormattedValueDebounced = () => {
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// Make sure this is fired after the change event of _inputNode, so that formattedValue
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// is guaranteed to be calculated
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setTimeout(this._reflectBackFormattedValueToUser);
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};
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this.addEventListener('user-input-changed', this._onUserInputChanged);
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// Connect the value found in <input> to the formatting/parsing/serializing loop as a
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// fallback mechanism. Assume the user uses the value property of the
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// `LionField`(recommended api) as the api (this is a downwards sync).
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// However, when no value is specified on `LionField`, have support for sync of the real
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// input to the `LionField` (upwards sync).
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if (typeof this.modelValue === 'undefined') {
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this._syncValueUpwards();
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}
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this._reflectBackFormattedValueToUser();
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if (this._inputNode) {
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this._inputNode.addEventListener(this.formatOn, this._reflectBackFormattedValueDebounced);
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this._inputNode.addEventListener('input', this._proxyInputEvent);
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}
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}
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disconnectedCallback() {
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super.disconnectedCallback();
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this.removeEventListener('user-input-changed', this._onUserInputChanged);
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if (this._inputNode) {
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this._inputNode.removeEventListener('input', this._proxyInputEvent);
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this._inputNode.removeEventListener(
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this.formatOn,
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this._reflectBackFormattedValueDebounced,
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);
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}
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}
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},
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);
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