FieldVisibilityEventHandler: Add class

This extracts code from internal lovullo repo rating-fw (originally
Client#_hideFields), 5d4019f1973f9271f4b1bd24ce1f55b56ccda09e.

* src/event/FieldVisibilityEventHandler.js: Add class.
* test/event/FieldVisibilityEventHandlerTest.js: Add test case.

src/event/FieldVisibilityEventHandler.js

@@ -0,0 +1,111 @@
+/**
+ * Field visibility event handler
+ *
+ *  Copyright (C) 2017 LoVullo Associates, Inc.
+ *
+ *  This file is part of the Liza Data Collection Framework
+ *
+ *  Liza 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 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+const Class             = require( 'easejs' ).Class;
+const EventHandler      = require( './EventHandler' );
+const UnknownEventError = require( './UnknownEventError' );
+
+
+/**
+ * Shows/hides fields according to event id
+ *
+ * @todo use something more appropriate than Ui
+ * @todo should not be concerned with data validators
+ */
+module.exports = Class( 'FieldVisibilityEventHandler' )
+    .implement( EventHandler )
+    .extend(
+{
+    /**
+     * Client UI
+     * @type {Ui}
+     */
+    'private _ui': null,
+
+    /**
+     * Field data validator
+     * @type {DataValidator}
+     */
+    'private _data_validator': null,
+
+
+    /**
+     * Initialize with Client UI
+     *
+     * @param {Ui}            stepui         Client UI
+     * @param {DataValidator} data_validator field data validator
+     */
+    __construct( stepui, data_validator )
+    {
+        this._ui             = stepui;
+        this._data_validator = data_validator;
+    },
+
+
+    /**
+     * Show/hide specified fields
+     *
+     * If a given field is not known then it will be silently ignored; the
+     * callback `callback` will still be invoked.
+     *
+     * This relies on a poorly designed API that should change in the future.
+     *
+     * @param {string}             event_id event id
+     * @param {function(*,Object)} callback continuation to invoke on completion
+     *
+     * @param {elementName:string, indexes:Array.<number>} data
+     *
+     * @return {EventHandler} self
+     */
+    'public handle'( event_id, callback, { elementName: field_name, indexes } )
+    {
+        // TODO: Law of Demeter!
+        const group = this._ui.getCurrentStep()
+            .getElementGroup( field_name );
+
+        // we probably should care, but we don't right now
+        if ( !group )
+        {
+            callback();
+            return;
+        }
+
+        const action = ( () =>
+        {
+            switch ( event_id )
+            {
+                case 'show':
+                    return group.showField.bind( group );
+
+                case 'hide':
+                    return group.hideField.bind( group );
+
+                default:
+                    throw UnknownEventError( `Unknown visibility event: ${event_id}` );
+            }
+        } )();
+
+        this._data_validator.clearFailures( [ field_name ] );
+        indexes.forEach( field_i => action( field_name, field_i ) );
+
+        callback();
+    }
+} );

test/event/FieldVisibilityEventHandlerTest.js

@@ -0,0 +1,145 @@
+/**
+ * Test case for FieldVisibilityEventHandler
+ *
+ *  Copyright (C) 2017 LoVullo Associates, Inc.
+ *
+ *  This file is part of the Liza Data Collection Framework
+ *
+ *  Liza 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 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+const event  = require( '../../' ).event;
+const expect = require( 'chai' ).expect;
+const Class  = require( 'easejs' ).Class;
+
+const {
+    FieldVisibilityEventHandler: Sut,
+    UnknownEventError
+} = event;
+
+
+describe( 'FieldVisibilityEventHandler', () =>
+{
+    it( 'shows/hides each element index', done =>
+    {
+        const name   = 'field_name';
+        const shown  = { [name]: [] };
+        const hidden = { [name]: [] };
+
+        const sut = Sut(
+            createMockStepUi(
+                name,
+                ( field, index ) => shown[ field ].push( index ),
+                ( field, index ) => hidden[ field ].push( index )
+            ),
+            createStubDataProvider()
+        );
+
+        // purposefully sparse indexes
+        const show_indexes   = [ 2, 4, ];
+        const hide_indexes = [ 0, 3, ];
+
+        const show_data = {
+            elementName: name,
+            indexes:     show_indexes,
+        };
+
+        const hide_data = {
+            elementName: name,
+            indexes:     hide_indexes,
+        };
+
+        sut.handle( 'show', () =>
+        {
+            // implicitly ensures proper name is passed
+            expect( shown[ name ] ).to.deep.equal( show_indexes );
+
+            sut.handle( 'hide', () =>
+            {
+                expect( hidden[ name ] ).to.deep.equal( hide_indexes );
+                done();
+            }, hide_data );
+        }, show_data );
+    } );
+
+
+    it( 'throws error given unknown event', () =>
+    {
+        expect( () =>
+        {
+            Sut( createMockStepUi() ).handle( 'unknown', () => {}, {} );
+        } ).to.throw( UnknownEventError );
+    } );
+
+
+    it( 'ignores unknown groups', done =>
+    {
+        expect( () =>
+        {
+            Sut( {
+                getCurrentStep: () => ( { getElementGroup: () => null } )
+            } ).handle( 'hide', done, {} )
+        } ).to.not.throw( Error );
+    } );
+
+
+    it( 'clears failures on hidden fields', done =>
+    {
+        const name = 'foo_bar';
+
+        const hide_data = {
+            elementName: name,
+            indexes:     [ 0 ],
+        };
+
+        Sut(
+            createMockStepUi( name, () => {}, () => {} ),
+            createStubDataProvider( failures =>
+            {
+                expect( failures )
+                    .to.deep.equal( [ name ] )
+
+                // we don't care about the rest of the processing at this
+                // point
+                done();
+            } )
+        ).handle( 'hide', () => {}, hide_data );
+    } );
+} );
+
+
+function createMockStepUi( expected_name, showf, hidef )
+{
+    return {
+        getCurrentStep: () => ( {
+            getElementGroup( field_name )
+            {
+                expect( field_name ).to.equal( expected_name );
+
+                return {
+                    showField: showf,
+                    hideField: hidef,
+                };
+            }
+        } ),
+    };
+}
+
+
+function createStubDataProvider( fail_callback )
+{
+    return {
+        clearFailures: fail_callback || () => {},
+    };
+}