From 7d4d33901809c236a139530d60200e606315d5de Mon Sep 17 00:00:00 2001
From: Geomitron <22552797+Geomitron@users.noreply.github.com>
Date: Tue, 11 Feb 2020 23:52:22 -0500
Subject: [PATCH] Download Selected button, Various small improvements

---
 .../components/browse/browse.component.html   |  2 +-
 src/app/components/browse/browse.component.ts |  3 +
 .../chart-sidebar.component.html              |  8 +--
 .../chart-sidebar/chart-sidebar.component.ts  | 27 ++++-----
 .../result-table-row.component.ts             |  4 ++
 .../result-table/result-table.component.html  |  4 +-
 .../result-table/result-table.component.ts    | 18 ++++--
 .../search-bar/search-bar.component.html      |  1 -
 .../status-bar/status-bar.component.html      | 16 +++++
 .../browse/status-bar/status-bar.component.ts | 60 +++++++++++++++++--
 src/app/core/directives/checkbox.directive.ts | 26 +++++---
 src/app/core/services/download.service.ts     | 10 +++-
 .../ipc/BatchSongDetailsHandler.ipc.ts        | 22 +++++++
 src/electron/shared/ElectronUtilFunctions.ts  | 11 ++++
 src/electron/shared/ErrorMessages.ts          |  2 +-
 src/electron/shared/IPCHandler.ts             |  6 ++
 src/electron/shared/UtilFunctions.ts          | 30 ++++++----
 17 files changed, 192 insertions(+), 58 deletions(-)
 create mode 100644 src/electron/ipc/BatchSongDetailsHandler.ipc.ts
 create mode 100644 src/electron/shared/ElectronUtilFunctions.ts

diff --git a/src/app/components/browse/browse.component.html b/src/app/components/browse/browse.component.html
index 4f3f90e..a00b2b0 100644
--- a/src/app/components/browse/browse.component.html
+++ b/src/app/components/browse/browse.component.html
@@ -14,4 +14,4 @@
     </div>
   </div>
 </div>
-<app-status-bar #statusBar></app-status-bar>
\ No newline at end of file
+<app-status-bar #statusBar (deselectSongs)="resultTable.onSongsDeselected($event)"></app-status-bar>
\ No newline at end of file
diff --git a/src/app/components/browse/browse.component.ts b/src/app/components/browse/browse.component.ts
index 695f1e6..f2b047f 100644
--- a/src/app/components/browse/browse.component.ts
+++ b/src/app/components/browse/browse.component.ts
@@ -19,7 +19,10 @@ export class BrowseComponent {
 
   onResultsUpdated(results: SongResult[]) {
     this.resultTable.results = results
+    this.resultTable.onNewSearch()
+    this.resultTable.checkAll
     this.chartSidebar.selectedVersion = undefined
     this.statusBar.resultCount = results.length
+    this.statusBar.selectedResults = []
   }
 }
\ No newline at end of file
diff --git a/src/app/components/browse/chart-sidebar/chart-sidebar.component.html b/src/app/components/browse/chart-sidebar/chart-sidebar.component.html
index f6db76d..3211984 100644
--- a/src/app/components/browse/chart-sidebar/chart-sidebar.component.html
+++ b/src/app/components/browse/chart-sidebar/chart-sidebar.component.html
@@ -17,15 +17,15 @@
   <div id="textPanel" class="content">
     <span class="header">{{selectedVersion?.avTagName}}</span>
     <div class="description">
-      <div>{{charterPlural}} {{selectedVersion?.charters}}</div>
-      <div *ngIf="selectedVersion?.tags">Tags: {{selectedVersion.tags}}</div>
-      <div>Audio Length: {{getSongLength()}}</div>
+      <div><b>{{charterPlural}}</b> {{selectedVersion?.charters}}</div>
+      <div *ngIf="selectedVersion?.tags"><b>Tags:</b> {{selectedVersion.tags}}</div>
+      <div><b>Audio Length:</b> {{getSongLength()}}</div>
       <!-- TODO: add difficulty icons -->
     </div>
 
   </div>
   <div class="ui positive buttons">
-    <div class="ui button" (click)="onDownloadClicked()">Download Latest</div>
+    <div class="ui button" (click)="onDownloadClicked()">Download{{getVersions().length > 1 ? ' Latest' : ''}}</div>
     <div *ngIf="getVersions().length > 1" id="versionDropdown" class="ui floating dropdown icon button">
       <i class="dropdown icon"></i>
       <div class="menu">
diff --git a/src/app/components/browse/chart-sidebar/chart-sidebar.component.ts b/src/app/components/browse/chart-sidebar/chart-sidebar.component.ts
index 499f716..b2fee1f 100644
--- a/src/app/components/browse/chart-sidebar/chart-sidebar.component.ts
+++ b/src/app/components/browse/chart-sidebar/chart-sidebar.component.ts
@@ -4,6 +4,7 @@ import { ElectronService } from '../../../core/services/electron.service'
 import { VersionResult } from '../../../../electron/shared/interfaces/songDetails.interface'
 import { AlbumArtService } from '../../../core/services/album-art.service'
 import { DownloadService } from '../../../core/services/download.service'
+import { groupBy } from 'src/electron/shared/UtilFunctions'
 
 @Component({
   selector: 'app-chart-sidebar',
@@ -17,7 +18,7 @@ export class ChartSidebarComponent {
   charterPlural: string
   albumArtBuffer: Buffer
 
-  charts: { chartID: number, versions: VersionResult[] }[]
+  charts: VersionResult[][]
 
   constructor(private electronService: ElectronService, private albumArtService: AlbumArtService, private downloadService: DownloadService) { }
 
@@ -26,16 +27,7 @@ export class ChartSidebarComponent {
     const albumArt = this.albumArtService.getImage(result.id)
     const results = await this.electronService.invoke('song-details', result.id)
 
-    // Group results by chartID
-    this.charts = []
-    for (const result of results) {
-      const matchingChart = this.charts.find(chart => chart.chartID == result.chartID)
-      if (matchingChart != undefined) {
-        matchingChart.versions.push(result)
-      } else {
-        this.charts.push({ chartID: result.chartID, versions: [result] })
-      }
-    }
+    this.charts = groupBy(results, 'chartID')
     this.initChartDropdown()
 
     this.albumArtBuffer = await albumArt
@@ -53,12 +45,12 @@ export class ChartSidebarComponent {
    * Initializes the chart dropdown from <this.charts> (or removes it if there's only one chart)
    */
   private async initChartDropdown() {
-    this.switchChart(this.charts[0].chartID)
+    this.switchChart(this.charts[0][0].chartID)
     await new Promise<void>(resolve => setTimeout(() => resolve(), 0)) // Wait for *ngIf to update DOM
     const values = this.charts.map(chart => {
-      const version = chart.versions[0]
+      const version = chart[0]
       return {
-        value: chart.chartID,
+        value: version.chartID,
         text: version.avTagName,
         name: `${version.avTagName} <b>[${version.charters}]</b>`
       }
@@ -74,8 +66,8 @@ export class ChartSidebarComponent {
    * @param chartID The ID of the chart to display.
    */
   private switchChart(chartID: number) {
-    const chart = this.charts.find(chart => chart.chartID == chartID)
-    this.selectedVersion = chart.versions[0]
+    const chart = this.charts.find(chart => chart[0].chartID == chartID)
+    this.selectedVersion = chart[0]
     this.charterPlural = this.selectedVersion.charterIDs.split('&').length == 1 ? 'Charter:' : 'Charters:'
     this.initVersionDropdown()
   }
@@ -88,6 +80,7 @@ export class ChartSidebarComponent {
       return 'Unknown'
     }
     let seconds = Math.round(this.selectedVersion.song_length / 1000)
+    if (seconds < 60) { return `${seconds} second${seconds == 1 ? '' : 's'}` }
     let minutes = Math.floor(seconds / 60)
     let hours = 0
     while (minutes > 59) {
@@ -138,6 +131,6 @@ export class ChartSidebarComponent {
   }
 
   getVersions() {
-    return this.charts.find(chart => chart.chartID == this.selectedVersion.chartID).versions
+    return this.charts.find(chart => chart[0].chartID == this.selectedVersion.chartID)
   }
 }
\ No newline at end of file
diff --git a/src/app/components/browse/result-table/result-table-row/result-table-row.component.ts b/src/app/components/browse/result-table/result-table-row/result-table-row.component.ts
index 0b3a2fd..3e89508 100644
--- a/src/app/components/browse/result-table/result-table-row/result-table-row.component.ts
+++ b/src/app/components/browse/result-table/result-table-row/result-table-row.component.ts
@@ -15,6 +15,10 @@ export class ResultTableRowComponent implements AfterViewInit {
 
   constructor() { }
 
+  get songID() {
+    return this.result.id
+  }
+
   ngAfterViewInit() {
     $(this.checkbox.nativeElement).checkbox({
       onChecked: () => {
diff --git a/src/app/components/browse/result-table/result-table.component.html b/src/app/components/browse/result-table/result-table.component.html
index 10ee95e..b75e8a0 100644
--- a/src/app/components/browse/result-table/result-table.component.html
+++ b/src/app/components/browse/result-table/result-table.component.html
@@ -5,8 +5,8 @@
   <thead>
     <!-- NOTE: it would be nice to make this header sticky, but Fomantic-UI doesn't currently support that -->
     <tr>
-      <th appCheckbox (checked)="checkAll($event)" id="checkboxColumn" class="collapsing">
-        <div class="ui checkbox">
+      <th class="collapsing" id="checkboxColumn">
+        <div class="ui checkbox" id="checkbox" #checkboxColumn appCheckbox (checked)="checkAll($event)">
           <input type="checkbox">
         </div>
       </th>
diff --git a/src/app/components/browse/result-table/result-table.component.ts b/src/app/components/browse/result-table/result-table.component.ts
index 4af12b3..fa30db9 100644
--- a/src/app/components/browse/result-table/result-table.component.ts
+++ b/src/app/components/browse/result-table/result-table.component.ts
@@ -1,26 +1,24 @@
-import { Component, AfterViewInit, Input, Output, EventEmitter, ViewChildren, QueryList } from '@angular/core'
+import { Component, Input, Output, EventEmitter, ViewChildren, QueryList, ViewChild } from '@angular/core'
 import { SongResult } from '../../../../electron/shared/interfaces/search.interface'
 import { ResultTableRowComponent } from './result-table-row/result-table-row.component'
+import { CheckboxDirective } from 'src/app/core/directives/checkbox.directive'
 
 @Component({
   selector: 'app-result-table',
   templateUrl: './result-table.component.html',
   styleUrls: ['./result-table.component.scss']
 })
-export class ResultTableComponent implements AfterViewInit {
+export class ResultTableComponent {
   @Input() results: SongResult[]
 
   @Output() rowClicked = new EventEmitter<SongResult>()
   @Output() songChecked = new EventEmitter<SongResult>()
   @Output() songUnchecked = new EventEmitter<SongResult>()
 
+  @ViewChild(CheckboxDirective, { static: true }) checkboxColumn: CheckboxDirective
   @ViewChildren('tableRow') tableRows: QueryList<ResultTableRowComponent>
 
   constructor() { }
-  
-  ngAfterViewInit() {
-    $('.ui.checkbox').checkbox()
-  }
 
   onRowClicked(result: SongResult) {
     this.rowClicked.emit(result)
@@ -37,4 +35,12 @@ export class ResultTableComponent implements AfterViewInit {
   checkAll(isChecked: boolean) {
     this.tableRows.forEach(row => row.check(isChecked))
   }
+
+  onSongsDeselected(songs: SongResult['id'][]) {
+    this.tableRows.forEach(row => row.check(!songs.includes(row.songID)))
+  }
+
+  onNewSearch() {
+    this.checkboxColumn.check(false)
+  }
 }
\ No newline at end of file
diff --git a/src/app/components/browse/search-bar/search-bar.component.html b/src/app/components/browse/search-bar/search-bar.component.html
index 0192d58..b5668f9 100644
--- a/src/app/components/browse/search-bar/search-bar.component.html
+++ b/src/app/components/browse/search-bar/search-bar.component.html
@@ -1,6 +1,5 @@
 <div class="ui bottom attached borderless menu">
   <div class="item">
-    <!-- TODO: refactor this html into multiple sub-components -->
     <!-- TODO: add advanced search -->
     <div class="ui icon input">
       <input #searchBox type="text" placeholder=" Search..." (keyup.enter)="onSearch(searchBox.value)">
diff --git a/src/app/components/browse/status-bar/status-bar.component.html b/src/app/components/browse/status-bar/status-bar.component.html
index 7225139..280b3c5 100644
--- a/src/app/components/browse/status-bar/status-bar.component.html
+++ b/src/app/components/browse/status-bar/status-bar.component.html
@@ -11,6 +11,22 @@
     </div>
   </a>
 
+  <div id="selectedModal" class="ui modal">
+    <div class="header">Some selected songs have more than one chart!</div>
+    <div class="scrolling content">
+      <div class="ui segments">
+        <div class="ui segment" *ngFor="let chartGroup of chartGroups">
+          <p *ngFor="let chart of chartGroup">{{chart.avTagName}} <b>[{{chart.charters}}]</b></p>
+        </div>
+      </div>
+    </div>
+    <div class="actions">
+      <div class="ui approve button" (click)="downloadAllCharts()">Download all charts for each song</div>
+      <div class="ui cancel button" (click)="deselectSongsWithMultipleCharts()">Deselect these songs</div>
+      <div class="ui cancel button">Cancel</div>
+    </div>
+  </div>
+
   <div id="downloadsModal" class="ui modal">
     <i class="inside close icon"></i>
     <div class="header">Downloads</div>
diff --git a/src/app/components/browse/status-bar/status-bar.component.ts b/src/app/components/browse/status-bar/status-bar.component.ts
index ef8c3d8..5e3f769 100644
--- a/src/app/components/browse/status-bar/status-bar.component.ts
+++ b/src/app/components/browse/status-bar/status-bar.component.ts
@@ -1,6 +1,9 @@
-import { Component, ChangeDetectorRef } from '@angular/core'
+import { Component, ChangeDetectorRef, Output, EventEmitter } from '@angular/core'
 import { SongResult } from 'src/electron/shared/interfaces/search.interface'
 import { DownloadService } from 'src/app/core/services/download.service'
+import { ElectronService } from 'src/app/core/services/electron.service'
+import { groupBy } from 'src/electron/shared/UtilFunctions'
+import { VersionResult } from 'src/electron/shared/interfaces/songDetails.interface'
 
 @Component({
   selector: 'app-status-bar',
@@ -9,12 +12,16 @@ import { DownloadService } from 'src/app/core/services/download.service'
 })
 export class StatusBarComponent {
 
+  @Output() deselectSongs = new EventEmitter<SongResult['id'][]>()
+
   resultCount = 0
   downloading = false
   percent = 0
   selectedResults: SongResult[] = []
+  batchResults: VersionResult[]
+  chartGroups: VersionResult[][]
 
-  constructor(downloadService: DownloadService, ref: ChangeDetectorRef) {
+  constructor(private electronService: ElectronService, private downloadService: DownloadService, ref: ChangeDetectorRef) {
     downloadService.onDownloadUpdated(() => {
       this.downloading = downloadService.downloadCount > 0
       this.percent = downloadService.totalPercent
@@ -36,9 +43,50 @@ export class StatusBarComponent {
     this.selectedResults = this.selectedResults.filter(oldResult => oldResult.id != result.id)
   }
 
-  downloadSelected() {
-    // TODO send query to get versions; for any with more than one chart, show modal for confirmation:
-    // "some selected songs have more than one chart: ___" [download all charts for each song] [deselect these songs] [X]
-    console.log(this.selectedResults)
+  async downloadSelected() {
+    this.chartGroups = []
+    this.batchResults = await this.electronService.invoke('batch-song-details', this.selectedResults.map(result => result.id))
+    const versionGroups = groupBy(this.batchResults, 'songID')
+    for (const versionGroup of versionGroups) {
+      if (versionGroup.findIndex(version => version.chartID != versionGroup[0].chartID) != -1) {
+        // Must have multiple charts of this song
+        this.chartGroups.push(versionGroup.filter(version => version.versionID == version.latestVersionID))
+      }
+    }
+
+    if (this.chartGroups.length == 0) {
+      for (const versions of versionGroups) {
+        const downloadVersion = versions.find(version => version.versionID == version.latestVersionID)
+        const downloadSong = this.selectedResults.find(song => song.id == downloadVersion.songID)
+        this.downloadService.addDownload(
+          downloadVersion.versionID, {
+          avTagName: downloadVersion.avTagName,
+          artist: downloadSong.artist,
+          charter: downloadVersion.charters,
+          links: JSON.parse(downloadVersion.downloadLink)
+        })
+      }
+    } else {
+      $('#selectedModal').modal('show')
+      //[download all charts for each song] [deselect these songs] [X]
+    }
+  }
+
+  downloadAllCharts() {
+    for (const version of this.batchResults) {
+      if (version.versionID != version.latestVersionID) { continue }
+      const downloadSong = this.selectedResults.find(song => song.id == version.songID)
+      this.downloadService.addDownload(
+        version.versionID, {
+        avTagName: version.avTagName,
+        artist: downloadSong.artist,
+        charter: version.charters,
+        links: JSON.parse(version.downloadLink)
+      })
+    }
+  }
+
+  deselectSongsWithMultipleCharts() {
+    this.deselectSongs.emit(this.chartGroups.map(group => group[0].songID))
   }
 }
\ No newline at end of file
diff --git a/src/app/core/directives/checkbox.directive.ts b/src/app/core/directives/checkbox.directive.ts
index 3db5a3b..9cbbec9 100644
--- a/src/app/core/directives/checkbox.directive.ts
+++ b/src/app/core/directives/checkbox.directive.ts
@@ -1,19 +1,29 @@
-import { Directive, ElementRef, Output, EventEmitter } from '@angular/core'
+import { Directive, ElementRef, Output, EventEmitter, AfterViewInit } from '@angular/core'
 
 @Directive({
   selector: '[appCheckbox]'
 })
-export class CheckboxDirective {
+export class CheckboxDirective implements AfterViewInit {
   @Output() checked = new EventEmitter<boolean>()
 
-  private _checked = false
+  constructor(private checkbox: ElementRef) { }
 
-  constructor(element: ElementRef) {
-    $(element.nativeElement).checkbox({
-      onChange: () => {
-        this._checked = !this._checked
-        this.checked.emit(this._checked)
+  ngAfterViewInit() {
+    $(this.checkbox.nativeElement).checkbox({
+      onChecked: () => {
+        this.checked.emit(true)
+      },
+      onUnchecked: () => {
+        this.checked.emit(false)
       }
     })
   }
+
+  async check(isChecked: boolean) {
+    if (isChecked) {
+      $(this.checkbox.nativeElement).checkbox('check')
+    } else {
+      $(this.checkbox.nativeElement).checkbox('uncheck')
+    }
+  }
 }
\ No newline at end of file
diff --git a/src/app/core/services/download.service.ts b/src/app/core/services/download.service.ts
index d5c22c1..3e1b920 100644
--- a/src/app/core/services/download.service.ts
+++ b/src/app/core/services/download.service.ts
@@ -41,7 +41,15 @@ export class DownloadService {
   }
 
   onDownloadUpdated(callback: (download: DownloadProgress) => void) {
-    this.downloadUpdatedEmitter.subscribe(_.throttle(callback, 30))
+    const debouncedCallback = _.throttle(callback, 30)
+    this.downloadUpdatedEmitter.subscribe((download: DownloadProgress) => {
+      if (this.downloads.findIndex(oldDownload => oldDownload.versionID == download.versionID) == -1) {
+        // If this is a new download item, don't call debouncedCallback; it may miss adding new versions to the list
+        callback(download)
+      } else {
+        debouncedCallback(download)
+      }
+    })
   }
 
   cancelDownload(versionID: number) {
diff --git a/src/electron/ipc/BatchSongDetailsHandler.ipc.ts b/src/electron/ipc/BatchSongDetailsHandler.ipc.ts
new file mode 100644
index 0000000..bc852a6
--- /dev/null
+++ b/src/electron/ipc/BatchSongDetailsHandler.ipc.ts
@@ -0,0 +1,22 @@
+import { IPCInvokeHandler } from '../shared/IPCHandler'
+import Database from '../shared/Database'
+import { VersionResult } from '../shared/interfaces/songDetails.interface'
+
+export default class BatchSongDetailsHandler implements IPCInvokeHandler<'batch-song-details'> {
+  event: 'batch-song-details' = 'batch-song-details'
+  // TODO: add method documentation
+
+  async handler(songIDs: number[]) {
+    const db = await Database.getInstance()
+
+    return db.sendQuery(this.getVersionQuery(songIDs)) as Promise<VersionResult[]>
+  }
+
+  private getVersionQuery(songIDs: number[]) {
+    return `
+      SELECT *
+      FROM VersionMetaFull
+      WHERE songID IN (${songIDs.join(',')});
+    `
+  }
+}
\ No newline at end of file
diff --git a/src/electron/shared/ElectronUtilFunctions.ts b/src/electron/shared/ElectronUtilFunctions.ts
new file mode 100644
index 0000000..1979786
--- /dev/null
+++ b/src/electron/shared/ElectronUtilFunctions.ts
@@ -0,0 +1,11 @@
+import InitSettingsHandler from '../ipc/InitSettingsHandler.ipc'
+import { basename } from 'path'
+
+/**
+ * @param absoluteFilepath The absolute filepath to a folder
+ * @returns The relative filepath from the scanned folder to <absoluteFilepath>
+ */
+export async function getRelativeFilepath(absoluteFilepath: string) {
+  const settings = await InitSettingsHandler.getSettings()
+  return basename(settings.libraryPath) + absoluteFilepath.substring(settings.libraryPath.length)
+}
\ No newline at end of file
diff --git a/src/electron/shared/ErrorMessages.ts b/src/electron/shared/ErrorMessages.ts
index b3a5105..3ed7b87 100644
--- a/src/electron/shared/ErrorMessages.ts
+++ b/src/electron/shared/ErrorMessages.ts
@@ -1,5 +1,5 @@
 import { red } from 'cli-color'
-import { getRelativeFilepath } from './UtilFunctions'
+import { getRelativeFilepath } from './ElectronUtilFunctions'
 
 // TODO: add better error reporting (through the UI)
 
diff --git a/src/electron/shared/IPCHandler.ts b/src/electron/shared/IPCHandler.ts
index 82a69a5..155475f 100644
--- a/src/electron/shared/IPCHandler.ts
+++ b/src/electron/shared/IPCHandler.ts
@@ -7,6 +7,7 @@ import { Download, NewDownload, DownloadProgress } from './interfaces/download.i
 import { DownloadHandler } from '../ipc/download/DownloadHandler'
 import { Settings } from './Settings'
 import InitSettingsHandler from '../ipc/InitSettingsHandler.ipc'
+import BatchSongDetailsHandler from '../ipc/BatchSongDetailsHandler.ipc'
 
 /**
  * To add a new IPC listener:
@@ -21,6 +22,7 @@ export function getIPCInvokeHandlers(): IPCInvokeHandler<keyof IPCInvokeEvents>[
     new InitSettingsHandler(),
     new SearchHandler(),
     new SongDetailsHandler(),
+    new BatchSongDetailsHandler(),
     new AlbumArtHandler()
   ]
 }
@@ -42,6 +44,10 @@ export type IPCInvokeEvents = {
     input: SongResult['id']
     output: VersionResult[]
   }
+  'batch-song-details': {
+    input: number[]
+    output: VersionResult[]
+  }
 }
 
 export interface IPCInvokeHandler<E extends keyof IPCInvokeEvents> {
diff --git a/src/electron/shared/UtilFunctions.ts b/src/electron/shared/UtilFunctions.ts
index 5ebe87c..f02eea8 100644
--- a/src/electron/shared/UtilFunctions.ts
+++ b/src/electron/shared/UtilFunctions.ts
@@ -1,16 +1,5 @@
 let sanitize = require('sanitize-filename')
 
-/**
- * @param absoluteFilepath The absolute filepath to a folder
- * @returns The relative filepath from the scanned folder to <absoluteFilepath>
- */
-export function getRelativeFilepath(absoluteFilepath: string) {
-  // TODO: figure out how these functions should use <settings> (like an async initialization script that
-  //          loads everything and connects to the database, etc...)
-  // return basename(scanSettings.songsFolderPath) + absoluteFilepath.substring(scanSettings.songsFolderPath.length)
-  return absoluteFilepath
-}
-
 /**
  * @returns A random UUID
  */
@@ -53,4 +42,23 @@ export function sanitizeFilename(filename: string): string {
  */
 export function interpolate(val: number, fromA: number, fromB: number, toA: number, toB: number) {
   return ((val - fromA) / (fromB - fromA)) * (toB - toA) + toA
+}
+
+/**
+ * Splits <objectList> into multiple arrays, grouping by matching <key> values.
+ * @param objectList A list of objects.
+ * @param key A key from the list of objects.
+ */
+export function groupBy<T>(objectList: T[], key: keyof T) {
+  const results: T[][] = []
+  for (const object of objectList) {
+    const matchingGroup = results.find(result => result[0][key] == object[key])
+    if (matchingGroup != undefined) {
+      matchingGroup.push(object)
+    } else {
+      results.push([object])
+    }
+  }
+
+  return results
 }
\ No newline at end of file