Enable the login button only when exam has started

client/uis/screen.ts

@@ -23,6 +23,7 @@ export interface UIExamModeElements {
 	examStartText: HTMLSpanElement;
 	examEndText: HTMLSpanElement;
 	examStartButton: HTMLButtonElement;
+	examStartTimer: HTMLParagraphElement;
 }
 
 export abstract class UIScreen {

client/uis/screens/examscreen.ts

@@ -11,6 +11,8 @@ export class ExamModeUI extends UIScreen {
 	private _examMode: boolean = false;
 	private _examIds: number[] = [];
 	private _loginScreen: LoginScreenUI;
+	private _examStartButtonEnableInterval: ReturnType<typeof setInterval> | null = null;
+	private _examStartTime = new Date("2099-01-01T00:00:00Z"); // Set to a future date so that the button is disabled by default
 	protected _events: AuthenticatorEvents = {
 		authenticationStart: () => {
 			this._disableForm();
@@ -43,6 +45,7 @@ export class ExamModeUI extends UIScreen {
 			examStartText: document.getElementById('exam-mode-start') as HTMLSpanElement,
 			examEndText: document.getElementById('exam-mode-end') as HTMLSpanElement,
 			examStartButton: document.getElementById('exam-mode-start-button') as HTMLButtonElement,
+			examStartTimer: document.getElementById('exam-mode-start-timer') as HTMLParagraphElement,
 		} as UIExamModeElements;
 
 		this._initForm();
@@ -100,6 +103,16 @@ export class ExamModeUI extends UIScreen {
 		});
 	}
 
+	private _clearExamStartTimer(): void {
+		const form = this._form as UIExamModeElements;
+		if (this._examStartButtonEnableInterval) {
+			clearTimeout(this._examStartButtonEnableInterval);
+			this._examStartButtonEnableInterval = null;
+		}
+		form.examStartTimer.innerText = "Click the arrow below to start your exam.";
+		this._enableOrDisableSubmitButton();
+	}
+
 	private _populateData(examsToPopulate: ExamForHost[]): void {
 		const form = this._form as UIExamModeElements;
 
@@ -108,6 +121,9 @@ export class ExamModeUI extends UIScreen {
 			form.examProjectsText.innerText = '';
 			form.examStartText.innerText = 'unknown';
 			form.examEndText.innerText = 'unknown';
+			// Clear the timeout for the exam start button and disable it
+			this._examStartTime = new Date("2099-01-01T00:00:00Z");
+			this._clearExamStartTimer();
 		}
 		else {
 			// Find all exams in the data.json file that match the ids in the exams variable
@@ -144,14 +160,42 @@ export class ExamModeUI extends UIScreen {
 			form.examProjectsText.innerText = projectsText;
 			form.examStartText.innerText = earliestExam.toLocaleTimeString("en-NL", { hour: '2-digit', minute: '2-digit' });
 			form.examEndText.innerText = latestExam.toLocaleTimeString("en-NL", { hour: '2-digit', minute: '2-digit' });
+
+			// Enable or disable the exam start button based on the current time
+			this._clearExamStartTimer();
+			this._examStartTime = earliestExam;
+			this._enableOrDisableSubmitButton();
+			if (this._examStartTime.getTime() > Date.now()) {
+				this._examStartButtonEnableInterval = setInterval(() => {
+					const timeLeft = Math.floor((this._examStartTime.getTime() - Date.now()) / 1000);
+					const minutes = Math.floor(timeLeft / 60);
+					const seconds = timeLeft % 60;
+					const formattedTime = `${(minutes > 0 ? `${minutes} minutes and ` : '')} ${seconds} seconds`;
+					form.examStartTimer.innerText = `You may start your exam in ${formattedTime}.`;
+
+					if (this._examStartTime.getTime() <= Date.now()) {
+						// Clear the timer and enable the button
+						this._clearExamStartTimer();
+						return;
+					}
+				}, 1000);
+			}
 		}
 	}
 
 	// Returns true if the exam-start button is disabled, false otherwise
 	protected _enableOrDisableSubmitButton(): boolean {
 		const form = this._form as UIExamModeElements;
-		form.examStartButton.disabled = false; // Always enable the button
-		return false;
+		const buttonDisabled = this._examStartTime.getTime() > Date.now(); // Disable the button if the exam start time is in the future
+		form.examStartButton.disabled = buttonDisabled;
+		if (!buttonDisabled) {
+			form.examStartTimer.innerText = "Click the arrow below to start your exam.";
+			const focusInput = this._getInputToFocusOn();
+			if (focusInput) {
+				focusInput.focus();
+			}
+		}
+		return buttonDisabled;
 	}
 
 	protected _wigglePasswordInput(clearInput: boolean = true): void {

static/index.html

@@ -53,7 +53,7 @@ <h4 id="active-user-session-login-name">username</h4>
 				<h3>This computer is reserved for an exam between <span id="exam-mode-start">...</span> and <span id="exam-mode-end">...</span>.</h3>
 				<p><span id="exam-mode-projects"></span></p>
 				<br>
-				<p>Click the arrow below to start your exam.</p>
+				<p id="exam-mode-start-timer">Click the arrow below to start your exam.</p>
 				<button type="submit" id="exam-mode-start-button" title="Start your exam">&#10149;</button>
 			</form>