Major 2.0 (#20)

* New 2.0 version + DependencyInjection library

* Updated docs and repo settings (devcontainers, vscode, github, etc.)

* Added tests

* Fixed bugs

* Minor test project refactoring

* Updated projects
- Added symbol packages
- Updated package versions to pre-release

* Updated SECURITY.md

* Added GitHub Actions workflows

libraries/SimpleOTP/Totp.cs

@@ -0,0 +1,98 @@
+namespace SimpleOTP;
+
+/// <summary>
+/// Represents a Time-based One-Time Password (TOTP) generator.
+/// </summary>
+public class Totp : Otp
+{
+	/// <summary>
+	/// Gets or sets the time period (in seconds) for which each generated OTP is valid.
+	/// </summary>
+	/// <remarks>Also used to calculate the current counter value.</remarks>
+	public int Period { get; set; } = 30;
+
+	#region Constructors
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Totp"/> class with the specified secret key.
+	/// </summary>
+	/// <param name="secret">The secret key used for generating OTP codes.</param>
+	public Totp(OtpSecret secret) : base(secret) { }
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Totp"/> class with the specified secret key and number of OTP code digits.
+	/// </summary>
+	/// <param name="secret">The secret key used for generating OTP codes.</param>
+	/// <param name="period">The time period (in seconds) for which each generated OTP is valid.</param>
+	public Totp(OtpSecret secret, int period) : base(secret) =>
+		Period = period;
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Totp"/> class with the specified secret key, number of OTP code digits, and time period.
+	/// </summary>
+	/// <param name="secret">The secret key used for generating OTP codes.</param>
+	/// <param name="period">The time period (in seconds) for which each generated OTP is valid.</param>
+	/// <param name="digits">The number of digits in the OTP code.</param>
+	public Totp(OtpSecret secret, int period, int digits) : base(secret, digits) =>
+		Period = period;
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Totp"/> class with the specified secret key, hash algorithm, and time period.
+	/// </summary>
+	/// <param name="secret">The secret key used for generating OTP codes.</param>
+	/// <param name="period">The time period (in seconds) for which each generated OTP is valid.</param>
+	/// <param name="algorithm">The algorithm used for generating OTP codes.</param>
+	public Totp(OtpSecret secret, int period, OtpAlgorithm algorithm) : base(secret, algorithm) =>
+		Period = period;
+
+	/// <summary>
+	/// Initializes a new instance of the <see cref="Totp"/> class with the specified secret key, hash algorithm, number of digits, and time period.
+	/// </summary>
+	/// <param name="secret">The secret key used for generating OTP codes.</param>
+	/// <param name="period">The time period (in seconds) for which each generated OTP is valid.</param>
+	/// <param name="algorithm">The algorithm used for generating OTP codes.</param>
+	/// <param name="digits">The number of digits in the OTP code.</param>
+	public Totp(OtpSecret secret, int period, OtpAlgorithm algorithm, int digits) : base(secret, algorithm, digits) =>
+		Period = period;
+
+	#endregion
+
+	/// <summary>
+	/// Generates an OTP based on the specified counter value.
+	/// </summary>
+	/// <param name="counter">The counter value to use for OTP generation.</param>
+	/// <returns>An instance of <see cref="OtpCode"/> representing the generated OTP.</returns>
+	public override OtpCode Generate(long counter) =>
+		new(Compute(counter), Digits, DateTime.UnixEpoch.AddSeconds((counter + 1) * Period));
+
+	/// <summary>
+	/// Generates an OTP based on the specified date and time.
+	/// </summary>
+	/// <param name="date">The date and time to use for OTP generation.</param>
+	/// <returns>An instance of <see cref="OtpCode"/> representing the generated OTP.</returns>
+	public OtpCode Generate(DateTimeOffset date) =>
+		Generate(date.ToUnixTimeSeconds() / Period);
+
+
+	/// <summary>
+	/// Validates an OTP code with tolerance and base counter value, and returns the resynchronization value.
+	/// </summary>
+	/// <param name="code">The OTP code to validate.</param>
+	/// <param name="tolerance">The tolerance span for code validation.</param>
+	/// <param name="baseTime">The base timestamp value.</param>
+	/// <param name="resyncValue">The resynchronization value. Indicates how much given OTP code is ahead or behind the current counter value.</param>
+	/// <returns><c>true</c> if the OTP code is valid; otherwise, <c>false</c>.</returns>
+	/// <exception cref="InvalidOperationException">
+	/// Implementation for the <see cref="Otp.Algorithm"/> algorithm was not found.
+	/// Use <see cref="HashAlgorithmProviders.AddProvider(OtpAlgorithm)"/> to register an implementation.
+	/// </exception>
+	public bool Validate(OtpCode code, ToleranceSpan tolerance, DateTimeOffset baseTime, out int resyncValue) =>
+		Validate(code, tolerance, baseTime.ToUnixTimeSeconds() / 30, out resyncValue);
+
+	/// <summary>
+	/// Gets the current counter value based on the current UTC time and the configured time period.
+	/// </summary>
+	/// <returns>The current counter value.</returns>
+	protected override long GetCounter() =>
+		DateTimeOffset.UtcNow.ToUnixTimeSeconds() / Period;
+}