feat: initial project commit

src/Result/Result.Equality.cs

@@ -0,0 +1,115 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Contracts;
+using System.Numerics;
+
+namespace Geekeey.Extensions.Result;
+
+public readonly partial struct Result<T> : IEquatable<Result<T>>, IEquatable<T>,
+	IEqualityOperators<Result<T>, Result<T>, bool>, IEqualityOperators<Result<T>, T, bool>
+{
+	/// <summary>
+	/// Checks whether the result is equal to another result. Results are equal if both results are success values and
+	/// the success values are equal, or if both results are failures.
+	/// </summary>
+	/// <param name="other">The result to check for equality with the current result.</param>
+	[Pure]
+	public bool Equals(Result<T> other)
+		=> Equals(this, other, EqualityComparer<T>.Default);
+
+	/// <summary>
+	/// Checks whether the result is equal to another result. Results are equal if both results are success values and
+	/// the success values are equal, or if both results are failures.
+	/// </summary>
+	/// <param name="other">The result to check for equality with the current result.</param>
+	/// <param name="comparer">The equality comparer to use for comparing values.</param>
+	[Pure]
+	public bool Equals(Result<T> other, IEqualityComparer<T> comparer)
+		=> Equals(this, other, comparer);
+
+	/// <summary>
+	/// Checks whether the result is a success value and the success value is equal to another value.
+	/// </summary>
+	/// <param name="other">The value to check for equality with the success value of the result.</param>
+	[Pure]
+	public bool Equals(T? other)
+		=> Equals(this, other, EqualityComparer<T>.Default);
+
+	/// <summary>
+	/// Checks whether the result is a success value and the success value is equal to another value using a specified
+	/// equality comparer.
+	/// </summary>
+	/// <param name="other">The value to check for equality with the success value of the result.</param>
+	/// <param name="comparer">The equality comparer to use for comparing values.</param>
+	[Pure]
+	public bool Equals(T? other, IEqualityComparer<T> comparer)
+		=> Equals(this, other, comparer);
+
+	/// <inheritdoc/>
+	[Pure]
+	public override bool Equals(object? other)
+		=> other is T x && Equals(x) || other is Result<T> r && Equals(r);
+
+	/// <inheritdoc/>
+	[Pure]
+	public override int GetHashCode()
+		=> GetHashCode(this, EqualityComparer<T>.Default);
+
+	internal static bool Equals(Result<T> a, Result<T> b, IEqualityComparer<T> comparer)
+	{
+		if (!a._success || !b._success) return !a._success && !b._success;
+		if (a.Value is null || b.Value is null) return a.Value is null && b.Value is null;
+		return comparer.Equals(a.Value, b.Value);
+	}
+
+	internal static bool Equals(Result<T> a, T? b, IEqualityComparer<T> comparer)
+	{
+		if (!a._success) return false;
+		if (a.Value is null || b is null) return a.Value is null && b is null;
+		return comparer.Equals(a.Value, b);
+	}
+
+	internal static int GetHashCode(Result<T> result, IEqualityComparer<T> comparer)
+	{
+		if (result is { _success: true, Value: not null })
+			return comparer.GetHashCode(result.Value);
+		return 0;
+	}
+
+	/// <summary>
+	/// Checks whether two results are equal. Results are equal if both results are success values and the success
+	/// values are equal, or if both results are failures.
+	/// </summary>
+	/// <param name="a">The first result to compare.</param>
+	/// <param name="b">The second result to compare.</param>
+	[Pure]
+	[ExcludeFromCodeCoverage]
+	public static bool operator ==(Result<T> a, Result<T> b) => a.Equals(b);
+
+	/// <summary>
+	/// Checks whether two results are not equal. Results are equal if both results are success values and the success
+	/// values are equal, or if both results are failures.
+	/// </summary>
+	/// <param name="a">The first result to compare.</param>
+	/// <param name="b">The second result to compare.</param>
+	[Pure]
+	[ExcludeFromCodeCoverage]
+	public static bool operator !=(Result<T> a, Result<T> b) => !a.Equals(b);
+
+	/// <summary>
+	/// Checks whether a result is a success value and the success value is equal to another value.
+	/// </summary>
+	/// <param name="a">The result to compare.</param>
+	/// <param name="b">The value to check for equality with the success value in the result.</param>
+	[Pure]
+	[ExcludeFromCodeCoverage]
+	public static bool operator ==(Result<T> a, T? b) => a.Equals(b);
+
+	/// <summary>
+	/// Checks whether a result either does not have a value, or the value is not equal to another value.
+	/// </summary>
+	/// <param name="a">The result to compare.</param>
+	/// <param name="b">The value to check for inequality with the success value in the result.</param>
+	[Pure]
+	[ExcludeFromCodeCoverage]
+	public static bool operator !=(Result<T> a, T? b) => !a.Equals(b);
+}