/*
    Copyright (C) 2014-2019 de4dot@gmail.com

    This file is part of dnSpy

    dnSpy 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.

    dnSpy 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 dnSpy.  If not, see <http://www.gnu.org/licenses/>.
*/

using System;

namespace dnSpy.Contracts.Debugger.DotNet.Evaluation {
	/// <summary>
	/// Return value of methods creating <see cref="DbgDotNetValue"/>s
	/// </summary>
	public readonly struct DbgDotNetValueResult {
		/// <summary>
		/// Gets the value or null if there was an error (<see cref="ErrorMessage"/>).
		/// If <see cref="ValueIsException"/> is true, this is the thrown exception value.
		/// </summary>
		public DbgDotNetValue? Value { get; }

		/// <summary>
		/// true if <see cref="Value"/> contains the thrown exception instead of the expected return value / field value
		/// </summary>
		public bool ValueIsException { get; }

		/// <summary>
		/// Gets the error message or null if there was no error
		/// </summary>
		public string? ErrorMessage { get; }

		/// <summary>
		/// true if there was an error, see <see cref="ErrorMessage"/>
		/// </summary>
		public bool HasError => ErrorMessage is not null;

		/// <summary>
		/// true if there's no error and no exception was thrown
		/// </summary>
		public bool IsNormalResult => !HasError && !ValueIsException;

		/// <summary>
		/// Creates a normal result
		/// </summary>
		/// <param name="value">Value</param>
		/// <returns></returns>
		public static DbgDotNetValueResult Create(DbgDotNetValue value) =>
			new DbgDotNetValueResult(value, valueIsException: false);

		/// <summary>
		/// Creates an exception result
		/// </summary>
		/// <param name="value">Exception value</param>
		/// <returns></returns>
		public static DbgDotNetValueResult CreateException(DbgDotNetValue value) =>
			new DbgDotNetValueResult(value, valueIsException: true);

		/// <summary>
		/// Creates an error result
		/// </summary>
		/// <param name="errorMessage">Error message</param>
		/// <returns></returns>
		public static DbgDotNetValueResult CreateError(string errorMessage) =>
			new DbgDotNetValueResult(errorMessage);

		DbgDotNetValueResult(DbgDotNetValue value, bool valueIsException) {
			Value = value ?? throw new ArgumentNullException(nameof(value));
			ValueIsException = valueIsException;
			ErrorMessage = null;
		}

		DbgDotNetValueResult(string errorMessage) {
			Value = null;
			ValueIsException = false;
			ErrorMessage = errorMessage ?? throw new ArgumentNullException(nameof(errorMessage));
		}
	}
}