DefaultWait{T}.cs

// <copyright file="DefaultWait{T}.cs" company="Selenium Committers">
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// or more contributor license agreements.  See the NOTICE file
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// regarding copyright ownership.  The SFC licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
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// </copyright>

using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Linq;
using System.Threading;

#nullable enable

namespace OpenQA.Selenium.Support.UI
{
    /// <summary>
    /// An implementation of the <see cref="IWait&lt;T&gt;"/> interface that may have its timeout and polling interval
    /// configured on the fly.
    /// </summary>
    /// <typeparam name="T">The type of object on which the wait it to be applied.</typeparam>
    public class DefaultWait<T> : IWait<T>
    {
        private readonly T input;
        private readonly IClock clock;
        private readonly List<Type> ignoredExceptions = new List<Type>();

        /// <summary>
        /// Initializes a new instance of the <see cref="DefaultWait&lt;T&gt;"/> class.
        /// </summary>
        /// <param name="input">The input value to pass to the evaluated conditions.</param>
        public DefaultWait(T input)
            : this(input, SystemClock.Instance)
        {
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="DefaultWait&lt;T&gt;"/> class.
        /// </summary>
        /// <param name="input">The input value to pass to the evaluated conditions.</param>
        /// <param name="clock">The clock to use when measuring the timeout.</param>
        /// <exception cref="ArgumentNullException">If <paramref name="clock"/> or <paramref name="input"/> are <see langword="null"/>.</exception>
        public DefaultWait(T input, IClock clock)
        {
            this.input = input ?? throw new ArgumentNullException(nameof(input), "input cannot be null"); ;
            this.clock = clock ?? throw new ArgumentNullException(nameof(clock), "clock cannot be null"); ;
        }

        /// <summary>
        /// Gets or sets how long to wait for the evaluated condition to be true. The default timeout is 500 milliseconds.
        /// </summary>
        public TimeSpan Timeout { get; set; } = DefaultSleepTimeout;

        /// <summary>
        /// Gets or sets how often the condition should be evaluated. The default timeout is 500 milliseconds.
        /// </summary>
        public TimeSpan PollingInterval { get; set; } = DefaultSleepTimeout;

        /// <summary>
        /// Gets or sets the message to be displayed when time expires.
        /// </summary>
        public string Message { get; set; } = string.Empty;

        private static TimeSpan DefaultSleepTimeout => TimeSpan.FromMilliseconds(500);

        /// <summary>
        /// Configures this instance to ignore specific types of exceptions while waiting for a condition.
        /// Any exceptions not whitelisted will be allowed to propagate, terminating the wait.
        /// </summary>
        /// <param name="exceptionTypes">The types of exceptions to ignore.</param>
        public void IgnoreExceptionTypes(params Type[] exceptionTypes)
        {
            if (exceptionTypes == null)
            {
                throw new ArgumentNullException(nameof(exceptionTypes), "exceptionTypes cannot be null");
            }

            foreach (Type exceptionType in exceptionTypes)
            {
                if (!typeof(Exception).IsAssignableFrom(exceptionType))
                {
                    throw new ArgumentException("All types to be ignored must derive from System.Exception", nameof(exceptionTypes));
                }
            }

            this.ignoredExceptions.AddRange(exceptionTypes);
        }

        /// <summary>
        /// Repeatedly applies this instance's input value to the given function until one of the following
        /// occurs:
        /// <para>
        /// <list type="bullet">
        /// <item>the function returns neither null nor false</item>
        /// <item>the function throws an exception that is not in the list of ignored exception types</item>
        /// <item>the timeout expires</item>
        /// </list>
        /// </para>
        /// </summary>
        /// <typeparam name="TResult">The delegate's expected return type.</typeparam>
        /// <param name="condition">A delegate taking an object of type T as its parameter, and returning a TResult.</param>
        /// <returns>The delegate's return value.</returns>
        [return: NotNull]
        public virtual TResult Until<TResult>(Func<T, TResult?> condition)
        {
            return Until(condition, CancellationToken.None);
        }

        /// <summary>
        /// Repeatedly applies this instance's input value to the given function until one of the following
        /// occurs:
        /// <para>
        /// <list type="bullet">
        /// <item>the function returns neither null nor false</item>
        /// <item>the function throws an exception that is not in the list of ignored exception types</item>
        /// <item>the timeout expires</item>
        /// </list>
        /// </para>
        /// </summary>
        /// <typeparam name="TResult">The delegate's expected return type.</typeparam>
        /// <param name="condition">A delegate taking an object of type T as its parameter, and returning a TResult.</param>
        /// <param name="token">A cancellation token that can be used to cancel the wait.</param>
        /// <returns>The delegate's return value.</returns>
        [return: NotNull]
        public virtual TResult Until<TResult>(Func<T, TResult?> condition, CancellationToken token)
        {
            if (condition == null)
            {
                throw new ArgumentNullException(nameof(condition), "condition cannot be null");
            }

            var resultType = typeof(TResult);
            if ((resultType.IsValueType && resultType != typeof(bool)) || !typeof(object).IsAssignableFrom(resultType))
            {
                throw new ArgumentException($"Can only wait on an object or boolean response, tried to use type: {resultType}", nameof(condition));
            }

            Exception? lastException = null;
            var endTime = this.clock.LaterBy(this.Timeout);
            while (true)
            {
                token.ThrowIfCancellationRequested();

                try
                {
                    var result = condition(this.input);
                    if (resultType == typeof(bool))
                    {
                        if (result is true)
                        {
                            return result;
                        }
                    }
                    else
                    {
                        if (result != null)
                        {
                            return result;
                        }
                    }
                }
                catch (Exception ex)
                {
                    if (!this.IsIgnoredException(ex))
                    {
                        throw;
                    }

                    lastException = ex;
                }

                // Check the timeout after evaluating the function to ensure conditions
                // with a zero timeout can succeed.
                if (!this.clock.IsNowBefore(endTime))
                {
                    string timeoutMessage = string.Format(CultureInfo.InvariantCulture, "Timed out after {0} seconds", this.Timeout.TotalSeconds);
                    if (!string.IsNullOrEmpty(this.Message))
                    {
                        timeoutMessage += ": " + this.Message;
                    }

                    this.ThrowTimeoutException(timeoutMessage, lastException);
                }

                Thread.Sleep(this.PollingInterval);
            }
        }

        /// <summary>
        /// Throws a <see cref="WebDriverTimeoutException"/> with the given message.
        /// </summary>
        /// <param name="exceptionMessage">The message of the exception.</param>
        /// <param name="lastException">The last exception thrown by the condition.</param>
        /// <remarks>This method may be overridden to throw an exception that is
        /// idiomatic for a particular test infrastructure.</remarks>
        protected virtual void ThrowTimeoutException(string exceptionMessage, Exception? lastException)
        {
            throw new WebDriverTimeoutException(exceptionMessage, lastException);
        }

        private bool IsIgnoredException(Exception exception)
        {
            return this.ignoredExceptions.Any(type => type.IsAssignableFrom(exception.GetType()));
        }
    }
}