//
// ContractHelper.cs
//
// Authors:
//    Chris Bacon (chrisbacon76@gmail.com)
//
// Copyright 2010 Novell (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#if NET_4_5

using System;
using System.Text;
using System.Reflection;
using System.Runtime.ConstrainedExecution;
using System.Diagnostics.Contracts;
using System.Diagnostics;

namespace System.Runtime.CompilerServices
{
	public static class ContractHelper
	{
		[ReliabilityContract (Consistency.WillNotCorruptState, Cer.MayFail)]
		[DebuggerNonUserCode]
		public static string RaiseContractFailedEvent (ContractFailureKind failureKind, string userMessage, string conditionText, Exception innerException)
		{

			StringBuilder msg = new StringBuilder (60);
			switch (failureKind) {
			case ContractFailureKind.Assert:
				msg.Append ("Assertion failed");
				break;
			case ContractFailureKind.Assume:
				msg.Append ("Assumption failed");
				break;
			case ContractFailureKind.Invariant:
				msg.Append ("Invariant failed");
				break;
			case ContractFailureKind.Postcondition:
				msg.Append ("Postcondition failed");
				break;
			case ContractFailureKind.PostconditionOnException:
				msg.Append ("Postcondition failed after throwing an exception");
				break;
			case ContractFailureKind.Precondition:
				msg.Append ("Precondition failed");
				break;
			default:
				throw new NotSupportedException ("Not supported: " + failureKind);
			}
			if (conditionText != null) {
				msg.Append (": ");
				msg.Append (conditionText);
			} else {
				msg.Append ('.');
			}
			if (userMessage != null) {
				msg.Append ("  ");
				msg.Append (userMessage);
			}
			string msgString = msg.ToString ();

			Exception handlerException = null;
			bool unwind = false, handled = false;

			var contractFailed = Contract.InternalContractFailedEvent;
			if (contractFailed != null) {
				// Execute all event handlers
				var handlers = contractFailed.GetInvocationList ();
				var e = new ContractFailedEventArgs (failureKind, msgString, conditionText, innerException);
				foreach (var handler in handlers) {
					try {
						handler.DynamicInvoke (null, e);
					} catch (Exception ex) {
						e.SetUnwind ();
						// If multiple handlers throw an exception then the specification states that it
						// is undetermined which one becomes the InnerException.
						handlerException = ex.InnerException;
					}
				}
				unwind = e.Unwind;
				handled = e.Handled;
			}

			if (unwind) {
				Exception ex = innerException ?? handlerException;
				throw new ContractException (msgString, failureKind, conditionText, userMessage, ex);
			}

			return handled ? null : msgString;
		}

		[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
		[DebuggerNonUserCode]
		public static void TriggerFailure (ContractFailureKind kind, string displayMessage, string userMessage, string conditionText, Exception innerException)
		{
			StringBuilder msg = new StringBuilder (50);

			if (conditionText != null) {
				msg.Append ("Expression: ");
				msg.AppendLine (conditionText);
			}
			msg.Append ("Description: ");
			if (displayMessage != null) {
				msg.Append (displayMessage);
			}
			if (Environment.UserInteractive) {
				// FIXME: This should trigger an assertion.
				// But code will never get here at the moment, as Environment.UserInteractive currently
				// always returns false.
				throw new ContractShouldAssertException (msg.ToString ());
			} else {
				// Note that FailFast() currently throws a NotImplementedException()
				Environment.FailFast(msg.ToString()/*, new ExecutionEngineException()*/);
			}
		}

	}

}

#endif