/*************************************************************************************

   Extended WPF Toolkit

   Copyright (C) 2007-2013 Xceed Software Inc.

   This program is provided to you under the terms of the Microsoft Public
   License (Ms-PL) as published at http://wpftoolkit.codeplex.com/license 

   For more features, controls, and fast professional support,
   pick up the Plus Edition at http://xceed.com/wpf_toolkit

   Stay informed: follow @datagrid on Twitter or Like http://facebook.com/datagrids

  ***********************************************************************************/

/**************************************************************************\
    Copyright Microsoft Corporation. All Rights Reserved.
\**************************************************************************/

// Conditional to use more aggressive fail-fast behaviors when debugging.
#define DEV_DEBUG

// This file contains general utilities to aid in development.
// It is distinct from unit test Assert classes.
// Classes here generally shouldn't be exposed publicly since
// they're not particular to any library functionality.
// Because the classes here are internal, it's likely this file
// might be included in multiple assemblies.
namespace Standard
{
  using System;
  using System.Diagnostics;
  using System.Threading;

  /// <summary>A static class for verifying assumptions.</summary>
  internal static class Assert
  {
    private static void _Break()
    {
#if DEV_DEBUG
      Debugger.Break();
#else
            Debug.Assert(false);
#endif
    }

    /// <summary>A function signature for Assert.Evaluate.</summary>
    public delegate void EvaluateFunction();

    /// <summary>A function signature for Assert.Implies.</summary>
    /// <returns>Returns the truth of a predicate.</returns>
    public delegate bool ImplicationFunction();

    /// <summary>
    /// Executes the specified argument.
    /// </summary>
    /// <param name="argument">The function to execute.</param>
    [Conditional( "DEBUG" )]
    public static void Evaluate( EvaluateFunction argument )
    {
      IsNotNull( argument );
      argument();
    }

    /// <summary>Obsolete: Use Standard.Assert.AreEqual instead of Assert.Equals</summary>
    /// <typeparam name="T">The generic type to compare for equality.</typeparam>
    /// <param name="expected">The first generic type data to compare.  This is is the expected value.</param>
    /// <param name="actual">The second generic type data to compare.  This is the actual value.</param>
    [
        Obsolete( "Use Assert.AreEqual instead of Assert.Equals", false ),
        Conditional( "DEBUG" )
    ]
    public static void Equals<T>( T expected, T actual )
    {
      AreEqual( expected, actual );
    }

    /// <summary>
    /// Verifies that two generic type data are equal.  The assertion fails if they are not.
    /// </summary>
    /// <typeparam name="T">The generic type to compare for equality.</typeparam>
    /// <param name="expected">The first generic type data to compare.  This is is the expected value.</param>
    /// <param name="actual">The second generic type data to compare.  This is the actual value.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void AreEqual<T>( T expected, T actual )
    {
      if( null == expected )
      {
        // Two nulls are considered equal, regardless of type semantics.
        if( null != actual && !actual.Equals( expected ) )
        {
          _Break();
        }
      }
      else if( !expected.Equals( actual ) )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that two generic type data are not equal.  The assertion fails if they are.
    /// </summary>
    /// <typeparam name="T">The generic type to compare for inequality.</typeparam>
    /// <param name="notExpected">The first generic type data to compare.  This is is the value that's not expected.</param>
    /// <param name="actual">The second generic type data to compare.  This is the actual value.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void AreNotEqual<T>( T notExpected, T actual )
    {
      if( null == notExpected )
      {
        // Two nulls are considered equal, regardless of type semantics.
        if( null == actual || actual.Equals( notExpected ) )
        {
          _Break();
        }
      }
      else if( notExpected.Equals( actual ) )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that if the specified condition is true, then so is the result.
    /// The assertion fails if the condition is true but the result is false.
    /// </summary>
    /// <param name="condition">if set to <c>true</c> [condition].</param>
    /// <param name="result">
    /// A second Boolean statement.  If the first was true then so must this be.
    /// If the first statement was false then the value of this is ignored.
    /// </param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void Implies( bool condition, bool result )
    {
      if( condition && !result )
      {
        _Break();
      }
    }

    /// <summary>
    /// Lazy evaluation overload.  Verifies that if a condition is true, then so is a secondary value.
    /// </summary>
    /// <param name="condition">The conditional value.</param>
    /// <param name="result">A function to be evaluated for truth if the condition argument is true.</param>
    /// <remarks>
    /// This overload only evaluates the result if the first condition is true.
    /// </remarks>
    [Conditional( "DEBUG" )]
    public static void Implies( bool condition, ImplicationFunction result )
    {
      if( condition && !result() )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that a string has content.  I.e. it is not null and it is not empty.
    /// </summary>
    /// <param name="value">The string to verify.</param>
    [Conditional( "DEBUG" )]
    public static void IsNeitherNullNorEmpty( string value )
    {
      IsFalse( string.IsNullOrEmpty( value ) );
    }

    /// <summary>
    /// Verifies that a string has content.  I.e. it is not null and it is not purely whitespace.
    /// </summary>
    /// <param name="value">The string to verify.</param>
    [Conditional( "DEBUG" )]
    public static void IsNeitherNullNorWhitespace( string value )
    {
      if( string.IsNullOrEmpty( value ) )
      {
        _Break();
      }

      if( value.Trim().Length == 0 )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies the specified value is not null.  The assertion fails if it is.
    /// </summary>
    /// <typeparam name="T">The generic reference type.</typeparam>
    /// <param name="value">The value to check for nullness.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsNotNull<T>( T value ) where T : class
    {
      if( null == value )
      {
        _Break();
      }
    }

    [Conditional( "DEBUG" )]
    public static void IsDefault<T>( T value ) where T : struct
    {
      if( !value.Equals( default( T ) ) )
      {
        Assert.Fail();
      }
    }

    [Conditional( "DEBUG" )]
    public static void IsNotDefault<T>( T value ) where T : struct
    {
      if( value.Equals( default( T ) ) )
      {
        Assert.Fail();
      }
    }

    /// <summary>
    /// Verifies that the specified condition is false.  The assertion fails if it is true.
    /// </summary>
    /// <param name="condition">The expression that should be <c>false</c>.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsFalse( bool condition )
    {
      if( condition )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that the specified condition is false.  The assertion fails if it is true.
    /// </summary>
    /// <param name="condition">The expression that should be <c>false</c>.</param>
    /// <param name="message">The message to display if the condition is <c>true</c>.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsFalse( bool condition, string message )
    {
      if( condition )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that the specified condition is true.  The assertion fails if it is not.
    /// </summary>
    /// <param name="condition">A condition that is expected to be <c>true</c>.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsTrue( bool condition )
    {
      if( !condition )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that the specified condition is true.  The assertion fails if it is not.
    /// </summary>
    /// <param name="condition">A condition that is expected to be <c>true</c>.</param>
    /// <param name="message">The message to write in case the condition is <c>false</c>.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsTrue( bool condition, string message )
    {
      if( !condition )
      {
        _Break();
      }
    }

    /// <summary>
    /// This line should never be executed.  The assertion always fails.
    /// </summary>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void Fail()
    {
      _Break();
    }

    /// <summary>
    /// This line should never be executed.  The assertion always fails.
    /// </summary>
    /// <param name="message">The message to display if this function is executed.</param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void Fail( string message )
    {
      _Break();
    }

    /// <summary>
    /// Verifies that the specified object is null.  The assertion fails if it is not.
    /// </summary>
    /// <param name="item">The item to verify is null.</param>
    [Conditional( "DEBUG" )]
    public static void IsNull<T>( T item ) where T : class
    {
      if( null != item )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that the specified value is within the expected range.  The assertion fails if it isn't.
    /// </summary>
    /// <param name="lowerBoundInclusive">The lower bound inclusive value.</param>
    /// <param name="value">The value to verify.</param>
    /// <param name="upperBoundInclusive">The upper bound inclusive value.</param>
    [Conditional( "DEBUG" )]
    public static void BoundedDoubleInc( double lowerBoundInclusive, double value, double upperBoundInclusive )
    {
      if( value < lowerBoundInclusive || value > upperBoundInclusive )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verifies that the specified value is within the expected range.  The assertion fails if it isn't.
    /// </summary>
    /// <param name="lowerBoundInclusive">The lower bound inclusive value.</param>
    /// <param name="value">The value to verify.</param>
    /// <param name="upperBoundExclusive">The upper bound exclusive value.</param>
    [Conditional( "DEBUG" )]
    public static void BoundedInteger( int lowerBoundInclusive, int value, int upperBoundExclusive )
    {
      if( value < lowerBoundInclusive || value >= upperBoundExclusive )
      {
        _Break();
      }
    }

    /// <summary>
    /// Verify the current thread's apartment state is what's expected.  The assertion fails if it isn't
    /// </summary>
    /// <param name="expectedState">
    /// The expected apartment state for the current thread.
    /// </param>
    /// <remarks>This breaks into the debugger in the case of a failed assertion.</remarks>
    [Conditional( "DEBUG" )]
    public static void IsApartmentState( ApartmentState expectedState )
    {
      if( Thread.CurrentThread.GetApartmentState() != expectedState )
      {
        _Break();
      }
    }

    [Conditional( "DEBUG" )]
    public static void NullableIsNotNull<T>( T? value ) where T : struct
    {
      if( null == value )
      {
        _Break();
      }
    }

    [Conditional( "DEBUG" )]
    public static void NullableIsNull<T>( T? value ) where T : struct
    {
      if( null != value )
      {
        _Break();
      }
    }

    [Conditional( "DEBUG" )]
    public static void IsNotOnMainThread()
    {
      if( System.Windows.Application.Current.Dispatcher.CheckAccess() )
      {
        _Break();
      }
    }
  }
}