private Expression <Func <StoredEntry, bool> > TranslatePredicate(Expression <Func <IEntryState <TId, TData>, bool> > predicate)
{
Assert(predicate != null);
var parameter = Expression.Parameter(typeof(StoredEntry));
var body = ParameterExpressionReplacer.ReplaceParameter(predicate.Body, predicate.Parameters.First(), parameter);
return(Expression.Lambda <Func <StoredEntry, bool> >(body, parameter));
}
private Expression <TDelegate> ConvertExpression <TDelegate>(LambdaExpression expression)
where TDelegate : Delegate
{
var parameter = expression.Parameters.First();
var body = expression.Body;
var newParameter = Expression.Parameter(typeof(TRemote));
var newBody = ParameterExpressionReplacer.ReplaceParameter(body, parameter, newParameter);
return(Expression.Lambda <TDelegate>(newBody, newParameter));
}
private static Expression <Func <TEntry, bool> > BuildPredicate <TEntry>(TEntry comparand,
Expression <Func <TEntry, TEntry, bool> > equalityComparer)
{
Assert(comparand != null);
Assert(equalityComparer != null);
var idSelector = DataPropertyHelper.BuildPredicate(comparand);
var comparandConstant = Expression.Constant(comparand, typeof(TEntry));
var parameter = equalityComparer.Parameters.First();
var equality = ParameterExpressionReplacer.ReplaceParameter(equalityComparer.Body, equalityComparer.Parameters.Last(), comparandConstant);
var idEquality = ParameterExpressionReplacer.ReplaceParameter(idSelector.Body, idSelector.Parameters.First(), parameter);
var body = Expression.AndAlso(idEquality, equality);
return(Expression.Lambda <Func <TEntry, bool> >(body, parameter));
}
public static Expression <Func <TDataRepresentation, bool> > TranslatePredicate <TId, TData, TDataRepresentation>(Expression <Func <TData, bool> > predicate)
where TData : class
where TDataRepresentation : class, IDataRepresentation <TId, TData>
{
// The resulting predicate checks
// 1) If the entry's payload matches the specified predicate.
// 2) If the entry's data is not null (The entry is not deleted)
var parameter = Expression.Parameter(typeof(TDataRepresentation));
var dataAccessor = DataHelper <TId, TData> .Accessor;
var nullConstant = DataHelper <TId, TData> .Null;
var data = ParameterExpressionReplacer.ReplaceParameter(dataAccessor.Body, dataAccessor.Parameters.First(), parameter);
var isNull = Expression.ReferenceEqual(data, nullConstant);
var isNotNull = Expression.Not(isNull);
var matchesPredicate = ParameterExpressionReplacer.ReplaceParameter(predicate.Body, predicate.Parameters.First(), data);
var body = Expression.AndAlso(isNotNull, matchesPredicate);
return(Expression.Lambda <Func <TDataRepresentation, bool> >(body, parameter));
}
private static Expression <Func <TEntry, TEntry, bool> > BuildEqualityComparer <TEntry, TVersion>(Expression <Func <TEntry, TVersion> > versionSelector)
where TEntry : class
where TVersion : IEquatable <TVersion>
{
Assert(versionSelector != null);
var param1 = Expression.Parameter(typeof(TEntry), "left");
var param2 = Expression.Parameter(typeof(TEntry), "right");
var version1 = ParameterExpressionReplacer.ReplaceParameter(versionSelector.Body, versionSelector.Parameters.First(), param1);
var version2 = ParameterExpressionReplacer.ReplaceParameter(versionSelector.Body, versionSelector.Parameters.First(), param2);
var equalityMethod = typeof(IEquatable <TVersion>).GetMethod(nameof(Equals));
Assert(equalityMethod != null);
var call = Expression.Call(version1, equalityMethod, version2);
Expression equality;
if (typeof(TVersion).IsValueType)
{
equality = call;
}
else // (left == null && right == null) || (left != null && right != null && left.Equals(right));
{
var isNull1 = Expression.Equal(version1, Expression.Constant(null, typeof(TVersion)));
var isNull2 = Expression.Equal(version2, Expression.Constant(null, typeof(TVersion)));
var isNotNull1 = Expression.Not(isNull1);
var isNotNull2 = Expression.Not(isNull2);
var bothNull = Expression.AndAlso(isNull1, isNull2);
var bothNotNUll = Expression.AndAlso(isNotNull1, isNotNull2);
equality = Expression.OrElse(bothNull, Expression.AndAlso(bothNotNUll, call));
}
return(Expression.Lambda <Func <TEntry, TEntry, bool> >(equality, param1, param2));
}
