public static ISpecification <TRight> Combine <TLeft, TRight>(this ISpecification <TLeft> specification, ISpecification <TRight> other)
{
var leftQuery = (Query.Query)specification.Query;
var rightQuery = (Query.Query)other.Query;
var rightQueryItems = GetQueryChain(rightQuery);
var rightFirstClause = rightQueryItems[0];
if (leftQuery.Parameters.OutType != rightFirstClause.Parameters.InType)
{
throw new InvalidOperationException($"Left specification provide type {leftQuery.Parameters.OutType} that did not match right specification {rightFirstClause.Parameters.InType}");
}
var query = leftQuery;
foreach (var itm in rightQueryItems)
{
if (itm.Parameters.QueryType == QueryType.Empty)
{
continue;
}
query = new Query.Query(query, itm.Parameters, itm.EntityType);
}
return(new CustomSpecification <TRight>(query));
}
static Query.Query[] GetQueryChain(this Query.Query query)
{
var chain = new List <Query.Query>();
while (query != null)
{
chain.Add(query);
query = query.Parent;
}
chain.Reverse();
return(chain.ToArray());
}
public static ISpecification <T> Or <T>(this ISpecification <T> left, ISpecification <T> right)
{
var leftQuery = (Query.Query)left.Query;
var rightQuery = (Query.Query)right.Query;
var leftQueryItems = GetQueryChain(leftQuery);
var rightQueryItems = GetQueryChain(rightQuery);
leftQuery = leftQueryItems.Last();
rightQuery = rightQueryItems.SkipWhile(x => x.Parameters.QueryType == QueryType.Empty).First();
if (leftQueryItems.Last().Parameters.QueryType != QueryType.Where)
{
throw new InvalidOperationException("Left specification must ending with Where expression");
}
if (rightQueryItems.SkipWhile(x => x.Parameters.QueryType == QueryType.Empty).Count(x => x.Parameters.QueryType != QueryType.Where) > 0)
{
throw new InvalidOperationException("Right specification should contains only one Where clause");
}
var argumentParameter = Expression.Parameter(typeof(T), "obj");
var contextParameter = Expression.Parameter(typeof(IQueryContext), "context");
var leftExpression = (LambdaExpression)leftQuery.Parameters.Expression;
var leftPartExpression = new ReplaceExpressionVisitor <ParameterExpression, ParameterExpression>(
new ReplaceItem <ParameterExpression, ParameterExpression>(leftExpression.Parameters.First(x => x.Type == typeof(T)), argumentParameter),
new ReplaceItem <ParameterExpression, ParameterExpression>(leftExpression.Parameters.FirstOrDefault(x => x.Type == typeof(IQueryContext)), contextParameter))
.Visit(leftExpression.Body);
var rightExpression = (LambdaExpression)rightQuery.Parameters.Expression;
var rightPartExpression = new ReplaceExpressionVisitor <ParameterExpression, ParameterExpression>(
new ReplaceItem <ParameterExpression, ParameterExpression>(rightExpression.Parameters.First(x => x.Type == typeof(T)), argumentParameter),
new ReplaceItem <ParameterExpression, ParameterExpression>(rightExpression.Parameters.FirstOrDefault(x => x.Type == typeof(IQueryContext)), contextParameter))
.Visit(rightExpression.Body);
var resultExpressionBody = Expression.OrElse(leftPartExpression, rightPartExpression);
var query = new Query.Query(
leftQueryItems.Last().Parent,
new WhereQueryParameter(
typeof(T),
typeof(T),
Expression.Lambda(resultExpressionBody, argumentParameter, contextParameter),
QueryType.Where),
leftQuery.EntityType);
return(new CustomSpecification <T>(query));
}
