public static Expression <Func <T, T> > Project <T>(this QueryableProjectionContext context)
{
if (context.TryGetQueryableScope(out QueryableProjectionScope? scope))
{
return(scope.Project <T>());
}
throw ProjectionConvention_CouldNotProject();
}
public static QueryableProjectionScope AddScope(
this QueryableProjectionContext context,
Type runtimeType)
{
var parameterName = "p" + context.Scopes.Count;
var closure =
new QueryableProjectionScope(runtimeType, parameterName);
context.Scopes.Push(closure);
return(closure);
}
public static bool TryGetQueryableScope(
this QueryableProjectionContext ctx,
[NotNullWhen(true)] out QueryableProjectionScope?scope)
{
if (ctx.Scopes.Count > 0 &&
ctx.Scopes.Peek() is QueryableProjectionScope queryableScope)
{
scope = queryableScope;
return(true);
}
scope = null;
return(false);
}
private static ApplyProjection CreateApplicatorAsync <TEntityType>()
{
return((context, input) =>
{
if (input is null)
{
return input;
}
// if projections are already applied we can skip
var skipProjection =
context.LocalContextData.TryGetValue(SkipProjectionKey, out object?skip) &&
skip is true;
// ensure sorting is only applied once
context.LocalContextData =
context.LocalContextData.SetItem(SkipProjectionKey, true);
if (skipProjection)
{
return input;
}
var visitorContext =
new QueryableProjectionContext(
context,
context.ObjectType,
context.Field.Type.UnwrapRuntimeType());
var visitor = new QueryableProjectionVisitor();
visitor.Visit(visitorContext);
Expression <Func <TEntityType, TEntityType> > projection =
visitorContext.Project <TEntityType>();
input = input switch
{
IQueryable <TEntityType> q => q.Select(projection),
IEnumerable <TEntityType> e => e.AsQueryable().Select(projection),
QueryableExecutable <TEntityType> ex =>
ex.WithSource(ex.Source.Select(projection)),
_ => input
};
return input;
});
}
public override FieldMiddleware CreateExecutor <TEntityType>()
{
return(next => context => ExecuteAsync(next, context));
async ValueTask ExecuteAsync(
FieldDelegate next,
IMiddlewareContext context)
{
// first we let the pipeline run and produce a result.
await next(context).ConfigureAwait(false);
IQueryable <TEntityType>?source = null;
if (context.Result is IQueryable <TEntityType> q)
{
source = q;
}
else if (context.Result is IEnumerable <TEntityType> e)
{
source = e.AsQueryable();
}
if (source is not null)
{
var visitorContext =
new QueryableProjectionContext(
context,
context.ObjectType,
context.Field.Type.UnwrapRuntimeType());
var visitor = new QueryableProjectionVisitor();
visitor.Visit(visitorContext);
context.Result = source.Select(visitorContext.Project <TEntityType>());
}
}
}
public override FieldMiddleware CreateExecutor <TEntityType>()
{
return(next => context => ExecuteAsync(next, context));
async ValueTask ExecuteAsync(
FieldDelegate next,
IMiddlewareContext context)
{
// first we let the pipeline run and produce a result.
await next(context).ConfigureAwait(false);
if (context.Result is not null)
{
var visitorContext =
new QueryableProjectionContext(
context,
context.ObjectType,
context.Field.Type.UnwrapRuntimeType());
var visitor = new QueryableProjectionVisitor();
visitor.Visit(visitorContext);
Expression <Func <TEntityType, TEntityType> > projection =
visitorContext.Project <TEntityType>();
context.Result = context.Result switch
{
IQueryable <TEntityType> q => q.Select(projection),
IEnumerable <TEntityType> e => e.AsQueryable().Select(projection),
QueryableExecutable <TEntityType> ex =>
ex.WithSource(ex.Source.Select(projection)),
_ => context.Result
};
}
}
}
}
