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use crate::graph::GraphStorage;
use crate::*;
/// `drop_label("L")`: removes a label from the label set of each incoming vertex and emits the
/// same vertex.
#[derive(Clone)]
struct StepDropLabel {
label: CompactString,
}
impl fmt::Display for StepDropLabel {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
f,
"drop_label({})",
crate::value::literal::rhai_string(&self.label)
)
}
}
fn drop_label_step<'g, S: GraphStorage + 'g>(label: CompactString) -> GraphStep<'g, S> {
GraphStep::SideEffectMut("drop_label", Box::new(StepDropLabel { label }))
}
impl<'g, S: GraphStorage + 'g> GraphTraversalSource<'g, S> {
/// Removes `label` from the label set of each incoming vertex and lets the vertex continue.
///
/// A Graphersal extension: TinkerPop labels are immutable and TinkerPop has no such step, so
/// this adds to Gremlin rather than deviating from it. A vertex that does not carry the label
/// is unchanged (no error), so a bulk-n traverser changes its vertex once. Dropping the last
/// label leaves the vertex unlabeled, which is allowed unless the schema rejects it. With a
/// schema active the vertex must stay valid under its remaining labels (`Closed`: an
/// unlabeled vertex, a property no remaining label declares, or an incident edge no longer
/// matching a declared connection is rejected; `Open`/`Closed`: the remaining labels are
/// re-checked); a violation fails the traversal, whose unit rolls back. An edge is an error
/// whose help names [`Self::set_label`]; any other value is an error too.
///
/// ```rust
/// use graphersal::prelude::*;
///
/// let mut graph = TraversalGraph::tinkerpop_modern();
/// graph.traversal_mut().v("1").drop_label("person").next().unwrap();
/// assert_eq!(
/// graph.traversal().v(None).has_label("person").count().next().unwrap(),
/// Some(ElementProperty::from(3))
/// );
/// ```
pub fn drop_label(self, label: impl Into<CompactString>) -> Self {
self.push_step(drop_label_step(label.into()))
}
}
impl __ {
/// Anonymous `drop_label()`; see [`GraphTraversalSource::drop_label`].
pub fn drop_label<'g, S: GraphStorage + 'g>(
label: impl Into<CompactString>,
) -> AnonymousTraversal<'g, S> {
AnonymousTraversal::new().drop_label(label)
}
}
impl<'g, S: GraphStorage + 'g> AnonymousTraversal<'g, S> {
/// Anonymous `drop_label()`; see [`GraphTraversalSource::drop_label`].
pub fn drop_label(self, label: impl Into<CompactString>) -> Self {
self.push_step(drop_label_step(label.into()))
}
}
impl<'g, S: GraphStorage + 'g> GraphStepSideEffectMut<'g, S> for StepDropLabel {
fn process(
&self,
context: &mut TraverserContext<'_, S>,
source: Option<Traverser<S>>,
) -> TraverserResult<Vec<Traverser<S>>> {
let Some(source) = source else {
return Ok(Vec::new());
};
match &source.value {
TraverserValue::Vertex(node) => {
context.storage.remove_vertex_label(*node, &self.label)?;
}
other => {
return Err(Box::new(TraverserError::label_step_element_kind(
"drop_label",
other,
)));
}
}
Ok(vec![source])
}
fn extends_path(&self) -> bool {
false
}
fn clone_box(&self) -> Box<dyn GraphStepSideEffectMut<'g, S> + 'g> {
Box::new(self.clone())
}
}