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use crate::ElementId;
use crate::graph::Graph;
use crate::walker::builder::{EdgeWalkerBuilder, VertexWalkerBuilder};
use crate::walker::{EdgeWalker, VertexWalker, Walker};
use smallbox::{SmallBox, space};
// Use a reasonable size for the SmallBox - can be tuned
type BoxSpace = space::S32;
// Helper trait for boxed vertex walkers that provides both next() and context access
trait BoxedVertexWalkerOps<'graph, G: Graph, Context> {
fn next(&mut self, graph: &'graph G) -> Option<G::VertexId>;
fn ctx(&self) -> &Context;
fn ctx_mut(&mut self) -> &mut Context;
}
// Helper trait for boxed edge walkers that provides both next() and context access
trait BoxedEdgeWalkerOps<'graph, G: Graph, Context> {
fn next(&mut self, graph: &'graph G) -> Option<G::EdgeId>;
fn ctx(&self) -> &Context;
fn ctx_mut(&mut self) -> &mut Context;
}
// Blanket implementation for any vertex walker
impl<'graph, G: Graph, W, Context> BoxedVertexWalkerOps<'graph, G, Context> for W
where
W: VertexWalker<'graph, Graph = G, Context = Context>,
{
fn next(&mut self, graph: &'graph G) -> Option<G::VertexId> {
VertexWalker::next(self, graph)
}
fn ctx(&self) -> &Context {
Walker::ctx(self)
}
fn ctx_mut(&mut self) -> &mut Context {
Walker::ctx_mut(self)
}
}
// Blanket implementation for any edge walker
impl<'graph, G: Graph, W, Context> BoxedEdgeWalkerOps<'graph, G, Context> for W
where
W: EdgeWalker<'graph, Graph = G, Context = Context>,
{
fn next(&mut self, graph: &'graph G) -> Option<G::EdgeId> {
EdgeWalker::next(self, graph)
}
fn ctx(&self) -> &Context {
Walker::ctx(self)
}
fn ctx_mut(&mut self) -> &mut Context {
Walker::ctx_mut(self)
}
}
/// A boxed vertex walker that uses SmallBox for type erasure
/// This helps reduce monomorphization by hiding concrete walker types
pub struct BoxedVertexWalker<'graph, G: Graph, Context> {
// We box the entire walker using a trait object that provides all operations
inner: SmallBox<Box<dyn BoxedVertexWalkerOps<'graph, G, Context> + 'graph>, BoxSpace>,
}
impl<'graph, G: Graph, Context: Clone> BoxedVertexWalker<'graph, G, Context> {
pub(crate) fn new<W>(walker: W) -> Self
where
W: VertexWalker<'graph, Graph = G, Context = Context> + 'graph,
{
// Box the walker as a trait object that implements our ops trait
let boxed: Box<dyn BoxedVertexWalkerOps<'graph, G, Context> + 'graph> = Box::new(walker);
Self {
inner: SmallBox::new(boxed),
}
}
}
impl<'graph, G: Graph, Context: Clone + 'static> Walker<'graph>
for BoxedVertexWalker<'graph, G, Context>
{
type Graph = G;
type Context = Context;
fn next_element(&mut self, graph: &'graph Self::Graph) -> Option<ElementId<Self::Graph>> {
VertexWalker::next(self, graph).map(ElementId::Vertex)
}
fn ctx(&self) -> &Self::Context {
// Delegate to the inner walker's context
self.inner.as_ref().ctx()
}
fn ctx_mut(&mut self) -> &mut Self::Context {
// Delegate to the inner walker's context
self.inner.as_mut().ctx_mut()
}
}
impl<'graph, G: Graph, Context: Clone + 'static> VertexWalker<'graph>
for BoxedVertexWalker<'graph, G, Context>
{
fn next(&mut self, graph: &'graph Self::Graph) -> Option<<Self::Graph as Graph>::VertexId> {
// Delegate to the inner walker's next method
self.inner.as_mut().next(graph)
}
}
/// A boxed edge walker that uses SmallBox for type erasure
/// This helps reduce monomorphization by hiding concrete walker types
pub struct BoxedEdgeWalker<'graph, G: Graph, Context> {
// We box the entire walker using a trait object that provides all operations
inner: SmallBox<Box<dyn BoxedEdgeWalkerOps<'graph, G, Context> + 'graph>, BoxSpace>,
}
impl<'graph, G: Graph, Context: Clone> BoxedEdgeWalker<'graph, G, Context> {
pub(crate) fn new<W>(walker: W) -> Self
where
W: EdgeWalker<'graph, Graph = G, Context = Context> + 'graph,
{
// Box the walker as a trait object that implements our ops trait
let boxed: Box<dyn BoxedEdgeWalkerOps<'graph, G, Context> + 'graph> = Box::new(walker);
Self {
inner: SmallBox::new(boxed),
}
}
}
impl<'graph, G: Graph, Context: Clone + 'static> Walker<'graph>
for BoxedEdgeWalker<'graph, G, Context>
{
type Graph = G;
type Context = Context;
fn next_element(&mut self, graph: &'graph Self::Graph) -> Option<ElementId<Self::Graph>> {
EdgeWalker::next(self, graph).map(ElementId::Edge)
}
fn ctx(&self) -> &Self::Context {
// Delegate to the inner walker's context
self.inner.as_ref().ctx()
}
fn ctx_mut(&mut self) -> &mut Self::Context {
// Delegate to the inner walker's context
self.inner.as_mut().ctx_mut()
}
}
impl<'graph, G: Graph, Context: Clone + 'static> EdgeWalker<'graph>
for BoxedEdgeWalker<'graph, G, Context>
{
fn next(&mut self, graph: &'graph Self::Graph) -> Option<<Self::Graph as Graph>::EdgeId> {
// Delegate to the inner walker's next method
self.inner.as_mut().next(graph)
}
}
// Extension methods for builders to add boxed() method
impl<'graph, Mutability, Graph, Walker> VertexWalkerBuilder<'graph, Mutability, Graph, Walker>
where
Graph: crate::graph::Graph,
Walker: VertexWalker<'graph, Graph = Graph> + 'graph,
Walker::Context: Clone + 'static,
{
/// # Boxed Step
///
/// The `boxed` step performs type erasure to reduce monomorphization and improve compile times.
/// It wraps the current walker in a `SmallBox`, breaking the chain of nested generic types
/// that can grow exponentially in complex traversals.
///
/// ## When to Use
///
/// Use `boxed()` strategically in complex walker chains:
/// - **After 4+ chained operations** to prevent type explosion
/// - **When compile times become slow** due to deep walker nesting
/// - **At logical checkpoints** in long traversals
/// - **When storing walkers** in data structures
///
/// ## Performance Considerations
///
/// - **Pros**: Faster compilation, smaller binaries, stack allocation for small walkers
/// - **Cons**: 5-15% runtime overhead from indirect calls, lost inlining opportunities
/// - **Best for**: Complex traversals where graph I/O dominates computation
///
/// ## Example
///
/// ```rust
/// # use graph_api_lib::*;
/// # use graph_api_test::{populate_graph, Vertex, Edge};
/// # use graph_api_simplegraph::SimpleGraph;
/// # let mut graph = SimpleGraph::<Vertex, Edge>::new();
/// # populate_graph(&mut graph);
/// // Without boxing - complex nested types
/// let complex_type = graph
/// .walk()
/// .vertices(VertexSearch::scan())
/// .edges(EdgeSearch::scan())
/// .head()
/// .edges(EdgeSearch::scan())
/// .head();
/// // Type: Endpoints<Edges<Endpoints<Edges<Vertices<Empty>>>>>
///
/// // With strategic boxing - simpler types
/// let result: Vec<_> = graph
/// .walk()
/// .vertices(VertexSearch::scan())
/// .edges(EdgeSearch::scan())
/// .boxed() // ← Breaks type complexity here
/// .head()
/// .edges(EdgeSearch::scan())
/// .boxed() // ← And here for further reduction
/// .head()
/// .collect();
/// ```
///
/// ## Technical Details
///
/// This method uses `SmallBox<S32>` which attempts to store walkers on the stack
/// (up to 32 bytes) before falling back to heap allocation. This provides better
/// cache locality than regular `Box` for small walker states.
///
/// # Note
/// This method works with any context type that implements `Clone + 'static`.
/// The context is preserved through the boxing operation and updated on each `next()` call.
pub fn boxed(
self,
) -> VertexWalkerBuilder<
'graph,
Mutability,
Graph,
BoxedVertexWalker<'graph, Graph, Walker::Context>,
> {
self.with_vertex_walker(|walker| BoxedVertexWalker::new(walker))
}
}
impl<'graph, Mutability, Graph, Walker> EdgeWalkerBuilder<'graph, Mutability, Graph, Walker>
where
Graph: crate::graph::Graph,
Walker: EdgeWalker<'graph, Graph = Graph> + 'graph,
Walker::Context: Clone + 'static,
{
/// # Boxed Step (Edge Walker)
///
/// The `boxed` step performs type erasure to reduce monomorphization and improve compile times.
/// It wraps the current edge walker in a `SmallBox`, breaking the chain of nested generic types
/// that can grow exponentially in complex traversals.
///
/// ## When to Use
///
/// Use `boxed()` strategically in complex walker chains:
/// - **After 4+ chained operations** to prevent type explosion
/// - **When compile times become slow** due to deep walker nesting
/// - **At logical checkpoints** in long traversals
/// - **When storing walkers** in data structures
///
/// ## Performance Considerations
///
/// - **Pros**: Faster compilation, smaller binaries, stack allocation for small walkers
/// - **Cons**: 5-15% runtime overhead from indirect calls, lost inlining opportunities
/// - **Best for**: Complex traversals where graph I/O dominates computation
///
/// ## Example
///
/// ```rust
/// # use graph_api_lib::*;
/// # use graph_api_test::{populate_graph, Vertex, Edge};
/// # use graph_api_simplegraph::SimpleGraph;
/// # let mut graph = SimpleGraph::<Vertex, Edge>::new();
/// # populate_graph(&mut graph);
/// // Strategic boxing in edge-heavy traversals
/// let edges: Vec<_> = graph
/// .walk()
/// .vertices(VertexSearch::scan())
/// .edges(EdgeSearch::scan())
/// .filter(|e, _| e.label().contains("knows"))
/// .boxed() // ← Box complex edge walker chains
/// .collect();
/// ```
///
/// ## Technical Details
///
/// This method uses `SmallBox<S32>` which attempts to store walkers on the stack
/// (up to 32 bytes) before falling back to heap allocation. This provides better
/// cache locality than regular `Box` for small walker states.
///
/// # Note
/// This method works with any context type that implements `Clone + 'static`.
/// The context is preserved through the boxing operation and updated on each `next()` call.
pub fn boxed(
self,
) -> EdgeWalkerBuilder<'graph, Mutability, Graph, BoxedEdgeWalker<'graph, Graph, Walker::Context>>
{
self.with_edge_walker(|walker| BoxedEdgeWalker::new(walker))
}
}