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// Copyright (c) 2026 Austin Han <austinhan1024@gmail.com>
//
// This file is part of RocksGraph.
//
// RocksGraph is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// RocksGraph is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with RocksGraph. If not, see <https://www.gnu.org/licenses/>.
use crate::types::PIPELINE_PRODUCE_SIZE;
use std::rc::Rc;
use smallvec::SmallVec;
use crate::engine::volcano::steps::traits::ExplainNode;
use crate::{
engine::{
context::GraphCtx,
traverser::Traverser,
volcano::steps::traits::{CoreStep, StepRef},
},
types::error::StoreError,
};
/// A physical step that acts as a source, emitting a predefined vector of `Traverser` items.
#[derive(Debug)]
pub struct VecSourceStep {
// ── Dynamic/Runtime execution state ──
/// Predefined vector of traverser items to emit.
items: SmallVec<[Rc<Traverser>; PIPELINE_PRODUCE_SIZE]>,
}
impl VecSourceStep {
/// Creates an empty `VecSourceStep`.
pub fn empty() -> Self {
Self { items: SmallVec::new() }
}
/// Injects a collection of `Traverser` items into this source step.
/// These items will be emitted when `produce` is called.
pub fn inject(&mut self, items: SmallVec<[Rc<Traverser>; PIPELINE_PRODUCE_SIZE]>) {
self.items.extend(items);
}
}
impl CoreStep for VecSourceStep {
fn add_upper(&mut self, _upstream: StepRef) {
// `VecSourceStep` is a source step and does not have an upstream.
panic!("VecSourceStep is a source step and cannot have an upstream");
}
fn produce(
&mut self,
_ctx: &mut dyn GraphCtx,
) -> Result<Option<SmallVec<[Rc<Traverser>; PIPELINE_PRODUCE_SIZE]>>, StoreError> {
// Emits all currently held `Traverser` items and then clears its internal buffer.
if !self.items.is_empty() {
Ok(Some(std::mem::take(&mut self.items)))
} else {
Ok(None)
}
}
fn reset(&mut self) {
// Resets the step by clearing its internal buffer of items.
self.items.clear();
}
fn explain(&self) -> ExplainNode {
ExplainNode::new("VecSourceStep")
}
}