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//! This file defines the expected behaviours of a builder of graphs.
use crate::{error::Error, Graph};
/// A builder is actually just a graph that can be altered in more
/// ways than an extension graph can. It should not have any methods
/// from the Graph trait, though, as we shall convert a builder to a
/// normal final graph before using it.
pub trait Builder: Default {
/// Some graphs are labelled. This type should be the type of the
/// labels.
type Label;
/// The type of the result graph.
type Result: Graph;
/// Construct an empty builder with the capacity to hold a given
/// number of nodes.
///
/// Implementations may ignore this method, where the default
/// implementation just calls `Default::default`.
#[inline]
fn with_capacity(_size: usize) -> Self {
Self::default()
}
/// Add a vertex without children.
fn add_vertex(&mut self) -> usize;
/// Add an edge from the source to the target.
fn add_edge(&mut self, source: usize, target: usize, label: Self::Label) -> Result<(), Error>;
/// Remove an edge from the source to the target.
///
/// Since some graphs are labelled, the users are allowed to pass
/// a predicate to determine if an edge from the source to the
/// target should be removed.
fn remove_edge<F>(&mut self, source: usize, target: usize, predicate: F) -> Result<(), Error>
where
F: Fn(Self::Label) -> bool;
/// Convert the builder into a graph.
///
/// This is the purpose of having a builder.
fn build(self) -> Self::Result;
/// Convert the builder into a graph using a reference.
///
/// This is similar to [`build`][Builder::build], but takes an
/// immutable reference of the builder, so that the builder can
/// still be used later on.
fn build_ref(&self) -> Self::Result;
}
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