affected_core/

graph.rs

use petgraph::algo::{is_cyclic_directed, tarjan_scc};
use petgraph::graph::{DiGraph, NodeIndex};
use petgraph::visit::Bfs;
use std::collections::{HashMap, HashSet, VecDeque};

use crate::types::{PackageId, ProjectGraph};

/// Dependency graph wrapper around petgraph.
pub struct DepGraph {
    graph: DiGraph<PackageId, ()>,
    node_map: HashMap<PackageId, NodeIndex>,
}

impl DepGraph {
    /// Build from a ProjectGraph. Edges go from dependent → dependency.
    pub fn from_project_graph(pg: &ProjectGraph) -> Self {
        let mut graph = DiGraph::new();
        let mut node_map = HashMap::new();

        for id in pg.packages.keys() {
            let idx = graph.add_node(id.clone());
            node_map.insert(id.clone(), idx);
        }

        for (from, to) in &pg.edges {
            if let (Some(&from_idx), Some(&to_idx)) = (node_map.get(from), node_map.get(to)) {
                graph.add_edge(from_idx, to_idx, ());
            }
        }

        Self { graph, node_map }
    }

    /// Given a set of directly changed packages, return all transitively
    /// affected packages (changed + everything that depends on them).
    ///
    /// Uses BFS on the reversed graph: if A→B means "A depends on B",
    /// then in the reversed graph B→A, and BFS from a changed node B
    /// finds all packages that transitively depend on B.
    pub fn affected_by(&self, changed: &HashSet<PackageId>) -> HashSet<PackageId> {
        let reversed = petgraph::visit::Reversed(&self.graph);
        let mut result = HashSet::new();

        for pkg in changed {
            if let Some(&start) = self.node_map.get(pkg) {
                let mut bfs = Bfs::new(&reversed, start);
                while let Some(node) = bfs.next(&reversed) {
                    result.insert(self.graph[node].clone());
                }
            }
        }

        result
    }

    /// For each affected package, return the shortest dependency chain back to a
    /// directly changed package. Uses BFS on the reversed graph, tracking parents.
    pub fn explain_affected(
        &self,
        changed: &HashSet<PackageId>,
        affected: &HashSet<PackageId>,
    ) -> Vec<(PackageId, Vec<PackageId>)> {
        let mut parent: HashMap<NodeIndex, Option<NodeIndex>> = HashMap::new();
        let mut visited: HashSet<NodeIndex> = HashSet::new();
        let mut queue: VecDeque<NodeIndex> = VecDeque::new();

        // Initialize BFS from all changed packages
        for pkg in changed {
            if let Some(&idx) = self.node_map.get(pkg) {
                if visited.insert(idx) {
                    parent.insert(idx, None);
                    queue.push_back(idx);
                }
            }
        }

        // BFS on reversed graph (follow incoming edges)
        while let Some(current) = queue.pop_front() {
            for neighbor in self
                .graph
                .neighbors_directed(current, petgraph::Direction::Incoming)
            {
                if visited.insert(neighbor) {
                    parent.insert(neighbor, Some(current));
                    queue.push_back(neighbor);
                }
            }
        }

        let mut results = Vec::new();
        for pkg in affected {
            if let Some(&idx) = self.node_map.get(pkg) {
                if changed.contains(pkg) {
                    results.push((pkg.clone(), vec![pkg.clone()]));
                } else if parent.contains_key(&idx) {
                    let mut chain = vec![pkg.clone()];
                    let mut cur = idx;
                    while let Some(Some(prev)) = parent.get(&cur) {
                        chain.push(self.graph[*prev].clone());
                        cur = *prev;
                    }
                    results.push((pkg.clone(), chain));
                }
            }
        }

        results.sort_by(|a, b| a.0.cmp(&b.0));
        results
    }

    /// Check if the dependency graph contains any cycles.
    pub fn has_cycles(&self) -> bool {
        is_cyclic_directed(&self.graph)
    }

    /// Find and return all cycles in the graph (SCCs with size > 1).
    pub fn find_cycles(&self) -> Vec<Vec<PackageId>> {
        tarjan_scc(&self.graph)
            .into_iter()
            .filter(|scc| scc.len() > 1)
            .map(|scc| scc.into_iter().map(|idx| self.graph[idx].clone()).collect())
            .collect()
    }

    /// Enhanced DOT output where affected nodes are colored red and changed nodes are orange.
    pub fn to_dot_with_affected(
        &self,
        changed: &HashSet<PackageId>,
        affected: &HashSet<PackageId>,
    ) -> String {
        let mut lines = vec!["digraph dependencies {".to_string()];
        for (pkg_id, &idx) in &self.node_map {
            let label = &self.graph[idx].0;
            if changed.contains(pkg_id) {
                lines.push(format!(
                    "    \"{}\" [style=filled, fillcolor=orange];",
                    label
                ));
            } else if affected.contains(pkg_id) {
                lines.push(format!(
                    "    \"{}\" [style=filled, fillcolor=red, fontcolor=white];",
                    label
                ));
            }
        }
        for edge in self.graph.edge_indices() {
            let (a, b) = self.graph.edge_endpoints(edge).unwrap();
            lines.push(format!(
                "    \"{}\" -> \"{}\";",
                self.graph[a], self.graph[b]
            ));
        }
        lines.push("}".to_string());
        lines.join("\n")
    }

    /// Return all package IDs in the graph.
    pub fn all_packages(&self) -> Vec<&PackageId> {
        self.graph.node_weights().collect()
    }

    /// Generate DOT format output for graphviz visualization.
    pub fn to_dot(&self) -> String {
        let mut lines = vec!["digraph dependencies {".to_string()];
        for edge in self.graph.edge_indices() {
            let (a, b) = self.graph.edge_endpoints(edge).unwrap();
            lines.push(format!(
                "    \"{}\" -> \"{}\";",
                self.graph[a], self.graph[b]
            ));
        }
        lines.push("}".to_string());
        lines.join("\n")
    }

    /// Return all edges as (from, to) pairs for display.
    pub fn edges(&self) -> Vec<(&PackageId, &PackageId)> {
        self.graph
            .edge_indices()
            .map(|e| {
                let (a, b) = self.graph.edge_endpoints(e).unwrap();
                (&self.graph[a], &self.graph[b])
            })
            .collect()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::types::Package;
    use std::path::PathBuf;

    fn make_graph(names: &[&str], edges: &[(&str, &str)]) -> ProjectGraph {
        let mut packages = HashMap::new();
        for name in names {
            let id = PackageId(name.to_string());
            packages.insert(
                id.clone(),
                Package {
                    id: id.clone(),
                    name: name.to_string(),
                    version: None,
                    path: PathBuf::from(format!("/{name}")),
                    manifest_path: PathBuf::from(format!("/{name}/Cargo.toml")),
                },
            );
        }
        let edges = edges
            .iter()
            .map(|(a, b)| (PackageId(a.to_string()), PackageId(b.to_string())))
            .collect();
        ProjectGraph {
            packages,
            edges,
            root: PathBuf::from("/"),
        }
    }

    #[test]
    fn test_linear_chain() {
        // cli -> api -> core
        let pg = make_graph(&["core", "api", "cli"], &[("api", "core"), ("cli", "api")]);
        let dg = DepGraph::from_project_graph(&pg);

        let changed: HashSet<_> = [PackageId("core".into())].into();
        let affected = dg.affected_by(&changed);

        assert!(affected.contains(&PackageId("core".into())));
        assert!(affected.contains(&PackageId("api".into())));
        assert!(affected.contains(&PackageId("cli".into())));
        assert_eq!(affected.len(), 3);
    }

    #[test]
    fn test_leaf_change() {
        // cli -> api -> core
        let pg = make_graph(&["core", "api", "cli"], &[("api", "core"), ("cli", "api")]);
        let dg = DepGraph::from_project_graph(&pg);

        let changed: HashSet<_> = [PackageId("cli".into())].into();
        let affected = dg.affected_by(&changed);

        assert!(affected.contains(&PackageId("cli".into())));
        assert_eq!(affected.len(), 1);
    }

    #[test]
    fn test_diamond_dependency() {
        //   app
        //  /   \
        // ui   api
        //  \   /
        //  core
        let pg = make_graph(
            &["core", "ui", "api", "app"],
            &[
                ("ui", "core"),
                ("api", "core"),
                ("app", "ui"),
                ("app", "api"),
            ],
        );
        let dg = DepGraph::from_project_graph(&pg);

        let changed: HashSet<_> = [PackageId("core".into())].into();
        let affected = dg.affected_by(&changed);

        assert_eq!(affected.len(), 4);
    }

    #[test]
    fn test_isolated_package() {
        let pg = make_graph(&["core", "api", "standalone"], &[("api", "core")]);
        let dg = DepGraph::from_project_graph(&pg);

        let changed: HashSet<_> = [PackageId("core".into())].into();
        let affected = dg.affected_by(&changed);

        assert!(affected.contains(&PackageId("core".into())));
        assert!(affected.contains(&PackageId("api".into())));
        assert!(!affected.contains(&PackageId("standalone".into())));
    }
}