meta-ast 0.6.0

//! Dependency graph module for cross-file and symbol-level analysis.
//!
//! This module provides graph data structures and algorithms for analyzing
//! dependencies between source files and their contained symbols. It supports:
//!
//! - Building a directed graph from extracted symbols
//! - Computing strongly connected components (SCCs)
//! - Providing deployability hints based on cycle detection
//!
//! # Design as stated in RFC 0008
//!
//! The graph layer sits between the extraction layer and the output layer:
//! - `node.rs` defines `FileNode` and `SymbolNode` types
//! - `edge.rs` defines `EdgeKind` (Ownership, Import, Reference)
//! - `builder.rs` provides `GraphBuilder` for incremental construction
//! - `scc.rs` provides SCC analysis via Tarjan's algorithm
//!
//! # Example
//!
//! ```
//! use meta_ast::graph::{GraphBuilder, SccAnalysis, CodeGraph};
//! use meta_ast::model::SnapshotId;
//!
//! // Create builder and add files/symbols
//! let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
//! // ... add nodes and edges ...
//! let graph = builder.build();
//!
//! // Run SCC analysis
//! let scc = SccAnalysis::analyze(graph.graph());
//! ```

pub mod builder;
pub mod edge;
pub mod node;
pub mod resolver;
pub mod scc;

use std::collections::HashMap;

pub use builder::GraphBuilder;
pub use edge::{EdgeData, EdgeKind};
pub use node::{
    DataGraphNode, ExternalClassification, ExternalNode, FileNode, NodeData, SymbolNode,
};
pub use scc::{DeployabilityHint, Scc, SccAnalysis};

use crate::language::LangId;
use crate::model::{FileId, SnapshotId, SymbolId};
use petgraph::graph::{DiGraph, EdgeIndex, NodeIndex};

/// The canonical dependency graph for a codebase snapshot.
#[derive(Debug, Clone)]
pub struct CodeGraph {
    /// The underlying petgraph with our node/edge data types.
    graph: DiGraph<NodeData, EdgeData>,

    /// O(1) dedup index: (source, target, kind) -> EdgeIndex, kept in sync
    /// with `graph`. Every edge added through the normalized-add methods is
    /// registered here; the builder populates it in `GraphBuilder::build`.
    edge_index: HashMap<(NodeIndex, NodeIndex, EdgeKind), EdgeIndex>,

    /// Map from FileId to graph node index for O(1) lookup.
    pub(crate) file_to_index: HashMap<FileId, NodeIndex>,

    /// Map from SymbolId to graph node index for O(1) lookup.
    pub(crate) symbol_to_index: HashMap<SymbolId, NodeIndex>,

    /// Map from external raw path to graph node index for O(1) lookup.
    pub(crate) external_index: HashMap<String, NodeIndex>,

    /// Snapshot identifier for this graph as discussed before.
    pub snapshot_id: SnapshotId,
}

impl CodeGraph {
    /// Creates an empty CodeGraph for the given snapshot.
    pub fn new(snapshot_id: SnapshotId) -> Self {
        Self {
            graph: DiGraph::new(),
            edge_index: HashMap::new(),
            file_to_index: HashMap::new(),
            symbol_to_index: HashMap::new(),
            external_index: HashMap::new(),
            snapshot_id,
        }
    }

    /// Assemble a graph from builder parts without reindexing edges.
    ///
    /// The builder maintains the same `(source, target, kind)` dedup index
    /// during construction, so `build()` moves it directly.
    pub(crate) fn from_parts(
        graph: DiGraph<NodeData, EdgeData>,
        edge_index: HashMap<(NodeIndex, NodeIndex, EdgeKind), EdgeIndex>,
        file_to_index: HashMap<FileId, NodeIndex>,
        symbol_to_index: HashMap<SymbolId, NodeIndex>,
        external_index: HashMap<String, NodeIndex>,
        snapshot_id: SnapshotId,
    ) -> Self {
        Self {
            graph,
            edge_index,
            file_to_index,
            symbol_to_index,
            external_index,
            snapshot_id,
        }
    }
    /// Immutable access to the underlying petgraph graph for SCC analysis,
    /// serialization, and deploy algorithms.
    pub fn graph(&self) -> &DiGraph<NodeData, EdgeData> {
        &self.graph
    }

    /// Adds a raw node to the graph. Node additions do not affect edge
    /// normalization, so this is the only direct mutation needed by
    /// deploy/test code that injects synthetic nodes post-build.
    ///
    /// The caller remains responsible for registering the node in the
    /// index maps (`file_to_index`, `symbol_to_index`, `external_index`)
    /// when it is a `File`/`Symbol`/`External` node. This method does not
    /// sync those maps; a bare `Data` node needs no registration.
    pub fn add_node(&mut self, node: NodeData) -> NodeIndex {
        self.graph.add_node(node)
    }
    pub fn file_node_index(&self, file_id: FileId) -> Option<NodeIndex> {
        self.file_to_index.get(&file_id).copied()
    }
    pub fn symbol_node_index(&self, symbol_id: SymbolId) -> Option<NodeIndex> {
        self.symbol_to_index.get(&symbol_id).copied()
    }
    pub fn file_node(&self, file_id: FileId) -> Option<&FileNode> {
        let idx = self.file_node_index(file_id)?;
        self.graph.node_weight(idx).and_then(|data| data.as_file())
    }
    pub fn symbol_node(&self, symbol_id: SymbolId) -> Option<&SymbolNode> {
        let idx = self.symbol_node_index(symbol_id)?;
        self.graph
            .node_weight(idx)
            .and_then(|data| data.as_symbol())
    }
    pub fn file_count(&self) -> usize {
        self.file_to_index.len()
    }
    pub fn symbol_count(&self) -> usize {
        self.symbol_to_index.len()
    }
    pub fn external_count(&self) -> usize {
        self.external_index.len()
    }
    pub fn node_count(&self) -> usize {
        self.graph.node_count()
    }
    pub fn edge_count(&self) -> usize {
        self.graph.edge_count()
    }
    /// Resolves or creates the `External` node for a raw unresolved path, keeping
    /// `external_index` consistent so repeated loads reuse a single node.
    pub fn get_or_create_external_node(&mut self, raw_path: String, language: LangId) -> NodeIndex {
        if let Some(&idx) = self.external_index.get(&raw_path) {
            return idx;
        }
        let node = NodeData::External(ExternalNode {
            raw_path: raw_path.clone(),
            language,
            classification: None,
        });
        let idx = self.graph.add_node(node);
        self.external_index.insert(raw_path, idx);
        idx
    }
    /// Adds an edge, normalizing duplicate `(src, dst, kind)` triples by max-merging
    /// confidence so injected edges obey the same invariant as builder-constructed ones.
    /// The O(1) `edge_index` makes duplicate detection independent of out-degree.
    pub fn add_edge_normalized(
        &mut self,
        source: NodeIndex,
        target: NodeIndex,
        kind: EdgeKind,
        confidence: f32,
    ) {
        let confidence = confidence.clamp(0.0, 1.0);
        let key = (source, target, kind);
        if let Some(&edge_idx) = self.edge_index.get(&key) {
            let edge = &mut self.graph[edge_idx];
            edge.confidence = edge.confidence.max(confidence);
            return;
        }
        let edge_idx = self.graph.add_edge(
            source,
            target,
            EdgeData {
                kind,
                confidence,
                flow_kind: None,
            },
        );
        self.edge_index.insert(key, edge_idx);
    }

    /// Adds a Flow edge with a specific flow kind, normalizing duplicates by
    /// max-merging confidence (same (src, dst, Flow) triple). When a duplicate
    /// edge exists, the first non-None `flow_kind` is preserved. The lookup is
    /// O(1) via the dedup index.
    pub fn add_edge_normalized_with_flow(
        &mut self,
        source: NodeIndex,
        target: NodeIndex,
        kind: EdgeKind,
        confidence: f32,
        flow_kind: Option<crate::model::FlowKind>,
    ) {
        let confidence = confidence.clamp(0.0, 1.0);
        let key = (source, target, kind);
        if let Some(&edge_idx) = self.edge_index.get(&key) {
            let edge = &mut self.graph[edge_idx];
            edge.confidence = edge.confidence.max(confidence);
            if edge.flow_kind.is_none() {
                edge.flow_kind = flow_kind;
            }
            return;
        }
        let edge_idx = self.graph.add_edge(
            source,
            target,
            EdgeData {
                kind,
                confidence,
                flow_kind,
            },
        );
        self.edge_index.insert(key, edge_idx);
    }

    pub fn files(&self) -> impl Iterator<Item = (FileId, &FileNode)> + '_ {
        self.file_to_index.iter().filter_map(|(file_id, &idx)| {
            self.graph
                .node_weight(idx)
                .and_then(|data| data.as_file().map(|f| (*file_id, f)))
        })
    }
    pub fn symbols(&self) -> impl Iterator<Item = (SymbolId, &SymbolNode)> + '_ {
        self.symbol_to_index.iter().filter_map(|(symbol_id, &idx)| {
            self.graph
                .node_weight(idx)
                .and_then(|data| data.as_symbol().map(|s| (*symbol_id, s)))
        })
    }
    pub fn edges_of_kind(
        &self,
        kind: EdgeKind,
    ) -> impl Iterator<Item = (NodeIndex, NodeIndex)> + '_ {
        self.graph.edge_indices().filter_map(move |edge_idx| {
            let (source, target) = self.graph.edge_endpoints(edge_idx)?;
            let weight = self.graph.edge_weight(edge_idx)?;
            if weight.kind == kind {
                Some((source, target))
            } else {
                None
            }
        })
    }

    /// Reference edges as (source symbol, target symbol, confidence).
    ///
    /// Skips edges whose endpoints are not symbol nodes. Use for navigation
    /// and confidence-ranked completion.
    pub fn reference_edges(&self) -> impl Iterator<Item = (SymbolId, SymbolId, f32)> + '_ {
        self.graph.edge_indices().filter_map(move |edge_idx| {
            let weight = self.graph.edge_weight(edge_idx)?;
            if weight.kind != EdgeKind::Reference {
                return None;
            }
            let (source, target) = self.graph.edge_endpoints(edge_idx)?;
            let source_id = self.graph.node_weight(source)?.as_symbol()?.id;
            let target_id = self.graph.node_weight(target)?.as_symbol()?.id;
            Some((source_id, target_id, weight.confidence))
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::language::LangId;
    use crate::model::{LineColumn, SourceRange, Symbol, SymbolKind, Visibility, ids::SnapshotId};
    use std::path::PathBuf;

    fn test_range() -> SourceRange {
        SourceRange {
            byte_start: 0,
            byte_end: 10,
            start: LineColumn { line: 1, column: 0 },
            end: LineColumn {
                line: 1,
                column: 10,
            },
        }
    }

    fn test_file_node(id: u32, path: &str) -> NodeData {
        NodeData::File(FileNode {
            id: FileId::new(id).unwrap(),
            path: PathBuf::from(path),
            language: LangId::Rust,
            snapshot_id: SnapshotId::new(1).unwrap(),
        })
    }

    fn test_symbol(id: u32, name: &str) -> Symbol {
        Symbol {
            id: SymbolId::new(id).unwrap(),
            name: name.to_string(),
            kind: SymbolKind::Function,
            language: LangId::Rust,
            file_path: PathBuf::from("test.rs"),
            source_range: test_range(),
            visibility: Some(Visibility::Public),
            signature: None,
            docstring: None,
            is_async: false,
        }
    }

    #[test]
    fn code_graph_new_empty() {
        let graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        assert_eq!(graph.node_count(), 0);
        assert_eq!(graph.edge_count(), 0);
        assert_eq!(graph.snapshot_id.to_raw(), 1);
    }

    #[test]
    fn code_graph_file_lookup_returns_none_for_missing() {
        let graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        assert!(graph.file_node(FileId::new(1).unwrap()).is_none());
        assert!(graph.file_node_index(FileId::new(1).unwrap()).is_none());
    }

    #[test]
    fn code_graph_symbol_lookup_returns_none_for_missing() {
        let graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        assert!(graph.symbol_node(SymbolId::new(1).unwrap()).is_none());
        assert!(graph.symbol_node_index(SymbolId::new(1).unwrap()).is_none());
    }

    #[test]
    fn builder_produces_valid_code_graph() {
        let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
        let file_id = builder.add_file(PathBuf::from("test.rs"), LangId::Rust);
        let symbol = test_symbol(1, "main");
        let _sym_idx = builder.add_symbol(&symbol).unwrap();

        let graph = builder.build();

        assert_eq!(graph.file_count(), 1);
        assert_eq!(graph.symbol_count(), 1);
        assert_eq!(graph.node_count(), 2);
        assert_eq!(graph.edge_count(), 1); // ownership edge

        // Test lookups
        let file_lookup = graph.file_node(file_id);
        assert!(file_lookup.is_some());
        assert_eq!(file_lookup.unwrap().language, LangId::Rust);

        let sym_lookup = graph.symbol_node(SymbolId::new(1).unwrap());
        assert!(sym_lookup.is_some());
        assert_eq!(sym_lookup.unwrap().name, "main");
    }

    #[test]
    fn code_graph_iteration_over_files() {
        let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
        builder.add_file(PathBuf::from("a.rs"), LangId::Rust);
        builder.add_file(PathBuf::from("b.py"), LangId::Python);

        let graph = builder.build();
        let files: Vec<_> = graph.files().collect();

        assert_eq!(files.len(), 2);
    }

    #[test]
    fn code_graph_iteration_over_symbols() {
        let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
        let _file_id = builder.add_file(PathBuf::from("test.rs"), LangId::Rust);
        let sym1 = test_symbol(1, "func_a");
        let sym2 = test_symbol(2, "func_b");
        builder.add_symbol(&sym1).unwrap();
        builder.add_symbol(&sym2).unwrap();

        let graph = builder.build();
        let symbols: Vec<_> = graph.symbols().collect();

        assert_eq!(symbols.len(), 2);
    }

    #[test]
    fn code_graph_edges_of_kind_filtering() {
        let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
        let file1 = builder.add_file(PathBuf::from("a.rs"), LangId::Rust);
        let _file2 = builder.add_file(PathBuf::from("b.rs"), LangId::Rust);

        // Add import edge
        builder.add_import(file1, PathBuf::from("b.rs"));

        let graph = builder.build();

        let ownership_edges: Vec<_> = graph.edges_of_kind(EdgeKind::Ownership).collect();
        let import_edges: Vec<_> = graph.edges_of_kind(EdgeKind::Import).collect();

        assert_eq!(ownership_edges.len(), 0); // No symbols added
        assert_eq!(import_edges.len(), 1);
    }

    #[test]
    fn build_populated_edge_index_normalizes_post_build_edges() {
        let mut builder = GraphBuilder::new(SnapshotId::new(1).unwrap());
        let file_a = builder.add_file(PathBuf::from("a.rs"), LangId::Rust);
        let file_b = builder.add_file(PathBuf::from("b.rs"), LangId::Rust);
        builder.add_import(file_a, PathBuf::from("b.rs"));
        let mut graph = builder.build();
        assert_eq!(graph.edge_count(), 1);

        let a_idx = graph.file_node_index(file_a).unwrap();
        let b_idx = graph.file_node_index(file_b).unwrap();

        // Duplicate triple already indexed by build(): must max-merge, not grow.
        graph.add_edge_normalized(a_idx, b_idx, EdgeKind::Import, 0.5);
        graph.add_edge_normalized(a_idx, b_idx, EdgeKind::Import, 0.8);
        assert_eq!(graph.edge_count(), 1);

        // Distinct kind on the same pair is a new edge.
        graph.add_edge_normalized(a_idx, b_idx, EdgeKind::Reference, 0.9);
        assert_eq!(graph.edge_count(), 2);
    }

    #[test]
    fn add_edge_normalized_handles_multiple_edge_kinds_between_same_nodes() {
        let mut graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        let n1 = graph.add_node(test_file_node(1, "a.rs"));
        let n2 = graph.add_node(test_file_node(2, "b.rs"));

        // 1. Add Reference edge with confidence 0.7
        graph.add_edge_normalized(n1, n2, EdgeKind::Reference, 0.7);
        // 2. Add Import edge with confidence 0.5 (pushed to head of edge list)
        graph.add_edge_normalized(n1, n2, EdgeKind::Import, 0.5);
        // 3. Add Reference edge again with confidence 0.9 (should max-merge into existing Reference edge)
        graph.add_edge_normalized(n1, n2, EdgeKind::Reference, 0.9);

        let ref_count = graph
            .graph()
            .edges_connecting(n1, n2)
            .filter(|e| e.weight().kind == EdgeKind::Reference)
            .count();
        assert_eq!(
            ref_count, 1,
            "Expected 1 Reference edge, but found {ref_count}"
        );
        assert_eq!(graph.edge_count(), 2);
    }

    #[test]
    fn add_edge_normalized_with_flow_preserves_first_flow_kind() {
        use crate::model::{DataNodeId, DataScope, FlowKind};
        let mut graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        let n1 = graph.add_node(NodeData::Data(DataGraphNode {
            id: DataNodeId::new(1).unwrap(),
            symbol_id: None,
            name: Some("x".into()),
            scope: DataScope::Local,
            type_hint: None,
            source_range: test_range(),
        }));
        let n2 = graph.add_node(NodeData::Data(DataGraphNode {
            id: DataNodeId::new(2).unwrap(),
            symbol_id: None,
            name: Some("y".into()),
            scope: DataScope::Local,
            type_hint: None,
            source_range: test_range(),
        }));

        graph.add_edge_normalized_with_flow(n1, n2, EdgeKind::Flow, 0.9, Some(FlowKind::DefUse));
        graph.add_edge_normalized_with_flow(n1, n2, EdgeKind::Flow, 0.8, Some(FlowKind::Argument));

        assert_eq!(graph.edge_count(), 1);
        let edge = graph.graph().edges_connecting(n1, n2).next().unwrap();
        assert_eq!(edge.weight().flow_kind, Some(FlowKind::DefUse));
        assert_eq!(edge.weight().confidence, 0.9);
    }

    #[test]
    fn add_edge_normalized_duplicate_never_grows_edge_count() {
        let mut graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        let n1 = graph.add_node(test_file_node(1, "a.rs"));
        let n2 = graph.add_node(test_file_node(2, "b.rs"));

        graph.add_edge_normalized(n1, n2, EdgeKind::Import, 0.5);
        for confidence in [0.6, 0.3, 0.9, 0.4, 0.7] {
            graph.add_edge_normalized(n1, n2, EdgeKind::Import, confidence);
        }

        assert_eq!(graph.edge_count(), 1);
        let edge = graph.graph().edges_connecting(n1, n2).next().unwrap();
        assert_eq!(edge.weight().confidence, 0.9);
    }

    #[test]
    fn add_edge_normalized_counts_only_distinct_triples() {
        let mut graph = CodeGraph::new(SnapshotId::new(1).unwrap());
        let n1 = graph.add_node(test_file_node(1, "a.rs"));
        let n2 = graph.add_node(test_file_node(2, "b.rs"));
        let n3 = graph.add_node(test_file_node(3, "c.rs"));

        graph.add_edge_normalized(n1, n2, EdgeKind::Import, 0.5);
        graph.add_edge_normalized(n1, n2, EdgeKind::Reference, 0.6);
        graph.add_edge_normalized(n1, n3, EdgeKind::Reference, 0.7);
        graph.add_edge_normalized(n1, n2, EdgeKind::Import, 0.9);

        assert_eq!(graph.edge_count(), 3);
    }
}