nodex-core 0.2.2

pub mod cache;
pub mod resolver;
pub mod scanner;
pub mod validator;

use indexmap::IndexMap;
use rayon::prelude::*;
use std::collections::BTreeMap;
use std::path::Path;

use crate::config::Config;
use crate::error::{Error, Result};
use crate::model::{Graph, Node, RawEdge};
use crate::parser::{self, ParsedDocument};

use cache::BuildCache;
use resolver::{build_id_set, build_path_index, resolve_edges};
use validator::validate_supersedes_dag;

/// Build result with stats for CLI output.
pub struct BuildResult {
    pub graph: Graph,
    pub stats: BuildStats,
}

#[derive(Debug, serde::Serialize)]
pub struct BuildStats {
    pub nodes: usize,
    pub edges: usize,
    pub cached: usize,
    pub parsed: usize,
    #[serde(skip_serializing_if = "Vec::is_empty")]
    pub warnings: Vec<String>,
}

/// Build the full document graph.
pub fn build(root: &Path, config: &Config, full_rebuild: bool) -> Result<BuildResult> {
    // 1. Scan scope
    let paths = scanner::scan_scope(root, config)?;

    // 2. Load cache (unless full rebuild). Invalidates if config
    // changed OR if the nodex binary itself was upgraded — the cache
    // holds serialised `Node` / `RawEdge` / `Confidence` values, so a
    // struct-shape change in a new version would otherwise let an old
    // cache silently produce stale nodes on the next build. Mixing
    // `CARGO_PKG_VERSION` into the hashed input makes every upgrade a
    // one-time full rebuild, which is cheap and correct.
    //
    // `Config` is a plain, fully-serialisable struct — silently
    // falling back to an empty hash on serialisation failure (the
    // previous `unwrap_or_default`) would let a changed config reuse
    // stale cache entries. `expect` makes the invariant explicit so
    // anyone adding a non-serialisable field to `Config` fails fast.
    let cache_path = root.join(&config.output.dir).join("cache.json");
    let config_json = serde_json::to_string(config)
        .expect("Config is defined entirely over serializable primitives");
    let config_hash = cache::compute_hash(&format!(
        "nodex={}\n{}",
        env!("CARGO_PKG_VERSION"),
        config_json
    ));
    let (mut cache, cache_warning) = if full_rebuild {
        (BuildCache::default(), None)
    } else {
        BuildCache::load(&cache_path, &config_hash)
    };
    cache.config_hash = config_hash;

    // 3. Read file contents (parallel). Collect read errors for warning.
    let read_results: Vec<(
        std::path::PathBuf,
        std::result::Result<String, std::io::Error>,
    )> = paths
        .par_iter()
        .map(|rel_path| {
            let abs_path = root.join(rel_path);
            let result = std::fs::read_to_string(&abs_path);
            (rel_path.clone(), result)
        })
        .collect();

    let mut read_warnings = Vec::new();
    let mut file_contents: Vec<(std::path::PathBuf, String)> = Vec::new();
    for (rel_path, result) in read_results {
        match result {
            Ok(content) => file_contents.push((rel_path, content)),
            Err(e) => read_warnings.push(format!("skipped {}: {e}", rel_path.display())),
        }
    }

    // 4. Parse documents (parallel, with caching)
    let mut cached_count = 0usize;
    let mut parsed_count = 0usize;

    // Separate into cached hits and cache misses
    let mut cached_results: Vec<(Node, Vec<RawEdge>)> = Vec::new();
    let mut to_parse: Vec<(std::path::PathBuf, String)> = Vec::new();

    for (rel_path, content) in &file_contents {
        if let Some(entry) = cache.get(rel_path, content) {
            cached_results.push((
                entry.node.clone(),
                entry.raw_edges.iter().cloned().map(RawEdge::from).collect(),
            ));
            cached_count += 1;
        } else {
            to_parse.push((rel_path.clone(), content.clone()));
        }
    }

    // Parse cache misses in parallel
    let fresh_results: Vec<Result<(std::path::PathBuf, String, ParsedDocument)>> = to_parse
        .par_iter()
        .map(|(rel_path, content)| {
            let doc = parser::parse_document(rel_path, content, config)?;
            Ok((rel_path.clone(), content.clone(), doc))
        })
        .collect();

    let mut all_nodes: Vec<(String, Node)> = Vec::new();
    let mut all_raw_edges: Vec<(String, std::path::PathBuf, Vec<RawEdge>)> = Vec::new();

    // Collect cached results
    for (node, raw_edges) in cached_results {
        let id = node.id.clone();
        let path = node.path.clone();
        all_raw_edges.push((id.clone(), path, raw_edges));
        all_nodes.push((id, node));
    }

    // Collect fresh results and update cache
    for result in fresh_results {
        let (rel_path, content, doc) = result?;
        parsed_count += 1;

        cache.insert(rel_path, &content, doc.node.clone(), &doc.raw_edges);

        let id = doc.node.id.clone();
        let path = doc.node.path.clone();
        all_raw_edges.push((id.clone(), path, doc.raw_edges));
        all_nodes.push((id, doc.node));
    }

    // 5. Check for duplicate ids
    {
        let mut seen: BTreeMap<&str, &Path> = BTreeMap::new();
        for (id, node) in &all_nodes {
            if let Some(&first_path) = seen.get(id.as_str()) {
                return Err(Error::DuplicateId {
                    id: id.clone(),
                    first: first_path.to_path_buf(),
                    second: node.path.clone(),
                });
            }
            seen.insert(id.as_str(), &node.path);
        }
    }

    // 6. Build resolution indices
    let path_index = build_path_index(&all_nodes);
    let id_set = build_id_set(&all_nodes);

    // 7. Resolve edges
    let mut edges = Vec::new();
    for (source_id, source_path, raw_edges) in all_raw_edges {
        let resolved = resolve_edges(&source_id, raw_edges, &source_path, &path_index, &id_set);
        edges.extend(resolved);
    }

    // 7b. Translate each `superseded_by` scalar into its canonical
    //     `supersedes` edge. frontmatter `supersedes: [X]` on node N
    //     yields edge N → X; frontmatter `superseded_by: Y` on node M
    //     yields edge Y → M (same direction, different authoring style).
    //     Without this step, documents that author only the
    //     `superseded_by` field never show up in `backlinks` / `node`
    //     incoming, and `chain` had to traverse a scalar pointer that
    //     lived outside the edge graph — two representations of the
    //     same relation. Materialising both into edges unifies the
    //     graph so every query uses the same traversal.
    edges.extend(derive_superseded_by_edges(&all_nodes));

    // Dedupe by (source, target, relation) so documents that declare
    // both sides (N.supersedes=[X] AND X.superseded_by=N) produce a
    // single edge rather than two identical ones. The body-link
    // resolver never produces duplicates, so this only affects
    // frontmatter-sourced edges.
    dedupe_edges(&mut edges);

    // 8. Validate supersedes DAG
    validate_supersedes_dag(&edges)?;

    // 9. Sort edges for deterministic output
    edges.sort_by(|a, b| {
        a.source
            .cmp(&b.source)
            .then_with(|| a.relation.cmp(&b.relation))
            .then_with(|| a.location.cmp(&b.location))
    });

    // 10. Build sorted node map
    let mut node_map = IndexMap::new();
    all_nodes.sort_by(|a, b| a.0.cmp(&b.0));
    for (id, node) in all_nodes {
        node_map.insert(id, node);
    }

    // 11. Clean cache and save
    let valid_paths: Vec<_> = file_contents.iter().map(|(p, _)| p.clone()).collect();
    cache.retain_paths(&valid_paths);
    let mut warnings = read_warnings;
    if let Some(msg) = cache_warning {
        warnings.push(msg);
    }
    if let Err(e) = cache.save(&cache_path) {
        warnings.push(format!("cache save failed: {e}"));
    }

    let stats = BuildStats {
        nodes: node_map.len(),
        edges: edges.len(),
        cached: cached_count,
        parsed: parsed_count,
        warnings,
    };

    Ok(BuildResult {
        graph: Graph::new(node_map, edges),
        stats,
    })
}

/// Build the edges implied by `superseded_by` scalars. Each `M.superseded_by = Y`
/// becomes an edge `Y → M` with relation `"supersedes"`, matching the
/// canonical direction produced by `supersedes: [...]` vectors. When Y
/// isn't itself a known node id the synthesized edge is skipped — an
/// unresolved target here is better caught by the regular body-link
/// path than by being smuggled into the graph as `ResolvedTarget::Unresolved`.
fn derive_superseded_by_edges(
    all_nodes: &[(String, crate::model::Node)],
) -> Vec<crate::model::Edge> {
    use crate::model::{Confidence, Edge, ResolvedTarget};
    let known_ids: std::collections::BTreeSet<&str> =
        all_nodes.iter().map(|(id, _)| id.as_str()).collect();
    let mut out = Vec::new();
    for (id, node) in all_nodes {
        let Some(ref successor) = node.superseded_by else {
            continue;
        };
        if !known_ids.contains(successor.as_str()) {
            // `successor` isn't a known node id — skip. The standard
            // resolver will record this as an unresolved edge from the
            // body-link pipeline if the content references it.
            continue;
        }
        out.push(Edge {
            source: successor.clone(),
            target: ResolvedTarget::resolved(id.as_str()),
            relation: "supersedes".to_string(),
            confidence: Confidence::Extracted,
            location: format!("frontmatter:superseded_by@{id}"),
        });
    }
    out
}

/// Remove duplicate `(source, target, relation)` edges while preserving
/// the first occurrence's location. The canonical representation keeps
/// the original edge (usually a direct `supersedes` declaration) and
/// discards the mirrored one derived from `superseded_by`.
fn dedupe_edges(edges: &mut Vec<crate::model::Edge>) {
    use crate::model::ResolvedTarget;
    let mut seen: std::collections::BTreeSet<(String, String, String)> =
        std::collections::BTreeSet::new();
    edges.retain(|edge| {
        let target_key = match &edge.target {
            ResolvedTarget::Resolved { id } => format!("r:{id}"),
            ResolvedTarget::Unresolved { raw, .. } => format!("u:{raw}"),
        };
        seen.insert((edge.source.clone(), target_key, edge.relation.clone()))
    });
}