rdar 0.6.7

//! Deterministic review-impact analysis over the cached file graph.
//!
//! This is deliberately a file-level, conservative report. A reference to a
//! public name fans out to every public definer of that name, so ambiguity is
//! visible instead of silently choosing one target. The report is useful for
//! review triage and test selection; source remains authoritative for semantic
//! proof.

use std::collections::{BTreeMap, BTreeSet, VecDeque};

use serde::Serialize;

use crate::cache::ScanCache;
use crate::extract::{RefKind, SymKind, Vis};

/// One path reached from a changed file, with the shortest graph distance.
#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
pub struct ImpactPath {
    pub path: String,
    pub distance: usize,
}

/// One extracted definition involved in review impact.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize)]
pub struct ImpactDefinition {
    pub path: String,
    pub symbol: String,
    pub line: u32,
    pub end_line: u32,
    pub kind: SymKind,
    pub visibility: Vis,
}

/// One direct call/import edge incident to a changed file.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Serialize)]
pub struct ImpactEdge {
    pub from: String,
    pub from_symbol: Option<String>,
    pub to: String,
    pub to_symbol: String,
    pub reference_line: u32,
    pub kind: RefKind,
}

/// Historical co-change evidence attached by an explicit history request.
#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
pub struct HistoricalImpact {
    pub commits_scanned: usize,
    pub seed_commits: usize,
    pub candidates: Vec<crate::gitfacts::HistoryCoChange>,
    pub omitted: usize,
    pub bulk_commits_skipped: usize,
}

/// Review-impact report for a Git change set.
#[derive(Clone, Debug, PartialEq, Eq, Serialize)]
pub struct ImpactReport {
    /// The Git revision used as the comparison base.
    pub base: String,
    /// Maximum number of graph hops followed in each direction.
    pub depth: usize,
    /// All paths Git reported as changed, including non-source paths.
    pub changed: Vec<String>,
    /// Current extracted definitions in changed source files.
    pub changed_definitions: Vec<ImpactDefinition>,
    /// Direct call/import edges entering or leaving changed files.
    pub direct_edges: Vec<ImpactEdge>,
    /// Files that call or import changed public symbols, nearest first.
    pub callers: Vec<ImpactPath>,
    /// Files referenced by changed files, nearest first.
    pub dependencies: Vec<ImpactPath>,
    /// Changed or caller paths matching the stable test/spec naming heuristic.
    pub tests: Vec<String>,
    /// References from changed source files with no public definer.
    pub unresolved_refs: usize,
    /// Changed-file references whose public name has multiple definers.
    pub ambiguous_refs: usize,
    /// Optional historical evidence; absent unless explicitly requested.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub history: Option<HistoricalImpact>,
}

/// Build a deterministic impact report from one canonical scan cache.
pub fn analyze(
    cache: &ScanCache,
    base: impl Into<String>,
    changed: impl IntoIterator<Item = String>,
    depth: usize,
) -> ImpactReport {
    let changed: BTreeSet<String> = changed.into_iter().collect();
    let mut definitions_by_path: BTreeMap<String, Vec<ImpactDefinition>> = BTreeMap::new();
    let mut definers: BTreeMap<String, Vec<ImpactDefinition>> = BTreeMap::new();

    for (path, entry) in &cache.files {
        let Some(lang) = entry.lang else { continue };
        let Some(extraction) = cache.parses.get(&(lang, entry.hash)) else {
            continue;
        };
        for definition in &extraction.defs {
            let definition = ImpactDefinition {
                path: path.clone(),
                symbol: definition.name.clone(),
                line: definition.line,
                end_line: definition.end_line,
                kind: definition.kind,
                visibility: definition.vis,
            };
            definitions_by_path
                .entry(path.clone())
                .or_default()
                .push(definition.clone());
            if definition.visibility == Vis::Pub {
                definers
                    .entry(definition.symbol.clone())
                    .or_default()
                    .push(definition);
            }
        }
    }

    let mut dependencies: BTreeMap<String, BTreeSet<String>> = BTreeMap::new();
    let mut callers: BTreeMap<String, BTreeSet<String>> = BTreeMap::new();
    let mut direct_edges = Vec::new();
    let mut unresolved_refs = 0usize;
    let mut ambiguous_refs = 0usize;

    for (path, entry) in &cache.files {
        let Some(lang) = entry.lang else { continue };
        let Some(extraction) = cache.parses.get(&(lang, entry.hash)) else {
            continue;
        };
        for reference in &extraction.refs {
            let Some(targets) = definers.get(&reference.name) else {
                if changed.contains(path) {
                    unresolved_refs += 1;
                }
                continue;
            };
            let targets: Vec<&ImpactDefinition> = targets
                .iter()
                .filter(|target| target.path != *path)
                .collect();
            let target_paths: BTreeSet<&str> =
                targets.iter().map(|target| target.path.as_str()).collect();
            if changed.contains(path) && target_paths.len() > 1 {
                ambiguous_refs += 1;
            }
            for target in targets {
                dependencies
                    .entry(path.clone())
                    .or_default()
                    .insert(target.path.clone());
                callers
                    .entry(target.path.clone())
                    .or_default()
                    .insert(path.clone());
                if changed.contains(path) || changed.contains(&target.path) {
                    direct_edges.push(ImpactEdge {
                        from: path.clone(),
                        from_symbol: definitions_by_path
                            .get(path)
                            .and_then(|defs| enclosing_definition(defs, reference.line))
                            .map(|definition| definition.symbol.clone()),
                        to: target.path.clone(),
                        to_symbol: target.symbol.clone(),
                        reference_line: reference.line,
                        kind: reference.kind,
                    });
                }
            }
        }
    }

    let mut changed_definitions: Vec<ImpactDefinition> = changed
        .iter()
        .flat_map(|path| definitions_by_path.get(path).into_iter().flatten().cloned())
        .collect();
    changed_definitions.sort();
    direct_edges.sort();
    direct_edges.dedup();

    let caller_paths = reachable(&callers, &changed, depth);
    let dependency_paths = reachable(&dependencies, &changed, depth);
    let mut tests: BTreeSet<String> = changed
        .iter()
        .filter(|path| is_test_path(path))
        .cloned()
        .collect();
    tests.extend(
        caller_paths
            .iter()
            .filter(|entry| is_test_path(&entry.path))
            .map(|entry| entry.path.clone()),
    );

    ImpactReport {
        base: base.into(),
        depth,
        changed: changed.into_iter().collect(),
        changed_definitions,
        direct_edges,
        callers: caller_paths,
        dependencies: dependency_paths,
        tests: tests.into_iter().collect(),
        unresolved_refs,
        ambiguous_refs,
        history: None,
    }
}

/// Attach bounded Git co-change facts to an otherwise source-derived report.
pub fn attach_history(report: &mut ImpactReport, facts: crate::gitfacts::HistoryFacts) {
    report.history = Some(HistoricalImpact {
        commits_scanned: facts.commits_scanned,
        seed_commits: facts.seed_commits,
        candidates: facts.candidates,
        omitted: facts.omitted,
        bulk_commits_skipped: facts.bulk_commits_skipped,
    });
}

fn enclosing_definition(definitions: &[ImpactDefinition], line: u32) -> Option<&ImpactDefinition> {
    definitions
        .iter()
        .filter(|definition| definition.line <= line && line <= definition.end_line)
        .min_by_key(|definition| {
            (
                definition.end_line.saturating_sub(definition.line),
                definition.line,
                definition.symbol.as_str(),
            )
        })
}

fn reachable(
    graph: &BTreeMap<String, BTreeSet<String>>,
    starts: &BTreeSet<String>,
    depth: usize,
) -> Vec<ImpactPath> {
    if depth == 0 {
        return Vec::new();
    }
    let mut distances: BTreeMap<String, usize> = BTreeMap::new();
    let mut queue = VecDeque::new();
    for start in starts {
        distances.insert(start.clone(), 0);
        queue.push_back(start.clone());
    }
    while let Some(current) = queue.pop_front() {
        let Some(&distance) = distances.get(&current) else {
            continue;
        };
        if distance >= depth {
            continue;
        }
        let Some(next_paths) = graph.get(&current) else {
            continue;
        };
        for next in next_paths {
            let next_distance = distance + 1;
            let is_shorter = distances
                .get(next)
                .is_none_or(|known| next_distance < *known);
            if is_shorter {
                distances.insert(next.clone(), next_distance);
                queue.push_back(next.clone());
            }
        }
    }
    let mut out: Vec<ImpactPath> = distances
        .into_iter()
        .filter(|(path, distance)| !starts.contains(path) && *distance <= depth)
        .map(|(path, distance)| ImpactPath { path, distance })
        .collect();
    out.sort_by(|left, right| {
        left.distance
            .cmp(&right.distance)
            .then_with(|| left.path.cmp(&right.path))
    });
    out
}

fn is_test_path(path: &str) -> bool {
    let basename = path.rsplit('/').next().unwrap_or(path).to_ascii_lowercase();
    if basename.starts_with("test")
        || basename.contains("_test")
        || basename.contains(".test")
        || basename.contains("_spec")
        || basename.contains(".spec")
    {
        return true;
    }
    path.split('/').any(|part| {
        matches!(
            part.to_ascii_lowercase().as_str(),
            "test" | "tests" | "spec" | "specs"
        )
    })
}

/// Render the report for a human review loop.
pub fn render(report: &ImpactReport) -> String {
    let mut out = format!(
        "radar impact - base {} (depth {})\n",
        report.base, report.depth
    );
    section(
        &mut out,
        "changed",
        report.changed.iter().map(String::as_str),
    );
    section(
        &mut out,
        "changed definitions",
        report.changed_definitions.iter().map(|definition| {
            format!(
                "{}#{}:{}",
                definition.path, definition.symbol, definition.line
            )
        }),
    );
    section(
        &mut out,
        "direct edges",
        report.direct_edges.iter().map(|edge| {
            let from = edge.from_symbol.as_deref().map_or_else(
                || edge.from.clone(),
                |symbol| format!("{}#{}", edge.from, symbol),
            );
            format!(
                "{} -{:?} line {}-> {}#{}",
                from, edge.kind, edge.reference_line, edge.to, edge.to_symbol
            )
        }),
    );
    section(
        &mut out,
        "callers / affected",
        report
            .callers
            .iter()
            .map(|entry| format!("{} (distance {})", entry.path, entry.distance)),
    );
    section(
        &mut out,
        "dependencies",
        report
            .dependencies
            .iter()
            .map(|entry| format!("{} (distance {})", entry.path, entry.distance)),
    );
    section(&mut out, "tests", report.tests.iter().map(String::as_str));
    if let Some(history) = &report.history {
        section(
            &mut out,
            "historical co-change candidates",
            history.candidates.iter().map(|candidate| {
                let commit = candidate.latest_commit.chars().take(8).collect::<String>();
                format!(
                    "{} ({} commit(s), latest {})",
                    candidate.path, candidate.commits, commit
                )
            }),
        );
        out.push_str(&format!(
            "history commits scanned: {}   seed commits: {}   bulk commits skipped: {}   omitted: {}\n",
            history.commits_scanned,
            history.seed_commits,
            history.bulk_commits_skipped,
            history.omitted
        ));
    }
    out.push_str(&format!(
        "unresolved references: {}\nambiguous references: {}\n",
        report.unresolved_refs, report.ambiguous_refs
    ));
    out
}

fn section<'a, I, T>(out: &mut String, name: &str, entries: I)
where
    I: IntoIterator<Item = T>,
    T: std::fmt::Display + 'a,
{
    let entries: Vec<T> = entries.into_iter().collect();
    out.push_str(&format!("{name} ({}):\n", entries.len()));
    if entries.is_empty() {
        out.push_str("  none\n");
    } else {
        for entry in entries {
            out.push_str(&format!("  {entry}\n"));
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::cache::FileEntry;
    use crate::extract::{Extraction, RefKind, RefName, SymKind, Symbol};
    use crate::lang::Lang;

    fn file(cache: &mut ScanCache, path: &str, defs: &[&str], refs: &[&str]) {
        let hash = *blake3::hash(path.as_bytes()).as_bytes();
        cache.files.insert(
            path.to_string(),
            FileEntry {
                mtime: (1, 0),
                size: 1,
                ino: 0,
                hash,
                lang: Some(Lang::Python),
            },
        );
        cache.parses.insert(
            (Lang::Python, hash),
            Extraction {
                defs: defs
                    .iter()
                    .enumerate()
                    .map(|(line, name)| Symbol {
                        line: line as u32 + 1,
                        end_line: line as u32 + 2,
                        name: (*name).to_string(),
                        kind: SymKind::Fn,
                        vis: Vis::Pub,
                        sig: format!("def {name}()"),
                        terms: Vec::new(),
                    })
                    .collect(),
                refs: refs
                    .iter()
                    .enumerate()
                    .map(|(line, name)| RefName {
                        line: line as u32 + 10,
                        name: (*name).to_string(),
                        kind: RefKind::Call,
                    })
                    .collect(),
            },
        );
    }

    #[test]
    fn walks_callers_dependencies_and_tests_deterministically() {
        let mut cache = ScanCache::default();
        file(&mut cache, "core.py", &["changed"], &["helper"]);
        file(&mut cache, "util.py", &["helper"], &[]);
        file(&mut cache, "api.py", &["api"], &["changed"]);
        file(&mut cache, "tests/test_api.py", &[], &["api"]);

        let report = analyze(&cache, "HEAD", ["core.py".to_string()], 2);
        assert_eq!(report.changed, ["core.py"]);
        assert_eq!(report.changed_definitions[0].symbol, "changed");
        assert_eq!(report.direct_edges.len(), 2);
        assert_eq!(report.direct_edges[0].from, "api.py");
        assert_eq!(report.direct_edges[0].to_symbol, "changed");
        assert_eq!(report.dependencies[0].path, "util.py");
        assert_eq!(report.callers[0].path, "api.py");
        assert_eq!(report.callers[0].distance, 1);
        assert_eq!(report.tests, ["tests/test_api.py"]);
        assert_eq!(report.unresolved_refs, 0);
        assert!(render(&report).contains("callers / affected (2):"));
    }

    #[test]
    fn ambiguity_is_reported_and_name_resolution_fans_out() {
        let mut cache = ScanCache::default();
        file(&mut cache, "changed.py", &["run"], &["shared"]);
        file(&mut cache, "one.py", &["shared"], &[]);
        file(&mut cache, "two.py", &["shared"], &[]);

        let report = analyze(&cache, "HEAD", ["changed.py".to_string()], 1);
        assert_eq!(report.ambiguous_refs, 1);
        assert_eq!(
            report
                .dependencies
                .iter()
                .map(|entry| entry.path.as_str())
                .collect::<Vec<_>>(),
            ["one.py", "two.py"]
        );
    }
}