codemem-engine 0.18.0

//! Reference resolution into graph edges.
//!
//! Resolves unresolved references (by simple name) to their target symbols
//! and produces typed edges for the knowledge graph.

use crate::index::symbol::{Reference, ReferenceKind, Symbol};
use codemem_core::RelationshipType;
use std::collections::{HashMap, HashSet};

/// A resolved edge connecting two symbols by qualified name.
#[derive(Debug, Clone)]
pub struct ResolvedEdge {
    /// Qualified name of the source symbol.
    pub source_qualified_name: String,
    /// Qualified name of the resolved target symbol.
    pub target_qualified_name: String,
    /// The relationship type for this edge.
    pub relationship: RelationshipType,
    /// File path where the reference occurs.
    pub file_path: String,
    /// Line number of the reference.
    pub line: usize,
    /// R2: Confidence of the resolution (0.0 = guessed, 1.0 = exact match).
    pub resolution_confidence: f64,
}

/// A reference that could not be resolved to a known symbol.
/// Preserved for deferred cross-repo linking.
#[derive(Debug, Clone)]
pub struct UnresolvedRef {
    /// Qualified name of the source symbol containing this reference.
    pub source_node: String,
    /// The unresolved target name.
    pub target_name: String,
    /// Package hint extracted from import context (language-specific).
    pub package_hint: Option<String>,
    /// Kind of reference: "call", "import", "inherits", "implements", "type_usage".
    pub ref_kind: String,
    /// File where the reference occurs.
    pub file_path: String,
    /// Line number.
    pub line: usize,
}

/// Combined result of reference resolution: resolved edges + unresolved refs.
#[derive(Debug)]
pub struct ResolveResult {
    pub edges: Vec<ResolvedEdge>,
    pub unresolved: Vec<UnresolvedRef>,
}

/// Resolves references to target symbols and produces graph edges.
pub struct ReferenceResolver {
    /// Map of qualified_name -> Symbol for exact resolution.
    symbol_index: HashMap<String, Symbol>,
    /// Map of simple name -> Vec<qualified_name> for ambiguous resolution.
    name_index: HashMap<String, Vec<String>>,
    /// R2: Set of imported qualified names per file for scoring.
    file_imports: HashMap<String, HashSet<String>>,
}

impl ReferenceResolver {
    /// Create a new empty resolver.
    pub fn new() -> Self {
        Self {
            symbol_index: HashMap::new(),
            name_index: HashMap::new(),
            file_imports: HashMap::new(),
        }
    }

    /// Add symbols to the resolver's index.
    pub fn add_symbols(&mut self, symbols: &[Symbol]) {
        for sym in symbols {
            self.symbol_index
                .insert(sym.qualified_name.clone(), sym.clone());

            self.name_index
                .entry(sym.name.clone())
                .or_default()
                .push(sym.qualified_name.clone());
        }
    }

    /// R2: Register import references so the resolver can prefer imported symbols.
    pub fn add_imports(&mut self, references: &[Reference]) {
        for r in references {
            if r.kind == ReferenceKind::Import {
                self.file_imports
                    .entry(r.file_path.clone())
                    .or_default()
                    .insert(r.target_name.clone());
            }
        }
    }

    /// Resolve a single reference to a target symbol with confidence.
    ///
    /// Resolution strategy:
    /// 1. Exact match on qualified name (confidence 1.0)
    /// 2. R4: Cross-module path resolution — strip `crate::` prefix, try partial matches
    /// 3. Simple name match with R2 scoring heuristics (confidence varies)
    /// 4. Unresolved (returns None)
    pub fn resolve_with_confidence(&self, reference: &Reference) -> Option<(&Symbol, f64)> {
        // 1. Exact qualified name match
        if let Some(sym) = self.symbol_index.get(&reference.target_name) {
            return Some((sym, 1.0));
        }

        // R4: Try stripping `crate::` prefix for cross-module resolution
        if reference.target_name.starts_with("crate::") {
            let stripped = &reference.target_name["crate::".len()..];
            if let Some(sym) = self.symbol_index.get(stripped) {
                return Some((sym, 0.95));
            }
            // Try matching against all qualified names ending with this suffix
            for (qn, sym) in &self.symbol_index {
                if qn.ends_with(stripped) {
                    let prefix_len = qn.len() - stripped.len();
                    if prefix_len == 0 || qn[..prefix_len].ends_with("::") {
                        return Some((sym, 0.85));
                    }
                }
            }
        }

        // R4: Try matching `module::function` against `crate::module::function`
        if reference.target_name.contains("::") {
            let with_crate = format!("crate::{}", reference.target_name);
            if let Some(sym) = self.symbol_index.get(&with_crate) {
                return Some((sym, 0.9));
            }
            // Try suffix matching for partial paths
            for (qn, sym) in &self.symbol_index {
                if qn.ends_with(&reference.target_name) {
                    let prefix_len = qn.len() - reference.target_name.len();
                    if prefix_len == 0 || qn[..prefix_len].ends_with("::") {
                        return Some((sym, 0.8));
                    }
                }
            }
        }

        // 2. Simple name match with scoring heuristics
        let simple_name = reference
            .target_name
            .rsplit("::")
            .next()
            .unwrap_or(&reference.target_name);

        if let Some(candidates) = self.name_index.get(simple_name) {
            if candidates.len() == 1 {
                // Unambiguous
                let confidence = if simple_name == reference.target_name {
                    0.9 // Exact simple name match
                } else {
                    0.7 // Matched via last segment only
                };
                return self
                    .symbol_index
                    .get(&candidates[0])
                    .map(|s| (s, confidence));
            }

            // R2: Score candidates with heuristics
            let file_imports = self.file_imports.get(&reference.file_path);
            let mut best: Option<(&Symbol, f64)> = None;

            for qn in candidates {
                if let Some(sym) = self.symbol_index.get(qn) {
                    let mut score: f64 = 0.0;

                    // Prefer symbols imported in the same file
                    if let Some(imports) = file_imports {
                        if imports.contains(&sym.qualified_name)
                            || imports.iter().any(|imp| imp.ends_with(&sym.name))
                        {
                            score += 0.4;
                        }
                    }

                    // Prefer symbols in the same file
                    if sym.file_path == reference.file_path {
                        score += 0.3;
                    }

                    // Prefer exact name match (not just substring/last-segment)
                    if sym.name == reference.target_name {
                        score += 0.2;
                    }

                    // Prefer symbols in the same package/module (share path prefix)
                    let ref_module = extract_module_path(&reference.file_path);
                    let sym_module = extract_module_path(&sym.file_path);
                    if ref_module == sym_module {
                        score += 0.1;
                    }

                    if best.is_none() || score > best.unwrap().1 {
                        best = Some((sym, score));
                    }
                }
            }

            if let Some((sym, score)) = best {
                // Normalize score to a confidence value in [0.3, 0.8]
                let confidence = 0.3 + (score.min(1.0) * 0.5);
                return Some((sym, confidence));
            }
        }

        None
    }

    /// Map a reference kind to a relationship type and apply kind-specific
    /// confidence adjustments (e.g., Callback caps at 0.6).
    fn resolve_edge(&self, r: &Reference) -> Option<ResolvedEdge> {
        let (target, confidence) = self.resolve_with_confidence(r)?;
        let relationship = match r.kind {
            ReferenceKind::Call | ReferenceKind::Callback => RelationshipType::Calls,
            ReferenceKind::Import => RelationshipType::Imports,
            ReferenceKind::Inherits => RelationshipType::Inherits,
            ReferenceKind::Implements => RelationshipType::Implements,
            ReferenceKind::TypeUsage => RelationshipType::DependsOn,
        };
        // Callback references are speculative — cap confidence.
        let confidence = if r.kind == ReferenceKind::Callback {
            confidence.min(0.6)
        } else {
            confidence
        };
        Some(ResolvedEdge {
            source_qualified_name: r.source_qualified_name.clone(),
            target_qualified_name: target.qualified_name.clone(),
            relationship,
            file_path: r.file_path.clone(),
            line: r.line,
            resolution_confidence: confidence,
        })
    }

    /// Resolve all references into edges.
    ///
    /// Only produces edges for successfully resolved references.
    pub fn resolve_all(&self, references: &[Reference]) -> Vec<ResolvedEdge> {
        references
            .iter()
            .filter_map(|r| self.resolve_edge(r))
            .collect()
    }

    /// Resolve all references, collecting both resolved edges and unresolved refs.
    ///
    /// Like `resolve_all` but also preserves unresolved references with
    /// package hints for deferred cross-repo linking.
    pub fn resolve_all_with_unresolved(&self, references: &[Reference]) -> ResolveResult {
        let mut edges = Vec::new();
        let mut unresolved = Vec::new();

        for r in references {
            if let Some(edge) = self.resolve_edge(r) {
                edges.push(edge);
            } else {
                let package_hint = extract_package_hint(&r.target_name, r.kind);
                unresolved.push(UnresolvedRef {
                    source_node: r.source_qualified_name.clone(),
                    target_name: r.target_name.clone(),
                    package_hint,
                    ref_kind: r.kind.to_string(),
                    file_path: r.file_path.clone(),
                    line: r.line,
                });
            }
        }

        ResolveResult { edges, unresolved }
    }
}

/// Extract a package hint from an import target name.
///
/// Language-specific rules:
/// - Python: "requests.api.get" -> "requests" (first dot-segment)
/// - TS/JS: "@acme/shared" -> "@acme/shared" (scoped), "lodash" -> "lodash" (first segment)
/// - Go: "github.com/acme/utils" -> "github.com/acme/utils" (full module path)
/// - Java: "com.acme.shared.Validator" -> "com.acme.shared" (drop last segment = class name)
/// - Rust: "crate::module::item" -> None (local), "serde::Serialize" -> "serde" (first segment)
///
/// For Import references, the target_name is typically the full import path.
/// For Call references, package_hint is usually None (calls are to local symbols).
pub(crate) fn extract_package_hint(target_name: &str, kind: ReferenceKind) -> Option<String> {
    // Only extract hints from Import references — calls/inherits are usually local
    if kind != ReferenceKind::Import {
        return None;
    }

    // Skip local/relative imports
    if target_name.starts_with('.')
        || target_name.starts_with("crate::")
        || target_name.starts_with("super::")
        || target_name.starts_with("self::")
    {
        return None;
    }

    // Scoped npm packages: @scope/package
    if target_name.starts_with('@') {
        // @acme/shared-lib/utils -> @acme/shared-lib
        let parts: Vec<&str> = target_name.splitn(3, '/').collect();
        if parts.len() >= 2 {
            return Some(format!("{}/{}", parts[0], parts[1]));
        }
        return Some(target_name.to_string());
    }

    // Go module paths: github.com/user/repo, gopkg.in/yaml.v3, etc.
    // Detect by presence of '/' and a domain-like first segment with a known
    // hosting domain. A simple "contains dot" heuristic would misclassify
    // npm packages like socket.io/client or lodash.get/deep.
    if target_name.contains('/') {
        let first_segment = target_name.split('/').next().unwrap_or("");
        if is_go_module_domain(first_segment) {
            // Domain-based Go module path — use full path as package hint
            return Some(target_name.to_string());
        }
        // For non-domain slash paths (e.g., "lodash/merge"), extract first segment
        if !first_segment.is_empty() {
            return Some(first_segment.to_string());
        }
    }

    // Rust crate imports: tokio::sync -> "tokio"
    if target_name.contains("::") {
        let first = target_name.split("::").next()?;
        return Some(first.to_string());
    }

    // Python/TS/JS dot-separated: requests.api.get -> "requests"
    if target_name.contains('.') {
        let first = target_name.split('.').next()?;
        return Some(first.to_string());
    }

    // Single word import: "requests", "lodash", "flask"
    // Filter out Python stdlib modules that would pollute the package registry
    // with false matches. These will never correspond to an indexed namespace.
    if is_python_stdlib(target_name) {
        return None;
    }
    Some(target_name.to_string())
}

/// Check if a string looks like a Go module hosting domain.
/// Matches common Go module hosts and any domain with a dot + known code TLD.
fn is_go_module_domain(segment: &str) -> bool {
    matches!(
        segment,
        "github.com"
            | "gitlab.com"
            | "bitbucket.org"
            | "golang.org"
            | "google.golang.org"
            | "gopkg.in"
            | "go.uber.org"
            | "go.etcd.io"
            | "k8s.io"
            | "sigs.k8s.io"
            | "honnef.co"
            | "mvdan.cc"
    ) || (segment.contains('.')
        && segment.rsplit('.').next().is_some_and(|tld| {
            matches!(
                tld,
                "com" | "org" | "io" | "net" | "dev" | "in" | "cc" | "co"
            )
        }))
}

/// Common Python stdlib modules that should not produce package hints.
/// These single-word imports would create false registry matches.
fn is_python_stdlib(name: &str) -> bool {
    matches!(
        name,
        "os" | "sys"
            | "re"
            | "io"
            | "json"
            | "math"
            | "time"
            | "datetime"
            | "collections"
            | "itertools"
            | "functools"
            | "typing"
            | "logging"
            | "pathlib"
            | "subprocess"
            | "threading"
            | "multiprocessing"
            | "unittest"
            | "copy"
            | "abc"
            | "enum"
            | "dataclasses"
            | "contextlib"
            | "argparse"
            | "hashlib"
            | "hmac"
            | "secrets"
            | "socket"
            | "http"
            | "email"
            | "html"
            | "xml"
            | "csv"
            | "sqlite3"
            | "pickle"
            | "shelve"
            | "marshal"
            | "struct"
            | "codecs"
            | "string"
            | "textwrap"
            | "difflib"
            | "pprint"
            | "warnings"
            | "traceback"
            | "inspect"
            | "dis"
            | "ast"
            | "token"
            | "keyword"
            | "linecache"
            | "shutil"
            | "tempfile"
            | "glob"
            | "fnmatch"
            | "stat"
            | "fileinput"
            | "configparser"
            | "signal"
            | "errno"
            | "ctypes"
            | "types"
            | "weakref"
            | "array"
            | "bisect"
            | "heapq"
            | "queue"
            | "random"
            | "statistics"
            | "decimal"
            | "fractions"
            | "operator"
            | "uuid"
            | "base64"
            | "binascii"
            | "zlib"
            | "gzip"
            | "zipfile"
            | "tarfile"
            | "pdb"
            | "profile"
            | "cProfile"
            | "timeit"
            | "platform"
            | "sysconfig"
            | "builtins"
            | "asyncio"
            | "concurrent"
    )
}

/// Extract a module path from a file path for same-package heuristic.
/// e.g., "src/index/parser.rs" -> "src/index"
fn extract_module_path(file_path: &str) -> &str {
    file_path.rsplit_once('/').map(|(dir, _)| dir).unwrap_or("")
}

impl Default for ReferenceResolver {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
#[path = "tests/resolver_tests.rs"]
mod tests;