mati 0.1.2

//! Trait-based import resolution system.
//!
//! Each supported language implements [`LanguageResolver`] to map import
//! statements into repo-relative file paths. The [`ResolverRegistry`] provides
//! dispatch by language, and [`FileIndex`] provides O(1) file existence checks
//! plus helper queries needed by language-specific resolvers.
//!
//! # Architecture
//!
//! ```text
//! build_edges()
//!   → ResolverRegistry::resolve(import, file, language, &file_index)
//!       → dispatches to LanguageResolver::resolve(import, file, &file_index)
//!           → returns Option<String> (repo-relative target path)
//! ```
//!
//! Adding a new language resolver:
//! 1. Create `src/analysis/resolvers/<lang>.rs`
//! 2. Implement `LanguageResolver` for your struct
//! 3. Register in `ResolverRegistry::new()`

pub mod c;
pub mod cpp;
pub mod elixir;
pub mod go;
pub mod haskell;
pub mod java;
pub mod python;
pub mod ruby;
pub mod rust;
pub mod scala;
pub mod typescript;

use std::collections::HashMap;
use std::collections::HashSet;
use std::path::PathBuf;

use crate::analysis::parser::import::ImportKind;
use crate::analysis::parser::ImportStatement;
use crate::analysis::walker::Language;

// ── LanguageResolver trait ──────────────────────────────────────────────────

/// Trait for language-specific import resolution.
///
/// Each implementation maps an `ImportStatement` from a source file to a
/// repo-relative file path, using the `FileIndex` for existence checks.
pub trait LanguageResolver: Send + Sync {
    /// Resolve an import statement from `importing_file` into a repo-relative
    /// file path that exists in `file_index`. Return `None` if resolution fails
    /// or the import is external.
    fn resolve(
        &self,
        import: &ImportStatement,
        importing_file: &str,
        file_index: &FileIndex,
    ) -> Option<String>;

    /// The language(s) this resolver handles.
    fn language(&self) -> Language;

    /// A short human-readable name for debugging and logging.
    fn name(&self) -> &'static str;
}

// ── FileIndex ───────────────────────────────────────────────────────────────

/// Index of all known repo-relative file paths for O(1) existence checks.
///
/// Wraps a `HashSet<String>` with helper methods that language resolvers
/// commonly need. Linear-scan helpers (`files_with_prefix`, `files_with_stem`)
/// are acceptable at Layer 0 scale — optimize if benchmarks show a hot spot.
pub struct FileIndex {
    files: HashSet<String>,
    root: Option<PathBuf>,
    /// Crate root prefixes for Rust workspace resolution (e.g. `"src/"`,
    /// `"crates/regex/src/"`). Sorted longest-first so workspace member
    /// paths take precedence over the repo-root `src/`.
    crate_roots: Vec<String>,
    /// Map from workspace member crate name (snake_case, as used in `use`
    /// statements) to its crate root path (e.g. `"crates/regex/src/"`).
    /// Populated from each member's `[package].name` in Cargo.toml.
    /// Empty for non-Rust or single-crate projects.
    workspace_members: HashMap<String, String>,
    /// Scala source root prefixes discovered from file paths during init.
    /// E.g. `["zio-json/shared/src/main/scala/", "zio-json/jvm/src/test/scala/"]`.
    /// Used by the Scala resolver to find files in multi-project sbt layouts.
    scala_source_roots: Vec<String>,
    /// Ruby/Rails Zeitwerk autoload root directories discovered from file paths.
    /// E.g. `["app/models/", "app/controllers/", "core/app/models/"]`.
    /// Used by the Ruby resolver to map constant names to file paths.
    ruby_autoload_roots: Vec<String>,
    /// Ruby lib/ root directories for `require` resolution in monorepo layouts.
    /// E.g. `["lib/", "core/lib/", "api/lib/"]`.
    ruby_lib_roots: Vec<String>,
}

impl FileIndex {
    /// Create a new FileIndex from an iterator of repo-relative paths.
    pub fn new(paths: impl IntoIterator<Item = String>) -> Self {
        Self {
            files: paths.into_iter().collect(),
            root: None,
            crate_roots: Vec::new(),
            workspace_members: HashMap::new(),
            scala_source_roots: Vec::new(),
            ruby_autoload_roots: Vec::new(),
            ruby_lib_roots: Vec::new(),
        }
    }

    /// Create a FileIndex with a repo root for file content access.
    pub fn new_with_root(root: PathBuf, paths: impl IntoIterator<Item = String>) -> Self {
        Self {
            files: paths.into_iter().collect(),
            root: Some(root),
            crate_roots: Vec::new(),
            workspace_members: HashMap::new(),
            scala_source_roots: Vec::new(),
            ruby_autoload_roots: Vec::new(),
            ruby_lib_roots: Vec::new(),
        }
    }

    /// Set Rust crate root prefixes for workspace resolution.
    /// Roots are sorted longest-first so workspace member paths take
    /// precedence over the repo-root `src/`.
    pub fn set_crate_roots(&mut self, mut roots: Vec<String>) {
        roots.sort_by_key(|b| std::cmp::Reverse(b.len()));
        self.crate_roots = roots;
    }

    /// Returns the crate root prefix for the given file, if any.
    /// For single-crate projects: `Some("src/")`.
    /// For workspace files at `crates/foo/src/bar.rs`: `Some("crates/foo/src/")`.
    pub fn crate_root_for(&self, file_path: &str) -> Option<&str> {
        self.crate_roots
            .iter()
            .find(|root| file_path.starts_with(root.as_str()))
            .map(|s| s.as_str())
    }

    /// Set workspace member mapping (snake_case crate name → crate root path).
    pub fn set_workspace_members(&mut self, members: HashMap<String, String>) {
        self.workspace_members = members;
    }

    /// Returns the crate root path for a workspace member crate name.
    /// The first segment of an import path (e.g. `"grep_regex"` in
    /// `"grep_regex::matcher::Foo"`) is the name to look up.
    pub fn workspace_member_root(&self, crate_name: &str) -> Option<&str> {
        self.workspace_members.get(crate_name).map(|s| s.as_str())
    }

    /// True if workspace member mappings are configured.
    pub fn has_workspace_members(&self) -> bool {
        !self.workspace_members.is_empty()
    }

    /// Set Scala source root prefixes for multi-project sbt resolution.
    pub fn set_scala_source_roots(&mut self, roots: Vec<String>) {
        self.scala_source_roots = roots;
    }

    /// Returns the discovered Scala source root prefixes.
    pub fn scala_source_roots(&self) -> &[String] {
        &self.scala_source_roots
    }

    /// Set Ruby/Rails Zeitwerk autoload root directories.
    pub fn set_ruby_autoload_roots(&mut self, roots: Vec<String>) {
        self.ruby_autoload_roots = roots;
    }

    /// Returns the discovered Ruby autoload root directories.
    pub fn ruby_autoload_roots(&self) -> &[String] {
        &self.ruby_autoload_roots
    }

    /// Set Ruby lib/ root directories for monorepo require resolution.
    pub fn set_ruby_lib_roots(&mut self, roots: Vec<String>) {
        self.ruby_lib_roots = roots;
    }

    /// Returns the discovered Ruby lib/ root directories.
    pub fn ruby_lib_roots(&self) -> &[String] {
        &self.ruby_lib_roots
    }

    /// Read a file relative to the index root. Returns None if no root is
    /// configured or the file can't be read. Resolvers that need content
    /// access (like Go for go.mod) must tolerate None gracefully.
    pub fn read_file(&self, rel_path: &str) -> Option<String> {
        let root = self.root.as_ref()?;
        std::fs::read_to_string(root.join(rel_path)).ok()
    }

    /// Check if a repo-relative path exists in the index.
    pub fn contains(&self, path: &str) -> bool {
        self.files.contains(path)
    }

    /// Find all files whose path starts with the given prefix.
    /// Returns references to avoid allocation when only checking existence.
    pub fn files_with_prefix(&self, prefix: &str) -> Vec<&String> {
        self.files
            .iter()
            .filter(|f| f.starts_with(prefix))
            .collect()
    }

    /// Find all files whose stem (filename without extension) matches.
    /// Useful for Go package resolution where `foo.go` matches package `foo`.
    pub fn files_with_stem(&self, stem: &str) -> Vec<&String> {
        self.files
            .iter()
            .filter(|f| {
                std::path::Path::new(f.as_str())
                    .file_stem()
                    .and_then(|s| s.to_str())
                    == Some(stem)
            })
            .collect()
    }
}

// ── ResolverRegistry ────────────────────────────────────────────────────────

/// Dispatch registry that maps languages to their resolvers.
///
/// Constructed once per `build_edges` call. Languages without a registered
/// resolver simply return `None` for all imports (no edges created).
pub struct ResolverRegistry {
    resolvers: HashMap<Language, Box<dyn LanguageResolver>>,
}

impl ResolverRegistry {
    /// Create a registry with all currently implemented resolvers.
    pub fn new() -> Self {
        let mut resolvers: HashMap<Language, Box<dyn LanguageResolver>> = HashMap::new();
        resolvers.insert(Language::Rust, Box::new(rust::RustResolver));
        resolvers.insert(Language::Python, Box::new(python::PythonResolver));
        resolvers.insert(
            Language::TypeScript,
            Box::new(typescript::TypeScriptResolver),
        );
        resolvers.insert(
            Language::JavaScript,
            Box::new(typescript::TypeScriptResolver),
        );
        resolvers.insert(Language::Go, Box::new(go::GoResolver));
        resolvers.insert(Language::Java, Box::new(java::JavaResolver));
        resolvers.insert(Language::C, Box::new(c::CResolver));
        resolvers.insert(Language::Cpp, Box::new(cpp::CppResolver));
        resolvers.insert(Language::Ruby, Box::new(ruby::RubyResolver));
        resolvers.insert(Language::Scala, Box::new(scala::ScalaResolver));
        resolvers.insert(Language::Elixir, Box::new(elixir::ElixirResolver));
        resolvers.insert(Language::Haskell, Box::new(haskell::HaskellResolver));
        Self { resolvers }
    }

    /// Resolve an import statement for the given language.
    ///
    /// Returns `None` if:
    /// - The import is classified as `External` (skipped without resolution)
    /// - No resolver is registered for the language
    /// - The resolver cannot find a matching file
    pub fn resolve(
        &self,
        import: &ImportStatement,
        importing_file: &str,
        language: Language,
        file_index: &FileIndex,
    ) -> Option<String> {
        // External imports are never resolved — the parser already classified them.
        if import.kind == ImportKind::External {
            return None;
        }
        self.resolvers
            .get(&language)?
            .resolve(import, importing_file, file_index)
    }
}

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

// ── Shared helpers ─────────────────────────────────────────────────────────

/// Convert a PascalCase / CamelCase string to snake_case.
///
/// Handles acronyms and digit boundaries correctly:
/// - `UserNotification` → `user_notification`
/// - `HTTPServer` → `http_server`
/// - `JSONParser` → `json_parser`
/// - `API` → `api`
/// - `FooID` → `foo_id`
/// - `V2Parser` → `v2_parser`
/// - `XMLParserV2` → `xml_parser_v2`
///
/// Used by the Ruby and Elixir resolvers for Zeitwerk / Mix path conventions.
pub(crate) fn camel_to_snake(s: &str) -> String {
    let mut result = String::with_capacity(s.len() + 4);
    let chars: Vec<char> = s.chars().collect();

    for (i, &c) in chars.iter().enumerate() {
        if c.is_uppercase() {
            if i > 0 {
                let prev = chars[i - 1];
                let next_is_lower = chars.get(i + 1).is_some_and(|c| c.is_lowercase());
                // Insert underscore at word boundaries:
                // - lowercase/digit → uppercase: userN... → user_n...
                // - uppercase → uppercase+lowercase (acronym end): HTTP_S... → http_s...
                if prev.is_lowercase()
                    || prev.is_ascii_digit()
                    || (prev.is_uppercase() && next_is_lower)
                {
                    result.push('_');
                }
            }
            result.push(c.to_ascii_lowercase());
        } else {
            result.push(c);
        }
    }

    result
}

// ── Tests ───────────────────────────────────────────────────────────────────

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn file_index_contains() {
        let idx = FileIndex::new(vec!["src/main.rs".into(), "src/lib.rs".into()]);
        assert!(idx.contains("src/main.rs"));
        assert!(!idx.contains("src/foo.rs"));
    }

    #[test]
    fn file_index_prefix() {
        let idx = FileIndex::new(vec![
            "src/store/db.rs".into(),
            "src/store/mod.rs".into(),
            "src/main.rs".into(),
        ]);
        let results = idx.files_with_prefix("src/store/");
        assert_eq!(results.len(), 2);
    }

    #[test]
    fn file_index_stem() {
        let idx = FileIndex::new(vec![
            "src/utils.rs".into(),
            "lib/utils.py".into(),
            "src/main.rs".into(),
        ]);
        let results = idx.files_with_stem("utils");
        assert_eq!(results.len(), 2);
    }

    #[test]
    fn registry_skips_external() {
        let registry = ResolverRegistry::new();
        let idx = FileIndex::new(vec!["src/main.rs".into()]);
        let import = ImportStatement::new("react", ImportKind::External, 1);
        assert_eq!(
            registry.resolve(&import, "src/app.ts", Language::TypeScript, &idx),
            None
        );
    }

    #[test]
    fn registry_returns_none_for_unregistered_language() {
        let registry = ResolverRegistry::new();
        let idx = FileIndex::new(vec!["main.go".into()]);
        let import = ImportStatement::new("fmt", ImportKind::Normal, 1);
        assert_eq!(
            registry.resolve(&import, "main.go", Language::Go, &idx),
            None
        );
    }

    // ── camel_to_snake ─────────────────────────────────────────────────────

    #[test]
    fn camel_to_snake_simple_word() {
        assert_eq!(camel_to_snake("User"), "user");
        assert_eq!(camel_to_snake("Router"), "router");
    }

    #[test]
    fn camel_to_snake_multi_word() {
        assert_eq!(camel_to_snake("UserNotification"), "user_notification");
        assert_eq!(camel_to_snake("MyApp"), "my_app");
        assert_eq!(
            camel_to_snake("ApplicationController"),
            "application_controller"
        );
    }

    #[test]
    fn camel_to_snake_acronyms() {
        assert_eq!(camel_to_snake("HTTPServer"), "http_server");
        assert_eq!(camel_to_snake("JSONParser"), "json_parser");
        assert_eq!(camel_to_snake("XMLParser"), "xml_parser");
        assert_eq!(camel_to_snake("API"), "api");
        assert_eq!(camel_to_snake("HTTP"), "http");
    }

    #[test]
    fn camel_to_snake_trailing_acronym() {
        assert_eq!(camel_to_snake("FooID"), "foo_id");
        assert_eq!(camel_to_snake("UserAPI"), "user_api");
    }

    #[test]
    fn camel_to_snake_digit_boundaries() {
        assert_eq!(camel_to_snake("V2Parser"), "v2_parser");
        assert_eq!(camel_to_snake("XMLParserV2"), "xml_parser_v2");
    }

    #[test]
    fn camel_to_snake_already_lowercase() {
        assert_eq!(camel_to_snake("already_snake"), "already_snake");
    }

    #[test]
    fn camel_to_snake_empty() {
        assert_eq!(camel_to_snake(""), "");
    }

    #[test]
    fn camel_to_snake_single_char() {
        assert_eq!(camel_to_snake("A"), "a");
        assert_eq!(camel_to_snake("x"), "x");
    }
}