xlog-logic 0.9.2

//! Module resolution for XLOG programs.

use crate::ast::Program;
use crate::module::{module_path_to_string, LoadedModule, ModuleError, ModulePath};
use crate::parser::parse_program;
use std::collections::{HashMap, HashSet};
use std::fs;
use std::path::{Path, PathBuf};

/// Resolves and loads modules
pub struct ModuleResolver {
    /// Directories to search for modules
    search_paths: Vec<PathBuf>,
    /// Already loaded modules (path string -> module)
    loaded: HashMap<String, LoadedModule>,
    /// Currently loading (for cycle detection)
    loading: Vec<ModulePath>,
}

impl ModuleResolver {
    /// Create a new resolver with given search paths
    pub fn new(search_paths: Vec<PathBuf>) -> Self {
        Self {
            search_paths,
            loaded: HashMap::new(),
            loading: Vec::new(),
        }
    }

    /// Find the file for a module path
    pub fn find_module_file(&self, base_dir: &Path, module_path: &[String]) -> Option<PathBuf> {
        let relative_path = format!("{}.xlog", module_path.join("/"));

        // Try relative to base_dir first
        let candidate = base_dir.join(&relative_path);
        if candidate.exists() {
            return Some(candidate);
        }

        // Try search paths
        for search_path in &self.search_paths {
            let candidate = search_path.join(&relative_path);
            if candidate.exists() {
                return Some(candidate);
            }
        }

        None
    }

    /// Get the list of searched paths for error reporting
    fn searched_paths(&self, base_dir: &Path, module_path: &[String]) -> Vec<PathBuf> {
        let relative_path = format!("{}.xlog", module_path.join("/"));
        let mut searched = vec![base_dir.join(&relative_path)];
        for sp in &self.search_paths {
            searched.push(sp.join(&relative_path));
        }
        searched
    }

    /// Check if we're in a circular import
    fn check_cycle(&self, module_path: &[String]) -> Option<Vec<ModulePath>> {
        let path_str = module_path_to_string(module_path);
        for (i, loading_path) in self.loading.iter().enumerate() {
            if module_path_to_string(loading_path) == path_str {
                // Found cycle - return the cycle path
                let mut cycle: Vec<ModulePath> = self.loading[i..].to_vec();
                cycle.push(module_path.to_vec());
                return Some(cycle);
            }
        }
        None
    }

    /// Extract exports from a parsed program
    /// Returns (predicate exports, function exports)
    pub fn extract_exports(program: &Program) -> (HashSet<String>, HashSet<String>) {
        let mut pred_exports = HashSet::new();
        let mut func_exports = HashSet::new();

        // Add declared predicates that aren't private
        for pred in &program.predicates {
            if !pred.is_private {
                pred_exports.insert(pred.name.clone());
            }
        }

        // Add rule heads (all rules define public predicates unless declared private)
        for rule in &program.rules {
            // Check if this predicate was declared as private
            let is_private = program
                .predicates
                .iter()
                .any(|p| p.name == rule.head.predicate && p.is_private);
            if !is_private {
                pred_exports.insert(rule.head.predicate.clone());
            }
        }

        // Add functions that aren't private
        for func in &program.functions {
            if !func.is_private {
                func_exports.insert(func.name.clone());
            }
        }

        (pred_exports, func_exports)
    }

    /// Load a module from a path
    pub fn load_module(
        &mut self,
        base_dir: &Path,
        module_path: &[String],
    ) -> Result<&LoadedModule, ModuleError> {
        let path_key = module_path_to_string(module_path);

        // Already loaded?
        if self.loaded.contains_key(&path_key) {
            return Ok(self.loaded.get(&path_key).unwrap());
        }

        // Check for cycle
        if let Some(cycle) = self.check_cycle(module_path) {
            return Err(ModuleError::CircularImport { cycle });
        }

        // Find the file
        let source_file = self
            .find_module_file(base_dir, module_path)
            .ok_or_else(|| ModuleError::NotFound {
                path: module_path.to_vec(),
                searched: self.searched_paths(base_dir, module_path),
            })?;

        // Mark as loading
        self.loading.push(module_path.to_vec());

        // Read and parse
        let source = fs::read_to_string(&source_file).map_err(|e| ModuleError::ParseError {
            path: source_file.clone(),
            message: e.to_string(),
        })?;

        let program = parse_program(&source).map_err(|e| ModuleError::ParseError {
            path: source_file.clone(),
            message: e.to_string(),
        })?;

        // Extract exports
        let (exports, function_exports) = Self::extract_exports(&program);

        // Recursively load imports
        let module_dir = source_file.parent().unwrap_or(base_dir);
        for import in &program.imports {
            self.load_module(module_dir, &import.module_path)?;
        }

        // Remove from loading
        self.loading.pop();

        // Store loaded module
        let module = LoadedModule {
            path: module_path.to_vec(),
            source_file,
            exports,
            function_exports,
            program,
        };

        self.loaded.insert(path_key.clone(), module);
        Ok(self.loaded.get(&path_key).unwrap())
    }

    /// Check if a predicate can be imported from a module
    pub fn check_import(&self, module_path: &[String], predicate: &str) -> Result<(), ModuleError> {
        let path_key = module_path_to_string(module_path);
        let module = self
            .loaded
            .get(&path_key)
            .ok_or_else(|| ModuleError::NotFound {
                path: module_path.to_vec(),
                searched: vec![],
            })?;

        if !module.exports.contains(predicate) {
            return Err(ModuleError::PredicateNotFound {
                name: predicate.to_string(),
                module: module_path.to_vec(),
            });
        }

        Ok(())
    }

    /// Validate all imports in a program
    /// Returns (predicate imports, function imports) mapped to their source modules
    #[allow(clippy::type_complexity)]
    pub fn validate_imports(
        &self,
        program: &Program,
    ) -> Result<(HashMap<String, ModulePath>, HashMap<String, ModulePath>), ModuleError> {
        let mut imported_predicates: HashMap<String, ModulePath> = HashMap::new();
        let mut imported_functions: HashMap<String, ModulePath> = HashMap::new();

        for use_decl in &program.imports {
            let module = self
                .loaded
                .get(&module_path_to_string(&use_decl.module_path))
                .expect("module should be loaded");

            // Combine all available exports for wildcard imports
            let all_exports: HashSet<String> = module
                .exports
                .iter()
                .chain(module.function_exports.iter())
                .cloned()
                .collect();

            let names_to_import: Vec<String> = match &use_decl.imports {
                Some(specific) => specific.clone(),
                None => all_exports.iter().cloned().collect(),
            };

            for name in names_to_import {
                // Check if name exists as predicate or function
                let is_predicate = module.exports.contains(&name);
                let is_function = module.function_exports.contains(&name);

                if !is_predicate && !is_function {
                    return Err(ModuleError::PredicateNotFound {
                        name: name.clone(),
                        module: use_decl.module_path.clone(),
                    });
                }

                // Check for conflicts with predicates
                if is_predicate {
                    if let Some(prev_module) = imported_predicates.get(&name) {
                        if prev_module != &use_decl.module_path {
                            return Err(ModuleError::ImportConflict {
                                name,
                                module1: prev_module.clone(),
                                module2: use_decl.module_path.clone(),
                            });
                        }
                    }
                    imported_predicates.insert(name.clone(), use_decl.module_path.clone());
                }

                // Check for conflicts with functions
                if is_function {
                    if let Some(prev_module) = imported_functions.get(&name) {
                        if prev_module != &use_decl.module_path {
                            return Err(ModuleError::ImportConflict {
                                name,
                                module1: prev_module.clone(),
                                module2: use_decl.module_path.clone(),
                            });
                        }
                    }
                    imported_functions.insert(name.clone(), use_decl.module_path.clone());
                }
            }
        }

        Ok((imported_predicates, imported_functions))
    }

    /// Get a loaded module by path
    pub fn get_module(&self, module_path: &[String]) -> Option<&LoadedModule> {
        self.loaded.get(&module_path_to_string(module_path))
    }

    /// Check if a module is loaded
    pub fn is_loaded(&self, module_path: &str) -> bool {
        self.loaded.contains_key(module_path)
    }

    /// Get all loaded module paths (for testing)
    pub fn loaded_modules(&self) -> Vec<&str> {
        self.loaded.keys().map(|s| s.as_str()).collect()
    }

    /// Merge all imported modules into a program.
    /// Returns a new program with all imports resolved and merged.
    ///
    /// # Arguments
    /// * `program` - The main program with imports to resolve
    ///
    /// # Returns
    /// The program with all imports merged in
    pub fn merge_imports(&self, mut program: Program) -> Result<Program, ModuleError> {
        for use_decl in &program.imports.clone() {
            let path_key = module_path_to_string(&use_decl.module_path);
            let loaded_module =
                self.loaded
                    .get(&path_key)
                    .ok_or_else(|| ModuleError::NotFound {
                        path: use_decl.module_path.clone(),
                        searched: vec![],
                    })?;

            // Determine which items to import
            let imported_items = match &use_decl.imports {
                Some(items) if !items.is_empty() => {
                    // Import specific items
                    Some(items.iter().cloned().collect())
                }
                _ => {
                    // Import all public items
                    None
                }
            };

            // Merge the module into the program
            program.merge_from(&loaded_module.program, imported_items.as_ref());
        }

        Ok(program)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write;
    use tempfile::TempDir;

    fn create_test_module(dir: &Path, name: &str, content: &str) -> PathBuf {
        let path = dir.join(format!("{}.xlog", name));
        let mut file = fs::File::create(&path).unwrap();
        file.write_all(content.as_bytes()).unwrap();
        path
    }

    #[test]
    fn test_find_module_file() {
        let tmp = TempDir::new().unwrap();
        create_test_module(tmp.path(), "graph", "edge(1, 2).");

        let resolver = ModuleResolver::new(vec![]);
        let found = resolver.find_module_file(tmp.path(), &["graph".into()]);
        assert!(found.is_some());
    }

    #[test]
    fn test_module_not_found() {
        let tmp = TempDir::new().unwrap();
        let mut resolver = ModuleResolver::new(vec![]);

        let result = resolver.load_module(tmp.path(), &["nonexistent".into()]);
        assert!(matches!(result, Err(ModuleError::NotFound { .. })));
    }

    #[test]
    fn test_circular_import() {
        let tmp = TempDir::new().unwrap();
        create_test_module(tmp.path(), "a", "use b.");
        create_test_module(tmp.path(), "b", "use a.");

        let mut resolver = ModuleResolver::new(vec![]);
        let result = resolver.load_module(tmp.path(), &["a".into()]);
        assert!(matches!(result, Err(ModuleError::CircularImport { .. })));
    }

    #[test]
    fn test_load_simple_module() {
        let tmp = TempDir::new().unwrap();
        create_test_module(
            tmp.path(),
            "math",
            r#"
            pred add(u32, u32, u32).
            add(1, 2, 3).
        "#,
        );

        let mut resolver = ModuleResolver::new(vec![]);
        let result = resolver.load_module(tmp.path(), &["math".into()]);
        assert!(result.is_ok());
        let module = result.unwrap();
        assert!(module.exports.contains("add"));
    }

    #[test]
    fn test_private_not_exported() {
        let tmp = TempDir::new().unwrap();
        create_test_module(
            tmp.path(),
            "graph",
            r#"
            pred edge(u32, u32).
            private pred helper(u32).
            edge(1, 2).
            helper(1).
        "#,
        );

        let mut resolver = ModuleResolver::new(vec![]);
        let result = resolver.load_module(tmp.path(), &["graph".into()]);
        assert!(result.is_ok());
        let module = result.unwrap();
        assert!(module.exports.contains("edge"));
        assert!(!module.exports.contains("helper"));
    }

    #[test]
    fn test_search_paths() {
        let tmp = TempDir::new().unwrap();
        let lib_dir = tmp.path().join("lib");
        fs::create_dir(&lib_dir).unwrap();
        create_test_module(&lib_dir, "stdlib", "helper(1).");

        let resolver = ModuleResolver::new(vec![lib_dir.clone()]);
        let found = resolver.find_module_file(tmp.path(), &["stdlib".into()]);
        assert!(found.is_some());
        assert!(found.unwrap().starts_with(&lib_dir));
    }

    #[test]
    fn test_function_exports() {
        let tmp = TempDir::new().unwrap();
        create_test_module(
            tmp.path(),
            "mathfuncs",
            r#"
            func square(X) = X * X.
            func cube(X) = X * X * X.
            private func helper(X) = X.
        "#,
        );

        let mut resolver = ModuleResolver::new(vec![]);
        let result = resolver.load_module(tmp.path(), &["mathfuncs".into()]);
        assert!(result.is_ok());
        let module = result.unwrap();

        // Public functions should be exported
        assert!(module.function_exports.contains("square"));
        assert!(module.function_exports.contains("cube"));

        // Private function should not be exported
        assert!(!module.function_exports.contains("helper"));
    }

    #[test]
    fn test_mixed_exports() {
        let tmp = TempDir::new().unwrap();
        create_test_module(
            tmp.path(),
            "mixed",
            r#"
            pred value(i64).
            value(42).
            func double(X) = X * 2.
        "#,
        );

        let mut resolver = ModuleResolver::new(vec![]);
        let result = resolver.load_module(tmp.path(), &["mixed".into()]);
        assert!(result.is_ok());
        let module = result.unwrap();

        // Both predicate and function exports should be present
        assert!(module.exports.contains("value"));
        assert!(module.function_exports.contains("double"));
    }
}