harn_vm/vm/

modules.rs

use std::cell::RefCell;
use std::collections::{BTreeMap, HashSet};
use std::future::Future;
use std::path::{Path, PathBuf};
use std::pin::Pin;
use std::rc::Rc;

use crate::value::{ModuleFunctionRegistry, VmClosure, VmEnv, VmError, VmValue};

use super::{ScopeSpan, Vm};

#[derive(Clone)]
pub(crate) struct LoadedModule {
    pub(crate) functions: BTreeMap<String, Rc<VmClosure>>,
    pub(crate) public_names: HashSet<String>,
}

pub fn resolve_module_import_path(base: &Path, path: &str) -> PathBuf {
    let synthetic_current_file = base.join("__harn_import_base__.harn");
    if let Some(resolved) = harn_modules::resolve_import_path(&synthetic_current_file, path) {
        return resolved;
    }

    let mut file_path = base.join(path);

    if !file_path.exists() && file_path.extension().is_none() {
        file_path.set_extension("harn");
    }

    file_path
}

impl Vm {
    async fn load_module_from_source(
        &mut self,
        synthetic: PathBuf,
        source: &str,
    ) -> Result<LoadedModule, VmError> {
        if let Some(loaded) = self.module_cache.get(&synthetic).cloned() {
            return Ok(loaded);
        }

        let mut lexer = harn_lexer::Lexer::new(source);
        let tokens = lexer.tokenize().map_err(|e| {
            VmError::Runtime(format!("Import lex error in {}: {e}", synthetic.display()))
        })?;
        let mut parser = harn_parser::Parser::new(tokens);
        let program = parser.parse().map_err(|e| {
            VmError::Runtime(format!(
                "Import parse error in {}: {e}",
                synthetic.display()
            ))
        })?;

        self.imported_paths.push(synthetic.clone());
        let loaded = self.import_declarations(&program, None).await?;
        self.imported_paths.pop();
        self.module_cache.insert(synthetic, loaded.clone());
        Ok(loaded)
    }

    fn export_loaded_module(
        &mut self,
        module_path: &Path,
        loaded: &LoadedModule,
        selected_names: Option<&[String]>,
    ) -> Result<(), VmError> {
        let export_names: Vec<String> = if let Some(names) = selected_names {
            names.to_vec()
        } else if !loaded.public_names.is_empty() {
            loaded.public_names.iter().cloned().collect()
        } else {
            loaded.functions.keys().cloned().collect()
        };

        let module_name = module_path.display().to_string();
        for name in export_names {
            let Some(closure) = loaded.functions.get(&name) else {
                return Err(VmError::Runtime(format!(
                    "Import error: '{name}' is not defined in {module_name}"
                )));
            };
            if let Some(VmValue::Closure(_)) = self.env.get(&name) {
                return Err(VmError::Runtime(format!(
                    "Import collision: '{name}' is already defined when importing {module_name}. \
                     Use selective imports to disambiguate: import {{ {name} }} from \"...\""
                )));
            }
            self.env
                .define(&name, VmValue::Closure(Rc::clone(closure)), false)?;
        }
        Ok(())
    }

    /// Execute an import, reading and running the file's declarations.
    pub(super) fn execute_import<'a>(
        &'a mut self,
        path: &'a str,
        selected_names: Option<&'a [String]>,
    ) -> Pin<Box<dyn Future<Output = Result<(), VmError>> + 'a>> {
        Box::pin(async move {
            let _import_span = ScopeSpan::new(crate::tracing::SpanKind::Import, path.to_string());

            if let Some(module) = path.strip_prefix("std/") {
                if let Some(source) = crate::stdlib_modules::get_stdlib_source(module) {
                    let synthetic = PathBuf::from(format!("<stdlib>/{module}.harn"));
                    if self.imported_paths.contains(&synthetic) {
                        return Ok(());
                    }
                    let loaded = self
                        .load_module_from_source(synthetic.clone(), source)
                        .await?;
                    self.export_loaded_module(&synthetic, &loaded, selected_names)?;
                    return Ok(());
                }
                return Err(VmError::Runtime(format!(
                    "Unknown stdlib module: std/{module}"
                )));
            }

            let base = self
                .source_dir
                .clone()
                .unwrap_or_else(|| PathBuf::from("."));
            let file_path = resolve_module_import_path(&base, path);

            let canonical = file_path
                .canonicalize()
                .unwrap_or_else(|_| file_path.clone());
            if self.imported_paths.contains(&canonical) {
                return Ok(());
            }
            if let Some(loaded) = self.module_cache.get(&canonical).cloned() {
                return self.export_loaded_module(&canonical, &loaded, selected_names);
            }
            self.imported_paths.push(canonical.clone());

            let source = std::fs::read_to_string(&file_path).map_err(|e| {
                VmError::Runtime(format!(
                    "Import error: cannot read '{}': {e}",
                    file_path.display()
                ))
            })?;

            let mut lexer = harn_lexer::Lexer::new(&source);
            let tokens = lexer
                .tokenize()
                .map_err(|e| VmError::Runtime(format!("Import lex error: {e}")))?;
            let mut parser = harn_parser::Parser::new(tokens);
            let program = parser
                .parse()
                .map_err(|e| VmError::Runtime(format!("Import parse error: {e}")))?;

            let loaded = self.import_declarations(&program, Some(&file_path)).await?;
            self.imported_paths.pop();
            self.module_cache.insert(canonical.clone(), loaded.clone());
            self.export_loaded_module(&canonical, &loaded, selected_names)?;

            Ok(())
        })
    }

    /// Process top-level declarations from an imported module.
    fn import_declarations<'a>(
        &'a mut self,
        program: &'a [harn_parser::SNode],
        file_path: Option<&'a Path>,
    ) -> Pin<Box<dyn Future<Output = Result<LoadedModule, VmError>> + 'a>> {
        Box::pin(async move {
            let caller_env = self.env.clone();
            let old_source_dir = self.source_dir.clone();
            self.env = VmEnv::new();
            if let Some(fp) = file_path {
                if let Some(parent) = fp.parent() {
                    self.source_dir = Some(parent.to_path_buf());
                }
            }

            for node in program {
                match &node.node {
                    harn_parser::Node::ImportDecl { path: sub_path, .. } => {
                        self.execute_import(sub_path, None).await?;
                    }
                    harn_parser::Node::SelectiveImport {
                        names,
                        path: sub_path,
                        ..
                    } => {
                        self.execute_import(sub_path, Some(names)).await?;
                    }
                    _ => {}
                }
            }

            // Route top-level `var`/`let` bindings into a shared
            // `module_state` rather than `module_env`. If they appeared in
            // `module_env` (captured by each closure's lexical snapshot),
            // every call's per-invocation env clone would shadow them and
            // writes would land in a per-call copy discarded on return.
            let module_state: crate::value::ModuleState = {
                let mut init_env = self.env.clone();
                let init_nodes: Vec<harn_parser::SNode> = program
                    .iter()
                    .filter(|sn| {
                        matches!(
                            &sn.node,
                            harn_parser::Node::VarBinding { .. }
                                | harn_parser::Node::LetBinding { .. }
                        )
                    })
                    .cloned()
                    .collect();
                if !init_nodes.is_empty() {
                    let init_compiler = crate::Compiler::new();
                    let init_chunk = init_compiler
                        .compile(&init_nodes)
                        .map_err(|e| VmError::Runtime(format!("Import init compile error: {e}")))?;
                    // Save frame state so run_chunk_entry's top-level
                    // frame-pop doesn't restore self.env.
                    let saved_env = std::mem::replace(&mut self.env, init_env);
                    let saved_frames = std::mem::take(&mut self.frames);
                    let saved_handlers = std::mem::take(&mut self.exception_handlers);
                    let saved_iterators = std::mem::take(&mut self.iterators);
                    let saved_deadlines = std::mem::take(&mut self.deadlines);
                    let init_result = self.run_chunk(&init_chunk).await;
                    init_env = std::mem::replace(&mut self.env, saved_env);
                    self.frames = saved_frames;
                    self.exception_handlers = saved_handlers;
                    self.iterators = saved_iterators;
                    self.deadlines = saved_deadlines;
                    init_result?;
                }
                Rc::new(RefCell::new(init_env))
            };

            let module_env = self.env.clone();
            let registry: ModuleFunctionRegistry = Rc::new(RefCell::new(BTreeMap::new()));
            let source_dir = file_path.and_then(|fp| fp.parent().map(|p| p.to_path_buf()));
            let mut functions: BTreeMap<String, Rc<VmClosure>> = BTreeMap::new();
            let mut public_names: HashSet<String> = HashSet::new();

            for node in program {
                // Imports may carry `@deprecated` / `@test` etc. on top-level
                // fn decls; transparently peel the wrapper before pattern
                // matching the FnDecl shape.
                let inner = match &node.node {
                    harn_parser::Node::AttributedDecl { inner, .. } => inner.as_ref(),
                    _ => node,
                };
                let harn_parser::Node::FnDecl {
                    name,
                    params,
                    body,
                    is_pub,
                    ..
                } = &inner.node
                else {
                    continue;
                };

                let mut compiler = crate::Compiler::new();
                let module_source_file = file_path.map(|p| p.display().to_string());
                let func_chunk = compiler
                    .compile_fn_body(params, body, module_source_file)
                    .map_err(|e| VmError::Runtime(format!("Import compile error: {e}")))?;
                let closure = Rc::new(VmClosure {
                    func: Rc::new(func_chunk),
                    env: module_env.clone(),
                    source_dir: source_dir.clone(),
                    module_functions: Some(Rc::clone(&registry)),
                    module_state: Some(Rc::clone(&module_state)),
                });
                registry
                    .borrow_mut()
                    .insert(name.clone(), Rc::clone(&closure));
                self.env
                    .define(name, VmValue::Closure(Rc::clone(&closure)), false)?;
                // Publish into module_state so sibling fns can be read
                // as VALUES (e.g. `{handler: other_fn}` or as callbacks).
                // Closures captured module_env BEFORE fn decls were added,
                // so their static env alone can't resolve sibling fns.
                // Direct calls use the module_functions late-binding path;
                // value reads rely on this module_state entry.
                module_state.borrow_mut().define(
                    name,
                    VmValue::Closure(Rc::clone(&closure)),
                    false,
                )?;
                functions.insert(name.clone(), Rc::clone(&closure));
                if *is_pub {
                    public_names.insert(name.clone());
                }
            }

            // Re-export pass: for every `pub import ...` declaration in
            // the module, surface the imported closures in this module's
            // `functions`/`public_names` so callers that import this
            // module see the re-exported names.
            for node in program {
                let (sub_path, selective_names, is_pub_import) = match &node.node {
                    harn_parser::Node::ImportDecl {
                        path: sub_path,
                        is_pub,
                    } => (sub_path.clone(), None, *is_pub),
                    harn_parser::Node::SelectiveImport {
                        names,
                        path: sub_path,
                        is_pub,
                    } => (sub_path.clone(), Some(names.clone()), *is_pub),
                    _ => continue,
                };
                if !is_pub_import {
                    continue;
                }
                let cache_key = self.cache_key_for_import(&sub_path);
                let Some(loaded) = self.module_cache.get(&cache_key).cloned() else {
                    return Err(VmError::Runtime(format!(
                        "Re-export error: imported module '{sub_path}' was not loaded"
                    )));
                };
                let names_to_reexport: Vec<String> = match selective_names {
                    Some(names) => names,
                    None => {
                        if loaded.public_names.is_empty() {
                            loaded.functions.keys().cloned().collect()
                        } else {
                            loaded.public_names.iter().cloned().collect()
                        }
                    }
                };
                for name in names_to_reexport {
                    let Some(closure) = loaded.functions.get(&name) else {
                        return Err(VmError::Runtime(format!(
                            "Re-export error: '{name}' is not exported by '{sub_path}'"
                        )));
                    };
                    if let Some(existing) = functions.get(&name) {
                        if !Rc::ptr_eq(existing, closure) {
                            return Err(VmError::Runtime(format!(
                                "Re-export collision: '{name}' is defined here and also \
                                 re-exported from '{sub_path}'"
                            )));
                        }
                    }
                    functions.insert(name.clone(), Rc::clone(closure));
                    public_names.insert(name);
                }
            }

            self.env = caller_env;
            self.source_dir = old_source_dir;

            Ok(LoadedModule {
                functions,
                public_names,
            })
        })
    }

    /// Return the path key that `execute_import` would use to cache the
    /// LoadedModule for this import string. Used by the re-export pass to
    /// look up the already-loaded source module after `execute_import`
    /// has populated [`Vm::module_cache`].
    fn cache_key_for_import(&self, path: &str) -> PathBuf {
        if let Some(module) = path.strip_prefix("std/") {
            return PathBuf::from(format!("<stdlib>/{module}.harn"));
        }
        let base = self
            .source_dir
            .clone()
            .unwrap_or_else(|| PathBuf::from("."));
        let file_path = resolve_module_import_path(&base, path);
        file_path.canonicalize().unwrap_or(file_path)
    }

    /// Load a module file and return the exported function closures that
    /// would be visible to a wildcard import.
    pub async fn load_module_exports(
        &mut self,
        path: &Path,
    ) -> Result<BTreeMap<String, Rc<VmClosure>>, VmError> {
        let path_str = path.to_string_lossy().into_owned();
        self.execute_import(&path_str, None).await?;

        let mut file_path = if path.is_absolute() {
            path.to_path_buf()
        } else {
            self.source_dir
                .clone()
                .unwrap_or_else(|| PathBuf::from("."))
                .join(path)
        };
        if !file_path.exists() && file_path.extension().is_none() {
            file_path.set_extension("harn");
        }

        let canonical = file_path
            .canonicalize()
            .unwrap_or_else(|_| file_path.clone());
        let loaded = self.module_cache.get(&canonical).cloned().ok_or_else(|| {
            VmError::Runtime(format!(
                "Import error: failed to cache loaded module '{}'",
                canonical.display()
            ))
        })?;

        let export_names: Vec<String> = if loaded.public_names.is_empty() {
            loaded.functions.keys().cloned().collect()
        } else {
            loaded.public_names.iter().cloned().collect()
        };

        let mut exports = BTreeMap::new();
        for name in export_names {
            let Some(closure) = loaded.functions.get(&name) else {
                return Err(VmError::Runtime(format!(
                    "Import error: exported function '{name}' is missing from {}",
                    canonical.display()
                )));
            };
            exports.insert(name, Rc::clone(closure));
        }

        Ok(exports)
    }

    /// Load synthetic source keyed by a synthetic module path and return
    /// the exported function closures that a wildcard import would expose.
    pub async fn load_module_exports_from_source(
        &mut self,
        source_key: impl Into<PathBuf>,
        source: &str,
    ) -> Result<BTreeMap<String, Rc<VmClosure>>, VmError> {
        let synthetic = source_key.into();
        let loaded = self
            .load_module_from_source(synthetic.clone(), source)
            .await?;
        let export_names: Vec<String> = if loaded.public_names.is_empty() {
            loaded.functions.keys().cloned().collect()
        } else {
            loaded.public_names.iter().cloned().collect()
        };

        let mut exports = BTreeMap::new();
        for name in export_names {
            let Some(closure) = loaded.functions.get(&name) else {
                return Err(VmError::Runtime(format!(
                    "Import error: exported function '{name}' is missing from {}",
                    synthetic.display()
                )));
            };
            exports.insert(name, Rc::clone(closure));
        }

        Ok(exports)
    }

    /// Load a module by import path (`std/foo`, relative module path, or
    /// package import) and return the exported function closures that a
    /// wildcard import would expose.
    pub async fn load_module_exports_from_import(
        &mut self,
        import_path: &str,
    ) -> Result<BTreeMap<String, Rc<VmClosure>>, VmError> {
        self.execute_import(import_path, None).await?;

        if let Some(module) = import_path.strip_prefix("std/") {
            let synthetic = PathBuf::from(format!("<stdlib>/{module}.harn"));
            let loaded = self.module_cache.get(&synthetic).cloned().ok_or_else(|| {
                VmError::Runtime(format!(
                    "Import error: failed to cache loaded module '{}'",
                    synthetic.display()
                ))
            })?;
            let mut exports = BTreeMap::new();
            let export_names: Vec<String> = if loaded.public_names.is_empty() {
                loaded.functions.keys().cloned().collect()
            } else {
                loaded.public_names.iter().cloned().collect()
            };
            for name in export_names {
                let Some(closure) = loaded.functions.get(&name) else {
                    return Err(VmError::Runtime(format!(
                        "Import error: exported function '{name}' is missing from {}",
                        synthetic.display()
                    )));
                };
                exports.insert(name, Rc::clone(closure));
            }
            return Ok(exports);
        }

        let base = self
            .source_dir
            .clone()
            .unwrap_or_else(|| PathBuf::from("."));
        let file_path = resolve_module_import_path(&base, import_path);
        self.load_module_exports(&file_path).await
    }
}