use std::path::{Path, PathBuf};

use avril_core::{Error, ModuleLoader};

use crate::caps::PathTarget;
use crate::modules::{ModuleGraph, ResolutionMode, lexical_absolute};

use oxc::allocator::Allocator;
use oxc::parser::Parser;
use oxc::span::SourceType;

/// Static CommonJS named exports.
pub(crate) fn named_exports(source: &str) -> Vec<String> {
    use oxc::ast::ast::{
        AssignmentTarget, CallExpression, Expression, ObjectPropertyKind, PropertyKey,
    };
    use oxc::ast_visit::{Visit, walk};
    use oxc::syntax::identifier::is_identifier_name;

    fn valid_name(name: &str) -> bool {
        // Synthetic ESM wrappers need importable identifiers; string-keyed
        // properties like `exports["foo-bar"]` stay available via `default`.
        !name.is_empty() && is_identifier_name(name)
    }

    fn string_key(key: &PropertyKey<'_>) -> Option<String> {
        match key {
            PropertyKey::StaticIdentifier(identifier) => Some(identifier.name.to_string()),
            PropertyKey::StringLiteral(literal) => Some(literal.value.to_string()),
            _ => None,
        }
    }

    fn expr_is_exports(expr: &Expression<'_>) -> bool {
        matches!(expr, Expression::Identifier(identifier) if identifier.name == "exports")
    }

    fn expr_is_module_exports(expr: &Expression<'_>) -> bool {
        match expr {
            Expression::StaticMemberExpression(member) => {
                matches!(&member.object, Expression::Identifier(object) if object.name == "module")
                    && member.property.name == "exports"
            }
            _ => false,
        }
    }

    #[derive(Default)]
    struct Collector {
        names: std::collections::BTreeSet<String>,
    }

    impl<'a> Visit<'a> for Collector {
        fn visit_assignment_expression(&mut self, expr: &oxc::ast::ast::AssignmentExpression<'a>) {
            let mut direct: Option<String> = None;
            let mut object_assign: Option<&Expression<'a>> = None;
            match &expr.left {
                AssignmentTarget::StaticMemberExpression(member) => {
                    let prop = member.property.name.to_string();
                    if expr_is_exports(&member.object) || expr_is_module_exports(&member.object) {
                        direct = Some(prop);
                    } else if matches!(&member.object, Expression::Identifier(object) if object.name == "module")
                        && member.property.name == "exports"
                    {
                        // `module.exports = …` itself; object literal handled below.
                        object_assign = Some(&expr.right);
                    }
                }
                AssignmentTarget::ComputedMemberExpression(member) => {
                    let prop = match &member.expression {
                        Expression::StringLiteral(literal) => Some(literal.value.to_string()),
                        _ => None,
                    };
                    if let Some(prop) = prop
                        && (expr_is_exports(&member.object)
                            || expr_is_module_exports(&member.object))
                    {
                        direct = Some(prop);
                    }
                    // `module.exports = …` via computed `module["exports"]` is rare; skip.
                }
                _ => {}
            }
            if let Some(name) = direct
                && valid_name(&name)
            {
                self.names.insert(name);
            }
            // `module.exports = { a, b: …, "c": … }`.
            if let Some(right) = object_assign
                && let Expression::ObjectExpression(object) = right
            {
                for property in &object.properties {
                    match property {
                        ObjectPropertyKind::ObjectProperty(property) => {
                            if property.computed {
                                continue;
                            }
                            if let Some(name) = string_key(&property.key)
                                && valid_name(&name)
                            {
                                self.names.insert(name);
                            }
                        }
                        ObjectPropertyKind::SpreadProperty(_) => {}
                    }
                }
            }
            walk::walk_assignment_expression(self, expr);
        }

        fn visit_call_expression(&mut self, expr: &CallExpression<'a>) {
            if let Expression::StaticMemberExpression(callee) = &expr.callee
                && matches!(&callee.object, Expression::Identifier(object) if object.name == "Object")
                && callee.property.name == "defineProperty"
                && expr.arguments.len() >= 2
            {
                let target = expr.arguments.first().and_then(|arg| arg.as_expression());
                let name = expr.arguments.get(1).and_then(|arg| arg.as_expression());
                let is_exports_target = target.is_some_and(|target| {
                    expr_is_exports(target) || expr_is_module_exports(target)
                });
                if is_exports_target && let Some(Expression::StringLiteral(literal)) = name {
                    let name = literal.value.to_string();
                    if valid_name(&name) {
                        self.names.insert(name);
                    }
                }
            }
            walk::walk_call_expression(self, expr);
        }
    }

    let allocator = Allocator::default();
    let parsed = Parser::new(&allocator, source, SourceType::cjs()).parse();
    // On syntax errors return what was found; execution reports the error.
    let mut collector = Collector::default();
    collector.visit_program(&parsed.program);
    collector.names.into_iter().collect()
}

enum LocalLookup {
    Missing,
    Err(Error),
}

impl ModuleGraph {
    /// Shared synchronous source for `require` demand loads: verified npm
    /// bytes via `npm_source` (virtual-URL authority + integrity) or local
    /// files via `read_text` (source authority, no broader grant needed).
    /// Never performs network I/O.
    pub(crate) fn sync_source(&self, name: &str) -> Result<String, Error> {
        self.check_access(name)?;
        let source = if self.npm.owning_instance(Path::new(name)).is_some() {
            self.npm
                .npm_source(Path::new(name))
                .map_err(|error| Error::Module(error.to_string()))?
        } else if self.npm.is_reserved_npm_path(Path::new(name)) {
            return Err(Error::Module(format!(
                "npm cache path is not owned by a prepared instance: {name}"
            )));
        } else {
            crate::sources::read_text(&self.target(name)?, &self.authority)
                .map_err(|error| self.path_error(name, error))?
        };
        self.check_access(name)?;
        Ok(source)
    }

    pub(crate) fn require_referrer_path(referrer: &str) -> Option<PathBuf> {
        let path = Path::new(referrer);
        if path.is_absolute() {
            return lexical_absolute(path).ok();
        }
        if let Ok(url) = url::Url::parse(referrer)
            && url.scheme() == "file"
        {
            return lexical_absolute(&url.to_file_path().ok()?).ok();
        }
        None
    }

    fn resolve_npm_for_anchor(
        &self,
        anchor: &str,
        npm_specifier: &str,
        original: &str,
    ) -> Result<String, Error> {
        let root = self
            .packages
            .root(anchor)
            .map_err(|error| Error::Module(error.to_string()))?;
        let handles = self.npm_handles.borrow();
        let Some(handle) = handles.get(&root) else {
            return Err(Error::Module(format!(
                "npm package is not prepared in this context (sync require cannot acquire new packages): {original}"
            )));
        };
        self.npm
            .resolve_in(handle, npm_specifier, ResolutionMode::Require)
            .map(|resolved| {
                resolved
                    .path
                    .to_str()
                    .expect("npm paths are UTF-8")
                    .to_owned()
            })
            .map_err(|error| Error::Module(error.to_string()))
    }

    fn resolve_local_require(
        &self,
        specifier: &str,
        referrer_path: &Path,
    ) -> Result<String, Error> {
        let path = if specifier
            .get(..5)
            .is_some_and(|scheme| scheme.eq_ignore_ascii_case("file:"))
        {
            let url = url::Url::parse(specifier)
                .map_err(|_| Error::Module(format!("Invalid file URL: {specifier}")))?;
            if url.query().is_some() || url.fragment().is_some() {
                return Err(Error::Module(
                    "File URL queries and fragments are not supported yet".into(),
                ));
            }
            url.to_file_path()
                .map_err(|_| Error::Module(format!("Invalid file URL: {specifier}")))?
        } else {
            let path = Path::new(specifier);
            if path.is_absolute() {
                path.to_owned()
            } else if specifier.starts_with("./") || specifier.starts_with("../") {
                referrer_path.parent().unwrap_or(Path::new(".")).join(path)
            } else {
                return Err(Error::Module(format!(
                    "Unsupported module specifier for sync require (use import() instead): {specifier}"
                )));
            }
        };
        match self.local_file_require(&path, 0) {
            Ok(name) => Ok(name),
            Err(LocalLookup::Missing) => {
                Err(self.path_error(specifier, format!("Module not found: {}", path.display())))
            }
            Err(LocalLookup::Err(error)) => Err(error),
        }
    }

    fn local_file_require(&self, path: &Path, depth: usize) -> Result<String, LocalLookup> {
        if depth > 5 {
            return Err(LocalLookup::Err(Error::Module(
                "Local require lookup is too deep".into(),
            )));
        }
        match self.local_candidate(path) {
            Ok(name) => return Self::check_native(name).map_err(LocalLookup::Err),
            Err(LocalLookup::Missing) => {}
            Err(other) => return Err(other),
        }
        for extension in [".js", ".json", ".node"] {
            let mut candidate = path.as_os_str().to_owned();
            candidate.push(extension);
            let candidate_path = PathBuf::from(candidate);
            match self.local_candidate(&candidate_path) {
                Ok(name) => return Self::check_native(name).map_err(LocalLookup::Err),
                Err(LocalLookup::Missing) => continue,
                Err(other) => return Err(other),
            }
        }
        if self.local_is_dir(path) {
            match self.local_dir_main(path) {
                Ok(Some(main)) => {
                    let candidate = path.join(main);
                    match self.local_file_require(&candidate, depth + 1) {
                        Ok(name) => return Ok(name),
                        Err(LocalLookup::Missing) => {}
                        Err(other) => return Err(other),
                    }
                }
                Ok(None) => {}
                Err(error) => return Err(LocalLookup::Err(error)),
            }
            for index in ["index.js", "index.json", "index.cjs", "index.node"] {
                match self.local_candidate(&path.join(index)) {
                    Ok(name) => return Self::check_native(name).map_err(LocalLookup::Err),
                    Err(LocalLookup::Missing) => continue,
                    Err(other) => return Err(other),
                }
            }
        }
        Err(LocalLookup::Missing)
    }

    fn check_native(name: String) -> Result<String, Error> {
        if name.to_ascii_lowercase().ends_with(".node") {
            return Err(Error::Module(format!(
                "Native addons are not supported: {name}"
            )));
        }
        Ok(name)
    }

    fn local_candidate(&self, path: &Path) -> Result<String, LocalLookup> {
        let logical = lexical_absolute(path).map_err(LocalLookup::Err)?;
        if self.npm.is_reserved_npm_path(&logical) {
            return self.npm_local_candidate(&logical);
        }
        let target = match PathTarget::resolve(path) {
            Ok(target) => target,
            Err(_) => return Err(LocalLookup::Missing),
        };
        if self.npm.is_reserved_npm_path(target.as_path()) {
            return self.npm_local_candidate(target.as_path());
        }
        if let Err(error) = self.authority.check_local(&target) {
            return Err(LocalLookup::Err(
                self.path_error(&path.display().to_string(), error),
            ));
        }
        let resolved = target.as_path().to_owned();
        if !std::fs::symlink_metadata(&resolved).is_ok_and(|meta| meta.is_file()) {
            return Err(LocalLookup::Missing);
        }
        resolved
            .into_os_string()
            .into_string()
            .map_err(|_| LocalLookup::Err(Error::Module("Module paths must be valid UTF-8".into())))
    }

    fn npm_local_candidate(&self, path: &Path) -> Result<String, LocalLookup> {
        match self.npm.resolve_require_path(path) {
            Ok(Some(module)) => module.path.into_os_string().into_string().map_err(|_| {
                LocalLookup::Err(Error::Module("Module paths must be valid UTF-8".into()))
            }),
            Ok(None) => Err(LocalLookup::Missing),
            Err(error) => Err(LocalLookup::Err(Error::Module(error.to_string()))),
        }
    }

    fn local_is_dir(&self, path: &Path) -> bool {
        PathTarget::resolve(path)
            .ok()
            .filter(|target| self.authority.check_local(target).is_ok())
            .is_some_and(|target| target.as_path().is_dir())
    }

    fn local_dir_main(&self, dir: &Path) -> Result<Option<PathBuf>, Error> {
        let package = dir.join("package.json");
        let target = match PathTarget::resolve(&package) {
            Ok(target) => target,
            Err(_) => return Ok(None),
        };
        let Some(name) = target.as_path().to_str() else {
            return Ok(None);
        };
        let source = self.sync_source(name)?;
        let value: serde_json::Value = serde_json::from_str(&source).map_err(|error| {
            Error::Module(format!(
                "{}: invalid package.json: {error}",
                package.display()
            ))
        })?;
        let Some(main) = value.get("main").and_then(|entry| entry.as_str()) else {
            return Ok(None);
        };
        if main.is_empty() || main.contains('\0') {
            return Err(Error::Module(format!(
                "{}: invalid package.json main",
                package.display()
            )));
        }
        if main.contains("../") || main.starts_with("..") {
            return Ok(None);
        }
        let main = main.strip_prefix("./").unwrap_or(main);
        if main.is_empty()
            || main
                .split('/')
                .any(|part| part.is_empty() || part == "." || part == "..")
        {
            return Ok(None);
        }
        Ok(Some(PathBuf::from(main)))
    }
    pub(crate) fn require_resolve_sync(
        &self,
        specifier: &str,
        referrer: &str,
    ) -> Result<String, Error> {
        if specifier.starts_with("ext:") {
            return Err(Error::Module("Extension modules are private".into()));
        }
        if specifier.starts_with("node:") || specifier == "node" {
            return Err(Error::Module(format!(
                "node: builtin modules are not supported: {specifier}"
            )));
        }
        if specifier.starts_with("avril:") {
            return Ok(specifier.to_owned());
        }
        // Never expose internal extension modules via any path.
        // `require_resolve` itself performs no I/O beyond verified metadata
        // and canonicalized filesystem probes; capability checks happen in
        // the core `require` wrapper (and `require.resolve`) around this.
        if let Some(referrer_path) = Self::require_referrer_path(referrer) {
            if self.npm.is_reserved_npm_path(&referrer_path) {
                if self.npm.owning_instance(&referrer_path).is_none() {
                    return Err(Error::Module(format!(
                        "npm cache path is not owned by a prepared instance: {}",
                        referrer_path.display()
                    )));
                }
                return self
                    .npm
                    .resolve_from_file(specifier, &referrer_path, ResolutionMode::Require)
                    .map(|resolved| {
                        resolved
                            .path
                            .to_str()
                            .expect("npm paths are UTF-8")
                            .to_owned()
                    })
                    .map_err(|error| Error::Module(error.to_string()));
            }
            let anchor = referrer_path
                .to_str()
                .ok_or_else(|| Error::Module("Module paths must be valid UTF-8".into()))?;
            if let Some(mapped) =
                self.packages
                    .resolve_import_meta(specifier, anchor, &self.remote)?
            {
                match mapped {
                    crate::local_packages::Resolution::Specifier(target) => {
                        if target.starts_with("npm:") {
                            return self.resolve_npm_for_anchor(anchor, &target, specifier);
                        }
                        if target.starts_with("ext:") {
                            return Err(Error::Module("Extension modules are private".into()));
                        }
                        if target.starts_with("node:") || target == "node" {
                            return Err(Error::Module(format!(
                                "node: builtin modules are not supported: {specifier}"
                            )));
                        }
                        if target.starts_with("avril:")
                            || target.starts_with("jsr:")
                            || target.starts_with("http:")
                            || target.starts_with("https:")
                        {
                            return Err(Error::Module(format!(
                                "Unsupported module specifier for sync require (use import() instead): {specifier}"
                            )));
                        }
                        return self.resolve_local_require(&target, &referrer_path);
                    }
                    crate::local_packages::Resolution::Module(name) => {
                        if name.starts_with("ext:") {
                            return Err(Error::Module("Extension modules are private".into()));
                        }
                        return Ok(name);
                    }
                    crate::local_packages::Resolution::Remote(_) => {
                        return Err(Error::Module(format!(
                            "Unsupported module specifier for sync require (use import() instead): {specifier}"
                        )));
                    }
                }
            }
            if specifier.starts_with("npm:") {
                return self.resolve_npm_for_anchor(anchor, specifier, specifier);
            }
            return self.resolve_local_require(specifier, &referrer_path);
        }
        Err(Error::Module(format!(
            "Unsupported module specifier for sync require (use import() instead): {specifier}"
        )))
    }
}

#[cfg(test)]
mod require_referrer_tests {
    use super::ModuleGraph;

    #[test]
    fn referrer_paths_are_portable() {
        assert!(ModuleGraph::require_referrer_path("/tmp/a.cjs").is_some());
        assert!(ModuleGraph::require_referrer_path("file:///tmp/a.cjs").is_some());
        assert!(ModuleGraph::require_referrer_path("./a.cjs").is_none());
        assert!(ModuleGraph::require_referrer_path("https://example.test/a.js").is_none());
        assert!(ModuleGraph::require_referrer_path("avril:std").is_none());
    }

    #[cfg(windows)]
    #[test]
    fn windows_absolute_paths_resolve() {
        assert!(ModuleGraph::require_referrer_path(r"C:\proj\a.cjs").is_some());
    }
}