alef_backend_java/

gen_bindings.rs

use crate::type_map::{java_boxed_type, java_ffi_type, java_type};
use ahash::AHashSet;
use alef_codegen::naming::{to_class_name, to_java_name};
use alef_core::backend::{Backend, BuildConfig, Capabilities, GeneratedFile};
use alef_core::config::{AlefConfig, Language, resolve_output_dir};
use alef_core::ir::{ApiSurface, EnumDef, FunctionDef, PrimitiveType, TypeDef, TypeRef};
use heck::{ToLowerCamelCase, ToPascalCase, ToSnakeCase};
use std::fmt::Write;
use std::path::PathBuf;

/// Names that conflict with methods on `java.lang.Object` and are therefore
/// illegal as record component names or method names in generated Java code.
const JAVA_OBJECT_METHOD_NAMES: &[&str] = &[
    "wait",
    "notify",
    "notifyAll",
    "getClass",
    "hashCode",
    "equals",
    "toString",
    "clone",
    "finalize",
];

/// Sanitise a field/parameter name that would conflict with `java.lang.Object`
/// methods.  Conflicting names get a `_` suffix (e.g. `wait` -> `wait_`), which
/// is then converted to camelCase by `to_java_name`.
fn safe_java_field_name(name: &str) -> String {
    let java_name = to_java_name(name);
    if JAVA_OBJECT_METHOD_NAMES.contains(&java_name.as_str()) {
        format!("{}Value", java_name)
    } else {
        java_name
    }
}

pub struct JavaBackend;

impl JavaBackend {
    /// Convert crate name to main class name (PascalCase + "Rs" suffix).
    ///
    /// The "Rs" suffix ensures the raw FFI wrapper class has a distinct name from
    /// the public facade class (which strips the "Rs" suffix). Without this, the
    /// facade would delegate to itself, causing infinite recursion.
    fn resolve_main_class(api: &ApiSurface) -> String {
        let base = to_class_name(&api.crate_name.replace('-', "_"));
        if base.ends_with("Rs") {
            base
        } else {
            format!("{}Rs", base)
        }
    }
}

impl Backend for JavaBackend {
    fn name(&self) -> &str {
        "java"
    }

    fn language(&self) -> Language {
        Language::Java
    }

    fn capabilities(&self) -> Capabilities {
        Capabilities {
            supports_async: true,
            supports_classes: true,
            supports_enums: true,
            supports_option: true,
            supports_result: true,
            ..Capabilities::default()
        }
    }

    fn generate_bindings(&self, api: &ApiSurface, config: &AlefConfig) -> anyhow::Result<Vec<GeneratedFile>> {
        let package = config.java_package();
        let prefix = config.ffi_prefix();
        let main_class = Self::resolve_main_class(api);
        let package_path = package.replace('.', "/");

        let output_dir = resolve_output_dir(
            config.output.java.as_ref(),
            &config.crate_config.name,
            "packages/java/src/main/java/",
        );

        let base_path = PathBuf::from(&output_dir).join(&package_path);

        let mut files = Vec::new();

        // 0. package-info.java - required by Checkstyle
        let description = config
            .scaffold
            .as_ref()
            .and_then(|s| s.description.as_deref())
            .unwrap_or("High-performance HTML to Markdown converter.");
        files.push(GeneratedFile {
            path: base_path.join("package-info.java"),
            content: format!(
                "/**\n * {description}\n */\npackage {package};\n",
                description = description,
                package = package,
            ),
            generated_header: true,
        });

        // 1. NativeLib.java - FFI method handles
        files.push(GeneratedFile {
            path: base_path.join("NativeLib.java"),
            content: gen_native_lib(api, config, &package, &prefix),
            generated_header: true,
        });

        // 2. Main wrapper class
        files.push(GeneratedFile {
            path: base_path.join(format!("{}.java", main_class)),
            content: gen_main_class(api, config, &package, &main_class, &prefix),
            generated_header: true,
        });

        // 3. Exception class
        files.push(GeneratedFile {
            path: base_path.join(format!("{}Exception.java", main_class)),
            content: gen_exception_class(&package, &main_class),
            generated_header: true,
        });

        // Collect complex enums (enums with data variants and no serde tag) — use Object for these fields.
        // Tagged unions (serde_tag is set) are now generated as proper sealed interfaces
        // and can be deserialized as their concrete types, so they are NOT complex_enums.
        let complex_enums: AHashSet<String> = api
            .enums
            .iter()
            .filter(|e| e.serde_tag.is_none() && e.variants.iter().any(|v| !v.fields.is_empty()))
            .map(|e| e.name.clone())
            .collect();

        // Resolve language-level serde rename strategy (always wins over IR type-level).
        let lang_rename_all = config.serde_rename_all_for_language(Language::Java);

        // 4. Record types
        for typ in api.types.iter().filter(|typ| !typ.is_trait) {
            if !typ.is_opaque && !typ.fields.is_empty() {
                files.push(GeneratedFile {
                    path: base_path.join(format!("{}.java", typ.name)),
                    content: gen_record_type(&package, typ, &complex_enums, &lang_rename_all),
                    generated_header: true,
                });
                // Generate builder class for types with defaults
                if typ.has_default {
                    files.push(GeneratedFile {
                        path: base_path.join(format!("{}Builder.java", typ.name)),
                        content: gen_builder_class(&package, typ),
                        generated_header: true,
                    });
                }
            }
        }

        // Collect builder class names generated from record types with defaults,
        // so we can skip opaque types that would collide with them.
        let builder_class_names: AHashSet<String> = api
            .types
            .iter()
            .filter(|t| !t.is_opaque && !t.fields.is_empty() && t.has_default)
            .map(|t| format!("{}Builder", t.name))
            .collect();

        // 4b. Opaque handle types (skip if a pure-Java builder already covers this name)
        for typ in api.types.iter().filter(|typ| !typ.is_trait) {
            if typ.is_opaque && !builder_class_names.contains(&typ.name) {
                files.push(GeneratedFile {
                    path: base_path.join(format!("{}.java", typ.name)),
                    content: gen_opaque_handle_class(&package, typ, &prefix),
                    generated_header: true,
                });
            }
        }

        // 5. Enums
        for enum_def in &api.enums {
            files.push(GeneratedFile {
                path: base_path.join(format!("{}.java", enum_def.name)),
                content: gen_enum_class(&package, enum_def),
                generated_header: true,
            });
        }

        // 6. Error exception classes
        for error in &api.errors {
            for (class_name, content) in alef_codegen::error_gen::gen_java_error_types(error, &package) {
                files.push(GeneratedFile {
                    path: base_path.join(format!("{}.java", class_name)),
                    content,
                    generated_header: true,
                });
            }
        }

        // Build adapter body map (consumed by generators via body substitution)
        let _adapter_bodies = alef_adapters::build_adapter_bodies(config, Language::Java)?;

        Ok(files)
    }

    fn generate_public_api(&self, api: &ApiSurface, config: &AlefConfig) -> anyhow::Result<Vec<GeneratedFile>> {
        let package = config.java_package();
        let prefix = config.ffi_prefix();
        let main_class = Self::resolve_main_class(api);
        let package_path = package.replace('.', "/");

        let output_dir = resolve_output_dir(
            config.output.java.as_ref(),
            &config.crate_config.name,
            "packages/java/src/main/java/",
        );

        let base_path = PathBuf::from(&output_dir).join(&package_path);

        // Generate a high-level public API class that wraps the raw FFI class.
        // Class name = main_class without "Rs" suffix (e.g., HtmlToMarkdownRs -> HtmlToMarkdown)
        let public_class = main_class.trim_end_matches("Rs").to_string();
        let facade_content = gen_facade_class(api, &package, &public_class, &main_class, &prefix);

        Ok(vec![GeneratedFile {
            path: base_path.join(format!("{}.java", public_class)),
            content: facade_content,
            generated_header: true,
        }])
    }

    fn build_config(&self) -> Option<BuildConfig> {
        Some(BuildConfig {
            tool: "mvn",
            crate_suffix: "",
            depends_on_ffi: true,
            post_build: vec![],
        })
    }
}

// ---------------------------------------------------------------------------
// NativeLib.java - FFI method handles
// ---------------------------------------------------------------------------

fn gen_native_lib(api: &ApiSurface, config: &AlefConfig, package: &str, prefix: &str) -> String {
    // Generate the class body first, then scan it to determine which imports are needed.
    let mut body = String::with_capacity(2048);
    // Derive the native library name from the FFI output path (directory name with hyphens replaced
    // by underscores), falling back to `{ffi_prefix}_ffi`.
    let lib_name = config.ffi_lib_name();

    writeln!(body, "final class NativeLib {{").ok();
    writeln!(body, "    private static final Linker LINKER = Linker.nativeLinker();").ok();
    writeln!(body, "    private static final SymbolLookup LIB;").ok();
    writeln!(body).ok();
    writeln!(body, "    static {{").ok();
    writeln!(body, "        System.loadLibrary(\"{}\");", lib_name).ok();
    writeln!(body, "        LIB = SymbolLookup.loaderLookup();").ok();
    writeln!(body, "    }}").ok();
    writeln!(body).ok();

    // Generate method handles for free functions.
    // All functions get handles regardless of is_async — the FFI layer always exposes
    // synchronous C functions, and the Java async wrapper delegates to the sync method.
    for func in &api.functions {
        let ffi_name = format!("{}_{}", prefix, func.name.to_lowercase());
        let return_layout = gen_ffi_layout(&func.return_type);
        let param_layouts: Vec<String> = func.params.iter().map(|p| gen_ffi_layout(&p.ty)).collect();

        let layout_str = gen_function_descriptor(&return_layout, &param_layouts);

        let handle_name = format!("{}_{}", prefix.to_uppercase(), func.name.to_uppercase());

        writeln!(
            body,
            "    static final MethodHandle {} = LINKER.downcallHandle(",
            handle_name
        )
        .ok();
        writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", ffi_name).ok();
        writeln!(body, "        {}", layout_str).ok();
        writeln!(body, "    );").ok();
    }

    // free_string handle for releasing FFI-allocated strings
    {
        let free_name = format!("{}_free_string", prefix);
        let handle_name = format!("{}_FREE_STRING", prefix.to_uppercase());
        writeln!(body).ok();
        writeln!(
            body,
            "    static final MethodHandle {} = LINKER.downcallHandle(",
            handle_name
        )
        .ok();
        writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", free_name).ok();
        writeln!(body, "        FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)").ok();
        writeln!(body, "    );").ok();
    }

    // Error handling — use the FFI's last_error_code and last_error_context symbols
    {
        writeln!(
            body,
            "    static final MethodHandle {}_LAST_ERROR_CODE = LINKER.downcallHandle(",
            prefix.to_uppercase()
        )
        .ok();
        writeln!(body, "        LIB.find(\"{}_last_error_code\").orElseThrow(),", prefix).ok();
        writeln!(body, "        FunctionDescriptor.of(ValueLayout.JAVA_INT)").ok();
        writeln!(body, "    );").ok();

        writeln!(
            body,
            "    static final MethodHandle {}_LAST_ERROR_CONTEXT = LINKER.downcallHandle(",
            prefix.to_uppercase()
        )
        .ok();
        writeln!(
            body,
            "        LIB.find(\"{}_last_error_context\").orElseThrow(),",
            prefix
        )
        .ok();
        writeln!(body, "        FunctionDescriptor.of(ValueLayout.ADDRESS)").ok();
        writeln!(body, "    );").ok();
    }

    // Track emitted free handles to avoid duplicates (a type may appear both as
    // a function return type AND as an opaque type).
    let mut emitted_free_handles: AHashSet<String> = AHashSet::new();

    // Build the set of opaque type names so we can pick the right accessor below.
    let opaque_type_names: AHashSet<String> = api
        .types
        .iter()
        .filter(|t| t.is_opaque)
        .map(|t| t.name.clone())
        .collect();

    // Accessor handles for Named return types (struct pointer → field accessor + free)
    for func in &api.functions {
        if let TypeRef::Named(name) = &func.return_type {
            let type_snake = name.to_snake_case();
            let type_upper = type_snake.to_uppercase();
            let is_opaque = opaque_type_names.contains(name.as_str());

            if is_opaque {
                // Opaque handles: the caller wraps the pointer directly, no JSON needed.
                // No content accessor is emitted for opaque types.
            } else {
                // Non-opaque record types: use _to_json to serialize the full struct to JSON,
                // which the Java side then deserializes with ObjectMapper.
                // NOTE: _content returns only the markdown string field, not the full JSON.
                let to_json_handle = format!("{}_{}_TO_JSON", prefix.to_uppercase(), type_upper);
                let to_json_ffi = format!("{}_{}_to_json", prefix, type_snake);
                writeln!(body).ok();
                writeln!(
                    body,
                    "    static final MethodHandle {} = LINKER.downcallHandle(",
                    to_json_handle
                )
                .ok();
                writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", to_json_ffi).ok();
                writeln!(
                    body,
                    "        FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.ADDRESS)"
                )
                .ok();
                writeln!(body, "    );").ok();
            }

            // _free: (struct_ptr) -> void
            let free_handle = format!("{}_{}_FREE", prefix.to_uppercase(), type_upper);
            let free_ffi = format!("{}_{}_free", prefix, type_snake);
            if emitted_free_handles.insert(free_handle.clone()) {
                writeln!(body).ok();
                writeln!(
                    body,
                    "    static final MethodHandle {} = LINKER.downcallHandle(",
                    free_handle
                )
                .ok();
                writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", free_ffi).ok();
                writeln!(body, "        FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)").ok();
                writeln!(body, "    );").ok();
            }
        }
    }

    // FROM_JSON + FREE handles for non-opaque Named types used as parameters.
    // These allow serializing a Java record to JSON and passing it to the FFI.
    let mut emitted_from_json_handles: AHashSet<String> = AHashSet::new();
    for func in &api.functions {
        for param in &func.params {
            // Handle both Named and Optional<Named> params
            let inner_name = match &param.ty {
                TypeRef::Named(n) => Some(n.clone()),
                TypeRef::Optional(inner) => {
                    if let TypeRef::Named(n) = inner.as_ref() {
                        Some(n.clone())
                    } else {
                        None
                    }
                }
                _ => None,
            };
            if let Some(name) = inner_name {
                if !opaque_type_names.contains(name.as_str()) {
                    let type_snake = name.to_snake_case();
                    let type_upper = type_snake.to_uppercase();

                    // _from_json: (char*) -> struct_ptr
                    let from_json_handle = format!("{}_{}_FROM_JSON", prefix.to_uppercase(), type_upper);
                    let from_json_ffi = format!("{}_{}_from_json", prefix, type_snake);
                    if emitted_from_json_handles.insert(from_json_handle.clone()) {
                        writeln!(body).ok();
                        writeln!(
                            body,
                            "    static final MethodHandle {} = LINKER.downcallHandle(",
                            from_json_handle
                        )
                        .ok();
                        writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", from_json_ffi).ok();
                        writeln!(
                            body,
                            "        FunctionDescriptor.of(ValueLayout.ADDRESS, ValueLayout.ADDRESS)"
                        )
                        .ok();
                        writeln!(body, "    );").ok();
                    }

                    // _free: (struct_ptr) -> void
                    let free_handle = format!("{}_{}_FREE", prefix.to_uppercase(), type_upper);
                    let free_ffi = format!("{}_{}_free", prefix, type_snake);
                    if emitted_free_handles.insert(free_handle.clone()) {
                        writeln!(body).ok();
                        writeln!(
                            body,
                            "    static final MethodHandle {} = LINKER.downcallHandle(",
                            free_handle
                        )
                        .ok();
                        writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", free_ffi).ok();
                        writeln!(body, "        FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)").ok();
                        writeln!(body, "    );").ok();
                    }
                }
            }
        }
    }

    // Collect builder class names from record types with defaults, so we skip
    // opaque types that are superseded by a pure-Java builder class.
    let builder_class_names: AHashSet<String> = api
        .types
        .iter()
        .filter(|t| !t.is_opaque && !t.fields.is_empty() && t.has_default)
        .map(|t| format!("{}Builder", t.name))
        .collect();

    // Free handles for opaque types (handle pointer → void)
    for typ in api.types.iter().filter(|typ| !typ.is_trait) {
        if typ.is_opaque && !builder_class_names.contains(&typ.name) {
            let type_snake = typ.name.to_snake_case();
            let type_upper = type_snake.to_uppercase();
            let free_handle = format!("{}_{}_FREE", prefix.to_uppercase(), type_upper);
            let free_ffi = format!("{}_{}_free", prefix, type_snake);
            if emitted_free_handles.insert(free_handle.clone()) {
                writeln!(body).ok();
                writeln!(
                    body,
                    "    static final MethodHandle {} = LINKER.downcallHandle(",
                    free_handle
                )
                .ok();
                writeln!(body, "        LIB.find(\"{}\").orElseThrow(),", free_ffi).ok();
                writeln!(body, "        FunctionDescriptor.ofVoid(ValueLayout.ADDRESS)").ok();
                writeln!(body, "    );").ok();
            }
        }
    }

    writeln!(body, "}}").ok();

    // Now assemble the file with only the imports that are actually used in the body.
    let mut out = String::with_capacity(body.len() + 512);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    if body.contains("Arena") {
        writeln!(out, "import java.lang.foreign.Arena;").ok();
    }
    if body.contains("FunctionDescriptor") {
        writeln!(out, "import java.lang.foreign.FunctionDescriptor;").ok();
    }
    if body.contains("Linker") {
        writeln!(out, "import java.lang.foreign.Linker;").ok();
    }
    if body.contains("MemorySegment") {
        writeln!(out, "import java.lang.foreign.MemorySegment;").ok();
    }
    if body.contains("SymbolLookup") {
        writeln!(out, "import java.lang.foreign.SymbolLookup;").ok();
    }
    if body.contains("ValueLayout") {
        writeln!(out, "import java.lang.foreign.ValueLayout;").ok();
    }
    if body.contains("MethodHandle") {
        writeln!(out, "import java.lang.invoke.MethodHandle;").ok();
    }
    writeln!(out).ok();

    out.push_str(&body);

    out
}

// ---------------------------------------------------------------------------
// Main wrapper class
// ---------------------------------------------------------------------------

fn gen_main_class(api: &ApiSurface, _config: &AlefConfig, package: &str, class_name: &str, prefix: &str) -> String {
    // Build the set of opaque type names so we can distinguish opaque handles from records
    let opaque_types: AHashSet<String> = api
        .types
        .iter()
        .filter(|t| t.is_opaque)
        .map(|t| t.name.clone())
        .collect();

    // Generate the class body first, then scan it to determine which imports are needed.
    let mut body = String::with_capacity(4096);

    writeln!(body, "public final class {} {{", class_name).ok();
    writeln!(body, "    private {}() {{ }}", class_name).ok();
    writeln!(body).ok();

    // Generate static methods for free functions
    for func in &api.functions {
        // Always generate sync method
        gen_sync_function_method(&mut body, func, prefix, class_name, &opaque_types);
        writeln!(body).ok();

        // Also generate async wrapper if marked as async
        if func.is_async {
            gen_async_wrapper_method(&mut body, func);
            writeln!(body).ok();
        }
    }

    // Add helper methods only if they are referenced in the body
    gen_helper_methods(&mut body, prefix, class_name);

    writeln!(body, "}}").ok();

    // Now assemble the file with only the imports that are actually used in the body.
    let mut out = String::with_capacity(body.len() + 512);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    if body.contains("Arena") {
        writeln!(out, "import java.lang.foreign.Arena;").ok();
    }
    if body.contains("FunctionDescriptor") {
        writeln!(out, "import java.lang.foreign.FunctionDescriptor;").ok();
    }
    if body.contains("Linker") {
        writeln!(out, "import java.lang.foreign.Linker;").ok();
    }
    if body.contains("MemorySegment") {
        writeln!(out, "import java.lang.foreign.MemorySegment;").ok();
    }
    if body.contains("SymbolLookup") {
        writeln!(out, "import java.lang.foreign.SymbolLookup;").ok();
    }
    if body.contains("ValueLayout") {
        writeln!(out, "import java.lang.foreign.ValueLayout;").ok();
    }
    if body.contains("List<") {
        writeln!(out, "import java.util.List;").ok();
    }
    if body.contains("Map<") {
        writeln!(out, "import java.util.Map;").ok();
    }
    if body.contains("Optional<") {
        writeln!(out, "import java.util.Optional;").ok();
    }
    if body.contains("HashMap<") || body.contains("new HashMap") {
        writeln!(out, "import java.util.HashMap;").ok();
    }
    if body.contains("CompletableFuture") {
        writeln!(out, "import java.util.concurrent.CompletableFuture;").ok();
    }
    if body.contains("CompletionException") {
        writeln!(out, "import java.util.concurrent.CompletionException;").ok();
    }
    // Only import the short name `ObjectMapper` when it's used as a type reference (not just via
    // `createObjectMapper()` which uses fully qualified names internally).
    // Check for " ObjectMapper" (space before) which indicates use as a type, not a method name suffix.
    if body.contains(" ObjectMapper") {
        writeln!(out, "import com.fasterxml.jackson.databind.ObjectMapper;").ok();
    }
    writeln!(out).ok();

    out.push_str(&body);

    out
}

fn gen_sync_function_method(
    out: &mut String,
    func: &FunctionDef,
    prefix: &str,
    class_name: &str,
    opaque_types: &AHashSet<String>,
) {
    let params: Vec<String> = func
        .params
        .iter()
        .map(|p| {
            let ptype = java_type(&p.ty);
            format!("{} {}", ptype, to_java_name(&p.name))
        })
        .collect();

    let return_type = java_type(&func.return_type);

    writeln!(
        out,
        "    public static {} {}({}) throws {}Exception {{",
        return_type,
        to_java_name(&func.name),
        params.join(", "),
        class_name
    )
    .ok();

    writeln!(out, "        try (var arena = Arena.ofConfined()) {{").ok();

    // Collect non-opaque Named params that need FFI pointer cleanup after the call.
    // These are Rust-allocated by _from_json and must be freed with _free.
    let ffi_ptr_params: Vec<(String, String)> = func
        .params
        .iter()
        .filter_map(|p| {
            let inner_name = match &p.ty {
                TypeRef::Named(n) if !opaque_types.contains(n.as_str()) => Some(n.clone()),
                TypeRef::Optional(inner) => {
                    if let TypeRef::Named(n) = inner.as_ref() {
                        if !opaque_types.contains(n.as_str()) {
                            Some(n.clone())
                        } else {
                            None
                        }
                    } else {
                        None
                    }
                }
                _ => None,
            };
            inner_name.map(|type_name| {
                let cname = "c".to_string() + &to_java_name(&p.name);
                let type_snake = type_name.to_snake_case();
                let free_handle = format!("NativeLib.{}_{}_FREE", prefix.to_uppercase(), type_snake.to_uppercase());
                (cname, free_handle)
            })
        })
        .collect();

    // Marshal parameters (use camelCase Java names)
    for param in &func.params {
        marshal_param_to_ffi(out, &to_java_name(&param.name), &param.ty, opaque_types, prefix);
    }

    // Call FFI
    let ffi_handle = format!("NativeLib.{}_{}", prefix.to_uppercase(), func.name.to_uppercase());

    let call_args: Vec<String> = func
        .params
        .iter()
        .map(|p| ffi_param_name(&to_java_name(&p.name), &p.ty, opaque_types))
        .collect();

    // Emit a helper closure to free FFI-allocated param pointers (e.g. options created by _from_json)
    let emit_ffi_ptr_cleanup = |out: &mut String| {
        for (cname, free_handle) in &ffi_ptr_params {
            writeln!(out, "            if (!{}.equals(MemorySegment.NULL)) {{", cname).ok();
            writeln!(out, "                {}.invoke({});", free_handle, cname).ok();
            writeln!(out, "            }}").ok();
        }
    };

    if matches!(func.return_type, TypeRef::Unit) {
        writeln!(out, "            {}.invoke({});", ffi_handle, call_args.join(", ")).ok();
        emit_ffi_ptr_cleanup(out);
        writeln!(out, "        }} catch (Throwable e) {{").ok();
        writeln!(
            out,
            "            throw new {}Exception(\"FFI call failed\", e);",
            class_name
        )
        .ok();
        writeln!(out, "        }}").ok();
    } else if is_ffi_string_return(&func.return_type) {
        let free_handle = format!("NativeLib.{}_FREE_STRING", prefix.to_uppercase());
        writeln!(
            out,
            "            var resultPtr = (MemorySegment) {}.invoke({});",
            ffi_handle,
            call_args.join(", ")
        )
        .ok();
        emit_ffi_ptr_cleanup(out);
        writeln!(out, "            if (resultPtr.equals(MemorySegment.NULL)) {{").ok();
        writeln!(out, "                checkLastError();").ok();
        writeln!(out, "                return null;").ok();
        writeln!(out, "            }}").ok();
        writeln!(
            out,
            "            String result = resultPtr.reinterpret(Long.MAX_VALUE).getString(0);"
        )
        .ok();
        writeln!(out, "            {}.invoke(resultPtr);", free_handle).ok();
        writeln!(out, "            return result;").ok();
        writeln!(out, "        }} catch (Throwable e) {{").ok();
        writeln!(
            out,
            "            throw new {}Exception(\"FFI call failed\", e);",
            class_name
        )
        .ok();
        writeln!(out, "        }}").ok();
    } else if matches!(func.return_type, TypeRef::Named(_)) {
        // Named return types: FFI returns a struct pointer.
        let return_type_name = match &func.return_type {
            TypeRef::Named(name) => name,
            _ => unreachable!(),
        };
        let is_opaque = opaque_types.contains(return_type_name.as_str());

        writeln!(
            out,
            "            var resultPtr = (MemorySegment) {}.invoke({});",
            ffi_handle,
            call_args.join(", ")
        )
        .ok();
        emit_ffi_ptr_cleanup(out);
        writeln!(out, "            if (resultPtr.equals(MemorySegment.NULL)) {{").ok();
        writeln!(out, "                checkLastError();").ok();
        writeln!(out, "                return null;").ok();
        writeln!(out, "            }}").ok();

        if is_opaque {
            // Opaque handles: wrap the raw pointer directly, caller owns and will close()
            writeln!(out, "            return new {}(resultPtr);", return_type_name).ok();
        } else {
            // Record types: use _to_json to serialize the full struct to JSON, then deserialize.
            // NOTE: _content only returns the markdown string field, not a full JSON object.
            let type_snake = return_type_name.to_snake_case();
            let free_handle = format!("NativeLib.{}_{}_FREE", prefix.to_uppercase(), type_snake.to_uppercase());
            let to_json_handle = format!(
                "NativeLib.{}_{}_TO_JSON",
                prefix.to_uppercase(),
                type_snake.to_uppercase()
            );
            writeln!(
                out,
                "            var jsonPtr = (MemorySegment) {}.invoke(resultPtr);",
                to_json_handle
            )
            .ok();
            writeln!(out, "            {}.invoke(resultPtr);", free_handle).ok();
            writeln!(out, "            if (jsonPtr.equals(MemorySegment.NULL)) {{").ok();
            writeln!(out, "                checkLastError();").ok();
            writeln!(out, "                return null;").ok();
            writeln!(out, "            }}").ok();
            writeln!(
                out,
                "            String json = jsonPtr.reinterpret(Long.MAX_VALUE).getString(0);"
            )
            .ok();
            writeln!(
                out,
                "            NativeLib.{}_FREE_STRING.invoke(jsonPtr);",
                prefix.to_uppercase()
            )
            .ok();
            writeln!(
                out,
                "            return createObjectMapper().readValue(json, {}.class);",
                return_type_name
            )
            .ok();
        }

        writeln!(out, "        }} catch (Throwable e) {{").ok();
        writeln!(
            out,
            "            throw new {}Exception(\"FFI call failed\", e);",
            class_name
        )
        .ok();
        writeln!(out, "        }}").ok();
    } else if matches!(func.return_type, TypeRef::Vec(_)) {
        // Vec return types: FFI returns a JSON string pointer; deserialize into List<T>.
        let free_handle = format!("NativeLib.{}_FREE_STRING", prefix.to_uppercase());
        writeln!(
            out,
            "            var resultPtr = (MemorySegment) {}.invoke({});",
            ffi_handle,
            call_args.join(", ")
        )
        .ok();
        emit_ffi_ptr_cleanup(out);
        writeln!(out, "            if (resultPtr.equals(MemorySegment.NULL)) {{").ok();
        writeln!(out, "                return java.util.List.of();").ok();
        writeln!(out, "            }}").ok();
        writeln!(
            out,
            "            String json = resultPtr.reinterpret(Long.MAX_VALUE).getString(0);"
        )
        .ok();
        writeln!(out, "            {}.invoke(resultPtr);", free_handle).ok();
        // Determine the element type for deserialization
        let element_type = match &func.return_type {
            TypeRef::Vec(inner) => java_type(inner),
            _ => unreachable!(),
        };
        writeln!(
            out,
            "            return createObjectMapper().readValue(json, new com.fasterxml.jackson.core.type.TypeReference<java.util.List<{}>>() {{ }});",
            element_type
        )
        .ok();
        writeln!(out, "        }} catch (Throwable e) {{").ok();
        writeln!(
            out,
            "            throw new {}Exception(\"FFI call failed\", e);",
            class_name
        )
        .ok();
        writeln!(out, "        }}").ok();
    } else {
        writeln!(
            out,
            "            var primitiveResult = ({}) {}.invoke({});",
            java_ffi_return_cast(&func.return_type),
            ffi_handle,
            call_args.join(", ")
        )
        .ok();
        emit_ffi_ptr_cleanup(out);
        writeln!(out, "            return primitiveResult;").ok();
        writeln!(out, "        }} catch (Throwable e) {{").ok();
        writeln!(
            out,
            "            throw new {}Exception(\"FFI call failed\", e);",
            class_name
        )
        .ok();
        writeln!(out, "        }}").ok();
    }

    writeln!(out, "    }}").ok();
}

fn gen_async_wrapper_method(out: &mut String, func: &FunctionDef) {
    let params: Vec<String> = func
        .params
        .iter()
        .map(|p| {
            let ptype = java_type(&p.ty);
            format!("{} {}", ptype, to_java_name(&p.name))
        })
        .collect();

    let return_type = match &func.return_type {
        TypeRef::Unit => "Void".to_string(),
        other => java_boxed_type(other).to_string(),
    };

    let sync_method_name = to_java_name(&func.name);
    let async_method_name = format!("{}Async", sync_method_name);
    let param_names: Vec<String> = func.params.iter().map(|p| to_java_name(&p.name)).collect();

    writeln!(
        out,
        "    public static CompletableFuture<{}> {}({}) {{",
        return_type,
        async_method_name,
        params.join(", ")
    )
    .ok();
    writeln!(out, "        return CompletableFuture.supplyAsync(() -> {{").ok();
    writeln!(out, "            try {{").ok();
    writeln!(
        out,
        "                return {}({});",
        sync_method_name,
        param_names.join(", ")
    )
    .ok();
    writeln!(out, "            }} catch (Throwable e) {{").ok();
    writeln!(out, "                throw new CompletionException(e);").ok();
    writeln!(out, "            }}").ok();
    writeln!(out, "        }});").ok();
    writeln!(out, "    }}").ok();
}

// ---------------------------------------------------------------------------
// Exception class
// ---------------------------------------------------------------------------

fn gen_exception_class(package: &str, class_name: &str) -> String {
    let mut out = String::with_capacity(512);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();

    writeln!(out, "public class {}Exception extends Exception {{", class_name).ok();
    writeln!(out, "    private final int code;").ok();
    writeln!(out).ok();
    writeln!(out, "    public {}Exception(int code, String message) {{", class_name).ok();
    writeln!(out, "        super(message);").ok();
    writeln!(out, "        this.code = code;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(
        out,
        "    public {}Exception(String message, Throwable cause) {{",
        class_name
    )
    .ok();
    writeln!(out, "        super(message, cause);").ok();
    writeln!(out, "        this.code = -1;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(out, "    public int getCode() {{").ok();
    writeln!(out, "        return code;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out, "}}").ok();

    out
}

// ---------------------------------------------------------------------------
// High-level facade class (public API)
// ---------------------------------------------------------------------------

fn gen_facade_class(api: &ApiSurface, package: &str, public_class: &str, raw_class: &str, _prefix: &str) -> String {
    let mut body = String::with_capacity(4096);

    writeln!(body, "public final class {} {{", public_class).ok();
    writeln!(body, "    private {}() {{ }}", public_class).ok();
    writeln!(body).ok();

    // Generate static methods for free functions
    for func in &api.functions {
        // Sync method
        let params: Vec<String> = func
            .params
            .iter()
            .map(|p| {
                let ptype = java_type(&p.ty);
                format!("{} {}", ptype, to_java_name(&p.name))
            })
            .collect();

        let return_type = java_type(&func.return_type);

        if !func.doc.is_empty() {
            writeln!(body, "    /**").ok();
            for line in func.doc.lines() {
                writeln!(body, "     * {}", line).ok();
            }
            writeln!(body, "     */").ok();
        }

        writeln!(
            body,
            "    public static {} {}({}) throws {}Exception {{",
            return_type,
            to_java_name(&func.name),
            params.join(", "),
            raw_class
        )
        .ok();

        // Null checks for required parameters
        for param in &func.params {
            if !param.optional {
                let pname = to_java_name(&param.name);
                writeln!(
                    body,
                    "        java.util.Objects.requireNonNull({}, \"{} must not be null\");",
                    pname, pname
                )
                .ok();
            }
        }

        // Delegate to the raw FFI class
        let call_args: Vec<String> = func.params.iter().map(|p| to_java_name(&p.name)).collect();

        if matches!(func.return_type, TypeRef::Unit) {
            writeln!(
                body,
                "        {}.{}({});",
                raw_class,
                to_java_name(&func.name),
                call_args.join(", ")
            )
            .ok();
        } else {
            writeln!(
                body,
                "        return {}.{}({});",
                raw_class,
                to_java_name(&func.name),
                call_args.join(", ")
            )
            .ok();
        }

        writeln!(body, "    }}").ok();
        writeln!(body).ok();

        // Generate overload without optional params (convenience method)
        let has_optional = func.params.iter().any(|p| p.optional);
        if has_optional {
            let required_params: Vec<String> = func
                .params
                .iter()
                .filter(|p| !p.optional)
                .map(|p| {
                    let ptype = java_type(&p.ty);
                    format!("{} {}", ptype, to_java_name(&p.name))
                })
                .collect();

            writeln!(
                body,
                "    public static {} {}({}) throws {}Exception {{",
                return_type,
                to_java_name(&func.name),
                required_params.join(", "),
                raw_class
            )
            .ok();

            // Build call with null for optional params
            let full_args: Vec<String> = func
                .params
                .iter()
                .map(|p| {
                    if p.optional {
                        "null".to_string()
                    } else {
                        to_java_name(&p.name)
                    }
                })
                .collect();

            if matches!(func.return_type, TypeRef::Unit) {
                writeln!(body, "        {}({});", to_java_name(&func.name), full_args.join(", ")).ok();
            } else {
                writeln!(
                    body,
                    "        return {}({});",
                    to_java_name(&func.name),
                    full_args.join(", ")
                )
                .ok();
            }

            writeln!(body, "    }}").ok();
            writeln!(body).ok();
        }
    }

    writeln!(body, "}}").ok();

    // Now assemble the file with imports
    let mut out = String::with_capacity(body.len() + 512);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();

    // Check what imports are needed based on content
    let has_list = body.contains("List<");
    let has_map = body.contains("Map<");
    let has_optional = body.contains("Optional<");
    let has_imports = has_list || has_map || has_optional;

    if has_imports {
        writeln!(out).ok();
        if has_list {
            writeln!(out, "import java.util.List;").ok();
        }
        if has_map {
            writeln!(out, "import java.util.Map;").ok();
        }
        if has_optional {
            writeln!(out, "import java.util.Optional;").ok();
        }
    }

    writeln!(out).ok();
    out.push_str(&body);

    out
}

// ---------------------------------------------------------------------------
// Opaque handle classes
// ---------------------------------------------------------------------------

fn gen_opaque_handle_class(package: &str, typ: &TypeDef, prefix: &str) -> String {
    let mut out = String::with_capacity(1024);
    let class_name = &typ.name;
    let type_snake = class_name.to_snake_case();

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    writeln!(out, "import java.lang.foreign.MemorySegment;").ok();
    writeln!(out).ok();

    if !typ.doc.is_empty() {
        writeln!(out, "/**").ok();
        for line in typ.doc.lines() {
            writeln!(out, " * {}", line).ok();
        }
        writeln!(out, " */").ok();
    }

    writeln!(out, "public class {} implements AutoCloseable {{", class_name).ok();
    writeln!(out, "    private final MemorySegment handle;").ok();
    writeln!(out).ok();
    writeln!(out, "    {}(MemorySegment handle) {{", class_name).ok();
    writeln!(out, "        this.handle = handle;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(out, "    MemorySegment handle() {{").ok();
    writeln!(out, "        return this.handle;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(out, "    @Override").ok();
    writeln!(out, "    public void close() {{").ok();
    writeln!(
        out,
        "        if (handle != null && !handle.equals(MemorySegment.NULL)) {{"
    )
    .ok();
    writeln!(out, "            try {{").ok();
    writeln!(
        out,
        "                NativeLib.{}_{}_FREE.invoke(handle);",
        prefix.to_uppercase(),
        type_snake.to_uppercase()
    )
    .ok();
    writeln!(out, "            }} catch (Throwable e) {{").ok();
    writeln!(
        out,
        "                throw new RuntimeException(\"Failed to free {}: \" + e.getMessage(), e);",
        class_name
    )
    .ok();
    writeln!(out, "            }}").ok();
    writeln!(out, "        }}").ok();
    writeln!(out, "    }}").ok();
    writeln!(out, "}}").ok();

    out
}

// ---------------------------------------------------------------------------
// Record types (Java records)
// ---------------------------------------------------------------------------

/// Maximum line length before splitting record fields across multiple lines.
/// Checkstyle enforces 120 chars; we split at 100 to leave headroom for indentation.
const RECORD_LINE_WRAP_THRESHOLD: usize = 100;

fn gen_record_type(package: &str, typ: &TypeDef, complex_enums: &AHashSet<String>, lang_rename_all: &str) -> String {
    // Generate the record body first, then scan for needed imports.
    // For each field, if the language uses camelCase but the JSON key is snake_case
    // (the Rust default), annotate with @JsonProperty so Jackson maps correctly.
    let field_list: Vec<String> = typ
        .fields
        .iter()
        .map(|f| {
            // Complex enums (tagged unions with data) can't be simple Java enums.
            // Use Object for flexible Jackson deserialization.
            let is_complex = matches!(&f.ty, TypeRef::Named(n) if complex_enums.contains(n.as_str()));
            let ftype = if is_complex {
                "Object".to_string()
            } else if f.optional {
                format!("Optional<{}>", java_boxed_type(&f.ty))
            } else {
                java_type(&f.ty).to_string()
            };
            let jname = safe_java_field_name(&f.name);
            // When the language convention is camelCase but the JSON wire format uses
            // snake_case (the Rust/serde default), add an explicit @JsonProperty annotation
            // so Jackson serialises/deserialises using the correct snake_case key.
            if lang_rename_all == "camelCase" && f.name.contains('_') {
                format!("@JsonProperty(\"{}\") {} {}", f.name, ftype, jname)
            } else {
                format!("{} {}", ftype, jname)
            }
        })
        .collect();

    // Build the single-line form to check length and scan for imports.
    let single_line = format!("public record {}({}) {{ }}", typ.name, field_list.join(", "));

    // Build the actual record declaration, splitting across lines if too long.
    let mut record_block = String::new();
    if single_line.len() > RECORD_LINE_WRAP_THRESHOLD && field_list.len() > 1 {
        writeln!(record_block, "public record {}(", typ.name).ok();
        for (i, field) in field_list.iter().enumerate() {
            let comma = if i < field_list.len() - 1 { "," } else { "" };
            writeln!(record_block, "    {}{}", field, comma).ok();
        }
        writeln!(record_block, ") {{").ok();
    } else {
        writeln!(record_block, "public record {}({}) {{", typ.name, field_list.join(", ")).ok();
    }

    // Add builder() factory method if type has defaults
    if typ.has_default {
        writeln!(record_block, "    public static {}Builder builder() {{", typ.name).ok();
        writeln!(record_block, "        return new {}Builder();", typ.name).ok();
        writeln!(record_block, "    }}").ok();
    }

    writeln!(record_block, "}}").ok();

    // Scan the single-line form to determine which imports are needed
    let needs_json_property = field_list.iter().any(|f| f.contains("@JsonProperty("));
    let mut out = String::with_capacity(record_block.len() + 512);
    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    if single_line.contains("List<") {
        writeln!(out, "import java.util.List;").ok();
    }
    if single_line.contains("Map<") {
        writeln!(out, "import java.util.Map;").ok();
    }
    if single_line.contains("Optional<") {
        writeln!(out, "import java.util.Optional;").ok();
    }
    if needs_json_property {
        writeln!(out, "import com.fasterxml.jackson.annotation.JsonProperty;").ok();
    }
    writeln!(out).ok();
    write!(out, "{}", record_block).ok();

    out
}

// ---------------------------------------------------------------------------
// Enum classes
// ---------------------------------------------------------------------------

/// Apply a serde `rename_all` strategy to a variant name for Java codegen.
fn java_apply_rename_all(name: &str, rename_all: Option<&str>) -> String {
    match rename_all {
        Some("snake_case") => name.to_snake_case(),
        Some("camelCase") => name.to_lower_camel_case(),
        Some("PascalCase") => name.to_pascal_case(),
        Some("SCREAMING_SNAKE_CASE") => name.to_snake_case().to_uppercase(),
        Some("lowercase") => name.to_lowercase(),
        Some("UPPERCASE") => name.to_uppercase(),
        _ => name.to_lowercase(),
    }
}

fn gen_enum_class(package: &str, enum_def: &EnumDef) -> String {
    let has_data_variants = enum_def.variants.iter().any(|v| !v.fields.is_empty());

    // Tagged union: enum has a serde tag AND data variants → generate sealed interface hierarchy
    if enum_def.serde_tag.is_some() && has_data_variants {
        return gen_java_tagged_union(package, enum_def);
    }

    let mut out = String::with_capacity(1024);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    writeln!(out, "import com.fasterxml.jackson.annotation.JsonCreator;").ok();
    writeln!(out, "import com.fasterxml.jackson.annotation.JsonValue;").ok();
    writeln!(out).ok();

    writeln!(out, "public enum {} {{", enum_def.name).ok();

    for (i, variant) in enum_def.variants.iter().enumerate() {
        let comma = if i < enum_def.variants.len() - 1 { "," } else { ";" };
        // Use serde_rename if available, otherwise apply rename_all strategy
        let json_name = variant
            .serde_rename
            .clone()
            .unwrap_or_else(|| java_apply_rename_all(&variant.name, enum_def.serde_rename_all.as_deref()));
        writeln!(out, "    {}(\"{}\"){}", variant.name, json_name, comma).ok();
    }

    writeln!(out).ok();
    writeln!(out, "    private final String value;").ok();
    writeln!(out).ok();
    writeln!(out, "    {}(String value) {{", enum_def.name).ok();
    writeln!(out, "        this.value = value;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(out, "    @JsonValue").ok();
    writeln!(out, "    public String getValue() {{").ok();
    writeln!(out, "        return value;").ok();
    writeln!(out, "    }}").ok();
    writeln!(out).ok();
    writeln!(out, "    @JsonCreator").ok();
    writeln!(out, "    public static {} fromValue(String value) {{", enum_def.name).ok();
    writeln!(out, "        for ({} e : values()) {{", enum_def.name).ok();
    writeln!(out, "            if (e.value.equalsIgnoreCase(value)) {{").ok();
    writeln!(out, "                return e;").ok();
    writeln!(out, "            }}").ok();
    writeln!(out, "        }}").ok();
    writeln!(
        out,
        "        throw new IllegalArgumentException(\"Unknown value: \" + value);"
    )
    .ok();
    writeln!(out, "    }}").ok();

    writeln!(out, "}}").ok();

    out
}

/// Generate a Java sealed interface hierarchy for internally tagged enums.
///
/// Maps `#[serde(tag = "type_field", rename_all = "snake_case")]` Rust enums to
/// `@JsonTypeInfo` / `@JsonSubTypes` Java sealed interfaces with record implementations.
fn gen_java_tagged_union(package: &str, enum_def: &EnumDef) -> String {
    let tag_field = enum_def.serde_tag.as_deref().unwrap_or("type");

    // Collect variant names to detect Java type name conflicts.
    // If a variant is named "List", "Map", or "Optional", using those type names
    // inside the sealed interface would refer to the nested record, not java.util.*.
    // We use fully qualified names in that case.
    let variant_names: std::collections::HashSet<&str> = enum_def.variants.iter().map(|v| v.name.as_str()).collect();
    let optional_type = if variant_names.contains("Optional") {
        "java.util.Optional"
    } else {
        "Optional"
    };

    let mut out = String::with_capacity(2048);
    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();
    writeln!(out, "import com.fasterxml.jackson.annotation.JsonProperty;").ok();
    writeln!(out, "import com.fasterxml.jackson.annotation.JsonSubTypes;").ok();
    writeln!(out, "import com.fasterxml.jackson.annotation.JsonTypeInfo;").ok();

    // Check if any field types need list/map/optional imports (only when not conflicting)
    let needs_list = !variant_names.contains("List")
        && enum_def
            .variants
            .iter()
            .any(|v| v.fields.iter().any(|f| matches!(&f.ty, TypeRef::Vec(_))));
    let needs_map = !variant_names.contains("Map")
        && enum_def
            .variants
            .iter()
            .any(|v| v.fields.iter().any(|f| matches!(&f.ty, TypeRef::Map(_, _))));
    let needs_optional =
        !variant_names.contains("Optional") && enum_def.variants.iter().any(|v| v.fields.iter().any(|f| f.optional));
    if needs_list {
        writeln!(out, "import java.util.List;").ok();
    }
    if needs_map {
        writeln!(out, "import java.util.Map;").ok();
    }
    if needs_optional {
        writeln!(out, "import java.util.Optional;").ok();
    }
    writeln!(out).ok();

    // @JsonTypeInfo and @JsonSubTypes annotations
    writeln!(
        out,
        "@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = \"{tag_field}\", visible = false)"
    )
    .ok();
    writeln!(out, "@JsonSubTypes({{").ok();
    for (i, variant) in enum_def.variants.iter().enumerate() {
        let discriminator = variant
            .serde_rename
            .clone()
            .unwrap_or_else(|| java_apply_rename_all(&variant.name, enum_def.serde_rename_all.as_deref()));
        let comma = if i < enum_def.variants.len() - 1 { "," } else { "" };
        writeln!(
            out,
            "    @JsonSubTypes.Type(value = {}.{}.class, name = \"{}\"){}",
            enum_def.name, variant.name, discriminator, comma
        )
        .ok();
    }
    writeln!(out, "}})").ok();
    writeln!(out, "public sealed interface {} {{", enum_def.name).ok();

    // Nested records for each variant
    for variant in &enum_def.variants {
        writeln!(out).ok();
        if variant.fields.is_empty() {
            // Unit variant
            writeln!(out, "    record {}() implements {} {{", variant.name, enum_def.name).ok();
            writeln!(out, "    }}").ok();
        } else {
            // Build field list using fully qualified names where variant names shadow imports
            let field_parts: Vec<String> = variant
                .fields
                .iter()
                .map(|f| {
                    let json_name = f.name.trim_start_matches('_');
                    let ftype = if f.optional {
                        let inner = java_boxed_type(&f.ty);
                        let inner_str = inner.as_ref();
                        // Replace "List"/"Map" with fully qualified if conflicting
                        let inner_qualified = if inner_str.starts_with("List<") && variant_names.contains("List") {
                            inner_str.replacen("List<", "java.util.List<", 1)
                        } else if inner_str.starts_with("Map<") && variant_names.contains("Map") {
                            inner_str.replacen("Map<", "java.util.Map<", 1)
                        } else {
                            inner_str.to_string()
                        };
                        format!("{optional_type}<{inner_qualified}>")
                    } else {
                        let t = java_type(&f.ty);
                        let t_str = t.as_ref();
                        if t_str.starts_with("List<") && variant_names.contains("List") {
                            t_str.replacen("List<", "java.util.List<", 1)
                        } else if t_str.starts_with("Map<") && variant_names.contains("Map") {
                            t_str.replacen("Map<", "java.util.Map<", 1)
                        } else {
                            t_str.to_string()
                        }
                    };
                    let jname = safe_java_field_name(json_name);
                    format!("@JsonProperty(\"{json_name}\") {ftype} {jname}")
                })
                .collect();

            let single = format!(
                "    record {}({}) implements {} {{ }}",
                variant.name,
                field_parts.join(", "),
                enum_def.name
            );

            if single.len() > RECORD_LINE_WRAP_THRESHOLD && field_parts.len() > 1 {
                writeln!(out, "    record {}(", variant.name).ok();
                for (i, fp) in field_parts.iter().enumerate() {
                    let comma = if i < field_parts.len() - 1 { "," } else { "" };
                    writeln!(out, "        {}{}", fp, comma).ok();
                }
                writeln!(out, "    ) implements {} {{", enum_def.name).ok();
                writeln!(out, "    }}").ok();
            } else {
                writeln!(
                    out,
                    "    record {}({}) implements {} {{ }}",
                    variant.name,
                    field_parts.join(", "),
                    enum_def.name
                )
                .ok();
            }
        }
    }

    writeln!(out).ok();
    writeln!(out, "}}").ok();
    out
}

// ---------------------------------------------------------------------------
// Helper functions for FFI marshalling
// ---------------------------------------------------------------------------

fn gen_ffi_layout(ty: &TypeRef) -> String {
    match ty {
        TypeRef::Primitive(prim) => java_ffi_type(prim).to_string(),
        TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json => "ValueLayout.ADDRESS".to_string(),
        TypeRef::Bytes => "ValueLayout.ADDRESS".to_string(),
        TypeRef::Optional(inner) => gen_ffi_layout(inner),
        TypeRef::Vec(_) => "ValueLayout.ADDRESS".to_string(),
        TypeRef::Map(_, _) => "ValueLayout.ADDRESS".to_string(),
        TypeRef::Named(_) => "ValueLayout.ADDRESS".to_string(),
        TypeRef::Unit => "".to_string(),
        TypeRef::Duration => "ValueLayout.JAVA_LONG".to_string(),
    }
}

fn marshal_param_to_ffi(out: &mut String, name: &str, ty: &TypeRef, opaque_types: &AHashSet<String>, prefix: &str) {
    match ty {
        TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json => {
            let cname = "c".to_string() + name;
            writeln!(out, "            var {} = arena.allocateFrom({});", cname, name).ok();
        }
        TypeRef::Named(type_name) => {
            let cname = "c".to_string() + name;
            if opaque_types.contains(type_name.as_str()) {
                // Opaque handles: pass the inner MemorySegment via .handle()
                writeln!(out, "            var {} = {}.handle();", cname, name).ok();
            } else {
                // Non-opaque named types: serialize to JSON, call _from_json to get FFI pointer.
                // The pointer must be freed after the FFI call with _free.
                let type_snake = type_name.to_snake_case();
                let from_json_handle = format!(
                    "NativeLib.{}_{}_FROM_JSON",
                    prefix.to_uppercase(),
                    type_snake.to_uppercase()
                );
                let _free_handle = format!("NativeLib.{}_{}_FREE", prefix.to_uppercase(), type_snake.to_uppercase());
                writeln!(
                    out,
                    "            var {}Json = {} != null ? createObjectMapper().writeValueAsString({}) : null;",
                    cname, name, name
                )
                .ok();
                writeln!(
                    out,
                    "            var {}JsonSeg = {}Json != null ? arena.allocateFrom({}Json) : MemorySegment.NULL;",
                    cname, cname, cname
                )
                .ok();
                writeln!(out, "            var {} = {}Json != null", cname, cname).ok();
                writeln!(
                    out,
                    "                ? (MemorySegment) {}.invoke({}JsonSeg)",
                    from_json_handle, cname
                )
                .ok();
                writeln!(out, "                : MemorySegment.NULL;").ok();
            }
        }
        TypeRef::Optional(inner) => {
            // For optional types, marshal the inner type if not null
            match inner.as_ref() {
                TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json => {
                    let cname = "c".to_string() + name;
                    writeln!(
                        out,
                        "            var {} = {} != null ? arena.allocateFrom({}) : MemorySegment.NULL;",
                        cname, name, name
                    )
                    .ok();
                }
                TypeRef::Named(type_name) => {
                    let cname = "c".to_string() + name;
                    if opaque_types.contains(type_name.as_str()) {
                        writeln!(
                            out,
                            "            var {} = {} != null ? {}.handle() : MemorySegment.NULL;",
                            cname, name, name
                        )
                        .ok();
                    } else {
                        // Non-opaque named type in Optional: serialize to JSON and call _from_json
                        let type_snake = type_name.to_snake_case();
                        let from_json_handle = format!(
                            "NativeLib.{}_{}_FROM_JSON",
                            prefix.to_uppercase(),
                            type_snake.to_uppercase()
                        );
                        writeln!(
                            out,
                            "            var {}Json = {} != null ? createObjectMapper().writeValueAsString({}) : null;",
                            cname, name, name
                        )
                        .ok();
                        writeln!(out, "            var {}JsonSeg = {}Json != null ? arena.allocateFrom({}Json) : MemorySegment.NULL;", cname, cname, cname).ok();
                        writeln!(out, "            var {} = {}Json != null", cname, cname).ok();
                        writeln!(
                            out,
                            "                ? (MemorySegment) {}.invoke({}JsonSeg)",
                            from_json_handle, cname
                        )
                        .ok();
                        writeln!(out, "                : MemorySegment.NULL;").ok();
                    }
                }
                _ => {
                    // Other optional types (primitives) pass through
                }
            }
        }
        TypeRef::Vec(_) | TypeRef::Map(_, _) => {
            // Vec/Map types: serialize to JSON string, then pass as a C string via arena.
            let cname = "c".to_string() + name;
            writeln!(
                out,
                "            var {}Json = createObjectMapper().writeValueAsString({});",
                cname, name
            )
            .ok();
            writeln!(out, "            var {} = arena.allocateFrom({}Json);", cname, cname).ok();
        }
        _ => {
            // Primitives and others pass through directly
        }
    }
}

fn ffi_param_name(name: &str, ty: &TypeRef, _opaque_types: &AHashSet<String>) -> String {
    match ty {
        TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json => "c".to_string() + name,
        TypeRef::Named(_) => "c".to_string() + name,
        TypeRef::Vec(_) | TypeRef::Map(_, _) => "c".to_string() + name,
        TypeRef::Optional(inner) => match inner.as_ref() {
            TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json | TypeRef::Named(_) => {
                "c".to_string() + name
            }
            _ => name.to_string(),
        },
        _ => name.to_string(),
    }
}

/// Build a `FunctionDescriptor` string for a given return layout and parameter layouts.
/// Handles void returns (ofVoid) and non-void returns (of) correctly.
fn gen_function_descriptor(return_layout: &str, param_layouts: &[String]) -> String {
    if return_layout.is_empty() {
        // Void return
        if param_layouts.is_empty() {
            "FunctionDescriptor.ofVoid()".to_string()
        } else {
            format!("FunctionDescriptor.ofVoid({})", param_layouts.join(", "))
        }
    } else {
        // Non-void return
        if param_layouts.is_empty() {
            format!("FunctionDescriptor.of({})", return_layout)
        } else {
            format!("FunctionDescriptor.of({}, {})", return_layout, param_layouts.join(", "))
        }
    }
}

/// Returns true if the given return type maps to an FFI ADDRESS that represents a string
/// (i.e. the FFI returns `*mut c_char` which must be unmarshaled and freed).
fn is_ffi_string_return(ty: &TypeRef) -> bool {
    match ty {
        TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json => true,
        TypeRef::Optional(inner) => is_ffi_string_return(inner),
        _ => false,
    }
}

/// Returns the appropriate Java cast type for non-string FFI return values.
fn java_ffi_return_cast(ty: &TypeRef) -> &'static str {
    match ty {
        TypeRef::Primitive(prim) => match prim {
            PrimitiveType::Bool => "boolean",
            PrimitiveType::U8 | PrimitiveType::I8 => "byte",
            PrimitiveType::U16 | PrimitiveType::I16 => "short",
            PrimitiveType::U32 | PrimitiveType::I32 => "int",
            PrimitiveType::U64 | PrimitiveType::I64 | PrimitiveType::Usize | PrimitiveType::Isize => "long",
            PrimitiveType::F32 => "float",
            PrimitiveType::F64 => "double",
        },
        TypeRef::Bytes | TypeRef::Vec(_) | TypeRef::Map(_, _) | TypeRef::Named(_) => "MemorySegment",
        _ => "MemorySegment",
    }
}

fn gen_helper_methods(out: &mut String, prefix: &str, class_name: &str) {
    // Only emit helper methods that are actually called in the generated body.
    let needs_check_last_error = out.contains("checkLastError()");
    let needs_read_cstring = out.contains("readCString(");
    let needs_read_bytes = out.contains("readBytes(");
    let needs_create_object_mapper = out.contains("createObjectMapper()");

    if !needs_check_last_error && !needs_read_cstring && !needs_read_bytes && !needs_create_object_mapper {
        return;
    }

    writeln!(out, "    // Helper methods for FFI marshalling").ok();
    writeln!(out).ok();

    if needs_check_last_error {
        // Reads the last FFI error code and, if non-zero, reads the error message and throws.
        // Called immediately after a null-pointer return from an FFI call.
        writeln!(out, "    private static void checkLastError() throws Throwable {{").ok();
        writeln!(
            out,
            "        int errCode = (int) NativeLib.{}_LAST_ERROR_CODE.invoke();",
            prefix.to_uppercase()
        )
        .ok();
        writeln!(out, "        if (errCode != 0) {{").ok();
        writeln!(
            out,
            "            var ctxPtr = (MemorySegment) NativeLib.{}_LAST_ERROR_CONTEXT.invoke();",
            prefix.to_uppercase()
        )
        .ok();
        writeln!(
            out,
            "            String msg = ctxPtr.reinterpret(Long.MAX_VALUE).getString(0);"
        )
        .ok();
        writeln!(out, "            throw new {}Exception(errCode, msg);", class_name).ok();
        writeln!(out, "        }}").ok();
        writeln!(out, "    }}").ok();
        writeln!(out).ok();
    }

    if needs_create_object_mapper {
        // Emit a configured ObjectMapper factory:
        //   - findAndRegisterModules() to pick up jackson-datatype-jdk8 (Optional support)
        //   - ACCEPT_CASE_INSENSITIVE_ENUMS so enum names like "json_ld" match JsonLd, etc.
        // Field name mapping relies on explicit @JsonProperty annotations on record components
        // (generated by alef for snake_case FFI fields on camelCase Java records).
        writeln!(
            out,
            "    private static com.fasterxml.jackson.databind.ObjectMapper createObjectMapper() {{"
        )
        .ok();
        writeln!(out, "        return new com.fasterxml.jackson.databind.ObjectMapper()").ok();
        writeln!(
            out,
            "            .registerModule(new com.fasterxml.jackson.datatype.jdk8.Jdk8Module())"
        )
        .ok();
        writeln!(out, "            .findAndRegisterModules()").ok();
        writeln!(
            out,
            "            .setSerializationInclusion(com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL)"
        )
        .ok();
        writeln!(
            out,
            "            .configure(com.fasterxml.jackson.databind.MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS, true);"
        )
        .ok();
        writeln!(out, "    }}").ok();
        writeln!(out).ok();
    }

    if needs_read_cstring {
        writeln!(out, "    private static String readCString(MemorySegment ptr) {{").ok();
        writeln!(out, "        if (ptr == null || ptr.address() == 0) {{").ok();
        writeln!(out, "            return null;").ok();
        writeln!(out, "        }}").ok();
        writeln!(out, "        return ptr.getUtf8String(0);").ok();
        writeln!(out, "    }}").ok();
        writeln!(out).ok();
    }

    if needs_read_bytes {
        writeln!(
            out,
            "    private static byte[] readBytes(MemorySegment ptr, long len) {{"
        )
        .ok();
        writeln!(out, "        if (ptr == null || ptr.address() == 0) {{").ok();
        writeln!(out, "            return new byte[0];").ok();
        writeln!(out, "        }}").ok();
        writeln!(out, "        byte[] bytes = new byte[(int) len];").ok();
        writeln!(
            out,
            "        MemorySegment.copy(ptr, ValueLayout.JAVA_BYTE.byteSize() * 0, bytes, 0, (int) len);"
        )
        .ok();
        writeln!(out, "        return bytes;").ok();
        writeln!(out, "    }}").ok();
    }
}

// ---------------------------------------------------------------------------
// Builder class for types with defaults
// ---------------------------------------------------------------------------

/// Format a default value for an Optional field, wrapping it in Optional.of()
/// with proper Java literal syntax.
fn format_optional_value(ty: &TypeRef, default: &str) -> String {
    // Check if the default is already wrapped (e.g., "Optional.of(...)" or "Optional.empty()")
    if default.contains("Optional.") {
        return default.to_string();
    }

    // Unwrap Optional types to get the inner type
    let inner_ty = match ty {
        TypeRef::Optional(inner) => inner.as_ref(),
        other => other,
    };

    // Determine the proper literal suffix based on type
    let formatted_value = match inner_ty {
        TypeRef::Primitive(p) => match p {
            PrimitiveType::I64 | PrimitiveType::U64 | PrimitiveType::Isize | PrimitiveType::Usize => {
                // Add 'L' suffix for long values if not already present
                if default.ends_with('L') || default.ends_with('l') {
                    default.to_string()
                } else if default.parse::<i64>().is_ok() {
                    format!("{}L", default)
                } else {
                    default.to_string()
                }
            }
            PrimitiveType::F32 => {
                // Add 'f' suffix for float values if not already present
                if default.ends_with('f') || default.ends_with('F') {
                    default.to_string()
                } else if default.parse::<f32>().is_ok() {
                    format!("{}f", default)
                } else {
                    default.to_string()
                }
            }
            PrimitiveType::F64 => {
                // Double defaults can have optional 'd' suffix, but 0.0 is fine
                default.to_string()
            }
            _ => default.to_string(),
        },
        _ => default.to_string(),
    };

    format!("Optional.of({})", formatted_value)
}

fn gen_builder_class(package: &str, typ: &TypeDef) -> String {
    let mut body = String::with_capacity(2048);

    writeln!(body, "public class {}Builder {{", typ.name).ok();
    writeln!(body).ok();

    // Generate field declarations with defaults
    for field in &typ.fields {
        let field_name = safe_java_field_name(&field.name);

        // Skip unnamed tuple fields (name is "_0", "_1", "0", "1", etc.) — Java requires named fields
        if field.name.starts_with('_') && field.name[1..].chars().all(|c| c.is_ascii_digit())
            || field.name.chars().next().is_none_or(|c| c.is_ascii_digit())
        {
            continue;
        }

        // Duration maps to primitive `long` in the public record, but in builder
        // classes we use boxed `Long` so that `null` can represent "not set".
        let field_type = if field.optional {
            format!("Optional<{}>", java_boxed_type(&field.ty))
        } else if matches!(field.ty, TypeRef::Duration) {
            java_boxed_type(&field.ty).to_string()
        } else {
            java_type(&field.ty).to_string()
        };

        let default_value = if field.optional {
            // For Optional fields, always use Optional.empty() or Optional.of(value)
            if let Some(default) = &field.default {
                // If there's an explicit default, wrap it in Optional.of()
                format_optional_value(&field.ty, default)
            } else {
                // If no default, use Optional.empty()
                "Optional.empty()".to_string()
            }
        } else {
            // For non-Optional fields, use regular defaults
            if let Some(default) = &field.default {
                default.clone()
            } else {
                match &field.ty {
                    TypeRef::String | TypeRef::Char | TypeRef::Path => "\"\"".to_string(),
                    TypeRef::Json => "null".to_string(),
                    TypeRef::Bytes => "new byte[0]".to_string(),
                    TypeRef::Primitive(p) => match p {
                        PrimitiveType::Bool => "false".to_string(),
                        PrimitiveType::F32 | PrimitiveType::F64 => "0.0".to_string(),
                        _ => "0".to_string(),
                    },
                    TypeRef::Vec(_) => "List.of()".to_string(),
                    TypeRef::Map(_, _) => "Map.of()".to_string(),
                    TypeRef::Optional(_) => "Optional.empty()".to_string(),
                    TypeRef::Duration => "null".to_string(),
                    _ => "null".to_string(),
                }
            }
        };

        writeln!(body, "    private {} {} = {};", field_type, field_name, default_value).ok();
    }

    writeln!(body).ok();

    // Generate withXxx() methods
    for field in &typ.fields {
        // Skip unnamed tuple fields (name is "_0", "_1", "0", "1", etc.) — Java requires named fields
        if field.name.starts_with('_') && field.name[1..].chars().all(|c| c.is_ascii_digit())
            || field.name.chars().next().is_none_or(|c| c.is_ascii_digit())
        {
            continue;
        }

        let field_name = safe_java_field_name(&field.name);
        let field_name_pascal = to_class_name(&field.name);
        let field_type = if field.optional {
            format!("Optional<{}>", java_boxed_type(&field.ty))
        } else if matches!(field.ty, TypeRef::Duration) {
            java_boxed_type(&field.ty).to_string()
        } else {
            java_type(&field.ty).to_string()
        };

        writeln!(
            body,
            "    public {}Builder with{}({} value) {{",
            typ.name, field_name_pascal, field_type
        )
        .ok();
        writeln!(body, "        this.{} = value;", field_name).ok();
        writeln!(body, "        return this;").ok();
        writeln!(body, "    }}").ok();
        writeln!(body).ok();
    }

    // Generate build() method
    writeln!(body, "    public {} build() {{", typ.name).ok();
    writeln!(body, "        return new {}(", typ.name).ok();
    let non_tuple_fields: Vec<_> = typ
        .fields
        .iter()
        .filter(|f| {
            // Include named fields (skip unnamed tuple fields)
            !(f.name.starts_with('_') && f.name[1..].chars().all(|c| c.is_ascii_digit())
                || f.name.chars().next().is_none_or(|c| c.is_ascii_digit()))
        })
        .collect();
    for (i, field) in non_tuple_fields.iter().enumerate() {
        let field_name = safe_java_field_name(&field.name);
        let comma = if i < non_tuple_fields.len() - 1 { "," } else { "" };
        writeln!(body, "            {}{}", field_name, comma).ok();
    }
    writeln!(body, "        );").ok();
    writeln!(body, "    }}").ok();

    writeln!(body, "}}").ok();

    // Now assemble with conditional imports based on what's actually used in the body
    let mut out = String::with_capacity(body.len() + 512);

    writeln!(out, "// DO NOT EDIT - auto-generated by alef").ok();
    writeln!(out, "package {};", package).ok();
    writeln!(out).ok();

    if body.contains("List<") {
        writeln!(out, "import java.util.List;").ok();
    }
    if body.contains("Map<") {
        writeln!(out, "import java.util.Map;").ok();
    }
    if body.contains("Optional<") {
        writeln!(out, "import java.util.Optional;").ok();
    }

    writeln!(out).ok();
    out.push_str(&body);

    out
}