alef-backend-java 0.7.0

use crate::type_map::java_ffi_type;
use ahash::AHashSet;
use alef_core::ir::{PrimitiveType, TypeRef};
use heck::ToSnakeCase;
use std::fmt::Write;

/// Check if the return type is a string-like type that requires pointer-based
/// FFI return handling (allocate + free pattern).
pub(crate) fn is_ffi_string_return(ty: &TypeRef) -> bool {
    matches!(ty, TypeRef::String | TypeRef::Char | TypeRef::Path | TypeRef::Json)
}

/// Return the Java cast expression for a primitive FFI return type.
pub(crate) 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::Duration => "long",
        _ => "MemorySegment",
    }
}

pub(crate) 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(),
    }
}

pub(crate) 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
        }
    }
}

pub(crate) 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(),
    }
}

pub(crate) 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(", "))
        }
    }
}

pub(crate) 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();
    }
}