use heck::ToPascalCase;
use crate::backends::ffi::gen_visitor::callback_specs::{callback_specs_from_trait, gen_struct_fields};
use crate::backends::ffi::gen_visitor::context::{
context_field_specs, gen_context_inits, gen_context_setup, gen_context_struct_fields, gen_result_constants,
gen_result_decode_arms,
};
use crate::backends::ffi::gen_visitor::legacy_conversion::{
named_type_ref, visitor_function_spec, visitor_options_param,
};
use crate::backends::ffi::gen_visitor::protocol::VisitorProtocol;
use crate::backends::ffi::gen_visitor::visitor_refs::{gen_impl_methods, gen_visitor_ref_methods};
use crate::backends::ffi::template_env::render;
use crate::core::config::TraitBridgeConfig;
use crate::core::ir::FunctionDef;
#[cfg(test)]
pub fn gen_visitor_bindings(
prefix: &str,
core_import: &str,
embed_visitor_in_options: bool,
trait_def: &crate::core::ir::TypeDef,
bridge_cfg: Option<&TraitBridgeConfig>,
function: Option<&FunctionDef>,
) -> String {
gen_visitor_bindings_with_api(
prefix,
core_import,
embed_visitor_in_options,
trait_def,
bridge_cfg,
function,
None,
true,
)
}
#[allow(clippy::too_many_arguments)]
pub fn gen_visitor_bindings_with_api(
prefix: &str,
core_import: &str,
embed_visitor_in_options: bool,
trait_def: &crate::core::ir::TypeDef,
bridge_cfg: Option<&TraitBridgeConfig>,
function: Option<&FunctionDef>,
api: Option<&crate::core::ir::ApiSurface>,
emit_legacy_options_setter: bool,
) -> String {
let pascal_prefix = prefix.to_pascal_case();
let Some(api) = api else {
eprintln!("[alef] gen_visitor_bindings(ffi): visitor callbacks require API metadata");
return String::new();
};
let Some(bridge_cfg) = bridge_cfg else {
eprintln!("[alef] gen_visitor_bindings(ffi): visitor callbacks require trait_bridge metadata");
return String::new();
};
let Some(protocol) = VisitorProtocol::from_api(api, bridge_cfg) else {
return String::new();
};
let Some(context_def) = api.types.iter().find(|type_def| type_def.name == protocol.context_type) else {
return String::new();
};
let Some(result_metadata) = crate::codegen::visitor_result::visitor_result_metadata(api, bridge_cfg) else {
eprintln!(
"[alef] gen_visitor_bindings(ffi): trait bridge `{}` result_type metadata is required",
bridge_cfg.trait_name
);
return String::new();
};
let default_result = format!("{}::{}", protocol.result_path, result_metadata.default_variant.name);
let result_decode_arms = gen_result_decode_arms(&result_metadata, &default_result);
let specs = callback_specs_from_trait(trait_def, Some(bridge_cfg));
if specs.is_empty() {
eprintln!(
"[alef] gen_visitor_bindings(ffi): trait `{}` has no `{}`/`{}` visitor callback methods, skipping visitor callbacks",
trait_def.name, protocol.context_type, protocol.result_type
);
return String::new();
}
let callback_count = specs.len();
let trait_path = trait_def.rust_path.replace('-', "_");
let trait_name = &trait_def.name;
let options_type = function
.and_then(|func| visitor_options_param(func, Some(bridge_cfg)))
.and_then(|param| named_type_ref(¶m.ty))
.or(bridge_cfg.options_type.as_deref());
let Some(options_type) = options_type else {
eprintln!(
"[alef] gen_visitor_bindings(ffi): visitor callbacks require a configured or IR-derived options type, skipping visitor callbacks"
);
return String::new();
};
let options_field = bridge_cfg.resolved_options_field().unwrap_or("visitor");
let options_path = format!("{core_import}::{options_type}");
let context_fields = context_field_specs(context_def, api);
if context_fields.is_empty() {
eprintln!(
"[alef] gen_visitor_bindings(ffi): context_type `{}` has no FFI-compatible fields",
protocol.context_type
);
return String::new();
}
let result_constants = gen_result_constants(prefix, &result_metadata);
let context_struct_fields = gen_context_struct_fields(&context_fields);
let context_setup = gen_context_setup(&context_fields);
let context_inits = gen_context_inits(&context_fields);
let struct_fields = gen_struct_fields(&specs, &pascal_prefix);
let impl_methods = gen_impl_methods(&specs, &pascal_prefix, core_import, &protocol, &default_result);
let visitor_ref_methods = gen_visitor_ref_methods(&specs, core_import, &protocol);
let legacy_options_setter = if emit_legacy_options_setter {
gen_legacy_options_setter(
prefix,
&pascal_prefix,
&options_path,
options_field,
&trait_path,
&visitor_ref_methods,
)
} else {
String::new()
};
let visitor_function = function.and_then(|func| {
visitor_function_spec(
prefix,
func,
core_import,
Some(bridge_cfg),
embed_visitor_in_options,
options_field,
)
});
let context_path = protocol.context_path.clone();
let result_path = protocol.result_path.clone();
let mut out = format!(
r#"// ---------------------------------------------------------------------------
// Visitor / callback FFI — {callback_count} {trait_name} methods
// ---------------------------------------------------------------------------
{result_constants}
/// Opaque context passed to every C callback.
///
/// Fields reflect `{context_type}` from the Rust core. All string pointers are
/// valid only for the duration of the callback invocation.
#[repr(C)]
pub struct {pascal_prefix}Context {{
{context_struct_fields}
}}
/// C-facing callback struct for the visitor pattern.
///
/// Populate the function-pointer fields you care about; leave the rest null.
/// The `user_data` pointer is forwarded unchanged to every callback — use it
/// to thread your own context through the conversion.
///
/// # Field order
///
/// The field order matches the Go binding's expected C layout exactly.
///
/// # Callback return protocol
///
/// Callbacks return an `i32` visit-result code. When the code is
/// a string-payload variant, the callback must also write a heap-allocated,
/// null-terminated string into `*out_custom` and set `*out_len` to its byte
/// length (excluding the null terminator). The Rust side will read the string
/// and then call `free()` on the pointer.
///
/// For all other codes `out_custom` and `out_len` are not written.
///
/// # Callback signatures
///
/// All callbacks share the same leading parameters:
/// ```c
/// fn(ctx, user_data, out_custom, out_len, ...) -> i32
/// ```
/// followed by method-specific parameters documented on each field.
#[repr(C)]
pub struct {pascal_prefix}VisitorCallbacks {{
/// Arbitrary caller context forwarded to every callback.
pub user_data: *mut std::ffi::c_void,
{struct_fields}}}
// SAFETY: The `user_data` pointer is the caller's responsibility. We require
// callers to uphold thread-safety themselves (i.e. not share a visitor across
// threads without synchronisation). The callbacks themselves are `extern "C"`
// and therefore inherently `Send`.
unsafe impl Send for {pascal_prefix}VisitorCallbacks {{}}
// SAFETY: see Send impl above; the callbacks struct is effectively a POD vtable.
unsafe impl Sync for {pascal_prefix}VisitorCallbacks {{}}
/// Opaque handle wrapping a `{pascal_prefix}VisitorCallbacks` and implementing
/// the Rust `{trait_name}` trait.
///
/// Allocate with `{prefix}_visitor_create` and release with `{prefix}_visitor_free`.
/// The handle must NOT outlive the `{pascal_prefix}VisitorCallbacks` it was created from.
pub struct {pascal_prefix}Visitor {{
callbacks: {pascal_prefix}VisitorCallbacks,
/// CString storage for tag names / parent tags that we pass back to C.
/// RefCell is used for interior mutability; it is Send (Vec<CString> is Send) and
/// the outer Arc<Mutex> serialises all access, so Sync is not required on RefCell itself.
_tag_scratch: std::cell::RefCell<Vec<std::ffi::CString>>,
}}
// SAFETY: {pascal_prefix}Visitor is only accessed through the outer Arc<Mutex<dyn {trait_name} + Send>>
// which serialises access. The `user_data` pointer is the caller's responsibility.
unsafe impl Send for {pascal_prefix}Visitor {{}}
// SAFETY: see Send impl above; Sync is safe because all mutation goes through Mutex.
unsafe impl Sync for {pascal_prefix}Visitor {{}}
impl std::fmt::Debug for {pascal_prefix}Visitor {{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {{
f.debug_struct("{pascal_prefix}Visitor").finish_non_exhaustive()
}}
}}
/// Map a visit-result integer code + optional custom string pointer back to
/// the Rust result enum.
///
/// # Safety
///
/// `custom_ptr` must be either null or a pointer to a heap-allocated
/// null-terminated string that this function will take ownership of (freeing
/// it after reading).
unsafe fn decode_visit_result(
code: i32,
custom_ptr: *mut std::ffi::c_char,
) -> {result_path} {{
use {result_path} as VisitorResult;
match code {{
{result_decode_arms}
}}
}}
/// Build a temporary `{pascal_prefix}Context` from a Rust `{context_type}`, invoke
/// the provided callback, and decode the result.
///
/// The context passed to the C callback is only valid for the duration
/// of this function call.
unsafe fn call_with_ctx<F>(
ctx: &{context_path},
callback: F,
) -> {result_path}
where
F: FnOnce(
*const {pascal_prefix}Context,
*mut *mut std::ffi::c_char,
*mut usize,
) -> i32,
{{
{context_setup}
let c_ctx = {pascal_prefix}Context {{
{context_inits}
}};
let mut out_custom: *mut std::ffi::c_char = std::ptr::null_mut();
let mut out_len: usize = 0;
let code = callback(&c_ctx, &mut out_custom, &mut out_len);
// SAFETY: decode_visit_result takes ownership of out_custom when non-null.
unsafe {{ decode_visit_result(code, out_custom) }}
}}
/// Convert an `Option<&str>` to a C pointer: non-null CString when `Some`, null when `None`.
///
/// Returns `(ptr, Option<CString>)` — the `Option<CString>` must be kept alive
/// until after the pointer is consumed by the callback.
fn opt_str_to_c(s: Option<&str>) -> (*const std::ffi::c_char, Option<std::ffi::CString>) {{
match s {{
Some(val) => match std::ffi::CString::new(val) {{
Ok(cs) => {{
let ptr = cs.as_ptr();
(ptr, Some(cs))
}}
Err(_) => (std::ptr::null(), None),
}},
None => (std::ptr::null(), None),
}}
}}
impl {trait_path} for {pascal_prefix}Visitor {{
{impl_methods}}}
/// Create a new visitor handle from a callbacks struct.
///
/// The returned handle must be freed with `{prefix}_visitor_free`.
/// The `{pascal_prefix}VisitorCallbacks` struct is **copied** into the handle;
/// the caller may free it after this call returns.
///
/// Returns null on allocation failure.
///
/// # Safety
///
/// `callbacks` must point to a valid, fully initialised `{pascal_prefix}VisitorCallbacks`.
/// `user_data` (embedded in the struct) must remain valid and accessible from
/// any thread that calls `{prefix}_convert_with_visitor` until after
/// `{prefix}_visitor_free` is called.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn {prefix}_visitor_create(
callbacks: *const {pascal_prefix}VisitorCallbacks,
) -> *mut {pascal_prefix}Visitor {{
if callbacks.is_null() {{
return std::ptr::null_mut();
}}
// SAFETY: caller guarantees the pointer is valid.
let cbs = unsafe {{ callbacks.read() }};
let visitor = {pascal_prefix}Visitor {{
callbacks: cbs,
_tag_scratch: std::cell::RefCell::new(Vec::new()),
}};
Box::into_raw(Box::new(visitor))
}}
/// Free a visitor handle previously returned by `{prefix}_visitor_create`.
///
/// After this call the pointer is invalid and must not be used.
///
/// # Safety
///
/// `visitor` must have been returned by `{prefix}_visitor_create`, or be null.
/// Passing a null pointer is safe and has no effect.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn {prefix}_visitor_free(visitor: *mut {pascal_prefix}Visitor) {{
if !visitor.is_null() {{
// SAFETY: visitor was created with Box::into_raw.
unsafe {{ drop(Box::from_raw(visitor)); }}
}}
}}
{legacy_options_setter}"#,
prefix = prefix,
pascal_prefix = pascal_prefix,
callback_count = callback_count,
trait_name = trait_name,
context_type = protocol.context_type,
context_path = context_path,
result_constants = result_constants,
result_path = result_path,
result_decode_arms = result_decode_arms,
context_struct_fields = context_struct_fields,
context_setup = context_setup,
context_inits = context_inits,
trait_path = trait_path,
struct_fields = struct_fields,
impl_methods = impl_methods,
legacy_options_setter = legacy_options_setter,
);
if let Some(visitor_function) = visitor_function {
out.push_str(&render(
"ffi_visitor_with_callback_function.jinja",
minijinja::context! {
prefix,
with_visitor_fn_name => visitor_function.fn_name,
pascal_prefix,
trait_path,
visitor_ref_methods,
params => visitor_function.ffi_params,
param_conversions => visitor_function.param_conversions,
return_type => visitor_function.return_type,
call => visitor_function.call,
},
));
}
out
}
fn gen_legacy_options_setter(
prefix: &str,
pascal_prefix: &str,
options_path: &str,
options_field: &str,
trait_path: &str,
visitor_ref_methods: &str,
) -> String {
format!(
r#"
/// Attach a visitor to an options handle before calling `{prefix}_convert`.
///
/// The visitor will be invoked during conversion via the normal `{prefix}_convert` path.
/// The `visitor` pointer must remain valid until after `{prefix}_convert` returns.
///
/// Passing `null` for either argument is a no-op.
///
/// # Safety
///
/// `options` must be a non-null pointer returned by `{prefix}_conversion_options_from_json`,
/// valid for write access. `visitor` must be a non-null pointer returned by
/// `{prefix}_visitor_create`, or null. Both must remain valid for the duration of any
/// subsequent `{prefix}_convert` call.
#[unsafe(no_mangle)]
pub unsafe extern "C" fn {prefix}_options_set_visitor_handle(
options: *mut {options_path},
visitor: *mut {pascal_prefix}Visitor,
) {{
if options.is_null() || visitor.is_null() {{
return;
}}
struct VisitorRef(*mut {pascal_prefix}Visitor);
impl std::fmt::Debug for VisitorRef {{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {{
f.debug_struct("VisitorRef").finish_non_exhaustive()
}}
}}
// SAFETY: VisitorRef is a thin wrapper around a raw pointer to {pascal_prefix}Visitor which
// is itself Send + Sync. The caller guarantees the pointer remains valid during conversion.
unsafe impl Send for VisitorRef {{}}
// SAFETY: see Send impl above.
unsafe impl Sync for VisitorRef {{}}
impl {trait_path} for VisitorRef {{
{visitor_ref_methods} }}
// SAFETY: options is non-null (checked above); caller guarantees it is valid for write.
let options_ref = unsafe {{ &mut *options }};
options_ref.{options_field} = Some(std::sync::Arc::new(std::sync::Mutex::new(VisitorRef(visitor))));
}}"#,
)
}