generator.c
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generator.c
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	#include <stdlib.h>
	#include <string.h>

	#include "ant.h"
	#include "ptr.h"
	#include "errors.h"
	#include "internal.h"
	#include "runtime.h"
	#include "sugar.h"

	#include "gc/roots.h"
	#include "silver/engine.h"
	#include "modules/generator.h"
	#include "modules/iterator.h"
	#include "modules/symbol.h"

	enum { GENERATOR_NATIVE_TAG = 0x47454e52u }; // GENR

	typedef enum {
	GEN_SUSPENDED_START = 0,
	GEN_SUSPENDED_YIELD = 1,
	GEN_EXECUTING = 2,
	GEN_COMPLETED = 3,
	} generator_state_t;

	typedef struct generator_request {
	sv_resume_kind_t kind;
	ant_value_t value;
	ant_value_t promise;
	struct generator_request *next;
	} generator_request_t;

	typedef struct generator_data {
	coroutine_t *coro;
	generator_state_t state;
	generator_request_t *queue_head;
	generator_request_t *queue_tail;
	bool is_async;
	} generator_data_t;

	static ant_value_t generator_resume_kind(
	ant_t *js, ant_value_t gen,
	ant_value_t resume_value, sv_resume_kind_t resume_kind
	);

	static ant_value_t generator_result(ant_t *js, bool done, ant_value_t value) {
	ant_value_t result = js_mkobj(js);
	js_set(js, result, "done", js_bool(done));
	js_set(js, result, "value", value);
	return result;
	}

	static generator_data_t *generator_data(ant_value_t gen) {
	if (!js_check_native_tag(gen, GENERATOR_NATIVE_TAG)) return NULL;
	return (generator_data_t *)js_get_native_ptr(gen);
	}

	static generator_state_t generator_state(ant_value_t gen) {
	generator_data_t *data = generator_data(gen);
	return data ? data->state : GEN_COMPLETED;
	}

	static void generator_set_state(ant_value_t gen, generator_state_t state) {
	generator_data_t *data = generator_data(gen);
	if (data) data->state = state;
	}

	static bool generator_is_async(ant_value_t gen) {
	generator_data_t *data = generator_data(gen);
	return data && data->is_async;
	}

	static ant_value_t generator_async_wrap_result(ant_t *js, ant_value_t result) {
	ant_value_t promise = js_mkpromise(js);
	if (is_err(promise)) return promise;

	if (is_err(result)) {
	ant_value_t reject_value = js->thrown_exists ? js->thrown_value : result;
	js->thrown_exists = false;
	js->thrown_value = js_mkundef();
	js_reject_promise(js, promise, reject_value);
	} else js_resolve_promise(js, promise, result);

	return promise;
	}

	static generator_request_t generator_dequeue_request(generator_data_t data) {
	if (!data \|\| !data->queue_head) return NULL;
	generator_request_t *req = data->queue_head;
	data->queue_head = req->next;
	if (!data->queue_head) data->queue_tail = NULL;
	req->next = NULL;
	return req;
	}

	static void generator_free_queue(generator_data_t *data) {
	if (!data) return;
	generator_request_t *req = data->queue_head;

	while (req) {
	generator_request_t *next = req->next;
	free(req);
	req = next;
	}

	data->queue_head = NULL;
	data->queue_tail = NULL;
	}

	static ant_value_t generator_enqueue_request(
	ant_t *js, ant_value_t gen, sv_resume_kind_t kind, ant_value_t value
	) {
	generator_data_t *data = generator_data(gen);
	if (!data \|\| !data->is_async) return js_mkerr_typed(js, JS_ERR_TYPE, "Generator is already executing");

	ant_value_t promise = js_mkpromise(js);
	if (is_err(promise)) return promise;

	generator_request_t req = (generator_request_t )calloc(1, sizeof(*req));
	if (!req) return js_mkerr(js, "out of memory for generator request");

	*req = (generator_request_t){
	.kind = kind,
	.value = value,
	.promise = promise,
	.next = NULL,
	};

	if (data->queue_tail) data->queue_tail->next = req;
	else data->queue_head = req;
	data->queue_tail = req;

	return promise;
	}

	static void generator_settle_request_promise(ant_t *js, ant_value_t promise, ant_value_t result) {
	if (is_err(result)) {
	ant_value_t reject_value = js->thrown_exists ? js->thrown_value : result;
	js->thrown_exists = false;
	js->thrown_value = js_mkundef();
	js_reject_promise(js, promise, reject_value);
	} else js_resolve_promise(js, promise, result);
	}

	static void generator_process_queue(ant_t *js, ant_value_t gen) {
	generator_data_t *data = generator_data(gen);
	if (!data \|\| !data->is_async) return;

	GC_ROOT_SAVE(root_mark, js);
	GC_ROOT_PIN(js, gen);

	while (data->state != GEN_EXECUTING && data->queue_head) {
	generator_request_t *req = generator_dequeue_request(data);
	if (!req) break;

	GC_ROOT_PIN(js, req->value);
	GC_ROOT_PIN(js, req->promise);

	coroutine_t *coro = data->coro;
	if (coro) coro->async_promise = req->promise;

	ant_value_t result = generator_resume_kind(js, gen, req->value, req->kind);
	GC_ROOT_PIN(js, result);

	if (vtype(result) != T_PROMISE \|\| result != req->promise) {
	generator_settle_request_promise(js, req->promise, result);
	js_maybe_drain_microtasks_after_async_settle(js);
	}

	free(req);
	data = generator_data(gen);
	if (!data) break;
	}

	GC_ROOT_RESTORE(js, root_mark);
	}

	static coroutine_t *generator_coro(ant_value_t gen) {
	generator_data_t *data = generator_data(gen);
	return data ? data->coro : NULL;
	}

	static void generator_clear_coro(ant_value_t gen, coroutine_t *coro) {
	generator_data_t *data = generator_data(gen);
	if (data && data->coro == coro) data->coro = NULL;
	if (coro) coroutine_unhold(coro, CORO_HOLD_GENERATOR);
	}

	coroutine_t *generator_get_coro_for_gc(ant_value_t gen) {
	return generator_coro(gen);
	}

	void generator_mark_for_gc(ant_t *js, ant_value_t gen) {
	generator_data_t *data = generator_data(gen);
	if (!data) return;
	for (generator_request_t *req = data->queue_head; req; req = req->next) {
	gc_mark_value(js, req->value);
	gc_mark_value(js, req->promise);
	}
	}

	static ant_value_t generator_find_owner_in_list(ant_object_t head, coroutine_t coro) {
	for (ant_object_t *obj = head; obj; obj = obj->next) {
	ant_value_t candidate = js_obj_from_ptr(obj);
	generator_data_t *data = generator_data(candidate);
	if (data && data->coro == coro) return candidate;
	}
	return js_mkundef();
	}

	static ant_value_t generator_find_owner(ant_t js, coroutine_t coro) {
	ant_value_t gen = generator_find_owner_in_list(js->objects, coro);
	if (vtype(gen) != T_UNDEF) return gen;
	gen = generator_find_owner_in_list(js->objects_old, coro);
	if (vtype(gen) != T_UNDEF) return gen;
	return generator_find_owner_in_list(js->permanent_objects, coro);
	}

	bool generator_resume_pending_request(ant_t js, coroutine_t coro, ant_value_t result) {
	if (!coro \|\| coro->type != CORO_GENERATOR \|\| vtype(coro->async_promise) != T_PROMISE) return false;

	ant_value_t gen = generator_find_owner(js, coro);
	generator_data_t *data = generator_data(gen);
	if (!data \|\| !data->is_async) return false;

	GC_ROOT_SAVE(root_mark, js);
	GC_ROOT_PIN(js, gen);
	GC_ROOT_PIN(js, result);

	ant_value_t pending = coro->async_promise;
	GC_ROOT_PIN(js, pending);

	if (is_err(result)) {
	ant_value_t reject_value = js->thrown_exists ? js->thrown_value : result;
	js->thrown_exists = false;
	js->thrown_value = js_mkundef();

	GC_ROOT_PIN(js, reject_value);
	coro->async_promise = js_mkundef();
	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);

	js_reject_promise(js, pending, reject_value);
	js_maybe_drain_microtasks_after_async_settle(js);
	generator_process_queue(js, gen);
	GC_ROOT_RESTORE(js, root_mark);

	return true;
	}

	if (coro->sv_vm && coro->sv_vm->suspended) {
	if (vtype(coro->awaited_promise) != T_UNDEF) {
	generator_set_state(gen, GEN_EXECUTING);
	GC_ROOT_RESTORE(js, root_mark);
	return true;
	}

	ant_value_t out = generator_result(js, false, result);
	GC_ROOT_PIN(js, out);
	coro->async_promise = js_mkundef();
	generator_set_state(gen, GEN_SUSPENDED_YIELD);

	js_resolve_promise(js, pending, out);
	js_maybe_drain_microtasks_after_async_settle(js);
	generator_process_queue(js, gen);
	GC_ROOT_RESTORE(js, root_mark);

	return true;
	}

	ant_value_t out = generator_result(js, true, result);
	GC_ROOT_PIN(js, out);
	coro->async_promise = js_mkundef();

	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);

	js_resolve_promise(js, pending, out);
	js_maybe_drain_microtasks_after_async_settle(js);
	generator_process_queue(js, gen);
	GC_ROOT_RESTORE(js, root_mark);

	return true;
	}

	static void generator_finalize(ant_t js, ant_object_t obj) {
	ant_value_t gen = js_obj_from_ptr(obj);
	generator_data_t data = (generator_data_t )js_get_native_ptr(gen);

	if (!data) return;
	if (data->coro) generator_clear_coro(gen, data->coro);

	js_set_native_ptr(gen, NULL);
	js_set_native_tag(gen, 0);

	generator_free_queue(data);
	free(data);
	}

	static ant_value_t generator_resume_kind(
	ant_t *js, ant_value_t gen, ant_value_t resume_value, sv_resume_kind_t resume_kind
	) {
	GC_ROOT_SAVE(root_mark, js);
	GC_ROOT_PIN(js, gen);
	GC_ROOT_PIN(js, resume_value);
	coroutine_t *coro = generator_coro(gen);

	if (!coro \|\| !coro->sv_vm) {
	generator_set_state(gen, GEN_COMPLETED);
	if (resume_kind == SV_RESUME_THROW) {
	GC_ROOT_RESTORE(js, root_mark);
	return js_throw(js, resume_value);
	}

	ant_value_t out = generator_result(
	js, true, resume_kind == SV_RESUME_RETURN
	? resume_value : js_mkundef()
	);

	GC_ROOT_RESTORE(js, root_mark);
	return out;
	}

	generator_state_t state = generator_state(gen);
	if (state == GEN_EXECUTING) {
	ant_value_t queued = generator_enqueue_request(js, gen, resume_kind, resume_value);
	GC_ROOT_RESTORE(js, root_mark);
	return queued;
	}

	if (state == GEN_COMPLETED) {
	if (resume_kind == SV_RESUME_THROW) {
	GC_ROOT_RESTORE(js, root_mark);
	return js_throw(js, resume_value);
	}

	ant_value_t out = generator_result(
	js, true, resume_kind == SV_RESUME_RETURN
	? resume_value : js_mkundef()
	);

	GC_ROOT_RESTORE(js, root_mark);
	return out;
	}

	if (state == GEN_SUSPENDED_START && resume_kind == SV_RESUME_THROW) {
	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);
	GC_ROOT_RESTORE(js, root_mark);
	return js_throw(js, resume_value);
	}

	if (state == GEN_SUSPENDED_START && resume_kind == SV_RESUME_RETURN) {
	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);
	ant_value_t out = generator_result(js, true, resume_value);
	GC_ROOT_RESTORE(js, root_mark);
	return out;
	}

	generator_set_state(gen, GEN_EXECUTING);
	coroutine_t *saved_active = js->active_async_coro;

	coro->active_parent = saved_active;
	coro->active_prev = NULL;

	if (saved_active) saved_active->active_prev = coro;
	js->active_async_coro = coro;
	coroutine_hold(coro, CORO_HOLD_ACTIVE);

	ant_value_t result;
	if (state == GEN_SUSPENDED_START) {
	sv_closure_t *closure = (vtype(coro->async_func) == T_FUNC) ? js_func_closure(coro->async_func) : NULL;
	if (!closure \|\| !closure->func) result = js_mkerr(js, "invalid generator function");
	else result = sv_execute_closure_entry(
	coro->sv_vm, closure, coro->async_func,
	coro->super_val, coro->this_val, coro->args, coro->nargs, NULL
	);
	} else {
	coro->sv_vm->suspended_resume_value = resume_value;
	coro->sv_vm->suspended_resume_is_error = (resume_kind == SV_RESUME_THROW);
	coro->sv_vm->suspended_resume_kind = resume_kind;
	coro->sv_vm->suspended_resume_pending = true;
	result = sv_resume_suspended(coro->sv_vm);
	}

	GC_ROOT_PIN(js, result);
	js->active_async_coro = saved_active;
	if (saved_active) saved_active->active_prev = NULL;

	coro->active_parent = NULL;
	coro->active_prev = NULL;
	coroutine_unhold(coro, CORO_HOLD_ACTIVE);

	if (is_err(result)) {
	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);
	GC_ROOT_RESTORE(js, root_mark);
	return result;
	}

	if (coro->sv_vm && coro->sv_vm->suspended) {
	if (generator_is_async(gen) && vtype(coro->awaited_promise) != T_UNDEF) {
	generator_set_state(gen, GEN_EXECUTING);
	if (vtype(coro->async_promise) != T_PROMISE) {
	coro->async_promise = js_mkpromise(js);
	GC_ROOT_PIN(js, coro->async_promise);
	}

	ant_value_t out = coro->async_promise;
	GC_ROOT_RESTORE(js, root_mark);
	return out;
	}

	generator_set_state(gen, GEN_SUSPENDED_YIELD);
	ant_value_t out = generator_result(js, false, result);
	GC_ROOT_RESTORE(js, root_mark);

	return out;
	}

	generator_set_state(gen, GEN_COMPLETED);
	generator_clear_coro(gen, coro);

	ant_value_t out = generator_result(js, true, result);
	GC_ROOT_RESTORE(js, root_mark);

	return out;
	}

	static ant_value_t generator_resume(ant_t *js, ant_value_t gen, ant_value_t resume_value) {
	return generator_resume_kind(js, gen, resume_value, SV_RESUME_NEXT);
	}

	static ant_value_t generator_next(ant_t js, ant_value_t args, int nargs) {
	ant_value_t gen = js->this_val;
	if (vtype(gen) != T_GENERATOR)
	return js_mkerr_typed(js, JS_ERR_TYPE, "Generator.prototype.next called on incompatible receiver");

	ant_value_t resume_value = nargs > 0 ? args[0] : js_mkundef();
	ant_value_t result = generator_resume(js, gen, resume_value);

	if (generator_is_async(gen) && vtype(result) == T_PROMISE) return result;
	return generator_is_async(gen) ? generator_async_wrap_result(js, result) : result;
	}

	static ant_value_t generator_return(ant_t js, ant_value_t args, int nargs) {
	ant_value_t gen = js->this_val;
	if (vtype(gen) != T_GENERATOR)
	return js_mkerr_typed(js, JS_ERR_TYPE, "Generator.prototype.return called on incompatible receiver");

	generator_state_t state = generator_state(gen);
	if (state == GEN_EXECUTING && !generator_is_async(gen))
	return js_mkerr_typed(js, JS_ERR_TYPE, "Generator is already executing");

	ant_value_t value = nargs > 0 ? args[0] : js_mkundef();
	ant_value_t result = generator_resume_kind(js, gen, value, SV_RESUME_RETURN);

	if (generator_is_async(gen) && vtype(result) == T_PROMISE) return result;
	return generator_is_async(gen) ? generator_async_wrap_result(js, result) : result;
	}

	static ant_value_t generator_throw(ant_t js, ant_value_t args, int nargs) {
	ant_value_t gen = js->this_val;
	if (vtype(gen) != T_GENERATOR)
	return js_mkerr_typed(js, JS_ERR_TYPE, "Generator.prototype.throw called on incompatible receiver");

	generator_state_t state = generator_state(gen);
	if (state == GEN_EXECUTING && !generator_is_async(gen))
	return js_mkerr_typed(js, JS_ERR_TYPE, "Generator is already executing");

	ant_value_t value = nargs > 0 ? args[0] : js_mkundef();
	ant_value_t result = generator_resume_kind(js, gen, value, SV_RESUME_THROW);

	if (generator_is_async(gen) && vtype(result) == T_PROMISE) return result;
	return generator_is_async(gen) ? generator_async_wrap_result(js, result) : result;
	}

	static ant_value_t generator_async_dispose(ant_t js, ant_value_t args, int nargs) {
	ant_value_t gen = js->this_val;
	if (vtype(gen) != T_GENERATOR \|\| !generator_is_async(gen)) return js_mkerr_typed(
	js, JS_ERR_TYPE,
	"AsyncGenerator.prototype[Symbol.asyncDispose] called on incompatible receiver"
	);

	return generator_return(js, NULL, 0);
	}

	void init_generator_module(void) {
	ant_t *js = rt->js;
	ant_value_t proto = js_mkobj(js);

	js->sym.generator_proto = proto;
	js_set_proto_init(proto, js->sym.iterator_proto);

	js_set(js, proto, "next", js_mkfun(generator_next));
	js_set(js, proto, "return", js_mkfun(generator_return));
	js_set(js, proto, "throw", js_mkfun(generator_throw));
	js_set_sym(js, proto, get_toStringTag_sym(), js_mkstr(js, "Generator", 9));

	ant_value_t async_proto = js_mkobj(js);
	js->sym.async_generator_proto = async_proto;
	js_set_proto_init(async_proto, js->sym.async_iterator_proto);
	js_set(js, async_proto, "next", js_mkfun(generator_next));
	js_set(js, async_proto, "return", js_mkfun(generator_return));
	js_set(js, async_proto, "throw", js_mkfun(generator_throw));
	js_set_sym(js, async_proto, get_toStringTag_sym(), js_mkstr(js, "AsyncGenerator", 14));
	js_set_sym(js, async_proto, get_asyncDispose_sym(), js_mkfun(generator_async_dispose));

	ant_value_t async_generator_func_proto = js_get_slot(js_glob(js), SLOT_ASYNC_GENERATOR_PROTO);
	if (is_object_type(async_generator_func_proto)) {
	js_set(js, async_generator_func_proto, "prototype", async_proto);
	js_set_descriptor(js, js_as_obj(async_generator_func_proto), "prototype", 9, JS_DESC_C);
	js_set(js, async_proto, "constructor", async_generator_func_proto);
	js_set_descriptor(js, async_proto, "constructor", 11, JS_DESC_C);
	}

	init_async_iterator_helpers();
	}

	ant_value_t sv_call_generator_closure_dispatch(
	sv_vm_t caller_vm, ant_t js, sv_closure_t *closure,
	ant_value_t callee_func, ant_value_t super_val,
	ant_value_t this_val, ant_value_t *args, int argc
	) {
	if (!closure \|\| !closure->func) return js_mkerr(js, "invalid generator function");

	sv_vm_t *gen_vm = sv_vm_create(js, SV_VM_ASYNC);
	if (!gen_vm) return js_mkerr(js, "out of memory for generator VM");

	coroutine_t coro = (coroutine_t )CORO_MALLOC(sizeof(coroutine_t));
	if (!coro) {
	sv_vm_destroy(gen_vm);
	return js_mkerr(js, "out of memory for generator");
	}

	ant_value_t *copied_args = NULL;
	if (argc > 0 && args) {
	copied_args = (ant_value_t )CORO_MALLOC(sizeof(ant_value_t) (size_t)argc);
	if (!copied_args) {
	sv_vm_destroy(gen_vm);
	CORO_FREE(coro);
	return js_mkerr(js, "out of memory for generator args");
	}
	memcpy(copied_args, args, sizeof(ant_value_t) * (size_t)argc);
	}

	ant_value_t gen = js_mkgenerator(js);
	if (is_err(gen)) {
	if (copied_args) CORO_FREE(copied_args);
	sv_vm_destroy(gen_vm);
	CORO_FREE(coro);
	return gen;
	}

	generator_data_t data = (generator_data_t )calloc(1, sizeof(*data));
	if (!data) {
	if (copied_args) CORO_FREE(copied_args);
	sv_vm_destroy(gen_vm);
	CORO_FREE(coro);
	return js_mkerr(js, "out of memory for generator data");
	}

	*coro = (coroutine_t){
	.js = js,
	.type = CORO_GENERATOR,
	.this_val = this_val,
	.super_val = super_val,
	.new_target = js->new_target,
	.awaited_promise = js_mkundef(),
	.result = js_mkundef(),
	.async_func = callee_func,
	.args = copied_args,
	.nargs = argc,
	.active_parent = NULL,
	.is_settled = false,
	.is_error = false,
	.is_done = false,
	.resume_point = 0,
	.yield_value = js_mkundef(),
	.async_promise = js_mkundef(),
	.next = NULL,
	.mco = NULL,
	.owner_vm = gen_vm,
	.sv_vm = gen_vm,
	.mco_started = false,
	.is_ready = false,
	.did_suspend = false,
	.refcount = 1,
	.hold_bits = 0,
	.await_registered = false,
	.destroy_requested = false,
	};

	*data = (generator_data_t){
	.coro = coro,
	.state = GEN_SUSPENDED_START,
	.is_async = closure->func->is_async,
	};
	coroutine_hold(coro, CORO_HOLD_GENERATOR);
	coroutine_release(coro);

	js_set_native_ptr(gen, data);
	js_set_native_tag(gen, GENERATOR_NATIVE_TAG);
	js_set_finalizer(gen, generator_finalize);

	ant_value_t instance_proto = js_get(js, callee_func, "prototype");
	if (is_object_type(instance_proto)) js_set_proto_wb(js, gen, instance_proto);
	else if (data->is_async && is_object_type(js->sym.async_generator_proto))
	js_set_proto_wb(js, gen, js->sym.async_generator_proto);

	return gen;
	}

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