observable.c
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observable.c
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	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>

	#include "errors.h"
	#include "internal.h"
	#include "runtime.h"

	#include "modules/symbol.h"
	#include "modules/observable.h"

	static inline bool is_callable(jsval_t val) {
	uint8_t t = vtype(val);
	return t == T_FUNC \|\| t == T_CFUNC;
	}

	static bool subscription_closed(struct js *js, jsval_t subscription) {
	jsval_t observer = js_get_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER);
	return vtype(observer) == T_UNDEF;
	}

	static void cleanup_subscription(struct js *js, jsval_t subscription) {
	jsval_t cleanup = js_get_slot(js, subscription, SLOT_SUBSCRIPTION_CLEANUP);
	if (vtype(cleanup) == T_UNDEF) return;
	if (!is_callable(cleanup)) return;

	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_CLEANUP, js_mkundef());
	jsval_t result = js_call(js, cleanup, NULL, 0);

	if (vtype(result) == T_ERR) fprintf(stderr, "Error in subscription cleanup: %s\n", js_str(js, result));
	}

	static jsval_t create_subscription(struct js *js, jsval_t observer) {
	jsval_t subscription = js_mkobj(js);
	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER, observer);
	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_CLEANUP, js_mkundef());
	js_set(js, subscription, get_toStringTag_sym_key(), js_mkstr(js, "Subscription", 12));
	return subscription;
	}

	static jsval_t js_subscription_get_closed(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	jsval_t subscription = js_getthis(js);

	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Subscription.closed getter called on non-object");
	}
	return js_bool(subscription_closed(js, subscription));
	}

	static jsval_t js_subscription_unsubscribe(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	jsval_t subscription = js_getthis(js);

	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Subscription.unsubscribe called on non-object");
	}

	if (subscription_closed(js, subscription)) return js_mkundef();

	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER, js_mkundef());
	cleanup_subscription(js, subscription);

	return js_mkundef();
	}

	static void setup_subscription_methods(struct js *js, jsval_t subscription) {
	js_set(js, subscription, "unsubscribe", js_mkfun(js_subscription_unsubscribe));
	jsval_t closed_getter = js_mkfun(js_subscription_get_closed);
	js_set_getter_desc(js, subscription, "closed", 6, closed_getter, JS_DESC_E \| JS_DESC_C);
	}

	static jsval_t js_subobs_get_closed(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	jsval_t O = js_getthis(js);

	if (!is_special_object(O)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "SubscriptionObserver.closed getter called on non-object");
	}

	jsval_t subscription = js_get_slot(js, O, SLOT_DATA);
	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid SubscriptionObserver");
	}

	return js_bool(subscription_closed(js, subscription));
	}

	static jsval_t js_subobs_next(struct js js, jsval_t args, int nargs) {
	jsval_t O = js_getthis(js);

	if (!is_special_object(O)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "SubscriptionObserver.next called on non-object");
	}

	jsval_t subscription = js_get_slot(js, O, SLOT_DATA);
	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid SubscriptionObserver");
	}

	if (subscription_closed(js, subscription)) return js_mkundef();

	jsval_t observer = js_get_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER);
	if (!is_special_object(observer)) return js_mkundef();

	jsval_t nextMethod = js_get(js, observer, "next");
	if (is_callable(nextMethod)) {
	jsval_t value = (nargs > 0) ? args[0] : js_mkundef();
	jsval_t call_args[1] = {value};
	jsval_t result = js_call_with_this(js, nextMethod, observer, call_args, 1);
	if (vtype(result) == T_ERR) fprintf(stderr, "Error in observer.next: %s\n", js_str(js, result));
	}

	return js_mkundef();
	}

	static jsval_t js_subobs_error(struct js js, jsval_t args, int nargs) {
	jsval_t O = js_getthis(js);

	if (!is_special_object(O)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "SubscriptionObserver.error called on non-object");
	}

	jsval_t subscription = js_get_slot(js, O, SLOT_DATA);
	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid SubscriptionObserver");
	}

	if (subscription_closed(js, subscription)) return js_mkundef();

	jsval_t observer = js_get_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER);
	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER, js_mkundef());

	if (is_special_object(observer)) {
	jsval_t errorMethod = js_get(js, observer, "error");
	if (is_callable(errorMethod)) {
	jsval_t exception = (nargs > 0) ? args[0] : js_mkundef();
	jsval_t call_args[1] = {exception};
	jsval_t result = js_call_with_this(js, errorMethod, observer, call_args, 1);
	if (vtype(result) == T_ERR) fprintf(stderr, "Error in observer.error: %s\n", js_str(js, result));
	}
	}

	cleanup_subscription(js, subscription);
	return js_mkundef();
	}

	static jsval_t js_subobs_complete(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	jsval_t O = js_getthis(js);

	if (!is_special_object(O)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "SubscriptionObserver.complete called on non-object");
	}

	jsval_t subscription = js_get_slot(js, O, SLOT_DATA);
	if (!is_special_object(subscription)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Invalid SubscriptionObserver");
	}

	if (subscription_closed(js, subscription)) return js_mkundef();

	jsval_t observer = js_get_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER);
	js_set_slot(js, subscription, SLOT_SUBSCRIPTION_OBSERVER, js_mkundef());

	if (is_special_object(observer)) {
	jsval_t completeMethod = js_get(js, observer, "complete");
	if (is_callable(completeMethod)) {
	jsval_t result = js_call_with_this(js, completeMethod, observer, NULL, 0);
	if (vtype(result) == T_ERR) fprintf(stderr, "Error in observer.complete: %s\n", js_str(js, result));
	}
	}

	cleanup_subscription(js, subscription);
	return js_mkundef();
	}

	static jsval_t create_subscription_observer(struct js *js, jsval_t subscription) {
	jsval_t subobs = js_mkobj(js);

	js_set_slot(js, subobs, SLOT_DATA, subscription);
	js_set(js, subobs, "next", js_mkfun(js_subobs_next));
	js_set(js, subobs, "error", js_mkfun(js_subobs_error));
	js_set(js, subobs, "complete", js_mkfun(js_subobs_complete));
	js_set(js, subobs, get_toStringTag_sym_key(), js_mkstr(js, "SubscriptionObserver", 20));

	jsval_t closed_getter = js_mkfun(js_subobs_get_closed);
	js_set_getter_desc(js, subobs, "closed", 6, closed_getter, JS_DESC_E \| JS_DESC_C);

	return subobs;
	}

	static jsval_t js_cleanup_fn(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	jsval_t F = js_getcurrentfunc(js);
	jsval_t subscription = js_get_slot(js, F, SLOT_DATA);

	if (!is_special_object(subscription)) return js_mkundef();

	jsval_t unsubscribe = js_get(js, subscription, "unsubscribe");
	if (is_callable(unsubscribe)) {
	return js_call_with_this(js, unsubscribe, subscription, NULL, 0);
	}

	return js_mkundef();
	}

	static jsval_t execute_subscriber(struct js *js, jsval_t subscriber, jsval_t observer) {
	jsval_t call_args[1] = {observer};
	jsval_t subscriberResult = js_call(js, subscriber, call_args, 1);

	if (vtype(subscriberResult) == T_ERR) return subscriberResult;
	if (vtype(subscriberResult) == T_NULL \|\| vtype(subscriberResult) == T_UNDEF) return js_mkundef();
	if (is_callable(subscriberResult)) return subscriberResult;

	if (is_special_object(subscriberResult)) {
	jsval_t result = js_get(js, subscriberResult, "unsubscribe");
	if (vtype(result) == T_UNDEF) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Subscriber return value must have an unsubscribe method");
	}

	jsval_t cleanupFunction = js_mkobj(js);
	js_set_slot(js, cleanupFunction, SLOT_DATA, subscriberResult);
	js_set_slot(js, cleanupFunction, SLOT_CFUNC, js_mkfun(js_cleanup_fn));
	return js_obj_to_func(cleanupFunction);
	}

	return js_mkerr_typed(js, JS_ERR_TYPE, "Subscriber must return a function, an object with unsubscribe, or undefined");
	}

	static jsval_t js_observable_subscribe(struct js js, jsval_t args, int nargs) {
	jsval_t O = js_getthis(js);

	if (!is_special_object(O)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Observable.prototype.subscribe called on non-object");
	}

	jsval_t subscriber = js_get_slot(js, O, SLOT_OBSERVABLE_SUBSCRIBER);
	if (!is_callable(subscriber)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Observable has no [[Subscriber]] internal slot");
	}

	jsval_t observer;

	if (nargs > 0 && is_callable(args[0])) {
	jsval_t nextCallback = args[0];
	jsval_t errorCallback = (nargs > 1) ? args[1] : js_mkundef();
	jsval_t completeCallback = (nargs > 2) ? args[2] : js_mkundef();

	observer = js_mkobj(js);
	js_set(js, observer, "next", nextCallback);
	js_set(js, observer, "error", errorCallback);
	js_set(js, observer, "complete", completeCallback);
	} else if (nargs > 0 && is_special_object(args[0])) {
	observer = args[0];
	} else observer = js_mkobj(js);

	jsval_t subscription = create_subscription(js, observer);
	setup_subscription_methods(js, subscription);

	jsval_t start = js_get(js, observer, "start");
	if (is_callable(start)) {
	jsval_t start_args[1] = {subscription};
	jsval_t result = js_call_with_this(js, start, observer, start_args, 1);
	if (vtype(result) == T_ERR) {
	fprintf(stderr, "Error in observer.start: %s\n", js_str(js, result));
	}
	if (subscription_closed(js, subscription)) return subscription;
	}

	jsval_t subscriptionObserver = create_subscription_observer(js, subscription);
	jsval_t subscriberResult = execute_subscriber(js, subscriber, subscriptionObserver);

	if (vtype(subscriberResult) == T_ERR) {
	jsval_t thrown_error = js->thrown_value;
	js->thrown_value = js_mkundef();
	js->flags &= ~F_THROW;

	jsval_t error_args[1] = {thrown_error};
	jsval_t error_method = js_get(js, subscriptionObserver, "error");
	if (is_callable(error_method)) js_call_with_this(js, error_method, subscriptionObserver, error_args, 1);
	} else js_set_slot(js, subscription, SLOT_SUBSCRIPTION_CLEANUP, subscriberResult);

	if (subscription_closed(js, subscription)) cleanup_subscription(js, subscription);

	return subscription;
	}

	static jsval_t js_observable_symbol_observable(struct js js, jsval_t args, int nargs) {
	(void)args; (void)nargs;
	return js_getthis(js);
	}

	static jsval_t js_observable_constructor(struct js js, jsval_t args, int nargs) {
	if (nargs < 1) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Observable constructor requires a subscriber function");
	}

	jsval_t subscriber = args[0];
	if (!is_callable(subscriber)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Observable subscriber must be a function");
	}

	jsval_t proto = js_get_ctor_proto(js, "Observable", 10);
	jsval_t observable = js_mkobj(js);

	js_set_proto(js, observable, proto);
	js_set_slot(js, observable, SLOT_OBSERVABLE_SUBSCRIBER, subscriber);

	return observable;
	}

	static jsval_t js_of_subscriber(struct js js, jsval_t args, int nargs) {
	jsval_t F = js_getcurrentfunc(js);
	jsval_t items = js_get_slot(js, F, SLOT_DATA);

	if (nargs < 1) return js_mkundef();

	jsval_t observer = args[0];
	jsval_t subscription = js_get_slot(js, observer, SLOT_DATA);

	jsval_t length_val = js_get(js, items, "length");
	int length = (vtype(length_val) == T_NUM) ? (int)js_getnum(length_val) : 0;

	for (int i = 0; i < length; i++) {
	char key[16];
	snprintf(key, sizeof(key), "%d", i);
	jsval_t value = js_get(js, items, key);

	jsval_t next = js_get(js, observer, "next");
	if (is_callable(next)) {
	jsval_t next_args[1] = {value};
	js_call_with_this(js, next, observer, next_args, 1);
	}

	if (is_special_object(subscription) && subscription_closed(js, subscription)) return js_mkundef();
	}

	jsval_t complete = js_get(js, observer, "complete");
	if (is_callable(complete)) js_call_with_this(js, complete, observer, NULL, 0);

	return js_mkundef();
	}

	static jsval_t js_observable_of(struct js js, jsval_t args, int nargs) {
	jsval_t items = js_mkarr(js);
	for (int i = 0; i < nargs; i++) js_arr_push(js, items, args[i]);

	jsval_t subscriber_func = js_heavy_mkfun(js, js_of_subscriber, items);
	jsval_t ctor_args[1] = {subscriber_func};

	return js_observable_constructor(js, ctor_args, 1);
	}

	static jsval_t js_from_delegating(struct js js, jsval_t args, int nargs) {
	jsval_t F = js_getcurrentfunc(js);

	jsval_t observable = js_get_slot(js, F, SLOT_DATA);
	if (!is_special_object(observable)) return js_mkundef();

	jsval_t subscribe = js_get(js, observable, "subscribe");
	if (is_callable(subscribe)) {
	return js_call_with_this(js, subscribe, observable, args, nargs);
	}

	return js_mkundef();
	}

	static jsval_t js_from_iteration(struct js js, jsval_t args, int nargs) {
	jsval_t F = js_getcurrentfunc(js);
	jsval_t data = js_get_slot(js, F, SLOT_DATA);

	jsval_t iterable = js_get(js, data, "iterable");
	jsval_t iteratorMethod = js_get(js, data, "iteratorMethod");

	if (nargs < 1) return js_mkundef();

	jsval_t observer = args[0];
	jsval_t subscription = js_get_slot(js, observer, SLOT_DATA);

	if (!is_callable(iteratorMethod)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Object is not iterable");
	}

	jsval_t iterator = js_call_with_this(js, iteratorMethod, iterable, NULL, 0);
	if (!is_special_object(iterator)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Iterator must return an object");
	}

	jsval_t nextMethod = js_get(js, iterator, "next");
	if (!is_callable(nextMethod)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Iterator must have a next method");
	}

	while (true) {
	jsval_t next = js_call_with_this(js, nextMethod, iterator, NULL, 0);
	if (vtype(next) == T_ERR) return next;

	jsval_t done = js_get(js, next, "done");
	if (js_truthy(js, done)) {
	jsval_t complete = js_get(js, observer, "complete");
	if (is_callable(complete)) js_call_with_this(js, complete, observer, NULL, 0);
	return js_mkundef();
	}

	jsval_t nextValue = js_get(js, next, "value");
	jsval_t obs_next = js_get(js, observer, "next");
	if (is_callable(obs_next)) {
	jsval_t next_args[1] = {nextValue};
	js_call_with_this(js, obs_next, observer, next_args, 1);
	}

	if (is_special_object(subscription) && subscription_closed(js, subscription)) {
	jsval_t returnMethod = js_get(js, iterator, "return");
	if (is_callable(returnMethod)) js_call_with_this(js, returnMethod, iterator, NULL, 0);
	return js_mkundef();
	}
	}
	}

	static jsval_t js_observable_from(struct js js, jsval_t args, int nargs) {
	if (nargs < 1) return js_mkerr_typed(js, JS_ERR_TYPE, "Observable.from requires an argument");
	jsval_t x = args[0];

	if (vtype(x) == T_NULL \|\| vtype(x) == T_UNDEF) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Cannot convert null or undefined to observable");
	}

	jsval_t observableMethod = js_getprop_proto(js, x, get_observable_sym_key());

	if (is_callable(observableMethod)) {
	jsval_t observable = js_call_with_this(js, observableMethod, x, NULL, 0);

	if (!is_special_object(observable)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "@@observable must return an object");
	}

	jsval_t existing_subscriber = js_get_slot(js, observable, SLOT_OBSERVABLE_SUBSCRIBER);
	if (is_callable(existing_subscriber)) return observable;

	jsval_t subscriber_func = js_heavy_mkfun(js, js_from_delegating, observable);
	jsval_t ctor_args[1] = {subscriber_func};

	return js_observable_constructor(js, ctor_args, 1);
	}

	jsval_t iteratorMethod = js_get(js, x, get_iterator_sym_key());

	if (!is_callable(iteratorMethod) && vtype(x) == T_ARR) {
	jsval_t array_ctor = js_get(js, js_glob(js), "Array");
	jsval_t array_proto = js_get(js, array_ctor, "prototype");
	iteratorMethod = js_get(js, array_proto, get_iterator_sym_key());
	}

	if (!is_callable(iteratorMethod)) {
	return js_mkerr_typed(js, JS_ERR_TYPE, "Object is not observable or iterable");
	}

	jsval_t data = js_mkobj(js);
	js_set(js, data, "iterable", x);
	js_set(js, data, "iteratorMethod", iteratorMethod);

	jsval_t subscriber_func = js_heavy_mkfun(js, js_from_iteration, data);
	jsval_t ctor_args[1] = {subscriber_func};

	return js_observable_constructor(js, ctor_args, 1);
	}

	void init_observable_module(void) {
	struct js *js = rt->js;
	jsval_t global = js_glob(js);

	jsval_t observable_ctor = js_mkobj(js);
	jsval_t observable_proto = js_mkobj(js);

	js_set(js, observable_proto, "subscribe", js_mkfun(js_observable_subscribe));
	js_set(js, observable_proto, get_observable_sym_key(), js_mkfun(js_observable_symbol_observable));
	js_set(js, observable_proto, get_toStringTag_sym_key(), js_mkstr(js, "Observable", 10));

	js_set_slot(js, observable_ctor, SLOT_CFUNC, js_mkfun(js_observable_constructor));
	js_mkprop_fast(js, observable_ctor, "prototype", 9, observable_proto);
	js_mkprop_fast(js, observable_ctor, "name", 4, ANT_STRING("Observable"));
	js_set_descriptor(js, observable_ctor, "name", 4, 0);
	js_set(js, observable_ctor, "of", js_mkfun(js_observable_of));
	js_set(js, observable_ctor, "from", js_mkfun(js_observable_from));

	jsval_t Observable = js_obj_to_func(observable_ctor);
	js_set(js, observable_proto, "constructor", Observable);
	js_set(js, global, "Observable", Observable);
	}

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