#include "threads.h"

#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

struct Promise {
    int done;
    int refs;
    struct Environment* env;
    Object object;
    pthread_t thread;
};

Object clonePromise(Object src)
{
    src.promise->refs += 1;
    return src;
}

int isDone(struct Promise* promise)
{
    return promise->done;
}

int isPromise(Object src)
{
    return src.type == TYPE_PROMISE;
}

void cleanPromise(struct Promise* promise)
{
    promise->refs -= 1;
    if (promise->refs == 0) {
        deleteEnv(promise->env);
        cleanObject(&promise->object);
        free(promise);
    }
}

Object await(Object* params, int length, struct Environment* env)
{
    checkTypes(await);
    struct Promise* promise = params[0].promise;
    if (!promise->done) { // TODO: Does `done` need a mutex or other lock?
        pthread_join(promise->thread, NULL);
    }
    return cloneObject(promise->object);
}

void* doAsync(void* args)
{
    struct Promise* promise = args;

    Object cloned = promise->object;
    Object first_eval = eval(&cloned, promise->env);
    Object e = funcyEval(&first_eval, NULL, 0, promise->env);
    promise->object = e;
    promise->done = 1;

    cleanObject(&cloned);
    cleanPromise(promise);
    deleteEnv(promise->env);

    return NULL;
}

Object async(Object* params, int length, struct Environment* env)
{
    Object promise = newObject(TYPE_PROMISE);
    promise.promise = malloc(sizeof(struct Promise));
    *promise.promise = (struct Promise) {
        .refs = 2, // Held by doAsync and the returned object
        .done = 0,
        .env = env,
        .object = cloneObject(params[0]),
    };
    env->refs += 1;

    pthread_create(&promise.promise->thread, NULL, doAsync, promise.promise);
    return promise;
}