#define _GNU_SOURCE
#define _DARWIN_C_SOURCE
#include "yasl/loop.h"

#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

static void sleep_ms(int ms)
{
    struct timespec ts = {.tv_sec = ms / 1000, .tv_nsec = (long)(ms % 1000) * 1000000L};
    nanosleep(&ts, NULL);
}

/* Fail instead of hanging when a wake never arrives. */
static void on_alarm(int signo)
{
    (void)signo;
    static const char msg[] = "loop test timed out\n";
    ssize_t ignored = write(STDERR_FILENO, msg, sizeof(msg) - 1);
    (void)ignored;
    _exit(1);
}

struct post_log {
    struct yasl_loop *loop;
    char order[8];
    int count;
};

static void post_a(void *ud);

static void post_c(void *ud)
{
    struct post_log *log = ud;
    log->order[log->count++] = 'c';
}

static void post_a(void *ud)
{
    struct post_log *log = ud;
    log->order[log->count++] = 'a';
    assert(yasl_loop_post(log->loop, post_c, log));
}

static void post_b(void *ud)
{
    struct post_log *log = ud;
    log->order[log->count++] = 'b';
}

static void test_post_order(void)
{
    struct yasl_loop *l = yasl_loop_create();
    assert(l);
    assert(!yasl_loop_post(NULL, post_b, NULL));
    assert(!yasl_loop_post(l, NULL, NULL));

    struct post_log log = {.loop = l};
    assert(yasl_loop_post(l, post_a, &log));
    assert(yasl_loop_post(l, post_b, &log));
    assert(yasl_loop_step(l, 0) >= 1);
    /* A post made while posts run waits for a later step. */
    assert(log.count == 2 && memcmp(log.order, "ab", 2) == 0);
    assert(yasl_loop_step(l, 0) >= 1);
    assert(log.count == 3 && log.order[2] == 'c');

    /* Destroy drops posts that never ran. */
    assert(yasl_loop_post(l, post_b, &log));
    yasl_loop_destroy(l);
    assert(log.count == 3);
}

struct thread_ctx {
    struct yasl_loop *loop;
    bool kick;
    int signo;
    _Atomic bool ran;
};

static void mark_ran(void *ud)
{
    struct thread_ctx *ctx = ud;
    ctx->ran = true;
}

static void *wake_thread(void *ud)
{
    struct thread_ctx *ctx = ud;
    sleep_ms(30);
    if (ctx->signo)
        kill(getpid(), ctx->signo);
    else if (ctx->kick)
        yasl_loop_kick(ctx->loop);
    else
        assert(yasl_loop_post(ctx->loop, mark_ran, ctx));
    return NULL;
}

static void test_cross_thread(void)
{
    struct yasl_loop *l = yasl_loop_create();
    assert(l);

    struct thread_ctx post = {.loop = l};
    pthread_t t;
    assert(pthread_create(&t, NULL, wake_thread, &post) == 0);
    while (!post.ran)
        assert(yasl_loop_step(l, -1) >= 0);
    pthread_join(t, NULL);

    /* A kick ends an indefinite wait without running anything. */
    struct thread_ctx kick = {.loop = l, .kick = true};
    assert(pthread_create(&t, NULL, wake_thread, &kick) == 0);
    assert(yasl_loop_step(l, -1) >= 1);
    pthread_join(t, NULL);

    yasl_loop_destroy(l);
}

struct signal_log {
    struct yasl_loop *loop;
    int seen[NSIG];
    int total;
    bool unwatch;
};

static void on_signal(void *ud, int signo)
{
    struct signal_log *log = ud;
    assert(signo > 0 && signo < NSIG);
    log->seen[signo]++;
    log->total++;
    if (log->unwatch)
        yasl_loop_unwatch_signals(log->loop);
}

static volatile sig_atomic_t previous_handler_hits;

static void previous_handler(int signo)
{
    (void)signo;
    previous_handler_hits++;
}

static void step_until(struct yasl_loop *l, const int *counter, int want)
{
    while (*counter < want)
        assert(yasl_loop_step(l, -1) >= 0);
}

static void test_signals(void)
{
    struct sigaction prev = {.sa_handler = previous_handler};
    sigemptyset(&prev.sa_mask);
    assert(sigaction(SIGUSR2, &prev, NULL) == 0);

    struct yasl_loop *l = yasl_loop_create();
    struct yasl_loop *other = yasl_loop_create();
    assert(l && other);
    struct signal_log log = {.loop = l};

    const int bad[] = {SIGKILL};
    errno = 0;
    assert(!yasl_loop_watch_signals(l, bad, 1, on_signal, &log) && errno == EINVAL);
    const int sigs[] = {SIGUSR1, SIGUSR2, SIGCHLD};
    errno = 0;
    assert(!yasl_loop_watch_signals(l, sigs, 0, on_signal, &log) && errno == EINVAL);
    errno = 0;
    assert(!yasl_loop_watch_signals(l, sigs, 3, NULL, &log) && errno == EINVAL);
    assert(yasl_loop_watch_signals(l, sigs, 3, on_signal, &log));

    /* One signal belongs to one loop at a time. */
    errno = 0;
    assert(!yasl_loop_watch_signals(other, sigs, 1, on_signal, &log) && errno == EBUSY);

    /* Deliveries before the callback runs coalesce per signal. */
    raise(SIGUSR1);
    raise(SIGUSR1);
    raise(SIGUSR2);
    assert(yasl_loop_step(l, 0) >= 1);
    assert(log.seen[SIGUSR1] == 1 && log.seen[SIGUSR2] == 1);
    assert(previous_handler_hits == 0);

    /* A signal sent from another thread wakes an indefinite wait. */
    struct thread_ctx ctx = {.loop = l, .signo = SIGUSR1};
    pthread_t t;
    assert(pthread_create(&t, NULL, wake_thread, &ctx) == 0);
    step_until(l, &log.seen[SIGUSR1], 2);
    pthread_join(t, NULL);

    /* SIGCHLD arrives on the loop thread when a child exits. */
    pid_t child = fork();
    assert(child >= 0);
    if (child == 0) _exit(0);
    step_until(l, &log.seen[SIGCHLD], 1);
    int status;
    assert(waitpid(child, &status, 0) == child);

    /* Replacing the watch restores the signals it drops. */
    const int only_usr1[] = {SIGUSR1};
    assert(yasl_loop_watch_signals(l, only_usr1, 1, on_signal, &log));
    raise(SIGUSR2);
    assert(previous_handler_hits == 1);
    assert(yasl_loop_watch_signals(other, (const int[]){SIGUSR2}, 1, on_signal, &log));
    yasl_loop_unwatch_signals(other);
    assert(previous_handler_hits == 1);
    raise(SIGUSR2);
    assert(previous_handler_hits == 2);

    /* A callback may unwatch; the previous default action comes back. */
    log.unwatch = true;
    raise(SIGUSR1);
    step_until(l, &log.seen[SIGUSR1], 3);
    struct sigaction now;
    assert(sigaction(SIGUSR1, NULL, &now) == 0);
    assert(now.sa_handler == SIG_DFL);
    yasl_loop_unwatch_signals(l);

    /* Destroy unwatches. */
    log.unwatch = false;
    assert(yasl_loop_watch_signals(l, only_usr1, 1, on_signal, &log));
    yasl_loop_destroy(l);
    assert(sigaction(SIGUSR1, NULL, &now) == 0);
    assert(now.sa_handler == SIG_DFL);
    yasl_loop_destroy(other);

    struct sigaction dfl = {.sa_handler = SIG_DFL};
    sigemptyset(&dfl.sa_mask);
    sigaction(SIGUSR2, &dfl, NULL);
}

int main(void)
{
    signal(SIGALRM, on_alarm);
    alarm(10);
    test_post_order();
    test_cross_thread();
    test_signals();
    printf("Loop tests passed.\n");
    return 0;
}