#include "../../unity/unity.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <locale.h>

/* The program includes system.h before including this test, so program_name
   should already be declared. We only reference it here. */

static char *read_all_fd(int fd, size_t *out_len)
{
    size_t cap = 4096;
    size_t len = 0;
    char *buf = (char *)malloc(cap);
    if (!buf) return NULL;

    for (;;) {
        if (len == cap) {
            size_t ncap = cap * 2;
            char *nbuf = (char *)realloc(buf, ncap);
            if (!nbuf) { free(buf); return NULL; }
            buf = nbuf;
            cap = ncap;
        }
        ssize_t n = read(fd, buf + len, cap - len);
        if (n > 0) {
            len += (size_t)n;
            continue;
        } else if (n == 0) {
            break;
        } else {
            if (errno == EINTR) continue;
            free(buf);
            return NULL;
        }
    }
    /* NUL-terminate for convenience */
    if (len == cap) {
        char *nbuf = (char *)realloc(buf, cap + 1);
        if (!nbuf) { free(buf); return NULL; }
        buf = nbuf;
    }
    buf[len] = '\0';
    if (out_len) *out_len = len;
    return buf;
}

/* Helper to run usage(status) in a child, capturing stdout/stderr and exitcode. */
static int capture_usage(int status,
                         char **outp, size_t *outlenp,
                         char **errp, size_t *errlenp,
                         int *exitcodep)
{
    int pout[2];
    int perr[2];
    if (pipe(pout) == -1) return -1;
    if (pipe(perr) == -1) { close(pout[0]); close(pout[1]); return -1; }

    fflush(stdout);
    fflush(stderr);
    pid_t pid = fork();
    if (pid == -1) {
        close(pout[0]); close(pout[1]);
        close(perr[0]); close(perr[1]);
        return -1;
    }

    if (pid == 0) {
        /* Child: redirect stdout/stderr and call usage */
        /* Ensure locale is predictable so gettext returns English strings. */
        setlocale(LC_ALL, "C");
        /* Set program_name to expected value for messages. */
        extern char const *program_name;
        program_name = "factor";

        /* Redirect */
        close(pout[0]);
        close(perr[0]);
        if (dup2(pout[1], STDOUT_FILENO) == -1) _exit(127);
        if (dup2(perr[1], STDERR_FILENO) == -1) _exit(127);
        close(pout[1]);
        close(perr[1]);

        /* Call function under test; it will exit(status). */
        usage(status);
        /* Should not reach here, but ensure child exits. */
        _exit(127);
    }

    /* Parent */
    close(pout[1]);
    close(perr[1]);

    char *out = read_all_fd(pout[0], outlenp);
    char *err = read_all_fd(perr[0], errlenp);
    close(pout[0]);
    close(perr[0]);

    int wstatus = 0;
    if (waitpid(pid, &wstatus, 0) == -1) {
        free(out); free(err);
        return -1;
    }

    int code = 0;
    if (WIFEXITED(wstatus)) code = WEXITSTATUS(wstatus);
    else if (WIFSIGNALED(wstatus)) code = 128 + WTERMSIG(wstatus);
    else code = -1;
    if (exitcodep) *exitcodep = code;

    if (outp) *outp = out; else free(out);
    if (errp) *errp = err; else free(err);

    return 0;
}

void setUp(void) {
    /* nothing */
}

void tearDown(void) {
    /* nothing */
}

static void assert_contains(const char *haystack, const char *needle)
{
    TEST_ASSERT_NOT_NULL_MESSAGE(haystack, "haystack is NULL");
    TEST_ASSERT_NOT_NULL_MESSAGE(needle, "needle is NULL");
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(haystack, needle), "Expected substring not found");
}

void test_usage_success_outputs_usage_and_exits_zero(void)
{
    char *out = NULL, *err = NULL;
    size_t outlen = 0, errlen = 0;
    int exitcode = -1;

    int rc = capture_usage(EXIT_SUCCESS, &out, &outlen, &err, &errlen, &exitcode);
    TEST_ASSERT_EQUAL_INT(0, rc);

    /* Validate exit code */
    TEST_ASSERT_EQUAL_INT(EXIT_SUCCESS, exitcode);

    /* Should write to stdout, not stderr */
    TEST_ASSERT(out != NULL);
    TEST_ASSERT(outlen > 0);
    TEST_ASSERT(err != NULL);
    TEST_ASSERT_EQUAL_UINT64(0, (unsigned long long)errlen);

    /* Check for key substrings */
    assert_contains(out, "Usage: factor ");
    assert_contains(out, "[OPTION]");
    assert_contains(out, "-h, --exponents");

    free(out);
    free(err);
}

void test_usage_nonzero_writes_try_help_to_stderr_and_exits_status(void)
{
    char *out = NULL, *err = NULL;
    size_t outlen = 0, errlen = 0;
    int exitcode = -1;

    int rc = capture_usage(EXIT_FAILURE, &out, &outlen, &err, &errlen, &exitcode);
    TEST_ASSERT_EQUAL_INT(0, rc);

    /* Exit code should match provided status */
    TEST_ASSERT_EQUAL_INT(EXIT_FAILURE, exitcode);

    /* Should write to stderr, not stdout */
    TEST_ASSERT(out != NULL);
    TEST_ASSERT_EQUAL_UINT64(0, (unsigned long long)outlen);
    TEST_ASSERT(err != NULL);
    TEST_ASSERT(errlen > 0);

    /* Check try-help style content contains program name and --help */
    assert_contains(err, "factor");
    assert_contains(err, "--help");

    free(out);
    free(err);
}

void test_usage_propagates_arbitrary_nonzero_exit_code(void)
{
    char *out = NULL, *err = NULL;
    size_t outlen = 0, errlen = 0;
    int exitcode = -1;
    int status = 42; /* within 8-bit exit code range */

    int rc = capture_usage(status, &out, &outlen, &err, &errlen, &exitcode);
    TEST_ASSERT_EQUAL_INT(0, rc);

    /* Exit code should be exactly the provided status */
    TEST_ASSERT_EQUAL_INT(status, exitcode);

    /* Nonzero status: expect message on stderr */
    TEST_ASSERT(errlen > 0);

    free(out);
    free(err);
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_usage_success_outputs_usage_and_exits_zero);
    RUN_TEST(test_usage_nonzero_writes_try_help_to_stderr_and_exits_status);
    RUN_TEST(test_usage_propagates_arbitrary_nonzero_exit_code);
    return UNITY_END();
}