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

/* Helper to read all data from a fd into a malloc'd buffer.
   Returns buffer (NUL-terminated) and sets *len. On error, returns NULL. */
static char* tfu_read_all(int fd, size_t *len_out) {
    size_t cap = 4096;
    size_t len = 0;
    char *buf = (char*)malloc(cap + 1);
    if (!buf) return NULL;

    for (;;) {
        if (len == cap) {
            size_t new_cap = cap * 2;
            char *nb = (char*)realloc(buf, new_cap + 1);
            if (!nb) {
                free(buf);
                return NULL;
            }
            buf = nb;
            cap = new_cap;
        }
        ssize_t r = read(fd, buf + len, cap - len);
        if (r > 0) {
            len += (size_t)r;
            continue;
        } else if (r == 0) {
            break;
        } else {
            if (errno == EINTR) continue;
            free(buf);
            return NULL;
        }
    }
    buf[len] = '\0';
    if (len_out) *len_out = len;
    return buf;
}

typedef struct {
    char *out;
    size_t out_len;
    char *err;
    size_t err_len;
    int exit_code;   /* valid if term_sig == 0 */
    int term_sig;    /* nonzero if terminated by signal */
} tfu_capture_result;

/* Run usage(status) in a child, capturing stdout and stderr.
   Returns true on success, false on setup/fork errors. */
static bool tfu_run_usage_capture(int status, tfu_capture_result *res) {
    int out_pipe[2] = {-1, -1};
    int err_pipe[2] = {-1, -1};
    if (pipe(out_pipe) != 0) return false;
    if (pipe(err_pipe) != 0) {
        close(out_pipe[0]); close(out_pipe[1]);
        return false;
    }

    fflush(stdout);
    fflush(stderr);
    pid_t pid = fork();
    if (pid < 0) {
        close(out_pipe[0]); close(out_pipe[1]);
        close(err_pipe[0]); close(err_pipe[1]);
        return false;
    }

    if (pid == 0) {
        /* Child: redirect stdout/stderr and call usage. */
        /* Ensure C locale (but gettext defaults to C without setlocale). */
        setenv("LC_ALL", "C", 1);
        setlocale(LC_ALL, "");

        /* Redirect stdout and stderr to pipes. */
        if (dup2(out_pipe[1], STDOUT_FILENO) < 0) _exit(127);
        if (dup2(err_pipe[1], STDERR_FILENO) < 0) _exit(127);

        /* Close unused fds. */
        close(out_pipe[0]); close(out_pipe[1]);
        close(err_pipe[0]); close(err_pipe[1]);

        /* Call target (will exit). */
        usage(status);

        /* Should not reach here; ensure exit anyway. */
        _exit(127);
    }

    /* Parent: close write ends; read from read ends. */
    close(out_pipe[1]);
    close(err_pipe[1]);

    tfu_capture_result tmp = {0};
    tmp.out = tfu_read_all(out_pipe[0], &tmp.out_len);
    tmp.err = tfu_read_all(err_pipe[0], &tmp.err_len);
    close(out_pipe[0]);
    close(err_pipe[0]);

    int wstatus = 0;
    pid_t w = -1;
    do {
        w = waitpid(pid, &wstatus, 0);
    } while (w < 0 && errno == EINTR);

    if (w < 0) {
        free(tmp.out);
        free(tmp.err);
        return false;
    }

    if (WIFEXITED(wstatus)) {
        tmp.exit_code = WEXITSTATUS(wstatus);
        tmp.term_sig = 0;
    } else if (WIFSIGNALED(wstatus)) {
        tmp.term_sig = WTERMSIG(wstatus);
        tmp.exit_code = -1;
    } else {
        tmp.term_sig = -1;
        tmp.exit_code = -1;
    }

    *res = tmp;
    return true;
}

void setUp(void) {
    /* No global setup required. */
}

void tearDown(void) {
    /* No global teardown required. */
}

/* Helper to free capture result buffers. */
static void tfu_free_capture(tfu_capture_result *res) {
    if (!res) return;
    free(res->out);
    free(res->err);
    res->out = NULL;
    res->err = NULL;
    res->out_len = res->err_len = 0;
}

/* Test that usage(EXIT_SUCCESS) prints full help to stdout, nothing to stderr, and exits 0. */
void test_usage_success_prints_help_and_exits_zero(void) {
    tfu_capture_result r = {0};
    TEST_ASSERT_TRUE_MESSAGE(tfu_run_usage_capture(EXIT_SUCCESS, &r), "Failed to run usage in child");
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, r.term_sig, "Child terminated by signal");
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, r.exit_code, "Exit code mismatch for success usage");

    /* stdout should be non-empty and contain key option tokens and header */
    TEST_ASSERT_NOT_NULL(r.out);
    TEST_ASSERT_TRUE_MESSAGE(r.out_len > 0, "Expected stdout to be non-empty");
    TEST_ASSERT_NOT_NULL(r.err);
    TEST_ASSERT_EQUAL_UINT_MESSAGE(0u, r.err_len, "Expected stderr to be empty on success");

    /* Check for stable substrings in help output (C locale). */
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(r.out, "Usage:"), "Missing 'Usage:' line");
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(r.out, "-d, --delimiters"), "Missing -d, --delimiters");
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(r.out, "-s, --serial"), "Missing -s, --serial");
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(r.out, "-z, --zero-terminated"), "Missing -z, --zero-terminated");

    tfu_free_capture(&r);
}

/* Test that usage with nonzero status emits try-help to stderr and exits with that status. */
void test_usage_failure_emits_try_help_and_exits_with_status(void) {
    const int code = 42; /* arbitrary nonzero in 0..255 */
    tfu_capture_result r = {0};
    TEST_ASSERT_TRUE_MESSAGE(tfu_run_usage_capture(code, &r), "Failed to run usage in child");
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, r.term_sig, "Child terminated by signal");
    TEST_ASSERT_EQUAL_INT_MESSAGE(code, r.exit_code, "Exit code mismatch for failure usage");

    /* stderr should be non-empty and contain '--help' */
    TEST_ASSERT_NOT_NULL(r.err);
    TEST_ASSERT_TRUE_MESSAGE(r.err_len > 0, "Expected stderr to be non-empty on failure usage");
    TEST_ASSERT_NOT_NULL_MESSAGE(strstr(r.err, "--help"), "Expected '--help' hint in stderr");

    /* stdout should be empty */
    TEST_ASSERT_NOT_NULL(r.out);
    TEST_ASSERT_EQUAL_UINT_MESSAGE(0u, r.out_len, "Expected stdout to be empty on failure usage");

    tfu_free_capture(&r);
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_usage_success_prints_help_and_exits_zero);
    RUN_TEST(test_usage_failure_emits_try_help_and_exits_with_status);
    return UNITY_END();
}