#include "../../unity/unity.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 <stdio.h>

/* Helper to read all data from an fd into a NUL-terminated buffer. */
static char *read_all_fd(int fd, size_t *out_len) {
    size_t cap = 4096;
    size_t len = 0;
    char *buf = (char *)malloc(cap + 1);
    if (!buf) {
        *out_len = 0;
        return NULL;
    }
    for (;;) {
        if (len + 2048 > cap) {
            size_t ncap = cap * 2;
            char *nbuf = (char *)realloc(buf, ncap + 1);
            if (!nbuf) {
                free(buf);
                *out_len = 0;
                return NULL;
            }
            buf = nbuf;
            cap = ncap;
        }
        ssize_t r = read(fd, buf + len, (cap - len));
        if (r < 0) {
            if (errno == EINTR) continue;
            break;
        }
        if (r == 0) break;
        len += (size_t)r;
    }
    buf[len] = '\0';
    *out_len = len;
    return buf;
}

/* Spawn a child that calls usage(status) with program_name set to pname,
   capturing its stdout/stderr and exit status. Returns 0 on success. */
static int run_usage_and_capture(int status, const char *pname,
                                 char **out_buf, size_t *out_len,
                                 char **err_buf, size_t *err_len,
                                 int *exit_code) {
    int out_pipe[2];
    int err_pipe[2];
    if (pipe(out_pipe) != 0) return -1;
    if (pipe(err_pipe) != 0) { close(out_pipe[0]); close(out_pipe[1]); return -1; }

    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 -1;
    }

    if (pid == 0) {
        /* Child: redirect stdout/stderr, set environment and program_name, call usage. */
        /* Ensure predictable messages. */
        setenv("LC_ALL", "C", 1);
        setenv("LANG", "C", 1);

        /* Access program_name declared earlier via included headers in this TU. */
        extern char const *program_name;
        program_name = pname ? pname : "date";

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

        close(out_pipe[0]); close(out_pipe[1]);
        close(err_pipe[0]); close(err_pipe[1]);

        /* Call the target function; it will call exit(). */
        usage(status);

        /* Should not reach here, but just in case. */
        _exit(255);
    }

    /* Parent: close write ends, read outputs, wait for child. */
    close(out_pipe[1]);
    close(err_pipe[1]);

    char *outb = read_all_fd(out_pipe[0], out_len);
    char *errb = read_all_fd(err_pipe[0], err_len);

    close(out_pipe[0]);
    close(err_pipe[0]);

    int wstatus = 0;
    pid_t w = waitpid(pid, &wstatus, 0);
    if (w < 0) {
        if (outb) free(outb);
        if (errb) free(errb);
        return -1;
    }

    int ec = -1;
    if (WIFEXITED(wstatus)) {
        ec = WEXITSTATUS(wstatus);
    } else if (WIFSIGNALED(wstatus)) {
        ec = 128 + WTERMSIG(wstatus);
    }
    *exit_code = ec;
    *out_buf = outb ? outb : strdup("");
    *err_buf = errb ? errb : strdup("");
    return 0;
}

/* Simple substring check. */
static int str_contains(const char *haystack, const char *needle) {
    if (!haystack || !needle) return 0;
    return strstr(haystack, needle) != NULL;
}

void setUp(void) {
    /* Setup code here, or leave empty */
}
void tearDown(void) {
    /* Cleanup code here, or leave empty */
}

/* Tests */

void test_usage_success_outputs_usage_and_exits_success(void) {
    char *out = NULL, *err = NULL;
    size_t out_len = 0, err_len = 0;
    int ec = -1;

    int rc = run_usage_and_capture(0, "date", &out, &out_len, &err, &err_len, &ec);
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to run usage() in child process");
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, ec, "usage(0) should exit with status 0");

    /* stdout should contain the Usage header with program name, stderr should be empty */
    TEST_ASSERT_TRUE_MESSAGE(out_len > 0, "usage(0) should produce help on stdout");
    TEST_ASSERT_TRUE_MESSAGE(str_contains(out, "Usage: date"), "stdout should contain 'Usage: date'");
    TEST_ASSERT_EQUAL_UINT_MESSAGE(0u, err_len, "stderr should be empty for usage(0)");

    free(out);
    free(err);
}

void test_usage_nonzero_emits_try_help_and_exits_with_code(void) {
    char *out = NULL, *err = NULL;
    size_t out_len = 0, err_len = 0;
    int ec = -1;

    int rc = run_usage_and_capture(1, "date", &out, &out_len, &err, &err_len, &ec);
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to run usage() in child process");
    TEST_ASSERT_EQUAL_INT_MESSAGE(1, ec, "usage(1) should exit with status 1");

    /* Should not print full help to stdout; err should include --help hint. */
    TEST_ASSERT_EQUAL_UINT_MESSAGE(0u, out_len, "stdout should be empty for nonzero status");
    TEST_ASSERT_TRUE_MESSAGE(err_len > 0, "stderr should contain try-help message for nonzero status");
    TEST_ASSERT_TRUE_MESSAGE(str_contains(err, "--help"),
                             "stderr should contain '--help' in try-help message");

    free(out);
    free(err);
}

void test_usage_uses_program_name_variable(void) {
    char *out = NULL, *err = NULL;
    size_t out_len = 0, err_len = 0;
    int ec = -1;

    /* Set program name to a custom value and ensure it appears in the Usage line. */
    const char *custom = "mydate";
    int rc = run_usage_and_capture(0, custom, &out, &out_len, &err, &err_len, &ec);
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, rc, "Failed to run usage() in child process");
    TEST_ASSERT_EQUAL_INT_MESSAGE(0, ec, "usage(0) should exit with status 0");

    TEST_ASSERT_TRUE_MESSAGE(out_len > 0, "stdout should contain help text");
    TEST_ASSERT_TRUE_MESSAGE(str_contains(out, "Usage: mydate"),
                             "stdout should contain 'Usage: mydate'");
    TEST_ASSERT_EQUAL_UINT_MESSAGE(0u, err_len, "stderr should be empty for usage(0)");

    free(out);
    free(err);
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_usage_success_outputs_usage_and_exits_success);
    RUN_TEST(test_usage_nonzero_emits_try_help_and_exits_with_code);
    RUN_TEST(test_usage_uses_program_name_variable);
    return UNITY_END();
}