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

/* Access to static globals/functions is available since this file is included
   into the same translation unit after their definitions. */

static int saved_stdin_fd = -1;

/* Helper: set STDIN to the read end of a new pipe; return write end */
static int make_pipe_and_set_stdin(void) {
    int fds[2];
    if (pipe(fds) != 0) {
        TEST_FAIL_MESSAGE("pipe() failed");
    }
    /* fds[0] is read end, fds[1] is write end */
    if (dup2(fds[0], STDIN_FILENO) < 0) {
        close(fds[0]);
        close(fds[1]);
        TEST_FAIL_MESSAGE("dup2() failed to set STDIN");
    }
    close(fds[0]); /* read end duplicated to STDIN; close original */
    return fds[1]; /* return write end to caller */
}

void setUp(void) {
    /* Save current STDIN so we can restore it after each test */
    saved_stdin_fd = dup(STDIN_FILENO);
    if (saved_stdin_fd < 0) {
        TEST_FAIL_MESSAGE("dup(STDIN_FILENO) failed in setUp");
    }

    /* Reset EOF flag before each test */
    have_read_eof = false;

    /* Ensure caught_signals is an empty set to keep cleanup() safe if triggered */
    sigemptyset(&caught_signals);
}

void tearDown(void) {
    /* Restore STDIN */
    if (saved_stdin_fd >= 0) {
        if (dup2(saved_stdin_fd, STDIN_FILENO) < 0) {
            TEST_FAIL_MESSAGE("dup2() failed restoring STDIN");
        }
        close(saved_stdin_fd);
        saved_stdin_fd = -1;
    }
}

/* Test: when max_n_bytes == 0, returns 0 and does not touch have_read_eof */
void test_read_input_zero_max_does_not_change_eof(void) {
    have_read_eof = false;
    char buf[4] = {0};
    idx_t n = read_input(buf, 0);
    TEST_ASSERT_EQUAL_INT(0, (int)n);
    TEST_ASSERT_FALSE(have_read_eof);

    have_read_eof = true;
    n = read_input(buf, 0);
    TEST_ASSERT_EQUAL_INT(0, (int)n);
    TEST_ASSERT_TRUE(have_read_eof);
}

/* Test: reads available bytes and does not set EOF */
void test_read_input_reads_available_bytes(void) {
    int w = make_pipe_and_set_stdin();
    const char *msg = "hello world";
    size_t len = strlen(msg);
    ssize_t wr = write(w, msg, len);
    close(w);
    TEST_ASSERT_EQUAL_INT((int)len, (int)wr);

    char buf[64];
    memset(buf, 0, sizeof buf);
    idx_t n = read_input(buf, (idx_t)sizeof buf);
    TEST_ASSERT_EQUAL_INT((int)len, (int)n);
    TEST_ASSERT_EQUAL_MEMORY(msg, buf, len);
    TEST_ASSERT_FALSE(have_read_eof);
}

/* Test: EOF handling sets have_read_eof and returns 0; remains true on subsequent calls */
void test_read_input_sets_eof_when_no_data(void) {
    int w = make_pipe_and_set_stdin();
    /* No write; close writer to produce EOF */
    close(w);

    char buf[8];
    idx_t n1 = read_input(buf, (idx_t)sizeof buf);
    TEST_ASSERT_EQUAL_INT(0, (int)n1);
    TEST_ASSERT_TRUE(have_read_eof);

    /* Subsequent call should also return 0 and keep EOF true */
    idx_t n2 = read_input(buf, (idx_t)sizeof buf);
    TEST_ASSERT_EQUAL_INT(0, (int)n2);
    TEST_ASSERT_TRUE(have_read_eof);
}

/* Test: bounded read respects max_n_bytes less than available data */
void test_read_input_respects_max_bytes_limit(void) {
    int w = make_pipe_and_set_stdin();
    const char *msg = "abcdef";
    ssize_t wr = write(w, msg, 6);
    close(w);
    TEST_ASSERT_EQUAL_INT(6, (int)wr);

    char buf[4] = {0};
    idx_t n = read_input(buf, 3);
    TEST_ASSERT_EQUAL_INT(3, (int)n);
    TEST_ASSERT_EQUAL_MEMORY("abc", buf, 3);
    TEST_ASSERT_FALSE(have_read_eof);
}

/* Test: error path when STDIN is invalid causes process to exit with EXIT_FAILURE.
   Use fork to isolate the exit from the test runner. */
void test_read_input_on_bad_fd_exits_failure(void) {
    fflush(stdout);
    fflush(stderr);
    pid_t pid = fork();
    TEST_ASSERT_TRUE_MESSAGE(pid >= 0, "fork() failed");

    if (pid == 0) {
        /* Child: invalidate STDIN and call read_input */
        sigemptyset(&caught_signals); /* ensure cleanup() uses a known signal set */
        close(STDIN_FILENO);
        char buf[1];
        /* This should print an error and exit(EXIT_FAILURE) via cleanup_fatal */
        (void)read_input(buf, 1);

        /* If we get here, the function did not exit as expected */
        _exit(0);
    } else {
        int status = 0;
        pid_t wp = waitpid(pid, &status, 0);
        TEST_ASSERT_EQUAL_INT_MESSAGE(pid, wp, "waitpid failed");
        TEST_ASSERT_TRUE(WIFEXITED(status));
        TEST_ASSERT_EQUAL_INT(EXIT_FAILURE, WEXITSTATUS(status));
    }
}

int main(void) {
    UNITY_BEGIN();
    RUN_TEST(test_read_input_zero_max_does_not_change_eof);
    RUN_TEST(test_read_input_reads_available_bytes);
    RUN_TEST(test_read_input_sets_eof_when_no_data);
    RUN_TEST(test_read_input_respects_max_bytes_limit);
    RUN_TEST(test_read_input_on_bad_fd_exits_failure);
    return UNITY_END();
}