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

/* Helper: create a temp file with given data, return fd and path. */
static int create_temp_file_with_data(const void *data, size_t len, char *path_buf, size_t path_buf_sz)
{
    /* Create a template in current directory to avoid platform-specific temp dirs */
    const char *tmpl = "./test_copyfd_src_XXXXXX";
    if (path_buf_sz < strlen(tmpl) + 1)
        return -1;
    strcpy(path_buf, tmpl);
    int fd = mkstemp(path_buf);
    if (fd < 0)
        return -1;

    if (len > 0) {
        ssize_t wr = write(fd, data, len);
        if (wr < 0 || (size_t)wr != len) {
            int saved = errno;
            close(fd);
            unlink(path_buf);
            errno = saved;
            return -1;
        }
    }
    /* Rewind for reading */
    if (lseek(fd, 0, SEEK_SET) < 0) {
        int saved = errno;
        close(fd);
        unlink(path_buf);
        errno = saved;
        return -1;
    }
    return fd;
}

/* Helper: capture stdout to a temp file, run copy_fd, restore stdout, and validate. */
static char *run_and_check_copy_fd(int src_fd,
                                   uintmax_t n_bytes,
                                   enum Copy_fd_status expected_status,
                                   const void *expected_output,
                                   size_t expected_output_len)
{
    /* Flush stdout before redirect */
    fflush(stdout);

    /* Save current stdout */
    int saved_stdout = dup(STDOUT_FILENO);
    if (saved_stdout < 0) {
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "dup(STDOUT) failed: errno=%d", errno);
        return msg;
    }

    /* Create output capture file */
    char out_tmpl[] = "./test_copyfd_out_XXXXXX";
    int out_fd = mkstemp(out_tmpl);
    if (out_fd < 0) {
        close(saved_stdout);
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "mkstemp for stdout capture failed: errno=%d", errno);
        return msg;
    }

    /* Redirect stdout to capture file */
    if (dup2(out_fd, STDOUT_FILENO) < 0) {
        int saved = errno;
        close(out_fd);
        close(saved_stdout);
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "dup2 to redirect stdout failed: errno=%d", saved);
        return msg;
    }
    close(out_fd); /* Now captured by fd 1 */

    /* Call the function under test (no Unity asserts while redirected!) */
    enum Copy_fd_status st = copy_fd(src_fd, n_bytes);

    /* Ensure all data is flushed to the capture file */
    fflush(stdout);

    /* Restore stdout */
    if (dup2(saved_stdout, STDOUT_FILENO) < 0) {
        int saved = errno;
        close(saved_stdout);
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "dup2 to restore stdout failed: errno=%d", saved);
        return msg;
    }
    close(saved_stdout);

    /* Read back captured output */
    int cap_fd = open(out_tmpl, O_RDONLY);
    if (cap_fd < 0) {
        int saved = errno;
        unlink(out_tmpl);
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "open captured file failed: errno=%d", saved);
        return msg;
    }

    struct stat stbuf;
    if (fstat(cap_fd, &stbuf) < 0) {
        int saved = errno;
        close(cap_fd);
        unlink(out_tmpl);
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "fstat captured file failed: errno=%d", saved);
        return msg;
    }

    size_t cap_sz = (size_t)stbuf.st_size;
    char *cap = NULL;
    if (cap_sz > 0) {
        cap = (char*)malloc(cap_sz);
        if (!cap) {
            close(cap_fd);
            unlink(out_tmpl);
            char *msg = (char*)malloc(256);
            snprintf(msg, 256, "malloc(%zu) failed for capture buffer", cap_sz);
            return msg;
        }

        size_t off = 0;
        while (off < cap_sz) {
            ssize_t r = read(cap_fd, cap + off, cap_sz - off);
            if (r < 0) {
                int saved = errno;
                free(cap);
                close(cap_fd);
                unlink(out_tmpl);
                char *msg = (char*)malloc(256);
                snprintf(msg, 256, "read captured file failed: errno=%d", saved);
                return msg;
            }
            if (r == 0) break;
            off += (size_t)r;
        }
        /* cap_sz is from st_size; off should equal cap_sz. */
    }
    close(cap_fd);
    unlink(out_tmpl);

    /* Validate status */
    if (st != expected_status) {
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "Status mismatch: got %d, expected %d", (int)st, (int)expected_status);
        free(cap);
        return msg;
    }

    /* Validate output length */
    if (cap_sz != expected_output_len) {
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "Output length mismatch: got %zu, expected %zu", cap_sz, expected_output_len);
        free(cap);
        return msg;
    }

    /* Validate output content if any */
    if (cap_sz > 0 && memcmp(cap, expected_output, cap_sz) != 0) {
        /* Find first mismatch for easier debugging */
        size_t idx = 0;
        while (idx < cap_sz && ((unsigned char*)cap)[idx] == ((const unsigned char*)expected_output)[idx])
            idx++;
        char *msg = (char*)malloc(256);
        snprintf(msg, 256, "Output content mismatch at byte %zu", idx);
        free(cap);
        return msg;
    }

    free(cap);
    return NULL; /* success */
}

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

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

static void fill_pattern(char *buf, size_t len)
{
    for (size_t i = 0; i < len; i++)
        buf[i] = (char)('A' + (i % 26));
}

/* Tests */

void test_copy_fd_zero_bytes_no_output(void)
{
    const char data[] = "ignored";
    char path[64];
    int fd = create_temp_file_with_data(data, sizeof(data) - 1, path, sizeof(path));
    TEST_ASSERT_MESSAGE(fd >= 0, "Failed to create temp source file");

    /* Request 0 bytes */
    char *err = run_and_check_copy_fd(fd, 0, COPY_FD_OK, "", 0);
    close(fd);
    unlink(path);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

void test_copy_fd_partial_copy(void)
{
    const char data[] = "abcdef";
    const size_t req = 3;
    char path[64];
    int fd = create_temp_file_with_data(data, sizeof(data) - 1, path, sizeof(path));
    TEST_ASSERT_MESSAGE(fd >= 0, "Failed to create temp source file");

    char *err = run_and_check_copy_fd(fd, req, COPY_FD_OK, data, req);
    close(fd);
    unlink(path);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

void test_copy_fd_exact_copy(void)
{
    const char data[] = "Hello, world!";
    const size_t len = sizeof(data) - 1;
    char path[64];
    int fd = create_temp_file_with_data(data, len, path, sizeof(path));
    TEST_ASSERT_MESSAGE(fd >= 0, "Failed to create temp source file");

    char *err = run_and_check_copy_fd(fd, len, COPY_FD_OK, data, len);
    close(fd);
    unlink(path);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

void test_copy_fd_oversized_request_unexpected_eof(void)
{
    const char data[] = "abcd";
    const size_t len = sizeof(data) - 1;
    const uintmax_t req = 10; /* larger than len */
    char path[64];
    int fd = create_temp_file_with_data(data, len, path, sizeof(path));
    TEST_ASSERT_MESSAGE(fd >= 0, "Failed to create temp source file");

    /* Expect all available bytes written, status UNEXPECTED_EOF */
    char *err = run_and_check_copy_fd(fd, req, COPY_FD_UNEXPECTED_EOF, data, len);
    close(fd);
    unlink(path);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

void test_copy_fd_read_error_returns_status(void)
{
    /* Create a file, then open it write-only to induce read error */
    const char data[] = "some data";
    char path[64];
    int tmpfd = create_temp_file_with_data(data, sizeof(data) - 1, path, sizeof(path));
    TEST_ASSERT_MESSAGE(tmpfd >= 0, "Failed to create temp source file");
    close(tmpfd);

    int wfd = open(path, O_WRONLY);
    TEST_ASSERT_MESSAGE(wfd >= 0, "Failed to open file write-only to induce read error");

    /* Expect READ_ERROR and no output */
    char *err = run_and_check_copy_fd(wfd, 5, COPY_FD_READ_ERROR, "", 0);
    close(wfd);
    unlink(path);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

void test_copy_fd_large_transfer_multiple_buffers(void)
{
    size_t len = (size_t)BUFSIZ * 3 + 123; /* span multiple reads */
    char *data = (char*)malloc(len);
    TEST_ASSERT_NOT_NULL(data);
    fill_pattern(data, len);

    char path[64];
    int fd = create_temp_file_with_data(data, len, path, sizeof(path));
    TEST_ASSERT_MESSAGE(fd >= 0, "Failed to create temp source file");

    char *err = run_and_check_copy_fd(fd, len, COPY_FD_OK, data, len);
    close(fd);
    unlink(path);
    free(data);

    TEST_ASSERT_NULL_MESSAGE(err, err ? err : "");
    free(err);
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_copy_fd_zero_bytes_no_output);
    RUN_TEST(test_copy_fd_partial_copy);
    RUN_TEST(test_copy_fd_exact_copy);
    RUN_TEST(test_copy_fd_oversized_request_unexpected_eof);
    RUN_TEST(test_copy_fd_read_error_returns_status);
    RUN_TEST(test_copy_fd_large_transfer_multiple_buffers);
    return UNITY_END();
}