/** @file io.c
 * @brief Enchanced base IO functions.
 */

#include <stdlib.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <poll.h>

#include "faux/faux.h"

/** @brief Writes data to file.
 *
 * The system write() can be interrupted by signal. This function will retry to
 * write in a case of interrupted call.
 *
 * @param [in] fd File descriptor.
 * @param [in] buf Buffer to write.
 * @param [in] n Number of bytes to write.
 * @return Number of bytes written or < 0 on error.
 */
ssize_t faux_write(int fd, const void *buf, size_t n)
{
	ssize_t bytes_written = 0;

	assert(fd != -1);
	assert(buf);
	if ((-1 == fd) || !buf)
		return -1;
	if (0 == n)
		return 0;

	do {
		bytes_written = write(fd, buf, n);
	} while ((bytes_written < 0) && (EINTR == errno));

	return bytes_written;
}


/** @brief Writes data block to file.
 *
 * The system write() can be interrupted by signal or can write less bytes
 * than specified. This function will continue to write data until all data
 * will be written or error occured. Function support even non-blocking file
 * descriptors. It uses poll() for such fd.
 *
 * @param [in] fd File descriptor.
 * @param [in] buf Buffer to write.
 * @param [in] n Number of bytes to write.
 * @return Number of bytes written.
 * < n then insufficient space or error (but some data was already written).
 * < 0 - error.
 */
ssize_t faux_write_block(int fd, const void *buf, size_t n)
{
	size_t total_written = 0;
	size_t left = n;
	const void *data = buf;
	struct pollfd fds = {};

	fds.fd = fd;
	fds.events = POLLOUT;
	do {
		int prc = 0;
		fds.revents = 0; // Reset revents before poll()
		prc = poll(&fds, 1, -1);
		if (prc < 0) {
			if (EINTR == errno)
				continue;
			if (total_written != 0)
				break;
			return -1;
		}
		if (fds.revents & POLLOUT) {
			ssize_t bytes_written = 0;
			bytes_written = faux_write(fd, data, left);
			if (bytes_written < 0) { // Error
				if (total_written != 0)
					break;
				return -1;
			}
			if (0 == bytes_written) // Insufficient space
				break;
			data += bytes_written;
			left = left - bytes_written;
			total_written += bytes_written;
		}
		if (fds.revents & (POLLHUP | POLLERR | POLLNVAL)) {
			if (total_written != 0)
				break;
			return -1;
		}
	} while (left > 0);

	return total_written;
}


/** @brief Reads data from file.
 *
 * The system read() can be interrupted by signal. This function will retry to
 * read if it was interrupted by signal.
 *
 * @param [in] fd File descriptor.
 * @param [in] buf Buffer to write.
 * @param [in] n Number of bytes to write.
 * @return Number of bytes readed or < 0 on error.
 * 0 bytes indicates EOF
 */
ssize_t faux_read(int fd, void *buf, size_t n)
{
	ssize_t bytes_readed = 0;

	assert(fd != -1);
	assert(buf);
	if ((-1 == fd) || !buf)
		return -1;
	if (0 == n)
		return 0;

	do {
		bytes_readed = read(fd, buf, n);
	} while ((bytes_readed < 0) && (EINTR == errno));

	return bytes_readed;
}


/** @brief Reads data block from file.
 *
 * The system read() can be interrupted by signal or can read less bytes
 * than specified. This function will continue to read data until all data
 * will be readed or error occured. Function works even for non-blocking
 * file descriptors.
 *
 * @param [in] fd File descriptor.
 * @param [in] buf Buffer to write.
 * @param [in] n Number of bytes to write.
 * @return Number of bytes readed.
 * < n EOF or error (but some data was already readed).
 * < 0 Error.
 */
size_t faux_read_block(int fd, void *buf, size_t n)
{
	size_t total_readed = 0;
	size_t left = n;
	void *data = buf;
	struct pollfd fds = {};

	fds.fd = fd;
	fds.events = POLLIN;
	do {
		int prc = 0;
		fds.revents = 0; // Reset revents before poll()
		prc = poll(&fds, 1, -1);
		if (prc < 0) {
			if (EINTR == errno)
				continue;
			if (total_readed != 0)
				break;
			return -1;
		}
		if (fds.revents & POLLIN) {
			ssize_t bytes_readed = 0;
			bytes_readed = read(fd, data, left);
			if (bytes_readed < 0) {
				if (total_readed != 0)
					break;
				return -1;
			}
			if (0 == bytes_readed) // EOF
				break;
			data += bytes_readed;
			left = left - bytes_readed;
			total_readed += bytes_readed;
		}
		if (fds.revents & (POLLHUP | POLLERR | POLLNVAL)) {
			if (total_readed != 0)
				break;
			return -1;
		}
	} while (left > 0);

	return total_readed;
}


/** @brief Reads whole file to buffer.
 *
 * Allocates buffer and read whole file to it.
 *
 * @param [in] path File name.
 * @param [out] buf Output buffer with file content.
 * @warn Buffer must be freed with faux_free().
 * @return Number of bytes readed.
 * = n Empty file. The data param will be set to NULL.
 * < 0 Error.
 */
ssize_t faux_read_whole_file(const char *path, void **data)
{
	ssize_t expected_size = 0;
	struct stat statbuf = {};
	char *buf = NULL;
	size_t buf_full_size = 0;
	ssize_t bytes_readed = 0;
	size_t total_readed = 0;
	int fd = -1;

	assert(path);
	assert(data);
	if (!path || !data)
		return -1;

	if (stat(path, &statbuf) < 0)
		return -1;

	// Regular file?
	if (!S_ISREG(statbuf.st_mode))
		return -1;

	// Get expected file size
	expected_size = faux_filesize(path);
	if (expected_size < 0)
		return -1;
	// Add some extra space to buffer. Because actual filesize can
	// differ while reading. Try to read more data than expected.
	expected_size++;

	// Open file
	fd = open(path, O_RDONLY);
	if (fd < 0)
		return -1;

	// Allocate buffer
	buf_full_size = expected_size;
	buf = faux_zmalloc(buf_full_size);
	if (!buf) {
		close(fd);
		return -1;
	}

	while ((bytes_readed = faux_read(fd, buf + total_readed,
		buf_full_size - total_readed)) > 0) {
		total_readed += bytes_readed;
		// Enlarge buffer if needed
		if (total_readed == buf_full_size) {
			char *p = NULL;
			buf_full_size = buf_full_size * 2;
			p = realloc(buf, buf_full_size);
			if (!p) {
				free(buf);
				close(fd);
				return -1;
			}
			buf = p;
		}
	}
	close(fd);

	// Something went wrong
	if (bytes_readed < 0) {
		free(buf);
		return -1;
	}

	// Empty file
	if (0 == total_readed) {
		free(buf);
		*data = NULL;
		return 0;
	}

	// Shrink buffer to actual data size
	if (total_readed < buf_full_size) {
		char *p = NULL;
		p = realloc(buf, total_readed);
		if (!p) {
			free(buf);
			return -1;
		}
		buf = p;
	}
	*data = buf;

	return total_readed;
}