#include "utils.h"

#include <stdarg.h>
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <errno.h>
#include <dirent.h>
#include <fcntl.h>
#include <openssl/evp.h>

char ERROR_BUFFER[ERROR_BUFFER_SIZE];

result_t success(void) {
	return EXIT_SUCCESS;
}

result_t failure(const char* format, ...) {
	va_list args;
	va_start(args, format);

	// Print the error message into the error buffer
	vsnprintf(ERROR_BUFFER, ERROR_BUFFER_SIZE, format, args);

	va_end(args);

	return EXIT_FAILURE;
}

const char* error(void) {
	return ERROR_BUFFER;
}

result_t format(char** _str, const char* format, ...) {
	// Initialize the output parameters
	*_str = NULL;

	// Calculate the length of the formatted string
	va_list args;
	va_start(args, format);

	int length = vsnprintf(NULL, 0, format, args);

	va_end(args);

	if (length < 0)
		return failure("Failed to calculate the length of the formatted string.");

	// Allocate memory for the formatted string
	errno = 0;
	char* str = malloc(length + 1);
	if (str == NULL)
		return failure("Failed to allocate memory for the formatted string (%s).", strerror(errno));

	// Format the string
	va_start(args, format);

	if (vsnprintf(str, length + 1, format, args) < 0)
		return failure("Failed to format the string.");

	va_end(args);

	// Return the formatted string
	*_str = str;
	return success();
}

result_t substring(char** _str, const char* str, size_t start, size_t length) {
	// Initialize the output parameters
	*_str = NULL;

	// Check the start index
	size_t str_length = strlen(str);

	if (start > str_length)
		return failure("The start index is out of range.");
	if (start + length > str_length)
		length = str_length - start;

	// Allocate memory for the substring
	errno = 0;
	char* substr = malloc(length + 1); // +1 for the null terminator
	if (substr == NULL)
		return failure("Failed to allocate memory for the substring (%s).", strerror(errno));

	// Copy the substring
	memcpy(substr, str + start, length);
	substr[length] = '\0';

	// Return the substring
	*_str = substr;
	return success();
}

result_t format_size(char** _str, uint64_t size) {
	// Initialize the output parameters
	*_str = NULL;

	// Format the size
	if (size < 1024ULL)
		return format(_str, "%lluB", size);
	if (size < 1024ULL * 1024)
		return format(_str, "%.2fKiB", size / (1024.0));
	if (size < 1024ULL * 1024 * 1024)
		return format(_str, "%.2fMiB", size / (1024.0 * 1024.0));
	if (size < 1024ULL * 1024 * 1024 * 1024)
		return format(_str, "%.2fGiB", size / (1024.0 * 1024.0 * 1024.0));
	if (size < 1024ULL * 1024 * 1024 * 1024 * 1024)
		return format(_str, "%.2fTiB", size / (1024.0 * 1024.0 * 1024.0 * 1024.0));
	if (size < 1024ULL * 1024 * 1024 * 1024 * 1024 * 1024)
		return format(_str, "%.2fPiB", size / (1024.0 * 1024.0 * 1024.0 * 1024.0 * 1024.0));

	return format(_str, "%.2fEiB", size / (1024.0 * 1024.0 * 1024.0 * 1024.0 * 1024.0 * 1024.0));
}

result_t parse_size(uint64_t* _size, const char* str) {
	// Initialize the output parameters
	*_size = 0;

	// Parse the size
	char* endptr;
	uint64_t size = strtoull(str, &endptr, 10);
	if (endptr == str)
		return failure("Failed to parse the size.");

	// Check the suffix
	if (*endptr == '\0') {
		// No suffix
		*_size = size;
		return success();
	}

	// Parse the suffix
	if (endptr[1] != '\0')
		return failure("Invalid size suffix.");

	switch (endptr[0]) {
	case 'B':
		*_size = size;
		return success();
	case 'K':
		*_size = size * 1024;
		return success();
	case 'M':
		*_size = size * 1024 * 1024;
		return success();
	case 'G':
		*_size = size * 1024 * 1024 * 1024;
		return success();
	case 'T':
		*_size = size * 1024 * 1024 * 1024 * 1024;
		return success();
	case 'P':
		*_size = size * 1024 * 1024 * 1024 * 1024 * 1024;
		return success();
	case 'E':
		*_size = size * 1024 * 1024 * 1024 * 1024 * 1024 * 1024;
		return success();
	default:
		return failure("Invalid size suffix.");
	}
}

result_t execute(int* _exit_code, char** _stdoutbuf, char** _stderrbuf, const char* executable, ...) {
	// Initialize the output parameters
	if (_exit_code != NULL)
		*_exit_code = 0;
	if (_stdoutbuf != NULL)
		*_stdoutbuf = NULL;
	if (_stderrbuf != NULL)
		*_stderrbuf = NULL;

	// Count the number of arguments to pass to the executable
	int argc = 1; // +1 for the executable itself

	va_list args;
	va_start(args, executable);

	while (va_arg(args, const char*) != NULL)
		argc++;

	va_end(args);

	// Allocate memory for the arguments array
	errno = 0;
	char** argv = malloc((argc + 1) * sizeof(char*)); // +1 for the NULL terminator
	if (argv == NULL)
		return failure("Failed to allocate memory for the arguments array (%s).", strerror(errno));

	// Fill the arguments array

	errno = 0;
	argv[0] = strdup(executable);
	if (argv[0] == NULL) {
		free(argv);
		return failure("Failed to duplicate the executable string (%s).", strerror(errno));
	}

	va_start(args, executable);

	for (int i = 1; i < argc; i++) {
		argv[i] = strdup(va_arg(args, const char*));
		if (argv[i] == NULL) {
			for (int j = 0; j < i; j++)
				free(argv[j]);
			free(argv);
			va_end(args);
			return failure("Failed to duplicate the argument string (%s).", strerror(errno));
		}
	}

	va_end(args);

	argv[argc] = NULL;

	// Create pipes for the standard output and standard error of the child process
	int stdout_pipe[2];
	errno = 0;
	if (pipe(stdout_pipe) < 0) {
		for (int i = 0; i < argc; i++)
			free(argv[i]);
		free(argv);
		return failure("Failed to create a pipe for the standard output of the child process (%s).", strerror(errno));
	}

	int stderr_pipe[2];
	errno = 0;
	if (pipe(stderr_pipe) < 0) {
		for (int i = 0; i < argc; i++)
			free(argv[i]);
		free(argv);
		close(stdout_pipe[0]);
		close(stdout_pipe[1]);
		return failure("Failed to create a pipe for the standard error of the child process (%s).", strerror(errno));
	}

	// Fork the child process
	errno = 0;
	pid_t pid = fork();

	if (pid < 0) {
		for (int i = 0; i < argc; i++)
			free(argv[i]);
		free(argv);
		close(stdout_pipe[0]);
		close(stdout_pipe[1]);
		close(stderr_pipe[0]);
		close(stderr_pipe[1]);
		return failure("Failed to fork the child process (%s).", strerror(errno));
	}

	if (pid == 0) {
		// Redirect the standard output and standard error of the child process
		close(stdout_pipe[0]);
		close(stderr_pipe[0]);

		if (dup2(stdout_pipe[1], STDOUT_FILENO) < 0)
			exit(EXIT_FAILURE);

		if (dup2(stderr_pipe[1], STDERR_FILENO) < 0)
			exit(EXIT_FAILURE);

		close(stdout_pipe[1]);
		close(stderr_pipe[1]);

		// Execute the child process
		errno = 0;
		execvp(executable, argv);

		// If the child process reaches this point, it failed to execute
		fprintf(stderr, "Failed to execute the child process (%s).\n", strerror(errno));
		exit(EXIT_FAILURE);
	}

	// Free the arguments array
	for (int i = 0; i < argc; i++)
		free(argv[i]);
	free(argv);

	// Close the write ends of the pipes
	close(stdout_pipe[1]);
	close(stderr_pipe[1]);

	// Wait for the child process to terminate
	int status;
	errno = 0;
	if (waitpid(pid, &status, 0) < 0) {
		close(stdout_pipe[0]);
		close(stderr_pipe[0]);
		return failure("Failed to wait for the child process to terminate (%s).", strerror(errno));
	}

	// Read the standard output and standard error of the child process
	if (_exit_code != NULL)
		*_exit_code = WEXITSTATUS(status);
	if (_stdoutbuf != NULL)
		read_fd(_stdoutbuf, stdout_pipe[0]);
	if (_stderrbuf != NULL)
		read_fd(_stderrbuf, stderr_pipe[0]);

	// Close the read ends of the pipes
	close(stdout_pipe[0]);
	close(stderr_pipe[0]);

	return success();
}

result_t read_fd(char** _str, int fd) {
	// Initialize the output parameters
	*_str = NULL;

	// Read the file descriptor
	size_t length = 0;
	size_t capacity = 4096;

	// Allocate memory for the output string
	errno = 0;
	char* str = malloc(capacity + 1); // +1 for the null terminator
	if (str == NULL)
		return failure("Failed to allocate memory for the output string (%s).", strerror(errno));

	ssize_t count;
	while (1) {
		// Read the file descriptor into the output string
		errno = 0;
		count = read(fd, str + length, capacity - length);
		if (count < 0) {
			free(str);
			return failure("Failed to read the file descriptor %d (%s).", fd, strerror(errno));
		}

		// Update the length of the output string
		length += count;
		if (count == 0)
			break;

		// Reallocate memory for the output string if necessary
		if (length >= capacity) {
			capacity *= 2;

			errno = 0;
			char* new_str = realloc(str, capacity + 1); // +1 for the null terminator
			if (new_str == NULL) {
				free(str);
				return failure("Failed to reallocate memory for the output string (%s).", strerror(errno));
			}
			str = new_str;
		}
	}

	// Null-terminate the string
	str[length] = '\0';

	// Return the output string
	*_str = str;
	return success();
}

result_t write_fd(int fd, const char* str) {
	// Write the string to the file descriptor
	size_t length = strlen(str);
	size_t written = 0;

	while (written < length) {
		// Try to write the entire string at once
		errno = 0;
		ssize_t count = write(fd, str + written, length - written);
		if (count < 0)
			return failure("Failed to write to the file descriptor %d (%s).", fd, strerror(errno));

		written += count;
	}

	return success();
}

result_t read_file(char** _str, const char* path) {
	// Initialize the output parameters
	*_str = NULL;

	// Open the file
	errno = 0;
	int fd = open(path, O_RDONLY);
	if (fd < 0)
		return failure("Failed to open the file '%s' (%s).", path, strerror(errno));

	// Read the file
	result_t result = read_fd(_str, fd);

	// Close the file
	close(fd);

	return result;
}

result_t write_file(const char* path, const char* str) {
	// Open the file
	errno = 0;
	int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (fd < 0)
		return failure("Failed to open the file '%s' (%s).", path, strerror(errno));

	// Write the string to the file
	result_t result = write_fd(fd, str);

	// Close the file
	close(fd);

	return result;
}

result_t copy_file(const char* src, const char* dst) {
	// Open the source file
	errno = 0;
	int src_fd = open(src, O_RDONLY);
	if (src_fd < 0)
		return failure("Failed to open the source file '%s' (%s).", src, strerror(errno));

	// Open the destination file
	errno = 0;
	int dst_fd = open(dst, O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (dst_fd < 0) {
		close(src_fd);
		return failure("Failed to open the destination file '%s' (%s).", dst, strerror(errno));
	}

	// Copy the source file to the destination file
	char buffer[4096];
	ssize_t count;

	while (1) {
		// Read from the source file
		errno = 0;
		count = read(src_fd, buffer, sizeof(buffer));
		if (count < 0) {
			close(src_fd);
			close(dst_fd);
			return failure("Failed to read from the source file '%s' (%s).", src, strerror(errno));
		}

		// If the end of the file is reached, stop copying
		if (count == 0)
			break;

		// Write to the destination file
		while (count > 0) {
			errno = 0;
			ssize_t written = write(dst_fd, buffer, count);
			if (written < 0) {
				close(src_fd);
				close(dst_fd);
				return failure("Failed to write to the destination file '%s' (%s).", dst, strerror(errno));
			}

			count -= written;
		}
	}

	// Close the source file
	close(src_fd);

	// Close the destination file
	close(dst_fd);

	return success();
}

result_t list_files(char*** _files, const char* path, bool (*filter)(const char*)) {
	// Initialize the output parameters
	*_files = NULL;

	// Allocate memory for the files array
	size_t length = 0;
	size_t capacity = 64;

	errno = 0;
	char** files = malloc(capacity * sizeof(char*));
	if (files == NULL)
		return failure("Failed to allocate memory for the files array (%s).", strerror(errno));

	// Open the directory
	errno = 0;
	DIR* dir = opendir(path);
	if (dir == NULL) {
		free(files);
		return failure("Failed to open the directory '%s' (%s).", path, strerror(errno));
	}

	// Read the directory
	struct dirent* entry;
	while (1) {
		// Read the next entry
		errno = 0;
		entry = readdir(dir);
		if (entry == NULL) {
			if (errno != 0) {
				for (size_t i = 0; i < length; i++)
					free(files[i]);
				free(files);
				closedir(dir);
				return failure("Failed to read the directory '%s' (%s).", path, strerror(errno));
			}
			break;
		}

		// Filter the entry
		if (filter != NULL && !filter(entry->d_name))
			continue;

		// Add the entry to the files array
		files[length] = strdup(entry->d_name);
		if (files[length] == NULL) {
			for (size_t i = 0; i < length; i++)
				free(files[i]);
			free(files);
			closedir(dir);
			return failure("Failed to allocate memory for the file name.");
		}

		length++;

		// Reallocate memory for the files array if necessary
		if (length > capacity) {
			capacity *= 2;

			errno = 0;
			char** new_files = realloc(files, capacity * sizeof(char*));
			if (new_files == NULL) {
				for (size_t i = 0; i < length; i++)
					free(files[i]);
				free(files);
				closedir(dir);
				return failure("Failed to reallocate memory for the files array (%s).", strerror(errno));
			}
			files = new_files;
		}
	}

	// Close the directory
	closedir(dir);

	// Null-terminate the files array
	files[length] = NULL;

	// Return the files array
	*_files = files;
	return success();
}

result_t md5sum(char** _md5, const char* path) {
	// Initialize the output parameters
	*_md5 = NULL;

	// Open the file
	errno = 0;
	int fd = open(path, O_RDONLY);
	if (fd < 0)
		return failure("Failed to open the file '%s' (%s).", path, strerror(errno));

	// Initialize the MD5 context
	EVP_MD_CTX* mdctx = EVP_MD_CTX_new();
	if (mdctx == NULL) {
		close(fd);
		return failure("Failed to initialize the MD5 context.");
	}

	if (EVP_DigestInit_ex(mdctx, EVP_md5(), NULL) != 1) {
		EVP_MD_CTX_free(mdctx);
		close(fd);
		return failure("Failed to initialize the MD5 context.");
	}

	// Read the file and update the MD5 context
	char buffer[4096];
	ssize_t count;

	while (1) {
		// Read from the file
		errno = 0;
		count = read(fd, buffer, sizeof(buffer));
		if (count < 0) {
			EVP_MD_CTX_free(mdctx);
			close(fd);
			return failure("Failed to read from the file '%s' (%s).", path, strerror(errno));
		}

		// If the end of the file is reached, stop updating the MD5 context
		if (count == 0)
			break;

		// Update the MD5 context
		if (EVP_DigestUpdate(mdctx, buffer, count) != 1) {
			EVP_MD_CTX_free(mdctx);
			close(fd);
			return failure("Failed to update the MD5 context.");
		}
	}

	// Finalize the MD5 context
	unsigned char md_value[EVP_MAX_MD_SIZE];
	unsigned int md_len;

	if (EVP_DigestFinal_ex(mdctx, md_value, &md_len) != 1) {
		EVP_MD_CTX_free(mdctx);
		close(fd);
		return failure("Failed to finalize the MD5 context.");
	}

	EVP_MD_CTX_free(mdctx);

	// Close the file
	close(fd);

	// Format the MD5 checksum
	errno = 0;
	char* md5 = malloc(2 * md_len + 1); // +1 for the null terminator
	if (md5 == NULL)
		return failure("Failed to allocate memory for the MD5 checksum (%s).", strerror(errno));

	for (unsigned int i = 0; i < md_len; i++)
		if (snprintf(md5 + 2 * i, 3, "%02x", md_value[i]) != 2) {
			free(md5);
			return failure("Failed to format the MD5 checksum.");
		}
	md5[2 * md_len] = '\0';

	// Return the MD5 checksum
	*_md5 = md5;
	return success();
}