#include <wctype.h>
#include <wchar.h>
#include <stdbool.h>
#include <string.h>
#include <locale.h>

typedef struct
{
	// True if user provided valid arguments, false on error
	bool valid_arguments;
	// User asked --help and it must be printed
	bool help_requested;
	// Number of input filenames found in arguments, if 0 stdin will be used
	size_t input_filename_count;
	// Name of the file where output will be printed, if NULL stdout will be used
	char* output_filename;
} arguments_t;

void init_arguments(arguments_t* arguments);
arguments_t parse_arguments(int argc, char* argv[]);
int print_help();
int reverse_speech(FILE* input_file, FILE* output_file);
int reverse_speech_in_file(const char* input_filename, FILE* output_file);

int main(int argc, char* argv[])
{
	setlocale(LC_ALL, "");

	// Fields in structures may be word-aligned, and it may requiere more bits
//	printf("sizeof(arguments_t): %zu\n", sizeof(arguments_t));

	// The entire local structure is overwritten by the struct returned by parse_arguments
	arguments_t arguments = parse_arguments(argc, argv);

	// If argument --help was provided, ignore the rest
	if ( arguments.help_requested )
		return print_help();

	// If the provided arguments are wrong, stop
	if ( ! arguments.valid_arguments )
		return 1;

	// Assume stdout as output file
	FILE* output_file = stdout;
	if ( arguments.output_filename )
	{
		// A filename was provided with "-o file" option, open it as output file
		output_file = fopen(arguments.output_filename, "w");
		if ( output_file == NULL )
			return fprintf(stderr, "reverse_speech: error: could not open %s\n", arguments.output_filename);
	}

	// If not input files were provided, use stdin
	int result = 0;
	if ( arguments.input_filename_count == 0 )
		result = reverse_speech(stdin, output_file);
	else
	{
		// One or more input files were provided
		// Traverse arguments again processing these input files
		for ( int index = 1; index < argc; ++index )
		{
			// Ignore options (they begin with '-')
			if ( argv[index][0] == '-' )
			{
				// Ignore output filename if it was provided
				if ( argv[index][1] == 'o' )
					++index;
			}
			else
			{
				// An input filename was found, process it
				// We do not stop processing other files if one fails
				result += reverse_speech_in_file(argv[index], output_file);
			}
		}
	}

	// If an output filename was used, close it
	if ( arguments.output_filename )
		fclose(output_file);

	return result;
}

int print_help()
{
	const char* const help =
	    "reverse_speech v1.0 [2016-Sep-23] jeissonh@gmail.com\n"
	    "Reverts speech in the concatenation of input text FILES\n"
	    "\n"
	    "  Usage: reverse_speech [FILES] [-o OUTPUT_FILE]\n"
	    "\n"
	    "Rvereesd sepceh dsiottroins lteetrs psotioins wtiihn wrods, but\n"
	    "keeipng frist and lsat lteetr. Hmuan barnis are albe to rseotre\n"
	    "mseasegs form tehse dsiottroins.\n"
	;
	printf("%s", help);
	return 0;
}

void init_arguments(arguments_t* arguments)
{
	(*arguments).help_requested = false;
	(*arguments).input_filename_count = 0;
	arguments->output_filename = NULL;
}

arguments_t parse_arguments(int argc, char* argv[])
{
	arguments_t result;
	init_arguments( &result );

	for ( int index = 1; index < argc; ++index )
	{
		if ( strcmp(argv[index], "--help") == 0 )
			result.help_requested = true;
		else if ( *argv[index] == '-' )
		{
			if ( strcmp(argv[index], "-o") == 0 )
			{
				if ( index + 1 < argc )
				{
					result.output_filename = argv[index + 1];
					++index;
				}
				else
				{
					fprintf(stderr, "reverse_speech: error: missing output filename\n");

				}
			}
		}
		else
			++result.input_filename_count;
	}
	return result;
}

int reverse_speech_in_file(const char* input_filename, FILE* output_file)
{
	FILE* input_file = fopen(input_filename, "r");
	if ( input_file == NULL )
	{
		fprintf(stderr, "reverse_speech: error: could not open %s\n", input_filename);
		return 2;
	}

	int result = reverse_speech(input_file, output_file);

	fclose(input_file);
	return result;
}

int reverse_speech(FILE* input_file, FILE* output_file)
{
	wchar_t previous = 0, current = 0, next = 0;
	if ( fwscanf(input_file, L"%lc", &current) == WEOF )
		return 0;

	while ( fwscanf(input_file, L"%lc", &next) != WEOF )
	{
		if ( iswalpha(previous) && iswalpha(current) && iswalpha(next) )
		{
			wint_t next2 = fgetwc(input_file);
			if ( iswalpha(next2) )
			{
				fwprintf(output_file, L"%lc", next);
				next = next2;
			}
			else if ( next2 != WEOF )
			{
				fwprintf(output_file, L"%lc", current);
				previous = current;
				current = next;
				next = next2;
			}
		}

		fwprintf(output_file, L"%lc", current);
		previous = current;
		current = next;
	}

	fwprintf(output_file, L"%lc", current);
	return 0;
}