#include "stdio.h"

#define MAX_REP 255

void rle_compress(char *infile, char *outfile)
{
	FILE *inf = fopen(infile, "rb");
	FILE *outf = fopen(outfile, "wb");
	char prevChar = 0, currChar = 0;
	bool first = true, rep = false;
	size_t rd = 0;
	unsigned char repCount = 0;
	while (!feof(inf))
	{
		rd = fread(&currChar, sizeof(char), 1, inf);
		if (rd == 0)
		{
			if (rep)
				fwrite(&repCount, sizeof(repCount), 1, outf);
			break;
		}
		if (!rep)
			fwrite(&currChar, sizeof(char), 1, outf);
		if (first) {
			first = false;
		}
		else
		{
			if (prevChar == currChar)
			{
				if (!rep) {
					rep = true;
					repCount = 2;
				} else {
					repCount++;
					if (repCount == MAX_REP)
					{
						fwrite(&repCount, sizeof(unsigned char), 1, outf);
						rep = false;
						repCount = 0;
						first = true;
					}
				}
			} else {
				if (rep)
				{
					fwrite(&repCount, sizeof(unsigned char), 1, outf);
					rep = false;
					repCount = 0;
					fwrite(&currChar, sizeof(char), 1, outf);
				}
			}
		}
		prevChar = currChar;
	}

	fclose(outf);
	fclose(inf);
}

void rle_decompress(char *infile, char *outfile)
{
	FILE *inf = fopen(infile, "rb");
	FILE *outf = fopen(outfile, "wb");

	unsigned char prevChar = 0, currChar = 0;
	bool rep = false, passOne = false;
	size_t rd;
	while (!feof(inf))
	{
		rd = fread(&currChar, sizeof(currChar), 1, inf);
		if (rd == 0)
			break;
		if (rep)
		{
			for (int i = 0; i < currChar - 2; i++)
				fwrite(&prevChar, sizeof(prevChar), 1, outf);
			rep = false;
			passOne = true;
		}
		else
		{
			fwrite(&currChar, sizeof(currChar), 1, outf);
			if (passOne)
				passOne = false;
			else if (currChar == prevChar)
				rep = true;
		}
		prevChar = currChar;
	}
	fclose(outf);
	fclose(inf);
}

int main(int argc, char *argv[])
{
	if (argc != 2)
	{
		printf("RLE Compressor by Gorodilova Love\nUsage:\n");
		printf("\trle.exe <c|d>\nwhere\n");
		printf("\t<c|d>    -  c - for compression, d - for decompression\n");
		return 0;
	}
	if ((argv[1][0] == 'c') || (argv[1][0] == 'C'))
		rle_compress("input.txt", "output.txt");
	else if ((argv[1][0] == 'd') || (argv[1][0] == 'D'))
		rle_decompress("input.txt", "output.txt");
	return 0;
}