ex-03: Added solution for rgb converter

exercise-03-rgb/main.c

@@ -0,0 +1,90 @@
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+#ifdef __PROGTEST__
+#define debug(...) ((void)0)
+#else
+#define debug(fmt, ...) fprintf(stdout, "[DEBUG %s:%d %s()] " fmt "\n", __FILE__, __LINE__, __func__, ##__VA_ARGS__)
+#endif
+
+bool is_numeric(const char* str) {
+	if(*str == '\0') return false;
+
+	for(;*str; str++) {
+		if(!isdigit(*str))
+			return false;
+	}
+	return true;
+}
+
+int invalid_input() {
+	printf("Nespravny vstup.\n");
+	return EXIT_FAILURE;
+}
+
+int main() {
+	char* input = NULL;
+	size_t len;
+
+	int rgb[3];
+
+	printf("Zadejte barvu v RGB formatu:\n");
+
+	ssize_t chars_read = getline(&input, &len, stdin);
+
+	if(chars_read == -1) {
+		printf("Failed to read from stdin\n");
+		return EXIT_FAILURE;
+	}
+
+	char* dst = input;
+	for(char * src = input; *src; src++) {
+		if(!isspace(*src)) {
+			*dst++ = *src;
+		}
+	}
+	*dst = '\0';
+
+	int trimmed_len = strlen(input);
+	if(strncmp(input, "rgb(", 4) != 0 || input[trimmed_len - 1] != ')') {
+		debug("%s not in rgb(xxx) format", input);
+		return invalid_input();
+	}
+
+	input[trimmed_len - 1] = '\0';
+	char* slice = input + 4;
+
+	char* token = strtok(slice, ",");
+
+	for(int i = 0; i < 3; i++) {
+		if(token == NULL) {
+			debug("Too few numbers");
+			return invalid_input();
+		}
+		if(!is_numeric(token)) {
+			debug("%s is not a number", token);
+			return invalid_input();
+		}
+
+		int parsed = atoi(token);
+
+		if(parsed < 0 || parsed > 255) {
+			debug("%d out of RGB range", parsed);
+			return invalid_input();
+		}
+
+		rgb[i] = parsed;
+		token = strtok(NULL, ",");
+	}
+
+	if(token != NULL) {
+		debug("Too many numbers");
+		return invalid_input();
+	}
+
+	printf("#%02X%02X%02X\n", rgb[0], rgb[1], rgb[2]);
+	return EXIT_SUCCESS;
+}