#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <time.h>
#include <math.h>

#define ROWS 10
#define COLS 11

const unsigned char TEXT[] = "\
ESXISTXFUNF\
ZEHNZWANZIG\
DREIVIERTEL\
VORGESTNACH\
HALBXELFUNF\
EINSXLEZWEI\
DREIXTXVIER\
SECHSXXACHT\
SIEBENZWOLF\
ZEHNEUNXUHR";

typedef struct {uint8_t start; uint16_t len;} word_t;

#define ES			((word_t) {.start=  0, .len=2})
#define IST			((word_t) {.start=  3, .len=3})
#define FUNF_PRE	((word_t) {.start=  7, .len=4})
#define ZEHN_PRE	((word_t) {.start= 11, .len=4})
#define ZWANZIG		((word_t) {.start= 15, .len=7})
#define VIERTEL		((word_t) {.start= 26, .len=7})
#define VOR			((word_t) {.start= 33, .len=3})
#define NACH		((word_t) {.start= 40, .len=4})
#define HALB		((word_t) {.start= 44, .len=4})
#define ELF			((word_t) {.start= 49, .len=3})
#define FUNF_UHR	((word_t) {.start= 51, .len=4})
#define EINS		((word_t) {.start= 55, .len=4})
#define ZWEI		((word_t) {.start= 62, .len=4})
#define DREI		((word_t) {.start= 66, .len=4})
#define VIER		((word_t) {.start= 73, .len=4})
#define SECHS		((word_t) {.start= 77, .len=5})
#define ACHT		((word_t) {.start= 84, .len=4})
#define SIEBEN		((word_t) {.start= 88, .len=6})
#define ZWOLF		((word_t) {.start= 94, .len=5})
#define ZEHN_UHR	((word_t) {.start= 99, .len=4})
#define NEUN		((word_t) {.start=102, .len=4})
#define UHR			((word_t) {.start=107, .len=3})

word_t HOURS[] = {
	ZWOLF, EINS, ZWEI, DREI, VIER, FUNF_UHR,
	SECHS, SIEBEN, ACHT, NEUN, ZEHN_UHR, ELF
};
word_t PARTS[] = {
	UHR, FUNF_PRE, ZEHN_PRE, VIERTEL,
	ZWANZIG, FUNF_PRE, HALB
};


uint8_t active[ROWS*COLS] = {0};

void set(word_t word) {
	for (unsigned int i = word.start; i < word.start + word.len; i++)
		active[i] = 1;
}

void reset(void) {
	memset(&active, 0, sizeof(active));
	set(ES);
	set(IST);
}


void settime(time_t ts) {

	unsigned int second = ts % 60;

	unsigned int minute = (ts / 60) % 60;
	float fminute = (float) minute + (float) second / 60;
	minute = 5 * (unsigned int) roundf(fminute / 5);

	unsigned int daylight_savings = 1;
	unsigned int hour   = (ts / (60*60) + 1 + daylight_savings) % 12;

	//printf("%02d:%02d\n", hour, minute);

	int before = 0;

	if (minute >= 25) {
		hour = (hour+1) % 12;
		before = 1;
		minute = 60-minute;
		if (minute == 35) {
			minute = 25;
			before = 0;
		}
	}

	//printf("%02d %s %02d\n", minute, before ? "vor" : "nach", hour);

	if (minute == 25)
		before = !before;

	reset();

	if (minute != 0 && minute != 30)
		set(before ? VOR : NACH);

	set(HOURS[hour]);
	set(PARTS[minute/5]);

	if (minute/5 == 5)
		set(HALB); // '5 before half' requires additional set

}


void dump() {

	const char WHITE[] = "\033[1;37m";
	const char  GRAY[] = "\033[0;30m";

	for (int i = 0; i < ROWS*COLS; i++) {

		int col = i % COLS;
		if (col == 0)
			printf("\n ");

		const char* color = active[i] ? WHITE : GRAY;

		printf("  %s%c", color, TEXT[i]);

	}

	#define RESET_COLORS "\033[0m"
	printf(RESET_COLORS "\n");

}

int main() {

	time_t ts = time(NULL);

	while (1) {
		printf("\033c");
		ts = time(NULL);
		settime(ts);
		dump();

		sleep(5);
	};

	return 0;

}