#include <signal.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <unistd.h>

#define SHOW_ALTERNATIVE_SCREEN "\033[?1049h"
#define SHOW_NORMAL_SCREEN      "\033[?1049l"
#define HIDE_CURSOR             "\033[?25l"
#define SHOW_CURSOR             "\033[?25h"
#define CLEAR_SCREEN            "\033[2J"

#define MOVE_CURSOR_HOME        "\033[H"
#define MOVE_CURSOR_UP          "\x1b[1A"
#define MOVE_CURSOR_DOWN        "\x1b[1B"
#define MOVE_CURSOR_RIGHT       "\x1b[1C"
#define MOVE_CURSOR_LEFT        "\x1b[1D"

#define MOVE_CURSOR_UP_X          "\x1b[%dA"
#define MOVE_CURSOR_DOWN_X        "\x1b[%dB"
#define MOVE_CURSOR_RIGHT_X       "\x1b[%dC"
#define MOVE_CURSOR_LEFT_X        "\x1b[%dD"

// man console_codes

// Directions
//   A - Up
//   B - Down
//   C - Right
//   D - Left

typedef struct {
	int line;
	int column;
	int number_of_display_lines;
	int number_of_display_columns;
	bool resized;
	bool update_display;
	bool should_exit;
	struct termios original_termios;
} State;

static State state = {0};

void sigwinch_handler(int signal)
{
	fprintf(stderr, "INFO: received signal \"%s\"\n", strsignal(signal));

	state.resized = true;
}

bool get_terminal_size()
{
	struct winsize ws;
	if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws)) {
		return false;
	}

	state.number_of_display_columns = ws.ws_col;
	state.number_of_display_lines = ws.ws_row;

	return true;
}

void enable_raw_mode(void)
{
	struct termios t = state.original_termios;

    if (tcgetattr(STDIN_FILENO, &state.original_termios) == -1) {
        perror("tcgetattr");
        exit(1);
    }

    t = state.original_termios;
    t.c_lflag &= ~(ECHO | ICANON | ISIG);  // turn off echo, canonical mode, signals
    t.c_iflag &= ~(IXON | ICRNL);          // disable Ctrl-S/Q and CR->NL
    t.c_oflag &= ~(OPOST);                 // disable all output processing
    t.c_cc[VMIN] = 1;                      // read() returns after 1 byte
    t.c_cc[VTIME] = 0;                     // no timeout

    if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &t) == -1) {
        perror("tcsetattr");
        exit(1);
    }
}

int draw_ui(void)
{
	get_terminal_size();

	printf("%s%s", CLEAR_SCREEN, MOVE_CURSOR_HOME);

	for (int i = 0; i < state.number_of_display_lines; i++) {
		printf(" ~ \n");
		printf(MOVE_CURSOR_LEFT_X, state.number_of_display_columns);
	}
}

int main(void)
{
	// TODO: switch to sigaction
	signal(SIGWINCH, sigwinch_handler);
	signal(SIGINT, SIG_IGN);

	enable_raw_mode();

	printf(SHOW_ALTERNATIVE_SCREEN);
	printf(HIDE_CURSOR);

	printf(MOVE_CURSOR_HOME);
	fflush(stdout);

	get_terminal_size();

	state.update_display = true;

	char c;
	while (true) {
		if (state.update_display) {
			draw_ui();

			state.update_display = false;
		}

        ssize_t n = read(STDIN_FILENO, &c, 1);
        if (n == -1) continue;

        if (c == 'q') break;

		switch (c) {
		case 'h':
			printf("%s%s", MOVE_CURSOR_LEFT, MOVE_CURSOR_LEFT);
			state.update_display = true;
			break;
		case 'j':
			printf("%s%s", MOVE_CURSOR_DOWN, MOVE_CURSOR_LEFT);
			state.update_display = true;
			break;
		case 'k':
			printf("%s%s", MOVE_CURSOR_UP, MOVE_CURSOR_LEFT);
			state.update_display = true;
			break;
		case 'l':
			state.update_display = true;
			break;
		}

		printf(CLEAR_SCREEN);

		printf("\033[43m \033[0m");

		fflush(stdout);
	}

    tcsetattr(STDIN_FILENO, TCSAFLUSH, &state.original_termios);
	printf(SHOW_NORMAL_SCREEN);
	printf(SHOW_CURSOR);
	fflush(stdout);

	return 0;
}