#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <assert.h>
#include <math.h>
#include <unistd.h>
#include <termios.h>

#include <glib.h>
#include <gio/gio.h>
#include <gio/gunixinputstream.h>
#include <gdk-pixbuf/gdk-pixbuf.h>
#include <gdk-pixbuf/gdk-pixdata.h>

static FILE* tty;
static int tty_fd;
static struct termios tty_tio;

static int char_width = 8;
static int char_height = 15;
static int window_columns = 25;
static int window_rows = 80;
static int window_width = 8 * 80;
static int window_height = 15 * 25;

static bool init_terminal(int fd);
static void close_terminal();

static bool init_terminal(int fd)
{
	const char *name_of_tty = ttyname(fd);
	if (!name_of_tty) {
		return FALSE;
	}

	tty = fopen(name_of_tty, "r+");
	if (tty == NULL) {
		g_printerr("Cannot open terminal %s", name_of_tty);
		return FALSE;
	}
	tty_fd = fileno(tty);

	tcgetattr(tty_fd, &tty_tio);
	struct termios tio = tty_tio;

	tio.c_lflag &= ~(ICANON | ECHO);
	tio.c_cc[VMIN] = 4;
	tio.c_cc[VTIME] = 1;
	tcsetattr(tty_fd, TCSADRAIN, &tio);

	// Try to get window width and height in pixels using a xterm command
	fprintf(tty, "\033[14;t");
	fflush(tty);

	if (fscanf(tty, "\033[4;%d;%dt", &window_height, &window_width) != 2) {
		close_terminal();
		return FALSE;
	}

	// Also use a xterm command to get the window size in chars,
	// (could also use termios...)
	fprintf(tty, "\033[18;t");
	fflush(tty);

	if (fscanf(tty, "\033[8;%d;%dt", &window_rows, &window_columns) != 2) {
		close_terminal();
		return FALSE;
	}

	// Now calculate char height & width based on the above data
	char_width = window_width / window_columns;
	char_height = window_height / window_rows;

	return TRUE;
}

static void close_terminal()
{
	tcsetattr(tty_fd, TCSADRAIN, &tty_tio);
	fclose(tty);
}

static gboolean view_pixbuf(GdkPixbuf *pixbuf)
{
	const gint max_width = window_width;
	const gint max_height = window_height - char_height;
	gint width = gdk_pixbuf_get_width(pixbuf);
	gint height = gdk_pixbuf_get_height(pixbuf);
	GdkPixbuf *scaled;

	if (width > max_width || height > max_height) {
		if (width > height) {
			height = floor((height / (double)width) * max_width);
			width = max_width;
		} else {
			width = floor((width / (double)height) * max_height);
			height = max_height;
		}

		scaled = gdk_pixbuf_scale_simple(pixbuf, width, height, GDK_INTERP_BILINEAR);
	} else {
		scaled = GDK_PIXBUF(g_object_ref(pixbuf));
	}

	GdkPixdata pixdata;
	gpointer pixdata_p = gdk_pixdata_from_pixbuf(&pixdata, scaled, TRUE);

	if (pixdata_p == NULL) {
		g_object_unref(scaled);
		return FALSE;
	}

	guint size;
	guint8 *data = gdk_pixdata_serialize(&pixdata, &size);
	gchar *str = g_base64_encode(data, size);

	fprintf(tty, "\033]v;%s\007", str);

	int rows = ceil(height / (double)char_height);
	while (rows > 0) {
		fprintf(tty, "\n");
		rows--;
	}

	fflush(tty);
	
	g_free(str);
	g_free(data);
	g_free(pixdata.pixel_data);
	g_object_unref(scaled);

	return TRUE;
}

int main(int argc, char * argv[])
{
	GError *error = NULL;

	if (!isatty(STDOUT_FILENO)) {
		g_printerr("Refusing to display image on not-terminal\n");
		return EXIT_FAILURE;
	}

	if (!init_terminal((STDOUT_FILENO))) {
		g_printerr("Refusing to display image on non-graphical terminal\n");
		return EXIT_FAILURE;
	}

	if (argc > 1) {
		int i;
		for (i = 1; i < argc; i++) {
			GdkPixbuf *pixbuf = gdk_pixbuf_new_from_file(argv[i], &error);
			if (pixbuf == NULL) {
				g_printerr("Failed to open image '%s': %s\n", argv[i], error->message);
				close_terminal();
				return EXIT_FAILURE;
			}
			if (!view_pixbuf(pixbuf)) {
				g_printerr("Failed to view image '%s'\n", argv[i]);
				close_terminal();
				return EXIT_FAILURE;
			}
			g_object_unref(pixbuf);
		}
	} else {
		GInputStream *input = g_unix_input_stream_new(STDIN_FILENO, FALSE);
		GdkPixbuf *pixbuf = gdk_pixbuf_new_from_stream(input, NULL, &error);
		if (pixbuf == NULL) {
			g_printerr("Failed to open stdin image: %s\n", error->message);
			close_terminal();
			return EXIT_FAILURE;
		}
		if (!view_pixbuf(pixbuf)) {
			g_printerr("Failed to view stdin image\n");
			close_terminal();
			return EXIT_FAILURE;
		}
		g_object_unref(pixbuf);
	}

	close_terminal();
	return EXIT_SUCCESS;
}