#pragma once

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

// The serial commands (src/nano/README.md) that bring the Nano from the image `shown` to
// `wanted`: over the rectangle that changed, one B command that switches dots off and one
// that switches dots on, then D (or D1 when instant). Only the changed dots are in them,
// so the Nano only touches those and the line stays short (scrolling text: a small
// window). Without `shown` (nullptr): F0 and the whole image as one B command.
//
// Bitmaps in drawBitmap format: rows of (width + 7) / 8 bytes, the most significant bit
// is the leftmost dot. `out(const char *)` gets the text in pieces. Returns the number of
// characters sent, 0 when nothing changed (then nothing is sent, not even D).
// Header only, so it is used by the ESP32 driver and tested with the Nano's parser.
template <typename Out>
size_t frameCommands(const uint8_t *wanted, const uint8_t *shown, uint8_t width, uint8_t height, bool instant,
					 Out out)
{
	const int row_bytes = (width + 7) / 8;
	auto dot = [row_bytes](const uint8_t *bitmap, int x, int y) {
		return (bitmap[y * row_bytes + x / 8] >> (7 - (x & 7))) & 1;
	};
	size_t sent = 0;
	auto emit = [&](const char *text) {
		out(text);
		sent += strlen(text);
	};

	int x0 = width, x1 = -1, y0 = height, y1 = -1;
	if (shown)
	{
		for (int y = 0; y < height; y++)
			for (int x = 0; x < width; x++)
				if (dot(wanted, x, y) != dot(shown, x, y))
				{
					x0 = x < x0 ? x : x0;
					x1 = x > x1 ? x : x1;
					y0 = y < y0 ? y : y0;
					y1 = y > y1 ? y : y1;
				}
		if (x1 < 0)
			return 0;
	}
	else
	{
		x0 = 0;
		y0 = 0;
		x1 = width - 1;
		y1 = height - 1;
		emit("F0\n");
	}

	// B needs a width that is a multiple of 4; dots past the right edge are never set
	int w = (x1 - x0 + 4) / 4 * 4, h = y1 - y0 + 1;
	// Whether a dot is in the command for this color
	auto in = [&](int x, int y, int color) {
		if (x >= width || dot(wanted, x, y) != color)
			return false;
		return !shown || dot(shown, x, y) != color;
	};
	for (int color = shown ? 0 : 1; color <= 1; color++)
	{
		bool any = false;
		for (int y = y0; y <= y1 && !any; y++)
			for (int x = x0; x <= x1 && !any; x++)
				any = in(x, y, color);
		if (!any)
			continue;

		char text[24];
		snprintf(text, sizeof(text), "B%02x%02x%02x%02x%d", x0, y0, w, h, color);
		emit(text);
		for (int y = y0; y <= y1; y++)
		{
			char row[64 + 1]; // up to 256 dots
			int n = 0;
			for (int i = 0; i < w / 4; i++)
			{
				int nibble = 0;
				for (int k = 0; k < 4; k++)
					if (in(x0 + i * 4 + k, y, color))
						nibble |= 8 >> k;
				row[n++] = "0123456789ABCDEF"[nibble];
			}
			row[n] = '\0';
			emit(row);
		}
		emit("\n");
	}
	emit(instant ? "D1\n" : "D\n");
	return sent;
}