#include <stdbool.h>
#include <stdint.h>

#include <app_event_manager.h>

#define MODULE display_test_module
#include <caf/events/module_state_event.h>
#include <caf/events/power_event.h>

#include <zephyr/device.h>
#include <zephyr/drivers/display.h>
#include <zephyr/drivers/led.h>
#include <zephyr/logging/log.h>
#include <zephyr/sys/util.h>

LOG_MODULE_REGISTER(MODULE, LOG_LEVEL_INF);

#define DISPLAY_TEST_LINE_PIXELS 320U
#define COLOR_RED 0xF800U
#define COLOR_GREEN 0x07E0U
#define COLOR_BLUE 0x001FU
#define COLOR_YELLOW 0xFFE0U

BUILD_ASSERT(DT_HAS_CHOSEN(zephyr_display), "Missing zephyr,display chosen node");
BUILD_ASSERT(DT_NODE_HAS_STATUS(DT_ALIAS(backlight), okay),
	     "Missing backlight alias");

static const struct device *const display_dev =
	DEVICE_DT_GET(DT_CHOSEN(zephyr_display));
static const struct device *const backlight_dev =
	DEVICE_DT_GET(DT_PARENT(DT_ALIAS(backlight)));
static const uint32_t backlight_idx = DT_NODE_CHILD_IDX(DT_ALIAS(backlight));
static uint16_t line_buf[DISPLAY_TEST_LINE_PIXELS];
static bool initialized;
static bool running;

static void fill_test_line(size_t width)
{
	const uint16_t colors[] = {
		COLOR_RED,
		COLOR_GREEN,
		COLOR_BLUE,
		COLOR_YELLOW,
	};
	size_t segment = MAX(width / ARRAY_SIZE(colors), 1U);

	for (size_t x = 0; x < width; x++) {
		size_t color_idx = MIN(x / segment, ARRAY_SIZE(colors) - 1U);

		line_buf[x] = colors[color_idx];
	}
}

static int draw_test_pattern(void)
{
	struct display_capabilities caps;
	struct display_buffer_descriptor desc;
	int err;

	display_get_capabilities(display_dev, &caps);
	LOG_INF("Display caps: %ux%u fmt:%u orient:%u info:0x%x",
		caps.x_resolution, caps.y_resolution,
		caps.current_pixel_format, caps.current_orientation,
		caps.screen_info);

	if (caps.x_resolution > ARRAY_SIZE(line_buf)) {
		LOG_ERR("Display width %u exceeds line buffer", caps.x_resolution);
		return -ENOMEM;
	}

	if (caps.current_pixel_format != PIXEL_FORMAT_RGB_565) {
		LOG_WRN("Unexpected pixel format %u", caps.current_pixel_format);
	}

	fill_test_line(caps.x_resolution);

	desc.width = caps.x_resolution;
	desc.height = 1U;
	desc.pitch = caps.x_resolution;
	desc.buf_size = caps.x_resolution * sizeof(line_buf[0]);

	for (uint16_t y = 0; y < caps.y_resolution; y++) {
		err = display_write(display_dev, 0U, y, &desc, line_buf);
		if (err) {
			LOG_ERR("display_write failed at line %u (%d)", y, err);
			return err;
		}
	}

	err = display_blanking_off(display_dev);
	if (err) {
		LOG_ERR("display_blanking_off failed (%d)", err);
		return err;
	}

	LOG_INF("Display test pattern rendered (%ux%u)",
		caps.x_resolution, caps.y_resolution);

	return 0;
}

static int module_init(void)
{
	int err;

	LOG_INF("Display test init on %s", display_dev->name);

	if (!device_is_ready(display_dev)) {
		LOG_ERR("Display device %s not ready", display_dev->name);
		return -ENODEV;
	}

	if (!device_is_ready(backlight_dev)) {
		LOG_ERR("Backlight device %s not ready", backlight_dev->name);
		return -ENODEV;
	}

	err = led_off(backlight_dev, backlight_idx);
	if (err) {
		LOG_ERR("Backlight off failed (%d)", err);
		return err;
	}

	LOG_INF("Backlight device %s channel %u ready",
		backlight_dev->name, backlight_idx);

	return 0;
}

static int module_start(void)
{
	int err;

	if (running) {
		return 0;
	}

	LOG_INF("Display test start");

	err = led_on(backlight_dev, backlight_idx);
	if (err) {
		LOG_ERR("Backlight enable failed (%d)", err);
		return err;
	}

	LOG_INF("Backlight enabled");
	k_sleep(K_MSEC(50));

	err = draw_test_pattern();
	if (err) {
		(void)led_off(backlight_dev, backlight_idx);
		return err;
	}

	running = true;

	return 0;
}

static void module_pause(void)
{
	if (!running) {
		return;
	}

	LOG_INF("Display test pause");
	(void)display_blanking_on(display_dev);
	(void)led_off(backlight_dev, backlight_idx);
	running = false;
}

static bool app_event_handler(const struct app_event_header *aeh)
{
	if (is_module_state_event(aeh)) {
		const struct module_state_event *event = cast_module_state_event(aeh);
		int err;

		if (check_state(event, MODULE_ID(main), MODULE_STATE_READY)) {
			LOG_INF("main READY received");
			if (!initialized) {
				err = module_init();
				if (err) {
					module_set_state(MODULE_STATE_ERROR);
					return false;
				}

				initialized = true;
			}

			err = module_start();
			if (err) {
				module_set_state(MODULE_STATE_ERROR);
			} else {
				module_set_state(MODULE_STATE_READY);
			}
		}

		return false;
	}

	if (is_power_down_event(aeh)) {
		if (initialized) {
			module_pause();
			module_set_state(MODULE_STATE_STANDBY);
		}

		return false;
	}

	if (is_wake_up_event(aeh)) {
		if (initialized) {
			int err = module_start();

			if (err) {
				module_set_state(MODULE_STATE_ERROR);
			} else {
				module_set_state(MODULE_STATE_READY);
			}
		}

		return false;
	}

	return false;
}

APP_EVENT_LISTENER(MODULE, app_event_handler);
APP_EVENT_SUBSCRIBE(MODULE, module_state_event);
APP_EVENT_SUBSCRIBE_EARLY(MODULE, power_down_event);
APP_EVENT_SUBSCRIBE(MODULE, wake_up_event);