/*
 * Copyright 2023 Google LLC
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#define DT_DRV_COMPAT gpio_qdec

#include <stdint.h>
#include <stdlib.h>

#include <zephyr/device.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/input/input.h>
#include <zephyr/kernel.h>

#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(input_gpio_qdec, CONFIG_INPUT_LOG_LEVEL);

#define GPIO_QDEC_GPIO_NUM 2

struct gpio_qdec_config {
	struct gpio_dt_spec gpio[GPIO_QDEC_GPIO_NUM];
	uint32_t sample_time_us;
	uint32_t idle_timeout_ms;
	uint16_t axis;
	uint8_t steps_per_period;
};

struct gpio_qdec_data {
	const struct device *dev;
	struct k_timer sample_timer;
	uint8_t prev_step;
	int32_t acc;
	struct k_work event_work;
	struct k_work_delayable idle_work;
	struct gpio_callback gpio_cb;
};

/* Positive transitions */
#define QDEC_LL_LH 0x01
#define QDEC_LH_HH 0x13
#define QDEC_HH_HL 0x32
#define QDEC_HL_LL 0x20

/* Negative transitions */
#define QDEC_LL_HL 0x02
#define QDEC_LH_LL 0x10
#define QDEC_HH_LH 0x31
#define QDEC_HL_HH 0x23

static uint8_t gpio_qdec_get_step(const struct device *dev)
{
	const struct gpio_qdec_config *cfg = dev->config;
	uint8_t step = 0x00;

	if (gpio_pin_get_dt(&cfg->gpio[0])) {
		step |= 0x01;
	}
	if (gpio_pin_get_dt(&cfg->gpio[1])) {
		step |= 0x02;
	}

	return step;
}

static void gpio_qdec_sample_timer_timeout(struct k_timer *timer)
{
	const struct device *dev = k_timer_user_data_get(timer);
	const struct gpio_qdec_config *cfg = dev->config;
	struct gpio_qdec_data *data = dev->data;
	int8_t delta = 0;
	unsigned int key;
	uint8_t step;

	step = gpio_qdec_get_step(dev);

	if (data->prev_step == step) {
		return;
	}

	switch ((data->prev_step << 4U) | step) {
	case QDEC_LL_LH:
	case QDEC_LH_HH:
	case QDEC_HH_HL:
	case QDEC_HL_LL:
		delta = 1;
		break;
	case QDEC_LL_HL:
	case QDEC_LH_LL:
	case QDEC_HH_LH:
	case QDEC_HL_HH:
		delta = -1;
		break;
	default:
		LOG_WRN("%s: lost steps", dev->name);
	}

	data->prev_step = step;

	key = irq_lock();
	data->acc += delta;
	irq_unlock(key);

	if (abs(data->acc) >= cfg->steps_per_period) {
		k_work_submit(&data->event_work);
	}

	k_work_reschedule(&data->idle_work, K_MSEC(cfg->idle_timeout_ms));
}

static void gpio_qdec_event_worker(struct k_work *work)
{
	struct gpio_qdec_data *data = CONTAINER_OF(
			work, struct gpio_qdec_data, event_work);
	const struct device *dev = data->dev;
	const struct gpio_qdec_config *cfg = dev->config;
	unsigned int key;
	int32_t acc;

	key = irq_lock();
	acc = data->acc / cfg->steps_per_period;
	data->acc -= acc * cfg->steps_per_period;
	irq_unlock(key);

	if (acc != 0) {
		input_report_rel(data->dev, cfg->axis, acc, true, K_FOREVER);
	}
}

static void gpio_qdec_irq_setup(const struct device *dev, bool enable)
{
	const struct gpio_qdec_config *cfg = dev->config;
	unsigned int flags = enable ? GPIO_INT_EDGE_BOTH : GPIO_INT_DISABLE;
	int ret;

	for (int i = 0; i < GPIO_QDEC_GPIO_NUM; i++) {
		const struct gpio_dt_spec *gpio = &cfg->gpio[i];

		ret = gpio_pin_interrupt_configure_dt(gpio, flags);
		if (ret != 0) {
			LOG_ERR("Pin %d interrupt configuration failed: %d", i, ret);
			return;
		}
	}
}

static void gpio_qdec_idle_worker(struct k_work *work)
{
	struct gpio_qdec_data *data = CONTAINER_OF(
			work, struct gpio_qdec_data, idle_work);
	const struct device *dev = data->dev;

	k_timer_stop(&data->sample_timer);

	gpio_qdec_irq_setup(dev, true);

	LOG_DBG("polling stop");
}

static void gpio_qdec_cb(const struct device *gpio_dev, struct gpio_callback *cb,
			 uint32_t pins)
{
	struct gpio_qdec_data *data = CONTAINER_OF(
			cb, struct gpio_qdec_data, gpio_cb);
	const struct device *dev = data->dev;
	const struct gpio_qdec_config *cfg = dev->config;

	gpio_qdec_irq_setup(dev, false);

	k_timer_start(&data->sample_timer, K_NO_WAIT,
		      K_USEC(cfg->sample_time_us));

	LOG_DBG("polling start");
}

static int gpio_qdec_init(const struct device *dev)
{
	const struct gpio_qdec_config *cfg = dev->config;
	struct gpio_qdec_data *data = dev->data;
	int ret;

	data->dev = dev;

	k_work_init(&data->event_work, gpio_qdec_event_worker);
	k_work_init_delayable(&data->idle_work, gpio_qdec_idle_worker);

	k_timer_init(&data->sample_timer, gpio_qdec_sample_timer_timeout, NULL);
	k_timer_user_data_set(&data->sample_timer, (void *)dev);

	gpio_init_callback(&data->gpio_cb, gpio_qdec_cb,
			   BIT(cfg->gpio[0].pin) | BIT(cfg->gpio[1].pin));
	for (int i = 0; i < GPIO_QDEC_GPIO_NUM; i++) {
		const struct gpio_dt_spec *gpio = &cfg->gpio[i];

		if (!gpio_is_ready_dt(gpio)) {
			LOG_ERR("%s is not ready", gpio->port->name);
			return -ENODEV;
		}

		ret = gpio_pin_configure_dt(gpio, GPIO_INPUT);
		if (ret != 0) {
			LOG_ERR("Pin %d configuration failed: %d", i, ret);
			return ret;
		}

		gpio_add_callback_dt(gpio, &data->gpio_cb);
	}

	data->prev_step = gpio_qdec_get_step(dev);

	gpio_qdec_irq_setup(dev, true);

	LOG_DBG("Device %s initialized", dev->name);

	return 0;
}

#define QDEC_GPIO_INIT(n)							\
	BUILD_ASSERT(DT_INST_PROP_LEN(n, gpios) == GPIO_QDEC_GPIO_NUM,		\
		     "input_gpio_qdec: gpios must have exactly two entries");	\
										\
	static const struct gpio_qdec_config gpio_qdec_cfg_##n = {		\
		.gpio = {GPIO_DT_SPEC_INST_GET_BY_IDX(n, gpios, 0),		\
			 GPIO_DT_SPEC_INST_GET_BY_IDX(n, gpios, 1)},		\
		.sample_time_us = DT_INST_PROP(n, sample_time_us),		\
		.idle_timeout_ms = DT_INST_PROP(n, idle_timeout_ms),		\
		.steps_per_period = DT_INST_PROP(n, steps_per_period),		\
		.axis = DT_INST_PROP(n, zephyr_axis),				\
	};									\
										\
	static struct gpio_qdec_data gpio_qdec_data_##n;			\
										\
	DEVICE_DT_INST_DEFINE(n, gpio_qdec_init, NULL,				\
			      &gpio_qdec_data_##n,				\
			      &gpio_qdec_cfg_##n,				\
			      POST_KERNEL, CONFIG_INPUT_INIT_PRIORITY,		\
			      NULL);

DT_INST_FOREACH_STATUS_OKAY(QDEC_GPIO_INIT)