/*
 * Copyright (c) 2018-2019 Peter Bigot Consulting, LLC
 * Copyright (c) 2019-2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include <zephyr/kernel.h>
#include <zephyr/init.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/drivers/adc.h>
#include <zephyr/drivers/sensor.h>
#include <zephyr/logging/log.h>

#include "battery.h"

LOG_MODULE_REGISTER(BATTERYVDD, CONFIG_ADC_LOG_LEVEL);

#define ZEPHYR_USER DT_PATH(zephyr_user)

/* Other boards may use dividers that only reduce battery voltage to
 * the maximum supported by the hardware (3.6 V)
 */
#define BATTERY_ADC_GAIN ADC_GAIN_1_6

struct io_channel_config {
	uint8_t channel;
};

struct divider_config {
	struct io_channel_config io_channel;
	struct gpio_dt_spec power_gpios;
	/* output_ohm is used as a flag value: if it is nonzero then
	 * the battery is measured through a voltage divider;
	 * otherwise it is assumed to be directly connected to Vdd.
	 */
	uint32_t output_ohm;
	uint32_t full_ohm;
};

static const struct divider_config dividervdd_config = {
	.io_channel = {
		DT_IO_CHANNELS_INPUT(ZEPHYR_USER),
	},
};

struct divider_data {
	const struct device *adc;
	struct adc_channel_cfg adc_cfg;
	struct adc_sequence adc_seq;
	int16_t raw;
};
static struct divider_data dividervdd_data = {
	.adc = DEVICE_DT_GET(DT_IO_CHANNELS_CTLR(ZEPHYR_USER)),
};

static int dividervdd_setup(void)
{
	const struct divider_config *cfg = &dividervdd_config;
	const struct io_channel_config *iocp = &cfg->io_channel;
	const struct gpio_dt_spec *gcp = &cfg->power_gpios;
	struct divider_data *ddp = &dividervdd_data;
	struct adc_sequence *asp = &ddp->adc_seq;
	struct adc_channel_cfg *accp = &ddp->adc_cfg;
	int rc;

	if (!device_is_ready(ddp->adc)) {
		LOG_ERR("ADC device is not ready %s", ddp->adc->name);
		return -ENOENT;
	}

	if (gcp->port) {
		if (!device_is_ready(gcp->port)) {
			LOG_ERR("%s: device not ready", gcp->port->name);
			return -ENOENT;
		}
		rc = gpio_pin_configure_dt(gcp, GPIO_OUTPUT_INACTIVE);
		if (rc != 0) {
			LOG_ERR("Failed to control feed %s.%u: %d",
				gcp->port->name, gcp->pin, rc);
			return rc;
		}
	}

	*asp = (struct adc_sequence){
		.channels = BIT(0),
		.buffer = &ddp->raw,
		.buffer_size = sizeof(ddp->raw),
		.oversampling = 4,
		.calibrate = true,
	};

#ifdef CONFIG_ADC_NRFX_SAADC
	*accp = (struct adc_channel_cfg){
		.gain = BATTERY_ADC_GAIN,
		.reference = ADC_REF_INTERNAL,
		.acquisition_time = ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 40),
	};

	accp->input_positive = SAADC_CH_PSELP_PSELP_VDD;

	asp->resolution = 14;
#else /* CONFIG_ADC_var */
#error Unsupported ADC
#endif /* CONFIG_ADC_var */

	rc = adc_channel_setup(ddp->adc, accp);
	LOG_INF("Setup VDD AIN%u got %d", iocp->channel, rc);

	return rc;
}

static bool battery_ok;

int batteryvdd_setup()
{
	int rc = dividervdd_setup();

	battery_ok = (rc == 0);
	LOG_INF("Battery VDD setup: %d %d", rc, battery_ok);
	return rc;
}

//SYS_INIT(batteryvdd_setup, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);

int16_t batteryvdd_sample(void)
{
	int16_t rc = -ENOENT;

	if (battery_ok) {
		struct divider_data *ddp = &dividervdd_data;
		//const struct divider_config *dcp = &dividervdd_config;
		struct adc_sequence *sp = &ddp->adc_seq;

		rc = adc_read(ddp->adc, sp);
		sp->calibrate = false;
		if (rc == 0) {
			int32_t val = ddp->raw;

			adc_raw_to_millivolts(adc_ref_internal(ddp->adc),
					      ddp->adc_cfg.gain,
					      sp->resolution,
					      &val);
				rc = val;
				LOG_INF("raw %u ~ %u mV", ddp->raw, val);
		}
	}

	return rc;
}