#include <inttypes.h>
#include <stddef.h>
#include <stdint.h>

#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <zephyr/drivers/adc.h>
#include <zephyr/kernel.h>

/** Setup code referenced from Zephyr ADC example **/
#if !DT_NODE_EXISTS(DT_PATH(zephyr_user)) || \
	!DT_NODE_HAS_PROP(DT_PATH(zephyr_user), io_channels)
#error "No suitable devicetree overlay specified"
#endif

#define DT_SPEC_AND_COMMA(node_id, prop, idx) \
    ADC_DT_SPEC_GET_BY_IDX(node_id, idx),

static const struct adc_dt_spec adc_channels[] = {
    DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user), io_channels, DT_SPEC_AND_COMMA)
};

static int setup = 0;

int
adc_init()
{
    for (int i = 0; i < ARRAY_SIZE(adc_channels); i++) {
        int err;
        const struct adc_dt_spec *chan = &adc_channels[i];

        if (!adc_is_ready_dt(chan)) {
            return (-1);
        }

        err = adc_channel_setup_dt(chan);
        if (err) {
            return (err);
        }
    }

    setup = 1;
    return (0);
}

int
adc_get_mv(int channel)
{
    uint16_t val_raw;
    int32_t val_mv;
    struct adc_sequence seq = {
        .buffer = &val_raw,
        .buffer_size = sizeof(val_raw)
    };
    const struct adc_dt_spec *chan;

    if ((channel >= ARRAY_SIZE(adc_channels)) ||
        (!setup)) {
        return (INT32_MIN);
    }

    chan = &adc_channels[channel];
    adc_sequence_init_dt(chan, &seq);

    if (adc_read_dt(chan, &seq) < 0) {
        return (INT32_MIN);
    }

    val_mv = (int32_t)val_raw;
    if (adc_raw_to_millivolts_dt(chan, &val_mv)) {
        return (INT32_MIN);
    }

    return (val_mv);
}