#include <array>
#include <cstdint>

namespace
{

constexpr std::uint32_t base_address               = 0x4004'c000u;
std::uint32_t volatile * const control_status_addr = reinterpret_cast<std::uint32_t*>(base_address + 0x0u);
std::uint32_t volatile * const result_addr         = reinterpret_cast<std::uint32_t*>(base_address + 0x4u);

void
select_input(std::uint32_t index)
{
    constexpr std::uint32_t ainsel = 0x111u;
    *control_status_addr = (*control_status_addr & ~(ainsel << 12)) | ((index & ainsel) << 12);
}

bool
ready()
{
    return (*control_status_addr & 1u << 8) != 0u;
}

bool
error()
{
    return (*control_status_addr & 1u << 9) != 0u;
}

void
start_once()
{
    *control_status_addr |= (1u << 2);
}

void
enable(bool en)
{
    *control_status_addr |= en ? (1u << 2) : 0u;
}

std::uint32_t
result()
{
    return *result_addr & 0x0000'0fffu;
}

std::array<std::uint32_t, 2> previous_samples { 0xffff'ffffu, 0xffff'ffffu };

}

namespace adc
{

struct Sample
{
    std::uint8_t value {0};
    bool changed {false};
};

void
init()
{
    enable(true);
}

std::array<Sample, 2>
get_samples()
{
    while (!ready());

    std::array<Sample, 2> samples {};
    for (std::size_t i = 0; i < samples.size(); i++)
    {
        select_input(i);
        start_once();

        while (!ready());

        std::uint32_t const measurement = result();
        samples[i].changed = measurement != previous_samples[i];
        previous_samples[i] = measurement;
        samples[i].value = measurement * 127u / 4095u; // TODO add hysteresis
    }

    return samples;
}

}