#include "meshtastic_presets.h"

#include <cmath>
#include <cstring>

namespace roro::meshtastic {

const uint8_t kDefaultKey[16] = {0xd4, 0xf1, 0xbb, 0x3a, 0x20, 0x29, 0x07, 0x59,
                                 0xf0, 0xbc, 0xff, 0xab, 0xcf, 0x4e, 0x69, 0x01};

// firmware src/mesh/MeshRadio.h (modemPresetToParams) and RadioInterface.cpp (PRESETS_EU_868).
const Preset kEu868Presets[] = {
    {"LongFast", 250, 11, 5},  {"LongSlow", 125, 12, 8},  {"MediumSlow", 250, 10, 5}, {"MediumFast", 250, 9, 5},
    {"ShortSlow", 250, 8, 5},  {"ShortFast", 250, 7, 5},  {"LongMod", 125, 11, 8},
};
const size_t kEu868PresetCount = sizeof kEu868Presets / sizeof kEu868Presets[0];

const Preset* findPreset(const char* name) {
    for (const Preset& p : kEu868Presets)
        if (std::strcmp(p.name, name) == 0) return &p;
    return nullptr;
}

uint32_t djb2(const char* s) {
    uint32_t h = 5381;
    for (; *s; ++s) h = (h << 5) + h + static_cast<unsigned char>(*s);
    return h;
}

uint8_t channelHash(const char* name, const uint8_t* key, size_t keyLen) {
    uint8_t h = 0;
    for (; *name; ++name) h ^= static_cast<uint8_t>(*name);
    for (size_t i = 0; i < keyLen; ++i) h ^= key[i];
    return h;
}

uint32_t eu868FrequencyHz(const Preset& preset, const char* channelName) {
    constexpr double kStartMHz = 869.4, kEndMHz = 869.65;
    double slotMHz = preset.bwKHz / 1000.0;
    uint32_t slots = static_cast<uint32_t>(std::lround((kEndMHz - kStartMHz) / slotMHz));
    const char* name = channelName && *channelName ? channelName : preset.name;
    uint32_t slot = slots ? djb2(name) % slots : 0;
    double mhz = kStartMHz + slotMHz / 2 + slot * slotMHz;
    return static_cast<uint32_t>(std::lround(mhz * 1e6));
}

}  // namespace roro::meshtastic