sysvars/src/sysvars.hpp

#ifndef _SYSVARS_H_
#define _SYSVARS_H_
// Key-Value JSON file store unit
// Ma za ukol ukladat/nacitat pary key-value do/z JSON

#include <Arduino.h>
#include <ArduinoJson.h>
#include <FS.h>
#ifndef USEDFS
# if defined(ESP32)
#  ifdef USE_LITTLEFS
#   include <LITTLEFS.h>
#   define USEDFS LITTLEFS
#  else
#   include <SPIFFS.h>
#   define USEDFS SPIFFS
#  endif
# else
#  include <LittleFS.h>
#  define USEDFS LittleFS
# endif
#endif

enum {
    SV_OK = 0,
    SV_UNSPECIFIED_ERROR = -1,
    SV_FILE_NOT_FOUND = -2,
    SV_DESERIALIZE_ERROR = -3,
    SV_WRONG_DATA_TYPE = -4,
    SV_FILE_WRITE_ERROR = -5,
    SV_KEY_NOT_FOUND = -6,
};

#if not defined(SYSVAR_FILE)
# define SYSVAR_FILE "/cfg.json"
#endif

#if not defined(SYSVAR_DOCUMENT_SIZE)
# define SYSVAR_DOCUMENT_SIZE (4096)
#endif

template <typename T>
T svGetV(const String& name, int* result = nullptr)
{
    T retval{};
    int res = SV_UNSPECIFIED_ERROR; // predpokladame chybu
    DynamicJsonDocument doc(SYSVAR_DOCUMENT_SIZE);
    File f;

    f = USEDFS.open(F(SYSVAR_FILE), "r");
    if (f) {
        DeserializationError err = deserializeJson(doc, f);
        if (err) {
            res = SV_DESERIALIZE_ERROR; // spatny JSON soubor
        } else {
            if (!doc.containsKey(name))
            {
                res = SV_KEY_NOT_FOUND; // chyba - nenalezeny klic
            } else {
                retval = doc[name].as<T>();
                res = SV_OK;
            }
        }
    } else {
        res = SV_FILE_NOT_FOUND; // chyba - nenalezeny soubor
    }
    if (result)
        *result = res; // navratovy kod, pokud nas zajima
    return retval;
}

template <typename T>
T svGetV(const String& name, int* result, const String& fname)
{
    T retval{};
    int res = SV_UNSPECIFIED_ERROR; // predpokladame chybu
    DynamicJsonDocument doc(SYSVAR_DOCUMENT_SIZE);
    File f;

    f = USEDFS.open(fname, "r");
    if (f) {
        DeserializationError err = deserializeJson(doc, f);
        if (err) {
            res = SV_DESERIALIZE_ERROR; // spatny JSON soubor
        } else {
            if (!doc.containsKey(name))
            {
                res = SV_KEY_NOT_FOUND; // chyba - nenalezeny klic
            } else {
                retval = doc[name].as<T>();
                res = SV_OK;
            }
        }
    } else {
        res = SV_FILE_NOT_FOUND; // chyba - nenalezeny soubor
    }
    if (result)
        *result = res; // navratovy kod, pokud nas zajima
    return retval;
}

template <typename T>
int svSetV(const String& name, T value)
{
    int res = SV_UNSPECIFIED_ERROR;
    DynamicJsonDocument doc(SYSVAR_DOCUMENT_SIZE);
    File f;

    f = USEDFS.open(F(SYSVAR_FILE), "r");
    if (f) {
        DeserializationError err = deserializeJson(doc, f);
        if (err) {
            res = SV_DESERIALIZE_ERROR; // spatny JSON soubor
        }
        f.close();
    }
    doc[name] = value;

    f = USEDFS.open(SYSVAR_FILE, "w");
    if (f) {
        serializeJson(doc, f);
        res = SV_OK;
    } else {
        res = SV_FILE_WRITE_ERROR;
    }
    return res;
}

template <typename T>
int svSetV(const String& name, T value, const String& fname)
{
    int res = SV_UNSPECIFIED_ERROR;
    DynamicJsonDocument doc(SYSVAR_DOCUMENT_SIZE);
    File f;

    f = USEDFS.open(fname, "r");
    if (f) {
        DeserializationError err = deserializeJson(doc, f);
        if (err) {
            res = SV_DESERIALIZE_ERROR; // spatny JSON soubor
        }
        f.close();
    }
    doc[name] = value;

    f = USEDFS.open(fname, "w");
    if (f) {
        serializeJson(doc, f);
        res = SV_OK;
    } else {
        res = SV_FILE_WRITE_ERROR;
    }

    return res;
}
#endif