odm/include/zarr.h

#pragma once
#include "GPL.h"
#include "cache.h"
#include "curlfuncs.h"
#include "nczarrcommon.h"
#include <json/json.h>
#include <variant>

class ZarrTypes: public NcZarrTypes
{
 protected:
 template<class VType> class ReadedData
 {
  //public:
  using Vec = std::vector<size_t>;

  private:
  Vec                                   start, chunkstart;
  ArrCounter                            mainind, chunkind, inchunkind;
  std::vector<std::unique_ptr<VType[]>> data;

  public:
  ReadedData(): mainind(Vec()), chunkind(Vec()), inchunkind(Vec()) {}

  ReadedData(size_t N, const size_t* start, const size_t* count, const size_t* csize, std::vector<std::unique_ptr<VType[]>>&& d):
      start(start, start + N),
      chunkstart(
          [](size_t N, const size_t* st, const size_t* cs)
          {
           Vec out(N);
           for(size_t i = 0; i < N; i++) out[i] = st[i] / cs[i];
           return out;
          }(N, start, csize)),
      mainind(Vec(count, count + N)),
      chunkind(
          [](size_t N, const size_t* st, const size_t* cn, const size_t* cs)
          {
           Vec out(N);
           for(size_t i = 0; i < N; i++) out[i] = (st[i] + cn[i]) / cs[i] - st[i] / cs[i] + 1;
           return out;
          }(N, start, count, csize)),
      inchunkind(Vec(csize, csize + N)),
      data(std::move(d))
  {
  }

  VType operator()(size_t lini) const
  {
   Vec ind = mainind.Index(lini, mainind.Count());
   Vec cind(ind.size()), inind(ind.size());

   for(size_t i = 0; i < ind.size(); i++)
   {
    cind[i]  = (ind[i] + start[i]) / inchunkind.Count(i) - chunkstart[i]; // indes of chunk
    inind[i] = (ind[i] + start[i]) % inchunkind.Count(i);                 // index inside chunk
   }
   size_t chunk  = chunkind.Index(cind);
   size_t inside = inchunkind.Index(inind);
   return data[chunk][inside];
  }
 };

 private:
 // Create attribute from json value
 static AttVT CreateAtt(const Json::Value& val)
 {
  if(val.type() == Json::intValue) return AttVT{std::in_place_type<int8>, val.asInt64()};
  if(val.type() == Json::uintValue) return AttVT(std::in_place_type<uint8>, val.asUInt64());
  if(val.type() == Json::realValue) return AttVT(std::in_place_type<double>, val.asDouble());
  if(val.type() == Json::stringValue)
  {
   auto str = val.asString();
   return AttVT(std::in_place_type<MString>, MString(str.c_str(), str.size()));
  }
  if(val.type() == Json::booleanValue) return AttVT(std::in_place_type<bool>, val.asBool());
  return AttVT();
 }

 public:
 // Read attributes from .zattrs
 static auto ReadAtts(const Json::Value& obj)
 {
  std::vector<Attribute> out;
  if(obj.type() != Json::objectValue) return out;
  const auto keys = obj.getMemberNames();
  for(const auto& key: keys)
   if(key != "_ARRAY_DIMENSIONS") out.emplace_back(key, CreateAtt(obj[key]));
  return out;
 }
};

class ZarrFunctions: public ZarrTypes
{
 std::unique_ptr<GenericCache> cache;
 CURLRAII                      chandle;
 MString                       url;

 std::vector<std::vector<size_t>> chunks;

 // Find variable names in metadata
 static std::vector<MString> ReadVarNames(const Json::Value& meta);

 Error AddVar(const MString& name, const Json::Value& zattrs, const Json::Value& zarray);

 protected:
 ZarrFunctions()
 {
  auto oldprefix = michlib::GPL.UsePrefix("ZARR");
  cache.reset(CreateCache(michlib::GPL.ParameterSValue("Cache", "")));
  michlib::GPL.UsePrefix(oldprefix);
  if(!cache)
  {
   michlib::errmessage("Can't init data cache");
   cache.reset(new FakeCache);
  }
 }

 template<class VType> RetVal<ReadedData<VType>> Read(const MString& var, const size_t* start, const size_t* count) const
 {
  using Vec = std::vector<size_t>;

  size_t       ind   = FindInd(var, vars);
  const size_t N     = vars[ind].NDim();
  const auto&  csize = chunks[ind];

  Vec chunkstart(
      [](size_t N, const size_t* st, const size_t* cs)
      {
       Vec out(N);
       for(size_t i = 0; i < N; i++) out[i] = st[i] / cs[i];
       return out;
      }(N, start, csize.data()));
  ArrCounter chunkind(
      [](size_t N, const size_t* st, const size_t* cn, const size_t* cs)
      {
       Vec out(N);
       for(size_t i = 0; i < N; i++) out[i] = (st[i] + cn[i] - 1) / cs[i] - st[i] / cs[i] + 1;
       return out;
      }(N, start, count, csize.data()));

  bool  havefill = vars[ind].Fill().index() > 0;
  VType fill     = std::visit(
      [](auto v)
      {
       if constexpr(std::is_convertible_v<decltype(v), VType>)
        return static_cast<VType>(v);
       else
        return std::numeric_limits<VType>::max();
      },
      vars[ind].Fill());

  std::vector<std::unique_ptr<VType[]>> cdata;

  size_t chunksize = 1;
  for(const auto c: csize) chunksize *= c;

  cdata.resize(chunkind.N());

  for(; chunkind; ++chunkind)
  {
   cdata[chunkind.Index()].reset(new VType[chunksize]);
   auto res = GetChunk(var, chunkind.VIndex(chunkstart), chunksize, sizeof(VType), cdata[chunkind.Index()].get(), havefill ? &fill : nullptr);
   if(!res) return res;
  }

  return ReadedData<VType>(N, start, count, csize.data(), std::move(cdata));
 }

 Error GetChunk(const MString& var, const std::vector<size_t>& chunkind, size_t chunksize, size_t elsize, void* data, const void* fill) const;

 public:
 Error Open(const MString& product, const MString& dataset, bool time = true);
};

using Zarr = NcZarrRead<ZarrFunctions>;