// Copyright (C) 2011  Carl Rogers
// Released under MIT License
// license available in LICENSE file, or at http://www.opensource.org/licenses/mit-license.php

#ifndef LIBCNPY_H_
#define LIBCNPY_H_

#include <string>
#include <stdexcept>
#include <sstream>
#include <vector>
#include <cstdio>
#include <typeinfo>
#include <iostream>
#include <cassert>
#include <zlib.h>
#include <map>
#include <memory>
#include <stdint.h>
#include <numeric>

namespace cnpy {

struct NpyArray {
  NpyArray(const std::vector<size_t> &_shape, size_t _word_size, bool _fortran_order)
      : shape(_shape), word_size(_word_size), fortran_order(_fortran_order)
  {
    num_vals = 1;
    for (size_t i = 0; i < shape.size(); i++)
      num_vals *= shape[i];
    data_holder = std::shared_ptr<std::vector<char>>(new std::vector<char>(num_vals * word_size));
  }

  NpyArray() : shape(0), word_size(0), fortran_order(0), num_vals(0)
  {
  }

  template<typename T> T *data()
  {
    return reinterpret_cast<T *>(&(*data_holder)[0]);
  }

  template<typename T> const T *data() const
  {
    return reinterpret_cast<T *>(&(*data_holder)[0]);
  }

  template<typename T> std::vector<T> as_vec() const
  {
    const T *p = data<T>();
    return std::vector<T>(p, p + num_vals);
  }

  size_t num_bytes() const
  {
    return data_holder->size();
  }

  std::shared_ptr<std::vector<char>> data_holder;
  std::vector<size_t> shape;
  size_t word_size;
  bool fortran_order;
  size_t num_vals;
};

using npz_t = std::map<std::string, NpyArray>;

char BigEndianTest();
char map_type(const std::type_info &t);
template<typename T> std::vector<char> create_npy_header(const std::vector<size_t> &shape);
void parse_npy_header(FILE *fp,
                      size_t &word_size,
                      std::vector<size_t> &shape,
                      bool &fortran_order);
void parse_npy_header(unsigned char *buffer,
                      size_t &word_size,
                      std::vector<size_t> &shape,
                      bool &fortran_order);
void parse_zip_footer(FILE *fp,
                      uint16_t &nrecs,
                      size_t &global_header_size,
                      size_t &global_header_offset);
npz_t npz_load(std::string fname);
NpyArray npz_load(std::string fname, std::string varname);
NpyArray npy_load(std::string fname);

template<typename T> std::vector<char> &operator+=(std::vector<char> &lhs, const T rhs)
{
  // write in little endian
  for (size_t byte = 0; byte < sizeof(T); byte++) {
    char val = *((char *)&rhs + byte);
    lhs.push_back(val);
  }
  return lhs;
}

template<> std::vector<char> &operator+=(std::vector<char> &lhs, const std::string rhs);
template<> std::vector<char> &operator+=(std::vector<char> &lhs, const char *rhs);

template<typename T>
void npy_save(std::string fname,
              const T *data,
              const std::vector<size_t> shape,
              std::string mode = "w")
{
  FILE *fp = NULL;
  std::vector<size_t> true_data_shape;  // if appending, the shape of existing + new data

  if (mode == "a")
    fp = fopen(fname.c_str(), "r+b");

  if (fp) {
    // file exists. we need to append to it. read the header, modify the array size
    size_t word_size;
    bool fortran_order;
    parse_npy_header(fp, word_size, true_data_shape, fortran_order);
    assert(!fortran_order);

    if (word_size != sizeof(T)) {
      std::cout << "libnpy error: " << fname << " has word size " << word_size
                << " but npy_save appending data sized " << sizeof(T) << "\n";
      assert(word_size == sizeof(T));
    }
    if (true_data_shape.size() != shape.size()) {
      std::cout << "libnpy error: npy_save attempting to append misdimensioned data to " << fname
                << "\n";
      assert(true_data_shape.size() != shape.size());
    }

    for (size_t i = 1; i < shape.size(); i++) {
      if (shape[i] != true_data_shape[i]) {
        std::cout << "libnpy error: npy_save attempting to append misshaped data to " << fname
                  << "\n";
        assert(shape[i] == true_data_shape[i]);
      }
    }
    true_data_shape[0] += shape[0];
  }
  else {
    fp = fopen(fname.c_str(), "wb");
    true_data_shape = shape;
  }

  std::vector<char> header = create_npy_header<T>(true_data_shape);
  size_t nels = std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<size_t>());

  fseek(fp, 0, SEEK_SET);
  fwrite(&header[0], sizeof(char), header.size(), fp);
  fseek(fp, 0, SEEK_END);
  fwrite(data, sizeof(T), nels, fp);
  fclose(fp);
}

template<typename T>
void npz_save(std::string zipname,
              std::string fname,
              const T *data,
              const std::vector<size_t> &shape,
              std::string mode = "w")
{
  // first, append a .npy to the fname
  fname += ".npy";

  // now, on with the show
  FILE *fp = NULL;
  uint16_t nrecs = 0;
  size_t global_header_offset = 0;
  std::vector<char> global_header;

  if (mode == "a")
    fp = fopen(zipname.c_str(), "r+b");

  if (fp) {
    // zip file exists. we need to add a new npy file to it.
    // first read the footer. this gives us the offset and size of the global header
    // then read and store the global header.
    // below, we will write the the new data at the start of the global header then append the
    // global header and footer below it
    size_t global_header_size;
    parse_zip_footer(fp, nrecs, global_header_size, global_header_offset);
    fseek(fp, global_header_offset, SEEK_SET);
    global_header.resize(global_header_size);
    size_t res = fread(&global_header[0], sizeof(char), global_header_size, fp);
    if (res != global_header_size) {
      throw std::runtime_error("npz_save: header read error while adding to existing zip");
    }
    fseek(fp, global_header_offset, SEEK_SET);
  }
  else {
    fp = fopen(zipname.c_str(), "wb");
  }

  std::vector<char> npy_header = create_npy_header<T>(shape);

  size_t nels = std::accumulate(shape.begin(), shape.end(), 1, std::multiplies<size_t>());
  size_t nbytes = nels * sizeof(T) + npy_header.size();

  // get the CRC of the data to be added
  uint32_t crc = crc32(0L, (uint8_t *)&npy_header[0], npy_header.size());
  crc = crc32(crc, (uint8_t *)data, nels * sizeof(T));

  // build the local header
  std::vector<char> local_header;
  local_header += "PK";                    // first part of sig
  local_header += (uint16_t)0x0403;        // second part of sig
  local_header += (uint16_t)20;            // min version to extract
  local_header += (uint16_t)0;             // general purpose bit flag
  local_header += (uint16_t)0;             // compression method
  local_header += (uint16_t)0;             // file last mod time
  local_header += (uint16_t)0;             // file last mod date
  local_header += (uint32_t)crc;           // crc
  local_header += (uint32_t)nbytes;        // compressed size
  local_header += (uint32_t)nbytes;        // uncompressed size
  local_header += (uint16_t)fname.size();  // fname length
  local_header += (uint16_t)0;             // extra field length
  local_header += fname;

  // build global header
  global_header += "PK";              // first part of sig
  global_header += (uint16_t)0x0201;  // second part of sig
  global_header += (uint16_t)20;      // version made by
  global_header.insert(global_header.end(), local_header.begin() + 4, local_header.begin() + 30);
  global_header += (uint16_t)0;  // file comment length
  global_header += (uint16_t)0;  // disk number where file starts
  global_header += (uint16_t)0;  // internal file attributes
  global_header += (uint32_t)0;  // external file attributes
  global_header += (uint32_t)
      global_header_offset;  // relative offset of local file header, since it begins where the
                             // global header used to begin
  global_header += fname;

  // build footer
  std::vector<char> footer;
  footer += "PK";                            // first part of sig
  footer += (uint16_t)0x0605;                // second part of sig
  footer += (uint16_t)0;                     // number of this disk
  footer += (uint16_t)0;                     // disk where footer starts
  footer += (uint16_t)(nrecs + 1);           // number of records on this disk
  footer += (uint16_t)(nrecs + 1);           // total number of records
  footer += (uint32_t)global_header.size();  // nbytes of global headers
  footer += (uint32_t)(global_header_offset + nbytes +
                       local_header.size());  // offset of start of global headers, since global
                                              // header now starts after newly written array
  footer += (uint16_t)0;  // zip file comment length

  // write everything
  fwrite(&local_header[0], sizeof(char), local_header.size(), fp);
  fwrite(&npy_header[0], sizeof(char), npy_header.size(), fp);
  fwrite(data, sizeof(T), nels, fp);
  fwrite(&global_header[0], sizeof(char), global_header.size(), fp);
  fwrite(&footer[0], sizeof(char), footer.size(), fp);
  fclose(fp);
}

template<typename T>
void npy_save(std::string fname, const std::vector<T> data, std::string mode = "w")
{
  std::vector<size_t> shape;
  shape.push_back(data.size());
  npy_save(fname, &data[0], shape, mode);
}

template<typename T>
void npz_save(std::string zipname,
              std::string fname,
              const std::vector<T> data,
              std::string mode = "w")
{
  std::vector<size_t> shape;
  shape.push_back(data.size());
  npz_save(zipname, fname, &data[0], shape, mode);
}

template<typename T> std::vector<char> create_npy_header(const std::vector<size_t> &shape)
{

  std::vector<char> dict;
  dict += "{'descr': '";
  dict += BigEndianTest();
  dict += map_type(typeid(T));
  dict += std::to_string(sizeof(T));
  dict += "', 'fortran_order': False, 'shape': (";
  dict += std::to_string(shape[0]);
  for (size_t i = 1; i < shape.size(); i++) {
    dict += ", ";
    dict += std::to_string(shape[i]);
  }
  if (shape.size() == 1)
    dict += ",";
  dict += "), }";
  // pad with spaces so that preamble+dict is modulo 16 bytes. preamble is 10 bytes. dict needs to
  // end with \n
  int remainder = 16 - (10 + dict.size()) % 16;
  dict.insert(dict.end(), remainder, ' ');
  dict.back() = '\n';

  std::vector<char> header;
  header += (char)0x93;
  header += "NUMPY";
  header += (char)0x01;  // major version of numpy format
  header += (char)0x00;  // minor version of numpy format
  header += (uint16_t)dict.size();
  header.insert(header.end(), dict.begin(), dict.end());

  return header;
}

}  // namespace cnpy

#endif