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

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

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
    {
        T tmp;
        if (num_vals != 0) {
            tmp = reinterpret_cast<T*>(&(*data_holder)[0]);
        }
        else {
            tmp = NULL;
        }
        return tmp;
    }

    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
