/////////////////////////////////////////////////////////////////
//
// IMPORTANT: This is a header-only library that is included
// by the graphics engine as well.  It cannot contain references
// to anything else in the engine.
//


#include <cstdio>
#include <cstdint>
#include <cstdlib>
#include <string_view>

///////////////////////////////////////////////////////////////
//
// BaseWriter
//
// This base class provides the following methods:
//
//     void write_uint8(uint64_t data)
//     void write_uint16(uint64_t data)
//     void write_uint32(uint64_t data)
//     void write_uint64(uint64_t data)
//     void write_int8(int64_t data)
//     void write_int16(int64_t data)
//     void write_int32(int64_t data)
//     void write_int64(int64_t data)
//     void write_char(char c)
//     void write_float(float data)
//     void write_double(double data)
//     void write_length(size_t data)
//     void write_string(std::string_view data)
//
// You should derive from BaseWriter using the CRTP pattern:
//
//     class DerivedWriter : public BaseWriter<DerivedWriter>
//
// You must provide two methods in the derived class:
//
//     write_bytes(const char *n, size_t size)
//     raise_truncated()
//
///////////////////////////////////////////////////////////////

template<class Derived>
class BaseWriter {
protected:
    template<class T>
    void write_value_core(T arg) {
        static_cast<Derived*>(this)->write_bytes((const char *)&arg, sizeof(arg));
    }

    template<class T, class XT>
    void write_int_core(XT arg) {
        T reduced = arg;
        if (XT(reduced) != arg) static_cast<Derived*>(this)->raise_truncated();
        write_value_core(reduced);
    }

public:

    void write_uint8(uint64_t data) { write_int_core<uint8_t, uint64_t>(data); }
    void write_uint16(uint64_t data) { write_int_core<uint16_t, uint64_t>(data); }
    void write_uint32(uint64_t data) { write_int_core<uint32_t, uint64_t>(data); }
    void write_uint64(uint64_t data) { write_int_core<uint64_t, uint64_t>(data); }
    void write_int8(int64_t data) { write_int_core<int8_t, int64_t>(data); }
    void write_int16(int64_t data) { write_int_core<int16_t, int64_t>(data); }
    void write_int32(int64_t data) { write_int_core<int32_t, int64_t>(data); }
    void write_int64(int64_t data) { write_int_core<int64_t, int64_t>(data); }
    
    void write_bool(bool b) { write_uint8(b ? 1:0); }
    void write_char(char c) { write_value_core(c); }
    void write_float(float arg) { write_value_core(arg); }
    void write_double(double arg) { write_value_core(arg); }

    void write_length(size_t len) {
        if (len >= 255) {
            write_uint8(0xFF);
            write_uint64(len);
        } else {
            write_uint8(len);
        }
    }

    void write_string(std::string_view s) {
        write_length(s.size());
        static_cast<Derived*>(this)->write_bytes(s.data(), s.size());
    }
};

///////////////////////////////////////////////////////////////
//
// BaseReader
//
// This base class provides the following methods:
//
//     uint8_t read_uint8();
//     uint16_t read_uint16();
//     uint32_t read_uint32();
//     uint64_t read_uint64();
//     int8_t read_int8();
//     int16_t read_int16();
//     int32_t read_int32();
//     int64_t read_int64();
//     bool read_bool();
//     char read_char();
//     float read_float();
//     double read_double();
//     size_t read_length();
//     String read_string_limit(uint64_t size);
//     String read_string();
//
// You should derive from BaseReader using the CRTP pattern:
//
//     class DerivedReader : public BaseReader<DerivedReader>
//
// The derived class must provide:
//
//     using read_string_type = std::string; // or compatible
//     void read_bytes_into(char *n, size_t size)
//     void handle_string_too_long();
//
// Error Handling:
//
//     It is up to the derived class whether it wants
//     to report errors using exceptions or flags.
//
//     If read_bytes_into discovers there's not enough bytes,
//     there are two valid options: throw an exception, OR,
//     set an error flag and fill the buffer with zeros.
//
//     If read_string discovers that the string is longer than
//     the allowed limit, it will call handle_string_too_long.
//     This function may either throw an exception, or set an
//     error flag.
//
///////////////////////////////////////////////////////////////

template<class Derived>
class BaseReader {
protected:
    template<class T>
    T read_value_core() {
        T result;
        Derived *dthis = static_cast<Derived*>(this);
        dthis->read_bytes_into((char *)(&result), sizeof(result));
        return result;
    }

public:

    uint8_t read_uint8() { return read_value_core<uint8_t>(); }
    uint16_t read_uint16() { return read_value_core<uint16_t>(); }
    uint32_t read_uint32() { return read_value_core<uint32_t>(); }
    uint64_t read_uint64() { return read_value_core<uint64_t>(); }
    int8_t read_int8() { return read_value_core<int8_t>(); }
    int16_t read_int16() { return read_value_core<int16_t>(); }
    int32_t read_int32() { return read_value_core<int32_t>(); }
    int64_t read_int64() { return read_value_core<int64_t>(); }
    
    bool read_bool() { return (bool)read_uint8(); }
    char read_char() { return read_value_core<char>(); }
    float read_float() { return read_value_core<float>(); }
    double read_double() { return read_value_core<double>(); }
    
    size_t read_length() {
        uint64_t len = read_uint8();
        if (len == 255) {
            len = read_uint64();
        }
        return len;
    }

    auto read_string_limit(uint64_t limit) {
        size_t len = read_length();
        Derived *dthis = static_cast<Derived*>(this);
        if (len > limit) {
            dthis->raise_string_too_long();
            len = 0;
        }
        typename Derived::read_string_type result(len, ' ');
        dthis->read_bytes_into(&(result[0]), len);
        return result;
    }

    auto read_string() { return read_string_limit(0x1000000); } // 16MB limit default
};