/*
  support_buffer.ino - Static binary buffer for Zigbee on Tasmota

  Copyright (C) 2020  Theo Arends and Stephan Hadinger

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

typedef struct SBuffer_impl {
  uint16_t size;                // size in bytes of the buffer
  uint16_t len;                 // current size of the data in buffer. Invariant: len <= size
  uint8_t buf[];                     // the actual data
} SBuffer_impl;



typedef class SBuffer {

protected:
  SBuffer(void) {
    // unused empty constructor except from subclass
  }

public:
  SBuffer(const size_t size) {
    _buf = (SBuffer_impl*) new char[size+4];   // add 4 bytes for size and len
    _buf->size = size;
    _buf->len = 0;
    //*((uint32_t*)_buf) = size;   // writing both size and len=0 in a single 32 bits write
  }

  inline size_t getSize(void) const { return _buf->size; }
  inline size_t size(void) const { return _buf->size; }
  inline size_t getLen(void) const { return _buf->len; }
  inline size_t len(void) const { return _buf->len; }
  inline uint8_t *getBuffer(void) const { return _buf->buf; }
  inline uint8_t *buf(size_t i = 0) const { return &_buf->buf[i]; }
  inline char    *charptr(size_t i = 0) const { return (char*) &_buf->buf[i]; }

  virtual ~SBuffer(void) {
    delete[] _buf;
  }

  inline void setLen(const size_t len) {
    uint16_t old_len = _buf->len;
    _buf->len = (len <= _buf->size) ? len : _buf->size;
    if (old_len < _buf->len) {
      memset((void*) &_buf->buf[old_len], 0, _buf->len - old_len);
    }
  }

  void set8(const size_t offset, const uint8_t data) {
    if (offset < _buf->len) {
      _buf->buf[offset] = data;
    }
  }

  size_t add8(const uint8_t data) {           // append 8 bits value
    if (_buf->len < _buf->size) {       // do we have room for 1 byte
      _buf->buf[_buf->len++] = data;
    }
    return _buf->len;
  }
  size_t add16(const uint16_t data) {           // append 16 bits value
    if (_buf->len < _buf->size - 1) {    // do we have room for 2 bytes
      _buf->buf[_buf->len++] = data;
      _buf->buf[_buf->len++] = data >> 8;
    }
    return _buf->len;
  }
  size_t add16BigEndian(const uint16_t data) {           // append 16 bits value
    if (_buf->len < _buf->size - 1) {    // do we have room for 2 bytes
      _buf->buf[_buf->len++] = data >> 8;
      _buf->buf[_buf->len++] = data;
    }
    return _buf->len;
  }
  size_t add32(const uint32_t data) {           // append 32 bits value
    if (_buf->len < _buf->size - 3) {     // do we have room for 4 bytes
      _buf->buf[_buf->len++] = data;
      _buf->buf[_buf->len++] = data >> 8;
      _buf->buf[_buf->len++] = data >> 16;
      _buf->buf[_buf->len++] = data >> 24;
    }
    return _buf->len;
  }
  size_t add32BigEndian(const uint32_t data) {           // append 32 bits value
    if (_buf->len < _buf->size - 3) {     // do we have room for 4 bytes
      _buf->buf[_buf->len++] = data >> 24;
      _buf->buf[_buf->len++] = data >> 16;
      _buf->buf[_buf->len++] = data >> 8;
      _buf->buf[_buf->len++] = data;
    }
    return _buf->len;
  }
  size_t add64(const uint64_t data) {           // append 64 bits value
    if (_buf->len < _buf->size - 7) {     // do we have room for 8 bytes
      _buf->buf[_buf->len++] = data;
      _buf->buf[_buf->len++] = data >> 8;
      _buf->buf[_buf->len++] = data >> 16;
      _buf->buf[_buf->len++] = data >> 24;
      _buf->buf[_buf->len++] = data >> 32;
      _buf->buf[_buf->len++] = data >> 40;
      _buf->buf[_buf->len++] = data >> 48;
      _buf->buf[_buf->len++] = data >> 56;
    }
    return _buf->len;
  }

  size_t addBuffer(const SBuffer &buf2) {
    if (len() + buf2.len() <= size()) {
      for (uint32_t i = 0; i < buf2.len(); i++) {
        _buf->buf[_buf->len++] = buf2.buf()[i];
      }
    }
    return _buf->len;
  }

  size_t addBuffer(const uint8_t *buf2, size_t len2) {
    if ((buf2) && (len() + len2 <= size())) {
      for (uint32_t i = 0; i < len2; i++) {
        _buf->buf[_buf->len++] = pgm_read_byte(&buf2[i]);
      }
    }
    return _buf->len;
  }

  size_t addBuffer(const char *buf2, size_t len2) {
    if ((buf2) && (len() + len2 <= size())) {
      for (uint32_t i = 0; i < len2; i++) {
        _buf->buf[_buf->len++] = pgm_read_byte(&buf2[i]);
      }
    }
    return _buf->len;
  }

  uint8_t get8(size_t offset) const {
    if (offset < _buf->len) {
      return _buf->buf[offset];
    } else {
      return 0;
    }
  }
  uint8_t read8(const size_t offset) const {
    if (offset < len()) {
      return _buf->buf[offset];
    }
    return 0;
  }
  uint16_t get16(const size_t offset) const {
    if (offset < len() - 1) {
      return _buf->buf[offset] | (_buf->buf[offset+1] << 8);
    }
    return 0;
  }
  uint16_t get16BigEndian(const size_t offset) const {
    if (offset < len() - 1) {
      return _buf->buf[offset+1] | (_buf->buf[offset] << 8);
    }
    return 0;
  }
  uint32_t get32(const size_t offset) const {
    if (offset < len() - 3) {
      return _buf->buf[offset] | (_buf->buf[offset+1] << 8) |
            (_buf->buf[offset+2] << 16) | (_buf->buf[offset+3] << 24);
    }
    return 0;
  }
  uint32_t get32BigEndian(const size_t offset) const {
    if (offset < len() - 3) {
      return _buf->buf[offset+3] | (_buf->buf[offset+2] << 8) |
            (_buf->buf[offset+1] << 16) | (_buf->buf[offset] << 24);
    }
    return 0;
  }
  int32_t get32IBigEndian(const size_t offset) const {
    if (offset < len() - 3) {
      return _buf->buf[offset+3] | (_buf->buf[offset+2] << 8) |
            (_buf->buf[offset+1] << 16) | (_buf->buf[offset] << 24);
    }
    return 0;
  }
  uint64_t get64(const size_t offset) const {
    if (offset < len() - 7) {
      return (uint64_t)_buf->buf[offset]          | ((uint64_t)_buf->buf[offset+1] <<  8) |
            ((uint64_t)_buf->buf[offset+2] << 16) | ((uint64_t)_buf->buf[offset+3] << 24) |
            ((uint64_t)_buf->buf[offset+4] << 32) | ((uint64_t)_buf->buf[offset+5] << 40) |
            ((uint64_t)_buf->buf[offset+6] << 48) | ((uint64_t)_buf->buf[offset+7] << 56);
    }
    return 0;
  }

  size_t strlen(const size_t offset) const {
    if (offset >= len()) { return 0; }
    size_t slen = strnlen((const char*) &_buf->buf[offset], len() - offset);
    if (slen == (len() - offset)) {
      return 0;   // we didn't find a NULL char
    } else {
      return slen;
    }
  }

  SBuffer subBuffer(const size_t start, size_t len) const {
    if (start >= _buf->len) {
      len = 0;
    } else if (start + len > _buf->len) {
      len = _buf->len - start;
    }

    SBuffer buf2(len);
    memcpy(buf2.buf(), buf()+start, len);
    buf2._buf->len = len;
    return buf2;
  }

  static SBuffer SBufferFromHex(const char *hex, size_t len) {
    size_t buf_len = (len + 3) / 2;
    SBuffer buf2(buf_len);
    uint8_t val;

    for (; len > 1; len -= 2) {
      val = asc2byte(*hex++) << 4;
      val |= asc2byte(*hex++);
      buf2.add8(val);
    }
    return buf2;
  }

protected:

  static uint8_t asc2byte(char chr) {
    uint8_t rVal = 0;
    if (isdigit(chr)) { rVal = chr - '0'; }
    else if (chr >= 'A' && chr <= 'F') { rVal = chr + 10 - 'A'; }
    else if (chr >= 'a' && chr <= 'f') { rVal = chr + 10 - 'a'; }
    return rVal;
  }

  static void unHex(const char* in, uint8_t *out, size_t len) {
  }

protected:
  SBuffer_impl * _buf;

} SBuffer;

typedef class PreAllocatedSBuffer : public SBuffer {

public:
  PreAllocatedSBuffer(const size_t size, void * buffer) {
    _buf = (SBuffer_impl*) buffer;
    _buf->size = size - 4;
    _buf->len = 0;
  }

  ~PreAllocatedSBuffer(void) {
    // don't deallocate
    _buf = nullptr;
  }
} PreAllocatedSBuffer;

// nullptr accepted
bool equalsSBuffer(const class SBuffer * buf1, const class SBuffer * buf2) {
  if (buf1 == buf2) { return true; }
  if (!buf1 && (buf2->len() == 0)) { return true; }
  if (!buf2 && (buf1->len() == 0)) { return true; }
  if (!buf1 || !buf2) { return false; }   // at least one buf is not empty
  // we know that both buf1 and buf2 are non-null
  if (buf1->len() != buf2->len()) { return false; }
  size_t len = buf1->len();
  for (uint32_t i=0; i<len; i++) {
    if (buf1->get8(i) != buf2->get8(i)) { return false; }
  }
  return true;
}