/*
  TwoWire.cpp - TWI/I2C library for Wiring & Arduino
  Copyright (c) 2006 Nicholas Zambetti.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include "twi-lowlevel.h"

#include "twi.h"

// local variables
uint8_t rxBuffer[BUFFER_LENGTH];
uint8_t rxBufferIndex = 0;
uint8_t rxBufferLength = 0;

uint8_t txAddress = 0;
uint8_t txBuffer[BUFFER_LENGTH];
uint8_t txBufferIndex = 0;
uint8_t txBufferLength = 0;

uint8_t transmitting = 0;
void (*user_onRequest)(void);
void (*user_onReceive)(int);

void onRequestService(void);
void onReceiveService(uint8_t*, int);

void twi_init_master(void)
{
  rxBufferIndex = 0;
  rxBufferLength = 0;

  txBufferIndex = 0;
  txBufferLength = 0;

  twi_init();
}

void twi_init_slave(uint8_t address)
{
  twi_setAddress(address);
  twi_attachSlaveTxEvent(onRequestService);
  twi_attachSlaveRxEvent(onReceiveService);
  twi_init_master();
}

uint8_t twi_request_from(uint8_t address, uint8_t quantity)
{
  // clamp to buffer length
  if(quantity > BUFFER_LENGTH){
    quantity = BUFFER_LENGTH;
  }
  // perform blocking read into buffer
  uint8_t read = twi_readFrom(address, rxBuffer, quantity);
  // set rx buffer iterator vars
  rxBufferIndex = 0;
  rxBufferLength = read;

  return read;
}

void twi_begin_transmission(uint8_t address)
{
  // indicate that we are transmitting
  transmitting = 1;
  // set address of targeted slave
  txAddress = address;
  // reset tx buffer iterator vars
  txBufferIndex = 0;
  txBufferLength = 0;
}

uint8_t twi_end_transmission(void)
{
  // transmit buffer (blocking)
  int8_t ret = twi_writeTo(txAddress, txBuffer, txBufferLength, 1);
  // reset tx buffer iterator vars
  txBufferIndex = 0;
  txBufferLength = 0;
  // indicate that we are done transmitting
  transmitting = 0;
  return ret;
}

// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void twi_send_byte(uint8_t data)
{
  if(transmitting){
  // in master transmitter mode
    // don't bother if buffer is full
    if(txBufferLength >= BUFFER_LENGTH){
      return;
    }
    // put byte in tx buffer
    txBuffer[txBufferIndex] = data;
    ++txBufferIndex;
    // update amount in buffer   
    txBufferLength = txBufferIndex;
  }else{
  // in slave send mode
    // reply to master
    twi_transmit(&data, 1);
  }
}

// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void twi_send(uint8_t* data, uint8_t quantity)
{
  if(transmitting){
  // in master transmitter mode
    for(uint8_t i = 0; i < quantity; ++i){
     twi_send_byte(data[i]);
    }
  }else{
  // in slave send mode
    // reply to master
    twi_transmit(data, quantity);
  }
}

// must be called in:
// slave tx event callback
// or after beginTransmission(address)
void twi_send_char(char* data)
{
  twi_send((uint8_t*)data, strlen(data));
}

// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
uint8_t twi_available(void)
{
  return rxBufferLength - rxBufferIndex;
}

// must be called in:
// slave rx event callback
// or after requestFrom(address, numBytes)
uint8_t twi_receive(void)
{
  // default to returning null char
  // for people using with char strings
  uint8_t value = '\0';
  
  // get each successive byte on each call
  if(rxBufferIndex < rxBufferLength){
    value = rxBuffer[rxBufferIndex];
    ++rxBufferIndex;
  }

  return value;
}

// behind the scenes function that is called when data is received
void onReceiveService(uint8_t* inBytes, int numBytes)
{
  // don't bother if user hasn't registered a callback
  if(!user_onReceive){
    return;
  }
  // don't bother if rx buffer is in use by a master requestFrom() op
  // i know this drops data, but it allows for slight stupidity
  // meaning, they may not have read all the master requestFrom() data yet
  if(rxBufferIndex < rxBufferLength){
    return;
  }
  // copy twi rx buffer into local read buffer
  // this enables new reads to happen in parallel
  for(uint8_t i = 0; i < numBytes; ++i){
    rxBuffer[i] = inBytes[i];    
  }
  // set rx iterator vars
  rxBufferIndex = 0;
  rxBufferLength = numBytes;
  // alert user program
  user_onReceive(numBytes);
}

// behind the scenes function that is called when data is requested
void onRequestService(void)
{
  // don't bother if user hasn't registered a callback
  if(!user_onRequest){
    return;
  }
  // reset tx buffer iterator vars
  // !!! this will kill any pending pre-master sendTo() activity
  txBufferIndex = 0;
  txBufferLength = 0;
  // alert user program
  user_onRequest();
}

// sets function called on slave write
void twi_set_on_receive( void (*function)(int) )
{
  user_onReceive = function;
}

// sets function called on slave read
void twi_set_on_request( void (*function)(void) )
{
  user_onRequest = function;
}