﻿/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

#include "Token.h"
#include "Exceptions.h"
#include "assert.h"
#include "TokenSource.h"
#include "support/Arrays.h"
#include "misc/Interval.h"
#include "RuleContext.h"
#include "WritableToken.h"

#include "UnbufferedTokenStream.h"

using namespace antlr4;

UnbufferedTokenStream::UnbufferedTokenStream(TokenSource *tokenSource) : UnbufferedTokenStream(tokenSource, 256) {
}

UnbufferedTokenStream::UnbufferedTokenStream(TokenSource *tokenSource, int /*bufferSize*/)
  : _tokenSource(tokenSource), _lastToken(nullptr), _lastTokenBufferStart(nullptr)
{
  InitializeInstanceFields();
  fill(1); // prime the pump
}

UnbufferedTokenStream::~UnbufferedTokenStream() {
}

Token* UnbufferedTokenStream::get(size_t i) const
{ // get absolute index
  size_t bufferStartIndex = getBufferStartIndex();
  if (i < bufferStartIndex || i >= bufferStartIndex + _tokens.size()) {
    throw IndexOutOfBoundsException(std::string("get(") + std::to_string(i) + std::string(") outside buffer: ")
      + std::to_string(bufferStartIndex) + std::string("..") + std::to_string(bufferStartIndex + _tokens.size()));
  }
  return _tokens[i - bufferStartIndex].get();
}

Token* UnbufferedTokenStream::LT(ssize_t i)
{
  if (i == -1) {
    return _lastToken;
  }

  sync(i);
  ssize_t index = static_cast<ssize_t>(_p) + i - 1;
  if (index < 0) {
    throw IndexOutOfBoundsException(std::string("LT(") + std::to_string(i) + std::string(") gives negative index"));
  }

  if (index >= static_cast<ssize_t>(_tokens.size())) {
    assert(_tokens.size() > 0 && _tokens.back()->getType() == EOF);
    return _tokens.back().get();
  }

  return _tokens[static_cast<size_t>(index)].get();
}

size_t UnbufferedTokenStream::LA(ssize_t i)
{
  return LT(i)->getType();
}

TokenSource* UnbufferedTokenStream::getTokenSource() const
{
  return _tokenSource;
}

std::string UnbufferedTokenStream::getText()
{
  return "";
}

std::string UnbufferedTokenStream::getText(RuleContext* ctx)
{
  return getText(ctx->getSourceInterval());
}

std::string UnbufferedTokenStream::getText(Token *start, Token *stop)
{
  return getText(misc::Interval(start->getTokenIndex(), stop->getTokenIndex()));
}

void UnbufferedTokenStream::consume()
{
  if (LA(1) == EOF) {
    throw IllegalStateException("cannot consume EOF");
  }

  // buf always has at least tokens[p==0] in this method due to ctor
  _lastToken = _tokens[_p].get(); // track last token for LT(-1)

  // if we're at last token and no markers, opportunity to flush buffer
  if (_p == _tokens.size() - 1 && _numMarkers == 0) {
    _tokens.clear();
    _p = 0;
    _lastTokenBufferStart = _lastToken;
  } else {
    ++_p;
  }

  ++_currentTokenIndex;
  sync(1);
}

/// <summary>
/// Make sure we have 'need' elements from current position <seealso cref="#p p"/>. Last valid
///  {@code p} index is {@code tokens.length-1}.  {@code p+need-1} is the tokens index 'need' elements
///  ahead.  If we need 1 element, {@code (p+1-1)==p} must be less than {@code tokens.length}.
/// </summary>
void UnbufferedTokenStream::sync(ssize_t want)
{
  ssize_t need = (static_cast<ssize_t>(_p) + want - 1) - static_cast<ssize_t>(_tokens.size()) + 1; // how many more elements we need?
  if (need > 0) {
    fill(static_cast<size_t>(need));
  }
}

/// <summary>
/// Add {@code n} elements to the buffer. Returns the number of tokens
/// actually added to the buffer. If the return value is less than {@code n},
/// then EOF was reached before {@code n} tokens could be added.
/// </summary>
size_t UnbufferedTokenStream::fill(size_t n)
{
  for (size_t i = 0; i < n; i++) {
    if (_tokens.size() > 0 && _tokens.back()->getType() == EOF) {
      return i;
    }

    add(_tokenSource->nextToken());
  }

  return n;
}

void UnbufferedTokenStream::add(std::unique_ptr<Token> t)
{
  WritableToken *writable = dynamic_cast<WritableToken *>(t.get());
  if (writable != nullptr) {
    writable->setTokenIndex(int(getBufferStartIndex() + _tokens.size()));
  }

  _tokens.push_back(std::move(t));
}

/// <summary>
/// Return a marker that we can release later.
/// <p/>
/// The specific marker value used for this class allows for some level of
/// protection against misuse where {@code seek()} is called on a mark or
/// {@code release()} is called in the wrong order.
/// </summary>
ssize_t UnbufferedTokenStream::mark()
{
  if (_numMarkers == 0) {
    _lastTokenBufferStart = _lastToken;
  }

  int mark = -_numMarkers - 1;
  _numMarkers++;
  return mark;
}

void UnbufferedTokenStream::release(ssize_t marker)
{
  ssize_t expectedMark = -_numMarkers;
  if (marker != expectedMark) {
    throw IllegalStateException("release() called with an invalid marker.");
  }

  _numMarkers--;
  if (_numMarkers == 0) { // can we release buffer?
    if (_p > 0) {
      // Copy tokens[p]..tokens[n-1] to tokens[0]..tokens[(n-1)-p], reset ptrs
      // p is last valid token; move nothing if p==n as we have no valid char
      _tokens.erase(_tokens.begin(), _tokens.begin() + static_cast<ssize_t>(_p));
      _p = 0;
    }

    _lastTokenBufferStart = _lastToken;
  }
}

size_t UnbufferedTokenStream::index()
{
  return _currentTokenIndex;
}

void UnbufferedTokenStream::seek(size_t index)
{ // seek to absolute index
  if (index == _currentTokenIndex) {
    return;
  }

  if (index > _currentTokenIndex) {
    sync(ssize_t(index - _currentTokenIndex));
    index = std::min(index, getBufferStartIndex() + _tokens.size() - 1);
  }

  size_t bufferStartIndex = getBufferStartIndex();
  if (bufferStartIndex > index) {
    throw IllegalArgumentException(std::string("cannot seek to negative index ") + std::to_string(index));
  }

  size_t i = index - bufferStartIndex;
  if (i >= _tokens.size()) {
    throw UnsupportedOperationException(std::string("seek to index outside buffer: ") + std::to_string(index) +
      " not in " + std::to_string(bufferStartIndex) + ".." + std::to_string(bufferStartIndex + _tokens.size()));
  }

  _p = i;
  _currentTokenIndex = index;
  if (_p == 0) {
    _lastToken = _lastTokenBufferStart;
  } else {
    _lastToken = _tokens[_p - 1].get();
  }
}

size_t UnbufferedTokenStream::size()
{
  throw UnsupportedOperationException("Unbuffered stream cannot know its size");
}

std::string UnbufferedTokenStream::getSourceName() const
{
  return _tokenSource->getSourceName();
}

std::string UnbufferedTokenStream::getText(const misc::Interval &interval)
{
  size_t bufferStartIndex = getBufferStartIndex();
  size_t bufferStopIndex = bufferStartIndex + _tokens.size() - 1;

  size_t start = interval.a;
  size_t stop = interval.b;
  if (start < bufferStartIndex || stop > bufferStopIndex) {
    throw UnsupportedOperationException(std::string("interval ") + interval.toString() +
      " not in token buffer window: " + std::to_string(bufferStartIndex) + ".." + std::to_string(bufferStopIndex));
  }

  size_t a = start - bufferStartIndex;
  size_t b = stop - bufferStartIndex;

  std::stringstream ss;
  for (size_t i = a; i <= b; i++) {
    Token *t = _tokens[i].get();
    if (i > 0)
      ss << ", ";
    ss << t->getText();
  }

  return ss.str();
}

size_t UnbufferedTokenStream::getBufferStartIndex() const
{
  return _currentTokenIndex - _p;
}

void UnbufferedTokenStream::InitializeInstanceFields()
{
  _p = 0;
  _numMarkers = 0;
  _currentTokenIndex = 0;
}