/* 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 "CommonTokenStream.h"

#include "Token.h"

using namespace antlr4;

CommonTokenStream::CommonTokenStream(TokenSource* tokenSource)
    : CommonTokenStream(tokenSource, Token::DEFAULT_CHANNEL) {}

CommonTokenStream::CommonTokenStream(TokenSource* tokenSource, size_t channel_)
    : BufferedTokenStream(tokenSource), channel(channel_) {}

ssize_t CommonTokenStream::adjustSeekIndex(size_t i) {
    return nextTokenOnChannel(i, channel);
}

Token* CommonTokenStream::LB(size_t k) {
    if (k == 0 || k > _p) {
        return nullptr;
    }

    ssize_t i = static_cast<ssize_t>(_p);
    size_t n = 1;
    // find k good tokens looking backwards
    while (n <= k) {
        // skip off-channel tokens
        i = previousTokenOnChannel(i - 1, channel);
        n++;
    }
    if (i < 0) {
        return nullptr;
    }

    return _tokens[i].get();
}

Token* CommonTokenStream::LT(ssize_t k) {
    lazyInit();
    if (k == 0) {
        return nullptr;
    }
    if (k < 0) {
        return LB(static_cast<size_t>(-k));
    }
    size_t i = _p;
    ssize_t n = 1; // we know tokens[p] is a good one
                   // find k good tokens
    while (n < k) {
        // skip off-channel tokens, but make sure to not look past EOF
        if (sync(i + 1)) {
            i = nextTokenOnChannel(i + 1, channel);
        }
        n++;
    }

    return _tokens[i].get();
}

int CommonTokenStream::getNumberOfOnChannelTokens() {
    int n = 0;
    fill();
    for (size_t i = 0; i < _tokens.size(); i++) {
        Token* t = _tokens[i].get();
        if (t->getChannel() == channel) {
            n++;
        }
        if (t->getType() == Token::EOF) {
            break;
        }
    }
    return n;
}
