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/*
 * Copyright (C) 2009-2011 Mathias Doenitz
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.parboiled.buffers;

import org.parboiled.common.IntArrayStack;
import org.parboiled.errors.ParserRuntimeException;
import org.parboiled.support.Chars;
import org.parboiled.support.IndexRange;
import org.parboiled.support.Position;

import java.util.Arrays;

import static org.parboiled.common.Preconditions.checkArgNotNull;
import static org.parboiled.common.Preconditions.checkArgument;

/**
 * Immutable default implementation of an InputBuffer.
 */
public class DefaultInputBuffer implements InputBuffer {
    private final int length;
    private final char[] buffer;

    // the indices of the newline characters in the buffer
    // built lazily, since the newline information is normally only needed in the case of parse errors when
    // error messages need to be generated
    private int[] newlines;

    /**
     * Constructs a new DefaultInputBuffer wrapping the given char array.
     * CAUTION: For performance reasons the given char array is not defensively copied.
     *
     * @param buffer the chars
     */
    public DefaultInputBuffer(char[] buffer) {
        checkArgNotNull(buffer, "buffer");
        this.buffer = buffer;
        this.length = buffer.length;
    }

    public char charAt(int index) {
        return 0 <= index && index < length ? buffer[index] :
                index - length > 100000 ? throwParsingException() : Chars.EOI;
    }

    private char throwParsingException() {
        throw new ParserRuntimeException("Parser read more than 100K chars beyond EOI, " +
                "verify that your grammar does not consume EOI indefinitely!");
    }

    public boolean test(int index, char[] characters) {
        int len = characters.length;
        if (index < 0 || index > length - len) {
            return false;
        }
        for (int i = 0; i < len; i++) {
            if (buffer[index + i] != characters[i]) return false;
        }
        return true;
    }

    public String extract(int start, int end) {
        if (start < 0) start = 0;
        if (end >= length) end = length;
        if (end <= start) return "";
        return new String(buffer, start, end - start);
    }

    public String extract(IndexRange range) {
        return new String(buffer, range.start, Math.min(range.end, length) - range.start);
    }

    public Position getPosition(int index) {
        buildNewlines();
        int line = getLine0(newlines, index);
        int column = index - (line > 0 ? newlines[line - 1] : -1);
        return new Position(line + 1, column);
    }

    public int getOriginalIndex(int index) {
        return index;
    }

    // returns the zero based input line number the character with the given index is found in
    private static int getLine0(int[] newlines, int index) {
        int j = Arrays.binarySearch(newlines, index);
        return j >= 0 ? j : -(j + 1);
    }

    public String extractLine(int lineNumber) {
        buildNewlines();
        checkArgument(0 < lineNumber && lineNumber <= newlines.length + 1);
        int start = lineNumber > 1 ? newlines[lineNumber - 2] + 1 : 0;
        int end = lineNumber <= newlines.length ? newlines[lineNumber - 1] : length;
        if (charAt(end - 1) == '\r') end--;
        return extract(start, end);
    }

    public int getLineCount() {
        buildNewlines();
        return newlines.length + 1;
    }

    private void buildNewlines() {
        if (newlines == null) {
            IntArrayStack newlines = new IntArrayStack();
            for (int i = 0; i < length; i++) {
                if (buffer[i] == '\n') {
                    newlines.push(i);
                }
            }
            this.newlines = new int[newlines.size()];
            newlines.getElements(this.newlines, 0);
        }
    }
}