package com.github.ncruces.utils;

public final class CharArraySequence implements CharSequence {
    private final char[] buf;
    private final int off, len;

    public CharArraySequence(char[] value) {
        buf = value;
        off = 0;
        len = value.length;
    }

    public CharArraySequence(char[] value, int offset, int length) {
        if ((offset | length | offset + length | value.length - offset - length) < 0) {
            throw new IndexOutOfBoundsException();
        }
        buf = value;
        off = offset;
        len = length;
    }

    @Override
    public int length() { return len; }

    @Override
    public String toString() { return String.valueOf(buf, off, len); }

    @Override
    public char charAt(int index) {
        if ((index | len - index - 1) < 0) {
            throw new IndexOutOfBoundsException();
        }
        return buf[off + index];
    }

    @Override
    public CharSequence subSequence(int start, int end) {
        int cnt = end - start;
        int rem = len - end;
        if ((start | end | cnt | rem) < 0) {
            throw new IndexOutOfBoundsException();
        }
        if ((start | rem) == 0) {
            return this;
        }
        return new CharArraySequence(off + start, cnt, buf);
    }

    private CharArraySequence(int offset, int length, char[] value) {
        off = offset;
        len = length;
        buf = value;
    }
}