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/*
 * Copyright (c) 2019 by Andrew Charneski.
 *
 * The author licenses this file to you 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 com.simiacryptus.util.binary;

import com.simiacryptus.ref.wrappers.RefStringBuilder;

import javax.annotation.Nonnull;

public class Interval {
  public final long start;
  public final long max;
  public final long length;

  public Interval(long start, long length, long max) {
    super();
    if (0 >= max)
      throw new IllegalArgumentException();
    if (0 > start || max <= start)
      throw new IllegalArgumentException();
    if (0 >= length)
      throw new IllegalArgumentException();
    if (max < start + length)
      throw new IllegalArgumentException();
    this.start = start;
    this.max = max;
    this.length = length;
  }

  public long end() {
    return start + length;
  }

  @Nonnull
  public Bits toBits() {
    int peekBits = (int) Math.ceil(Math.log(max) / Math.log(2)) + 4;
    Bits startBits = Bits.divide(start, max, peekBits).padRight(peekBits);
    Bits endBits = Bits.divide(end(), max, peekBits).padRight(peekBits);
    for (int i = 0; i < peekBits; i++) {
      long a = startBits.range(0, i).toLong();
      long b = endBits.range(0, i).toLong();
      if (b - a > 1) {
        Bits bits = new Bits(a + 1, i);
        assert Bits.ZERO.equals(bits.range(0, 1));
        return bits.range(1);
      }
    }
    throw new RuntimeException();
  }

  @Override
  public String toString() {
    final RefStringBuilder sb = new RefStringBuilder(
        "Interval{");
    sb.append("start=").append(start);
    sb.append(", length=").append(length);
    sb.append(", max=").append(max);
    sb.append('}');
    return sb.toString();
  }
}