/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.datasketches.memory.internal;

import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.ByteOrder;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Objects;
import java.util.Random;

import org.apache.datasketches.memory.Memory;

/**
 * @author Lee Rhodes
 */
public final class Util {

  private Util() { }

  public static final String LS = System.getProperty("line.separator");

  /**
   * Don't use sun.misc.Unsafe#copyMemory to copy blocks of memory larger than this
   * threshold, because internally it doesn't have safepoint polls, that may cause long
   * "Time To Safe Point" pauses in the application. This has been fixed in JDK 9 (see
   * https://bugs.openjdk.java.net/browse/JDK-8149596 and
   * https://bugs.openjdk.java.net/browse/JDK-8141491), but not in JDK 8, so the Memory library
   * should keep having this boilerplate as long as it supports Java 8.
   *
   * <p>A reference to this can be found in java.nio.Bits.</p>
   */
  public static final int UNSAFE_COPY_THRESHOLD_BYTES = 1024 * 1024;

  //Byte Order related
  public static final ByteOrder NATIVE_BYTE_ORDER = ByteOrder.nativeOrder();

  public static final ByteOrder NON_NATIVE_BYTE_ORDER = NATIVE_BYTE_ORDER == ByteOrder.LITTLE_ENDIAN
      ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN;

  public static ByteOrder otherByteOrder(final ByteOrder order) {
    return (order == NATIVE_BYTE_ORDER) ? NON_NATIVE_BYTE_ORDER : NATIVE_BYTE_ORDER;
  }

  /**
   * Returns true if the given byteOrder is the same as the native byte order.
   * @param byteOrder the given byte order
   * @return true if the given byteOrder is the same as the native byte order.
   */
  public static boolean isNativeByteOrder(final ByteOrder byteOrder) {
    if (byteOrder == null) {
      throw new IllegalArgumentException("ByteOrder parameter cannot be null.");
    }
    return ByteOrder.nativeOrder() == byteOrder;
  }

  /**
   * Searches a range of the specified array of longs for the specified value using the binary
   * search algorithm. The range must be sorted method) prior to making this call.
   * If it is not sorted, the results are undefined. If the range contains
   * multiple elements with the specified value, there is no guarantee which one will be found.
   * @param mem the Memory to be searched
   * @param fromLongIndex the index of the first element (inclusive) to be searched
   * @param toLongIndex the index of the last element (exclusive) to be searched
   * @param key the value to be searched for
   * @return index of the search key, if it is contained in the array within the specified range;
   * otherwise, (-(insertion point) - 1). The insertion point is defined as the point at which
   * the key would be inserted into the array: the index of the first element in the range greater
   * than the key, or toIndex if all elements in the range are less than the specified key.
   * Note that this guarantees that the return value will be &ge; 0 if and only if the key is found.
   */
  public static long binarySearchLongs(final Memory mem, final long fromLongIndex,
      final long toLongIndex, final long key) {
    ResourceImpl.checkBounds(fromLongIndex << 3, (toLongIndex - fromLongIndex) << 3, mem.getCapacity());
    long low = fromLongIndex;
    long high = toLongIndex - 1L;

    while (low <= high) {
      final long mid = (low + high) >>> 1;
      final long midVal = mem.getLong(mid << 3);

      if (midVal < key)      { low = mid + 1;  }
      else if (midVal > key) { high = mid - 1; }
      else                   { return mid;     } // key found
    }
    return -(low + 1); // key not found.
  }

  /**
   * Prepend the given string with zeros. If the given string is equal or greater than the given
   * field length, it will be returned without modification.
   * @param s the given string
   * @param fieldLength desired total field length including the given string
   * @return the given string prepended with zeros.
   */
  public static final String zeroPad(final String s, final int fieldLength) {
    return characterPad(s, fieldLength, '0', false);
  }

  /**
   * Prepend or postpend the given string with the given character to fill the given field length.
   * If the given string is equal or greater than the given field length, it will be returned
   * without modification.
   * @param s the given string
   * @param fieldLength the desired field length
   * @param padChar the desired pad character
   * @param postpend if true append the pacCharacters to the end of the string.
   * @return prepended or postpended given string with the given character to fill the given field
   * length.
   */
  public static final String characterPad(final String s, final int fieldLength,
      final char padChar, final boolean postpend) {
    final char[] chArr = s.toCharArray();
    final int sLen = chArr.length;
    if (sLen < fieldLength) {
      final char[] out = new char[fieldLength];
      final int blanks = fieldLength - sLen;

      if (postpend) {
        for (int i = 0; i < sLen; i++) {
          out[i] = chArr[i];
        }
        for (int i = sLen; i < fieldLength; i++) {
          out[i] = padChar;
        }
      } else { //prepend
        for (int i = 0; i < blanks; i++) {
          out[i] = padChar;
        }
        for (int i = blanks; i < fieldLength; i++) {
          out[i] = chArr[i - blanks];
        }
      }

      return String.valueOf(out);
    }
    return s;
  }

  /**
   * Return true if all the masked bits of value are zero
   * @param value the value to be tested
   * @param bitMask defines the bits of interest
   * @return true if all the masked bits of value are zero
   */
  public static final boolean isAllBitsClear(final long value, final long bitMask) {
    return (~value & bitMask) == bitMask;
  }

  /**
   * Return true if all the masked bits of value are one
   * @param value the value to be tested
   * @param bitMask defines the bits of interest
   * @return true if all the masked bits of value are one
   */
  public static final boolean isAllBitsSet(final long value, final long bitMask) {
    return (value & bitMask) == bitMask;
  }

  /**
   * Return true if any the masked bits of value are zero
   * @param value the value to be tested
   * @param bitMask defines the bits of interest
   * @return true if any the masked bits of value are zero
   */
  public static final boolean isAnyBitsClear(final long value, final long bitMask) {
    return (~value & bitMask) != 0;
  }

  /**
   * Return true if any the masked bits of value are one
   * @param value the value to be tested
   * @param bitMask defines the bits of interest
   * @return true if any the masked bits of value are one
   */
  public static final boolean isAnyBitsSet(final long value, final long bitMask) {
    return (value & bitMask) != 0;
  }

  /**
   * Creates random valid Character Code Points (as integers). By definition, valid CodePoints
   * are integers in the range 0 to Character.MAX_CODE_POINT, and exclude the surrogate values.
   * This is used in unit testing and characterization testing of the UTF8 class. Because the
   * characterization tools are in a separate package, this must remain public.
   *
   * @author Lee Rhodes
   */
  public static class RandomCodePoints {
    private Random rand; //
    private static final int ALL_CP = Character.MAX_CODE_POINT + 1;
    private static final int MIN_SUR = Character.MIN_SURROGATE;
    private static final int MAX_SUR = Character.MAX_SURROGATE;

    /**
     * @param deterministic if true, configure java.util.Random with a fixed seed.
     */
    public RandomCodePoints(final boolean deterministic) {
      rand = deterministic ? new Random(0) : new Random();
    }

    /**
     * Fills the given array with random valid Code Points from 0, inclusive, to
     * <i>Character.MAX_CODE_POINT</i>, inclusive.
     * The surrogate range, which is from <i>Character.MIN_SURROGATE</i>, inclusive, to
     * <i>Character.MAX_SURROGATE</i>, inclusive, is always <u>excluded</u>.
     * @param cpArr the array to fill
     */
    public final void fillCodePointArray(final int[] cpArr) {
      fillCodePointArray(cpArr, 0, ALL_CP);
    }

    /**
     * Fills the given array with random valid Code Points from <i>startCP</i>, inclusive, to
     * <i>endCP</i>, exclusive.
     * The surrogate range, which is from <i>Character.MIN_SURROGATE</i>, inclusive, to
     * <i>Character.MAX_SURROGATE</i>, inclusive, is always <u>excluded</u>.
     * @param cpArr the array to fill
     * @param startCP the starting Code Point, included.
     * @param endCP the ending Code Point, excluded. This value cannot exceed 0x110000.
     */
    public final void fillCodePointArray(final int[] cpArr, final int startCP, final int endCP) {
      final int arrLen = cpArr.length;
      final int numCP = Math.min(endCP, 0X110000) - Math.min(0, startCP);
      int idx = 0;
      while (idx < arrLen) {
        final int cp = startCP + rand.nextInt(numCP);
        if ((cp >= MIN_SUR) && (cp <= MAX_SUR)) {
          continue;
        }
        cpArr[idx++] = cp;
      }
    }

    /**
     * Return a single valid random Code Point from 0, inclusive, to
     * <i>Character.MAX_CODE_POINT</i>, inclusive.
     * The surrogate range, which is from <i>Character.MIN_SURROGATE</i>, inclusive, to
     * <i>Character.MAX_SURROGATE</i>, inclusive, is always <u>excluded</u>.
     * @return a single valid random CodePoint.
     */
    public final int getCodePoint() {
      return getCodePoint(0, ALL_CP);
    }

    /**
     * Return a single valid random Code Point from <i>startCP</i>, inclusive, to
     * <i>endCP</i>, exclusive.
     * The surrogate range, which is from <i>Character.MIN_SURROGATE</i>, inclusive, to
     * <i>Character.MAX_SURROGATE</i>, inclusive, is always <u>excluded</u>.
     * @param startCP the starting Code Point, included.
     * @param endCP the ending Code Point, excluded. This value cannot exceed 0x110000.
     * @return a single valid random CodePoint.
     */
    public final int getCodePoint(final int startCP, final int endCP) {
      final int numCP = Math.min(endCP, 0X110000) - Math.min(0, startCP);
      while (true) {
        final int cp = startCP + rand.nextInt(numCP);
        if ((cp < MIN_SUR) || (cp > MAX_SUR)) {
          return cp;
        }
      }
    }
  } //End class RandomCodePoints

  public static final void zeroCheck(final long value, final String arg) {
    if (value <= 0) {
      throw new IllegalArgumentException("The argument '" + arg + "' may not be negative or zero.");
    }
  }

  public static final void negativeCheck(final long value, final String arg) {
    if (value < 0) {
      throw new IllegalArgumentException("The argument '" + arg + "' may not be negative.");
    }
  }

  public static final void nullCheck(final Object obj, final String arg) {
    if (obj == null) {
      throw new IllegalArgumentException("The argument '" + arg + "' may not be null.");
    }
  }

  //Resources NOTE: these 3 methods are duplicated in Java/ datasketches/Util

  /**
   * Gets the absolute path of the given resource file's shortName.
   *
   * <p>Note that the ClassLoader.getResource(shortName) returns a URL,
   * which can have special characters, e.g., "%20" for spaces. This method
   * obtains the URL, converts it to a URI, then does a uri.getPath(), which
   * decodes any special characters in the URI path. This is required to make
   * obtaining resources operating-system independent.</p>
   *
   * @param shortFileName the last name in the pathname's name sequence.
   * @return the absolute path of the given resource file's shortName.
   */
  public static String getResourcePath(final String shortFileName) {
    Objects.requireNonNull(shortFileName, "input parameter " + shortFileName + " cannot be null.");
    try {
      final URL url = Util.class.getClassLoader().getResource(shortFileName);
      Objects.requireNonNull(url, "resource " + shortFileName + " could not be acquired.");
      final URI uri = url.toURI();
      //decodes any special characters
      final String path = uri.isAbsolute() ? Paths.get(uri).toAbsolutePath().toString() : uri.getPath();
      return path;
    } catch (final URISyntaxException e) {
      throw new IllegalArgumentException("Cannot find resource: " + shortFileName + LS + e);
    }
  }

  /**
   * Gets the file defined by the given resource file's shortFileName.
   * @param shortFileName the last name in the pathname's name sequence.
   * @return the file defined by the given resource file's shortFileName.
   */
  public static File getResourceFile(final String shortFileName) {
    return new File(getResourcePath(shortFileName));
  }

  /**
   * Returns a byte array of the contents of the file defined by the given resource file's
   * shortFileName.
   * @param shortFileName the last name in the pathname's name sequence.
   * @return a byte array of the contents of the file defined by the given resource file's
   * shortFileName.
   */
  public static byte[] getResourceBytes(final String shortFileName) {
    try {
      return Files.readAllBytes(Paths.get(getResourcePath(shortFileName)));
    } catch (final IOException e) {
      throw new IllegalArgumentException("Cannot read resource: " + shortFileName + LS + e);
    }
  }

}
