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// Copyright 2000-2024 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
package com.intellij.util.text;

import com.intellij.openapi.util.text.CharSequenceWithStringHash;
import com.intellij.openapi.util.text.Strings;
import org.jetbrains.annotations.NotNull;

public class CharArrayCharSequence implements CharSequenceBackedByArray, CharSequenceWithStringHash {
  protected final char[] myChars;
  protected final int myStart;
  protected final int myEnd;

  public CharArrayCharSequence(char @NotNull ... chars) {
    this(chars, 0, chars.length);
  }

  public CharArrayCharSequence(char @NotNull [] chars, int start, int end) {
    if (start < 0 || end > chars.length || start > end) {
      throw new IndexOutOfBoundsException("chars.length:" + chars.length + ", start:" + start + ", end:" + end);
    }
    myChars = chars;
    myStart = start;
    myEnd = end;
  }

  @Override
  public final int length() {
    return myEnd - myStart;
  }

  @Override
  public final char charAt(int index) {
    return myChars[index + myStart];
  }

  @Override
  public @NotNull CharSequence subSequence(int start, int end) {
    return start == 0 && end == length() ? this : new CharArrayCharSequence(myChars, myStart + start, myStart + end);
  }

  @Override
  public @NotNull String toString() {
    return new String(myChars, myStart, myEnd - myStart); //TODO StringFactory
  }

  @Override
  public char @NotNull [] getChars() {
    if (myStart == 0) return myChars;
    char[] chars = new char[length()];
    getChars(chars, 0);
    return chars;
  }

  @Override
  public void getChars(char @NotNull [] dst, int dstOffset) {
    System.arraycopy(myChars, myStart, dst, dstOffset, length());
  }

  @Override
  public boolean equals(Object anObject) {
    if (this == anObject) {
      return true;
    }
    if (anObject == null || getClass() != anObject.getClass() || length() != ((CharSequence) anObject).length()) {
      return false;
    }
    return CharArrayUtil.regionMatches(myChars, myStart, myEnd, (CharSequence) anObject);
  }

  /**
   * See {@link java.io.Reader#read(char[], int, int)};
   */
  public int readCharsTo(int start, char[] cbuf, int off, int len) {
    final int readChars = Math.min(len, length() - start);
    if (readChars <= 0) return -1;

    System.arraycopy(myChars, myStart + start, cbuf, off, readChars);
    return readChars;
  }

  private transient int hash;

  @Override
  public int hashCode() {
    int h = hash;
    if (h == 0) {
      hash = h = Strings.stringHashCode(myChars, myStart, myEnd);
    }
    return h;
  }
}