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/*
 * (C) Copyright IBM Corp. 1999-2003 - All Rights Reserved
 *
 * The original version of this source code and documentation is
 * copyrighted and owned by IBM. These materials are provided
 * under terms of a License Agreement between IBM and Sun.
 * This technology is protected by multiple US and International
 * patents. This notice and attribution to IBM may not be removed.
 */

package java.text;

import sun.text.bidi.BidiBase;

/**
 * This class implements the Unicode Bidirectional Algorithm.
 * <p>
 * A Bidi object provides information on the bidirectional reordering of the text
 * used to create it. This is required, for example, to properly display Arabic
 * or Hebrew text. These languages are inherently mixed directional, as they order
 * numbers from left-to-right while ordering most other text from right-to-left.
 * <p>
 * Once created, a Bidi object can be queried to see if the text it represents is
 * all left-to-right or all right-to-left. Such objects are very lightweight and
 * this text is relatively easy to process.
 * <p>
 * If there are multiple runs of text, information about the runs can be accessed
 * by indexing to get the start, limit, and level of a run. The level represents
 * both the direction and the 'nesting level' of a directional run. Odd levels
 * are right-to-left, while even levels are left-to-right. So for example level
 * 0 represents left-to-right text, while level 1 represents right-to-left text, and
 * level 2 represents left-to-right text embedded in a right-to-left run.
 *
 * @since 1.4
 */
public final class Bidi {

 /** Constant indicating base direction is left-to-right. */
 public static final int DIRECTION_LEFT_TO_RIGHT = 0;

 /** Constant indicating base direction is right-to-left. */
 public static final int DIRECTION_RIGHT_TO_LEFT = 1;

 /**
 * Constant indicating that the base direction depends on the first strong
 * directional character in the text according to the Unicode
 * Bidirectional Algorithm. If no strong directional character is present,
 * the base direction is left-to-right.
 */
 public static final int DIRECTION_DEFAULT_LEFT_TO_RIGHT = -2;

 /**
 * Constant indicating that the base direction depends on the first strong
 * directional character in the text according to the Unicode
 * Bidirectional Algorithm. If no strong directional character is present,
 * the base direction is right-to-left.
 */
 public static final int DIRECTION_DEFAULT_RIGHT_TO_LEFT = -1;

 private BidiBase bidiBase;

 /**
 * Create Bidi from the given paragraph of text and base direction.
 * @param paragraph a paragraph of text
 * @param flags a collection of flags that control the algorithm. The
 * algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
 * DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
 * Other values are reserved.
 */
 public Bidi(String paragraph, int flags) {
 if (paragraph == null) {
 throw new IllegalArgumentException("paragraph is null");
 }

 bidiBase = new BidiBase(paragraph.toCharArray(), 0, null, 0, paragraph.length(), flags);
 }

 /**
 * Create Bidi from the given paragraph of text.
 * <p>
 * The RUN_DIRECTION attribute in the text, if present, determines the base
 * direction (left-to-right or right-to-left). If not present, the base
 * direction is computes using the Unicode Bidirectional Algorithm, defaulting to left-to-right
 * if there are no strong directional characters in the text. This attribute, if
 * present, must be applied to all the text in the paragraph.
 * <p>
 * The BIDI_EMBEDDING attribute in the text, if present, represents embedding level
 * information. Negative values from -1 to -62 indicate overrides at the absolute value
 * of the level. Positive values from 1 to 62 indicate embeddings. Where values are
 * zero or not defined, the base embedding level as determined by the base direction
 * is assumed.
 * <p>
 * The NUMERIC_SHAPING attribute in the text, if present, converts European digits to
 * other decimal digits before running the bidi algorithm. This attribute, if present,
 * must be applied to all the text in the paragraph.
 *
 * @param paragraph a paragraph of text with optional character and paragraph attribute information
 *
 * @see java.awt.font.TextAttribute#BIDI_EMBEDDING
 * @see java.awt.font.TextAttribute#NUMERIC_SHAPING
 * @see java.awt.font.TextAttribute#RUN_DIRECTION
 */
 public Bidi(AttributedCharacterIterator paragraph) {
 if (paragraph == null) {
 throw new IllegalArgumentException("paragraph is null");
 }

 bidiBase = new BidiBase(0, 0);
 bidiBase.setPara(paragraph);
 }

 /**
 * Create Bidi from the given text, embedding, and direction information.
 * The embeddings array may be null. If present, the values represent embedding level
 * information. Negative values from -1 to -61 indicate overrides at the absolute value
 * of the level. Positive values from 1 to 61 indicate embeddings. Where values are
 * zero, the base embedding level as determined by the base direction is assumed.
 * @param text an array containing the paragraph of text to process.
 * @param textStart the index into the text array of the start of the paragraph.
 * @param embeddings an array containing embedding values for each character in the paragraph.
 * This can be null, in which case it is assumed that there is no external embedding information.
 * @param embStart the index into the embedding array of the start of the paragraph.
 * @param paragraphLength the length of the paragraph in the text and embeddings arrays.
 * @param flags a collection of flags that control the algorithm. The
 * algorithm understands the flags DIRECTION_LEFT_TO_RIGHT, DIRECTION_RIGHT_TO_LEFT,
 * DIRECTION_DEFAULT_LEFT_TO_RIGHT, and DIRECTION_DEFAULT_RIGHT_TO_LEFT.
 * Other values are reserved.
 */
 public Bidi(char[] text, int textStart, byte[] embeddings, int embStart, int paragraphLength, int flags) {
 if (text == null) {
 throw new IllegalArgumentException("text is null");
 }
 if (paragraphLength < 0) {
 throw new IllegalArgumentException("bad length: " + paragraphLength);
 }
 if (textStart < 0 || paragraphLength > text.length - textStart) {
 throw new IllegalArgumentException("bad range: " + textStart +
 " length: " + paragraphLength +
 " for text of length: " + text.length);
 }
 if (embeddings != null && (embStart < 0 || paragraphLength > embeddings.length - embStart)) {
 throw new IllegalArgumentException("bad range: " + embStart +
 " length: " + paragraphLength +
 " for embeddings of length: " + text.length);
 }

 bidiBase = new BidiBase(text, textStart, embeddings, embStart, paragraphLength, flags);
 }

 /**
 * Create a Bidi object representing the bidi information on a line of text within
 * the paragraph represented by the current Bidi. This call is not required if the
 * entire paragraph fits on one line.
 *
 * @param lineStart the offset from the start of the paragraph to the start of the line.
 * @param lineLimit the offset from the start of the paragraph to the limit of the line.
 * @return a {@code Bidi} object
 */
 public Bidi createLineBidi(int lineStart, int lineLimit) {
 AttributedString astr = new AttributedString("");
 Bidi newBidi = new Bidi(astr.getIterator());

 return bidiBase.setLine(this, bidiBase, newBidi, newBidi.bidiBase, lineStart, lineLimit);
 }

 /**
 * Return true if the line is not left-to-right or right-to-left. This means it either has mixed runs of left-to-right
 * and right-to-left text, or the base direction differs from the direction of the only run of text.
 *
 * @return true if the line is not left-to-right or right-to-left.
 */
 public boolean isMixed() {
 return bidiBase.isMixed();
 }

 /**
 * Return true if the line is all left-to-right text and the base direction is left-to-right.
 *
 * @return true if the line is all left-to-right text and the base direction is left-to-right
 */
 public boolean isLeftToRight() {
 return bidiBase.isLeftToRight();
 }

 /**
 * Return true if the line is all right-to-left text, and the base direction is right-to-left.
 * @return true if the line is all right-to-left text, and the base direction is right-to-left
 */
 public boolean isRightToLeft() {
 return bidiBase.isRightToLeft();
 }

 /**
 * Return the length of text in the line.
 * @return the length of text in the line
 */
 public int getLength() {
 return bidiBase.getLength();
 }

 /**
 * Return true if the base direction is left-to-right.
 * @return true if the base direction is left-to-right
 */
 public boolean baseIsLeftToRight() {
 return bidiBase.baseIsLeftToRight();
 }

 /**
 * Return the base level (0 if left-to-right, 1 if right-to-left).
 * @return the base level
 */
 public int getBaseLevel() {
 return bidiBase.getParaLevel();
 }

 /**
 * Return the resolved level of the character at offset. If offset is
 * {@literal <} 0 or &ge; the length of the line, return the base direction
 * level.
 *
 * @param offset the index of the character for which to return the level
 * @return the resolved level of the character at offset
 */
 public int getLevelAt(int offset) {
 return bidiBase.getLevelAt(offset);
 }

 /**
 * Return the number of level runs.
 * @return the number of level runs
 */
 public int getRunCount() {
 return bidiBase.countRuns();
 }

 /**
 * Return the level of the nth logical run in this line.
 * @param run the index of the run, between 0 and <code>getRunCount()</code>
 * @return the level of the run
 */
 public int getRunLevel(int run) {
 return bidiBase.getRunLevel(run);
 }

 /**
 * Return the index of the character at the start of the nth logical run in this line, as
 * an offset from the start of the line.
 * @param run the index of the run, between 0 and <code>getRunCount()</code>
 * @return the start of the run
 */
 public int getRunStart(int run) {
 return bidiBase.getRunStart(run);
 }

 /**
 * Return the index of the character past the end of the nth logical run in this line, as
 * an offset from the start of the line. For example, this will return the length
 * of the line for the last run on the line.
 * @param run the index of the run, between 0 and <code>getRunCount()</code>
 * @return limit the limit of the run
 */
 public int getRunLimit(int run) {
 return bidiBase.getRunLimit(run);
 }

 /**
 * Return true if the specified text requires bidi analysis. If this returns false,
 * the text will display left-to-right. Clients can then avoid constructing a Bidi object.
 * Text in the Arabic Presentation Forms area of Unicode is presumed to already be shaped
 * and ordered for display, and so will not cause this function to return true.
 *
 * @param text the text containing the characters to test
 * @param start the start of the range of characters to test
 * @param limit the limit of the range of characters to test
 * @return true if the range of characters requires bidi analysis
 */
 public static boolean requiresBidi(char[] text, int start, int limit) {
 return BidiBase.requiresBidi(text, start, limit);
 }

 /**
 * Reorder the objects in the array into visual order based on their levels.
 * This is a utility function to use when you have a collection of objects
 * representing runs of text in logical order, each run containing text
 * at a single level. The elements at <code>index</code> from
 * <code>objectStart</code> up to <code>objectStart + count</code>
 * in the objects array will be reordered into visual order assuming
 * each run of text has the level indicated by the corresponding element
 * in the levels array (at <code>index - objectStart + levelStart</code>).
 *
 * @param levels an array representing the bidi level of each object
 * @param levelStart the start position in the levels array
 * @param objects the array of objects to be reordered into visual order
 * @param objectStart the start position in the objects array
 * @param count the number of objects to reorder
 */
 public static void reorderVisually(byte[] levels, int levelStart, Object[] objects, int objectStart, int count) {
 BidiBase.reorderVisually(levels, levelStart, objects, objectStart, count);
 }

 /**
 * Display the bidi internal state, used in debugging.
 */
 public String toString() {
 return bidiBase.toString();
 }

}