package org.fife.ui.rsyntaxtextarea;

import javax.swing.text.TabExpander;

/**
 * Utility methods for dealing with tokens.
 *
 * @author Robert Futrell
 * @version 1.0
 */
public final class TokenUtils {

	private TokenUtils() {
	}

	/**
	 * Modifies the passed-in token list to start at the specified offset. For
	 * example, if the token list covered positions 20-60 in the document
	 * (inclusive) like so:
	 * 
	 * <pre>
	 *   [token1] -&gt; [token2] -&gt; [token3] -&gt; [token4]
	 *   20     30   31     40   41     50   51     60
	 * </pre>
	 * 
	 * and you used this method to make the token list start at position 44, then
	 * the token list would be modified to be the following:
	 * 
	 * <pre>
	 *   [part-of-old-token3] -&gt; [token4]
	 *   44                 50   51     60
	 * </pre>
	 * 
	 * Tokens that come before the specified position are forever lost, and the
	 * token containing that position is made to begin at that position if
	 * necessary. All token types remain the same as they were originally.
	 * <p>
	 *
	 * This method can be useful if you are only interested in part of a token list
	 * (i.e., the line it represents), but you don't want to modify the token list
	 * yourself.
	 *
	 * @param tokenList The list to make start at the specified position. This
	 *                  parameter is modified.
	 * @param pos       The position at which the new token list is to start. If
	 *                  this position is not in the passed-in token list, returned
	 *                  token list will either be <code>null</code> or the
	 *                  unpaintable token(s) at the end of the passed-in token list.
	 * @param e         How to expand tabs.
	 * @param textArea  The text area from which the token list came.
	 * @param x0        The initial x-pixel position of the old token list.
	 * @return Information about the "sub" token list. This will be
	 *         <code>null</code> if <code>pos</code> was not a valid offset into the
	 *         token list.
	 * @see #getSubTokenList(Token, int, TabExpander, RSyntaxTextArea, float,
	 *      TokenImpl)
	 */
	public static TokenSubList getSubTokenList(Token tokenList, int pos, TabExpander e, final RSyntaxTextArea textArea,
			float x0) {
		return getSubTokenList(tokenList, pos, e, textArea, x0, null);
	}

	/**
	 * Modifies the passed-in token list to start at the specified offset. For
	 * example, if the token list covered positions 20-60 in the document
	 * (inclusive) like so:
	 * 
	 * <pre>
	 *   [token1] -&gt; [token2] -&gt; [token3] -&gt; [token4]
	 *   20     30   31     40   41     50   51     60
	 * </pre>
	 * 
	 * and you used this method to make the token list start at position 44, then
	 * the token list would be modified to be the following:
	 * 
	 * <pre>
	 *   [part-of-old-token3] -&gt; [token4]
	 *   44                 50   51     60
	 * </pre>
	 * 
	 * Tokens that come before the specified position are forever lost, and the
	 * token containing that position is made to begin at that position if
	 * necessary. All token types remain the same as they were originally.
	 * <p>
	 *
	 * This method can be useful if you are only interested in part of a token list
	 * (i.e., the line it represents), but you don't want to modify the token list
	 * yourself.
	 *
	 * @param tokenList The list to make start at the specified position. This
	 *                  parameter is modified.
	 * @param pos       The position at which the new token list is to start. If
	 *                  this position is not in the passed-in token list, returned
	 *                  token list will either be <code>null</code> or the
	 *                  unpaintable token(s) at the end of the passed-in token list.
	 * @param e         How to expand tabs.
	 * @param textArea  The text area from which the token list came.
	 * @param x0        The initial x-pixel position of the old token list.
	 * @param tempToken A temporary token to use when creating the token list
	 *                  result. This may be <code>null</code> but callers can pass
	 *                  in a "buffer" token for performance if desired.
	 * @return Information about the "sub" token list. This will be
	 *         <code>null</code> if <code>pos</code> was not a valid offset into the
	 *         token list.
	 * @see #getSubTokenList(Token, int, TabExpander, RSyntaxTextArea, float)
	 */
	public static TokenSubList getSubTokenList(Token tokenList, int pos, TabExpander e, final RSyntaxTextArea textArea,
			float x0, TokenImpl tempToken) {
		if (tempToken == null) {
			tempToken = new TokenImpl();
		}
		Token t = tokenList;
		// Loop through the token list until you find the one that contains
		// pos. Remember the cumulative width of all of these tokens.
		while (t != null && t.isPaintable() && !t.containsPosition(pos)) {
			x0 += t.getWidth(textArea, e, x0);
			t = t.getNextToken();
		}
		// Make the token that contains pos start at pos.
		if (t != null && t.isPaintable()) {
			if (t.getOffset() != pos) {
				// Number of chars between p0 and token start.
				int difference = pos - t.getOffset();
				x0 += t.getWidthUpTo(t.length() - difference + 1, textArea, e, x0);
				tempToken.copyFrom(t);
				tempToken.makeStartAt(pos);
				return new TokenSubList(tempToken, x0);
			} else { // t.getOffset()==pos
				return new TokenSubList(t, x0);
			}
		}
		// This could be a null token, so we need to just return it.
		return new TokenSubList(tokenList, x0);
		// return null;
	}

	/**
	 * A sub-list of tokens.
	 */
	public static class TokenSubList {

		/**
		 * The "sub" token list.
		 */
		public Token tokenList;
		/**
		 * The width, in pixels, of the part of the token list "removed from the front."
		 * This way, you know the x-offset of the "new" token list.
		 */
		public float x;

		public TokenSubList(Token tokenList, float x) {
			this.tokenList = tokenList;
			this.x = x;
		}
	}
}