package com.redhat.ceylon.eclipse.code.editor;

import static com.redhat.ceylon.eclipse.code.editor.CeylonEditor.getFences;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DefaultTextDoubleClickStrategy;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.source.DefaultCharacterPairMatcher;

public class DoubleClickStrategy extends DefaultTextDoubleClickStrategy {
    
    protected final IdentifierDetector fWordDetector;
    protected final DefaultCharacterPairMatcher fPairMatcher;

    public DoubleClickStrategy() {
        fWordDetector = new IdentifierDetector();
        StringBuilder sb= new StringBuilder();
        String[][] fences= getFences();
        for(int i= 0; i < fences.length; i++) {
            sb.append(fences[i][0]);
            sb.append(fences[i][1]);
        }
        fPairMatcher= new DefaultCharacterPairMatcher(sb.toString().toCharArray());
    }
   
    private final class IdentifierDetector {
        private static final int UNKNOWN= -1;

        /* states */
        private static final int WS= 0;
        private static final int ID= 1;
        private static final int IDS= 2;

        /* directions */
        private static final int FORWARD= 0;
        private static final int BACKWARD= 1;

        /** The current state. */
        private int fState;
        /**
         * The state at the anchor (if already detected by going the other way),
         * or <code>UNKNOWN</code>.
         */
        private int fAnchorState;
        /** The current direction. */
        private int fDirection;
        /** The start of the detected word. */
        private int fStart;
        /** The end of the word. */
        private int fEnd;

        /**
         * Initializes the detector at offset <code>anchor</code>.
         *
         * @param anchor the offset of the double click
         */
        private void setAnchor(int anchor) {
            fState= UNKNOWN;
            fAnchorState= UNKNOWN;
            fDirection= UNKNOWN;

            fStart= anchor;
            fEnd= anchor - 1;
        }

        private boolean isIdentifierStart(char c) {
            return Character.isJavaIdentifierStart(c) && c!='$';
        }

        private boolean isIdentifierPart(char c) {
            return Character.isJavaIdentifierPart(c) && c!='$';
        }

        private boolean isWhitespace(char c) {
            return c==' '||c=='\r'||c=='\n'||c=='\t'||c=='\f';
        }

        /**
         * Try to add a character to the word going backward. Only call after forward calls!
         *
         * @param c the character to add
         * @param offset the offset of the character
         * @return <code>true</code> if further characters may be added to the word
         */
        private boolean backward(char c, int offset) {
            checkDirection(BACKWARD);
            switch (fState) {
                case IDS:
                    if (isWhitespace(c)) {
                        fState= WS;
                        return true;
                    }
                    if (isIdentifierStart(c)) {
                        fStart= offset;
                        fState= IDS;
                        return true;
                    }
                    if (isIdentifierPart(c)) {
                        fStart= offset;
                        fState= ID;
                        return true;
                    }
                    return false;
                case ID:
                    if (isIdentifierStart(c)) {
                        fStart= offset;
                        fState= IDS;
                        return true;
                    }
                    if (isIdentifierPart(c)) {
                        fStart= offset;
                        fState= ID;
                        return true;
                    }
                    return false;
                case WS:
                    if (isWhitespace(c)) {
                        return true;
                    }
                    return false;
                case UNKNOWN:
                    if (c == '.') {
                        fEnd= offset - 1;
                        fState= IDS;
                        fAnchorState= fState;
                        return true;
                    }
                    return false;
                default:
                    return false;
            }
        }

        /**
         * Try to add a character to the word going forward.
         *
         * @param c the character to add
         * @param offset the offset of the character
         * @return <code>true</code> if further characters may be added to the word
         */
        private boolean forward(char c, int offset) {
            checkDirection(FORWARD);
            switch (fState) {
                case WS:
                    if (isWhitespace(c)) {
                        fState= WS;
                        return true;
                    }
                    if (isIdentifierStart(c)) {
                        fEnd= offset;
                        fState= IDS;
                        return true;
                    }
                    return false;
                case IDS:
                case ID:
                    if (isIdentifierStart(c)) {
                        fEnd= offset;
                        fState= IDS;
                        return true;
                    }
                    if (isIdentifierPart(c)) {
                        fEnd= offset;
                        fState= ID;
                        return true;
                    }
                    return false;
                case UNKNOWN:
                    if (isIdentifierStart(c)) {
                        fEnd= offset;
                        fState= IDS;
                        fAnchorState= fState;
                        return true;
                    }
                    if (isIdentifierPart(c)) {
                        fEnd= offset;
                        fState= ID;
                        fAnchorState= fState;
                        return true;
                    }
                    if (isWhitespace(c)) {
                        fState= WS;
                        fAnchorState= fState;
                        return true;
                    }
                    return false;
                default:
                    return false;
            }
        }

        /**
         * If the direction changes, set state to be the previous anchor state.
         *
         * @param direction the new direction
         */
        private void checkDirection(int direction) {
            if (fDirection == direction)
                return;

            if (direction == FORWARD) {
                if (fStart <= fEnd)
                    fState= fAnchorState;
                else
                    fState= UNKNOWN;
            } else if (direction == BACKWARD) {
                if (fEnd >= fStart)
                    fState= fAnchorState;
                else
                    fState= UNKNOWN;
            }

            fDirection= direction;
        }

        /**
         * Returns the region containing <code>anchor</code> that is a java word.
         *
         * @param document the document from which to read characters
         * @param anchor the offset around which to select a word
         * @return the region describing a java word around <code>anchor</code>
         */
        public IRegion getWordSelection(IDocument document, int anchor) {
            try {
                final int min= 0;
                final int max= document.getLength();
                setAnchor(anchor);

                char c;

                int offset= anchor;
                while (offset < max) {
                    c= document.getChar(offset);
                    if (!forward(c, offset))
                        break;
                    ++offset;
                }

                offset= anchor; // use to not select the previous word when right behind it
                //offset= anchor - 1; // use to select the previous word when right behind it
                while (offset >= min) {
                    c= document.getChar(offset);
                    if (!backward(c, offset))
                        break;
                    --offset;
                }

                return new Region(fStart, fEnd - fStart + 1);
            } 
            catch (BadLocationException x) {
                return new Region(anchor, 0);
            }
        }
    }


    protected IRegion findWord(IDocument document, int anchor) {
        return fWordDetector.getWordSelection(document, anchor);
    }

    protected IRegion findExtendedDoubleClickSelection(IDocument document, int offset) {
        IRegion match= fPairMatcher.match(document, offset);
        if (match != null && match.getLength() >= 2)
            return new Region(match.getOffset() + 1, match.getLength() - 2);
        return findWord(document, offset);
    }
}

@@ -2285,32 +2285,43 @@
 art(c) && c!='$'
+ %7C%7C c=='%5C%5C'
 ;%0A        %7D%0A%0A   

include initial \ when selecting escaped identifier