/*******************************************************************************
 * Copyright (c) 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.ui.texteditor;

import java.util.ArrayList;

import org.eclipse.jface.fieldassist.IContentProposal;
import org.eclipse.jface.fieldassist.IContentProposalProvider;

/**
 * Content assist proposal provider for regular expressions.
 * <p>
 * Note: Replaces <code>RegExContentAssistProcessor</code> which was introduced in 3.0.
 * </p>
 *
 * @since 3.2
 */
final class RegExContentProposalProvider implements IContentProposalProvider {

	
	/**
	 * Proposal computer.
	 */
	private static class ProposalComputer {

		private static class Proposal implements IContentProposal {
			
			private String fContent;
			private String fLabel;
			private String fDescription;
			private int fCursorPosition;
			
			Proposal(String content, String label, String description, int cursorPosition) {
				fContent= content;
				fLabel= label;
				fDescription= description;
				fCursorPosition= cursorPosition;
			}
			
			public String getContent() {
				return fContent;
			}
			
			public String getLabel() {
				return fLabel;
			}
			
			public String getDescription() {
				return fDescription;
			}
			
			public int getCursorPosition() {
				return fCursorPosition;
			}
		}
		

		/**
		 * The whole regular expression.
		 */
		private final String fExpression;
		/**
		 * The document offset.
		 */
		private final int fDocumentOffset;
		/**
		 * The high-priority proposals.
		 */
		private final ArrayList fPriorityProposals;
		/**
		 * The low-priority proposals.
		 */
		private final ArrayList fProposals;
		/**
		 * <code>true</code> iff <code>fExpression</code> ends with an open escape.
		 */
		private final boolean fIsEscape;

		/**
		 * Creates a new Proposal Computer.
		 * @param contents the contents of the subject control
		 * @param position the cursor position
		 */
		public ProposalComputer(String contents, int position) {
			fExpression= contents;
			fDocumentOffset= position;
			fPriorityProposals= new ArrayList();
			fProposals= new ArrayList();
			
			boolean isEscape= false;
			esc: for (int i= position - 1; i >= 0; i--) {
				if (fExpression.charAt(i) == '\\')
					isEscape= !isEscape;
				else
					break esc;
			}
			fIsEscape= isEscape;
		}

		/**
		 * Computes applicable proposals for the find field.
		 * @return the proposals
		 */
		public IContentProposal[] computeFindProposals() {
			//characters
			addBsProposal("\\\\", RegExMessages.displayString_bs_bs, RegExMessages.additionalInfo_bs_bs); //$NON-NLS-1$
			addBracketProposal("\\0", 2, RegExMessages.displayString_bs_0, RegExMessages.additionalInfo_bs_0); //$NON-NLS-1$
			addBracketProposal("\\x", 2, RegExMessages.displayString_bs_x, RegExMessages.additionalInfo_bs_x); //$NON-NLS-1$
			addBracketProposal("\\u", 2, RegExMessages.displayString_bs_u, RegExMessages.additionalInfo_bs_u); //$NON-NLS-1$
			addBsProposal("\\t", RegExMessages.displayString_bs_t, RegExMessages.additionalInfo_bs_t); //$NON-NLS-1$
			addBsProposal("\\n", RegExMessages.displayString_bs_n, RegExMessages.additionalInfo_bs_n); //$NON-NLS-1$
			addBsProposal("\\r", RegExMessages.displayString_bs_r, RegExMessages.additionalInfo_bs_r); //$NON-NLS-1$
			addBsProposal("\\f", RegExMessages.displayString_bs_f, RegExMessages.additionalInfo_bs_f); //$NON-NLS-1$
			addBsProposal("\\a", RegExMessages.displayString_bs_a, RegExMessages.additionalInfo_bs_a); //$NON-NLS-1$
			addBsProposal("\\e", RegExMessages.displayString_bs_e, RegExMessages.additionalInfo_bs_e); //$NON-NLS-1$
			addBsProposal("\\c", RegExMessages.displayString_bs_c, RegExMessages.additionalInfo_bs_c); //$NON-NLS-1$
			
			if (! fIsEscape)
				addBracketProposal(".", 1, RegExMessages.displayString_dot, RegExMessages.additionalInfo_dot); //$NON-NLS-1$
			addBsProposal("\\d", RegExMessages.displayString_bs_d, RegExMessages.additionalInfo_bs_d); //$NON-NLS-1$
			addBsProposal("\\D", RegExMessages.displayString_bs_D, RegExMessages.additionalInfo_bs_D); //$NON-NLS-1$
			addBsProposal("\\s", RegExMessages.displayString_bs_s, RegExMessages.additionalInfo_bs_s); //$NON-NLS-1$
			addBsProposal("\\S", RegExMessages.displayString_bs_S, RegExMessages.additionalInfo_bs_S); //$NON-NLS-1$
			addBsProposal("\\w", RegExMessages.displayString_bs_w, RegExMessages.additionalInfo_bs_w); //$NON-NLS-1$
			addBsProposal("\\W", RegExMessages.displayString_bs_W, RegExMessages.additionalInfo_bs_W); //$NON-NLS-1$
			
			// back reference
			addBsProposal("\\", RegExMessages.displayString_bs_i, RegExMessages.additionalInfo_bs_i); //$NON-NLS-1$
			
			//quoting
			addBsProposal("\\", RegExMessages.displayString_bs, RegExMessages.additionalInfo_bs); //$NON-NLS-1$
			addBsProposal("\\Q", RegExMessages.displayString_bs_Q, RegExMessages.additionalInfo_bs_Q); //$NON-NLS-1$
			addBsProposal("\\E", RegExMessages.displayString_bs_E, RegExMessages.additionalInfo_bs_E); //$NON-NLS-1$
			
			//character sets
			if (! fIsEscape) {
				addBracketProposal("[]", 1, RegExMessages.displayString_set, RegExMessages.additionalInfo_set); //$NON-NLS-1$
				addBracketProposal("[^]", 2, RegExMessages.displayString_setExcl, RegExMessages.additionalInfo_setExcl); //$NON-NLS-1$
				addBracketProposal("[-]", 1, RegExMessages.displayString_setRange, RegExMessages.additionalInfo_setRange); //$NON-NLS-1$
				addProposal("&&", RegExMessages.displayString_setInter, RegExMessages.additionalInfo_setInter); //$NON-NLS-1$
			}
			if (! fIsEscape && fDocumentOffset > 0 && fExpression.charAt(fDocumentOffset - 1) == '\\') {
				addProposal("\\p{}", 3, RegExMessages.displayString_posix, RegExMessages.additionalInfo_posix); //$NON-NLS-1$
				addProposal("\\P{}", 3, RegExMessages.displayString_posixNot, RegExMessages.additionalInfo_posixNot); //$NON-NLS-1$
			} else {
				addBracketProposal("\\p{}", 3, RegExMessages.displayString_posix, RegExMessages.additionalInfo_posix); //$NON-NLS-1$
				addBracketProposal("\\P{}", 3, RegExMessages.displayString_posixNot, RegExMessages.additionalInfo_posixNot); //$NON-NLS-1$
			}
			
//			addBsProposal("\\p{Lower}", RegExMessages.displayString_bs_p{Lower}, RegExMessages.additionalInfo_bs_p{Lower}); //$NON-NLS-1$
//			addBsProposal("\\p{Upper}", RegExMessages.displayString_bs_p{Upper}, RegExMessages.additionalInfo_bs_p{Upper}); //$NON-NLS-1$
//			addBsProposal("\\p{ASCII}", RegExMessages.displayString_bs_p{ASCII}, RegExMessages.additionalInfo_bs_p{ASCII}); //$NON-NLS-1$
//			addBsProposal("\\p{Alpha}", RegExMessages.displayString_bs_p{Alpha}, RegExMessages.additionalInfo_bs_p{Alpha}); //$NON-NLS-1$
//			addBsProposal("\\p{Digit}", RegExMessages.displayString_bs_p{Digit}, RegExMessages.additionalInfo_bs_p{Digit}); //$NON-NLS-1$
//			addBsProposal("\\p{Alnum}", RegExMessages.displayString_bs_p{Alnum}, RegExMessages.additionalInfo_bs_p{Alnum}); //$NON-NLS-1$
//			addBsProposal("\\p{Punct}", RegExMessages.displayString_bs_p{Punct}, RegExMessages.additionalInfo_bs_p{Punct}); //$NON-NLS-1$
//			addBsProposal("\\p{Graph}", RegExMessages.displayString_bs_p{Graph}, RegExMessages.additionalInfo_bs_p{Graph}); //$NON-NLS-1$
//			addBsProposal("\\p{Print}", RegExMessages.displayString_bs_p{Print}, RegExMessages.additionalInfo_bs_p{Print}); //$NON-NLS-1$
//			addBsProposal("\\p{Blank}", RegExMessages.displayString_bs_p{Blank}, RegExMessages.additionalInfo_bs_p{Blank}); //$NON-NLS-1$
//			addBsProposal("\\p{Cntrl}", RegExMessages.displayString_bs_p{Cntrl}, RegExMessages.additionalInfo_bs_p{Cntrl}); //$NON-NLS-1$
//			addBsProposal("\\p{XDigit}", RegExMessages.displayString_bs_p{XDigit}, RegExMessages.additionalInfo_bs_p{XDigit}); //$NON-NLS-1$
//			addBsProposal("\\p{Space}", RegExMessages.displayString_bs_p{Space}, RegExMessages.additionalInfo_bs_p{Space}); //$NON-NLS-1$
//
//			addBsProposal("\\p{InGreek}", RegExMessages.displayString_bs_p{InGreek}, RegExMessages.additionalInfo_bs_p{InGreek}); //$NON-NLS-1$
//			addBsProposal("\\p{Lu}", RegExMessages.displayString_bs_p{Lu}, RegExMessages.additionalInfo_bs_p{Lu}); //$NON-NLS-1$
//			addBsProposal("\\p{Sc}", RegExMessages.displayString_bs_p{Sc}, RegExMessages.additionalInfo_bs_p{Sc}); //$NON-NLS-1$
//			addBsProposal("\\P{InGreek}", RegExMessages.displayString_bs_P{InGreek}, RegExMessages.additionalInfo_bs_P{InGreek}); //$NON-NLS-1$
			
			//boundary matchers
			if (fDocumentOffset == 0) {
				addPriorityProposal("^", RegExMessages.displayString_start, RegExMessages.additionalInfo_start); //$NON-NLS-1$
			} else if (fDocumentOffset == 1 && fExpression.charAt(0) == '^') {
				addBracketProposal("^", 1, RegExMessages.displayString_start, RegExMessages.additionalInfo_start); //$NON-NLS-1$
			}
			if (fDocumentOffset == fExpression.length()) {
				addProposal("$", RegExMessages.displayString_end, RegExMessages.additionalInfo_end); //$NON-NLS-1$
			}
			addBsProposal("\\b", RegExMessages.displayString_bs_b, RegExMessages.additionalInfo_bs_b); //$NON-NLS-1$
			addBsProposal("\\B", RegExMessages.displayString_bs_B, RegExMessages.additionalInfo_bs_B); //$NON-NLS-1$
			addBsProposal("\\A", RegExMessages.displayString_bs_A, RegExMessages.additionalInfo_bs_A); //$NON-NLS-1$
			addBsProposal("\\G", RegExMessages.displayString_bs_G, RegExMessages.additionalInfo_bs_G); //$NON-NLS-1$
			addBsProposal("\\Z", RegExMessages.displayString_bs_Z, RegExMessages.additionalInfo_bs_Z); //$NON-NLS-1$
			addBsProposal("\\z", RegExMessages.displayString_bs_z, RegExMessages.additionalInfo_bs_z); //$NON-NLS-1$
			
			if (! fIsEscape) {
				//capturing groups
				addBracketProposal("()", 1, RegExMessages.displayString_group, RegExMessages.additionalInfo_group); //$NON-NLS-1$
				
				//flags
				addBracketProposal("(?)", 2, RegExMessages.displayString_flag, RegExMessages.additionalInfo_flag); //$NON-NLS-1$
				addBracketProposal("(?:)", 3, RegExMessages.displayString_flagExpr, RegExMessages.additionalInfo_flagExpr); //$NON-NLS-1$
			
				//non-capturing group
				addBracketProposal("(?:)", 3, RegExMessages.displayString_nonCap, RegExMessages.additionalInfo_nonCap); //$NON-NLS-1$
				addBracketProposal("(?>)", 3, RegExMessages.displayString_atomicCap, RegExMessages.additionalInfo_atomicCap); //$NON-NLS-1$
				
				//lookaraound
				addBracketProposal("(?=)", 3, RegExMessages.displayString_posLookahead, RegExMessages.additionalInfo_posLookahead); //$NON-NLS-1$
				addBracketProposal("(?!)", 3, RegExMessages.displayString_negLookahead, RegExMessages.additionalInfo_negLookahead); //$NON-NLS-1$
				addBracketProposal("(?<=)", 4, RegExMessages.displayString_posLookbehind, RegExMessages.additionalInfo_posLookbehind); //$NON-NLS-1$
				addBracketProposal("(?<!)", 4, RegExMessages.displayString_negLookbehind, RegExMessages.additionalInfo_negLookbehind); //$NON-NLS-1$
				
				//greedy quantifiers
				addBracketProposal("?", 1, RegExMessages.displayString_quest, RegExMessages.additionalInfo_quest); //$NON-NLS-1$
				addBracketProposal("*", 1, RegExMessages.displayString_star, RegExMessages.additionalInfo_star); //$NON-NLS-1$
				addBracketProposal("+", 1, RegExMessages.displayString_plus, RegExMessages.additionalInfo_plus); //$NON-NLS-1$
				addBracketProposal("{}", 1, RegExMessages.displayString_exact, RegExMessages.additionalInfo_exact); //$NON-NLS-1$
				addBracketProposal("{,}", 1, RegExMessages.displayString_least, RegExMessages.additionalInfo_least); //$NON-NLS-1$
				addBracketProposal("{,}", 1, RegExMessages.displayString_count, RegExMessages.additionalInfo_count); //$NON-NLS-1$
				
				//lazy quantifiers
				addBracketProposal("??", 1, RegExMessages.displayString_questLazy, RegExMessages.additionalInfo_questLazy); //$NON-NLS-1$
				addBracketProposal("*?", 1, RegExMessages.displayString_starLazy, RegExMessages.additionalInfo_starLazy); //$NON-NLS-1$
				addBracketProposal("+?", 1, RegExMessages.displayString_plusLazy, RegExMessages.additionalInfo_plusLazy); //$NON-NLS-1$
				addBracketProposal("{}?", 1, RegExMessages.displayString_exactLazy, RegExMessages.additionalInfo_exactLazy); //$NON-NLS-1$
				addBracketProposal("{,}?", 1, RegExMessages.displayString_leastLazy, RegExMessages.additionalInfo_leastLazy); //$NON-NLS-1$
				addBracketProposal("{,}?", 1, RegExMessages.displayString_countLazy, RegExMessages.additionalInfo_countLazy); //$NON-NLS-1$
				
				//possessive quantifiers
				addBracketProposal("?+", 1, RegExMessages.displayString_questPoss, RegExMessages.additionalInfo_questPoss); //$NON-NLS-1$
				addBracketProposal("*+", 1, RegExMessages.displayString_starPoss, RegExMessages.additionalInfo_starPoss); //$NON-NLS-1$
				addBracketProposal("++", 1, RegExMessages.displayString_plusPoss, RegExMessages.additionalInfo_plusPoss); //$NON-NLS-1$
				addBracketProposal("{}+", 1, RegExMessages.displayString_exactPoss, RegExMessages.additionalInfo_exactPoss); //$NON-NLS-1$
				addBracketProposal("{,}+", 1, RegExMessages.displayString_leastPoss, RegExMessages.additionalInfo_leastPoss); //$NON-NLS-1$
				addBracketProposal("{,}+", 1, RegExMessages.displayString_countPoss, RegExMessages.additionalInfo_countPoss); //$NON-NLS-1$
				
				//alternative
				addBracketProposal("|", 1, RegExMessages.displayString_alt, RegExMessages.additionalInfo_alt); //$NON-NLS-1$
			}
			
			fPriorityProposals.addAll(fProposals);
			return (IContentProposal[]) fPriorityProposals.toArray(new IContentProposal[fProposals.size()]);
		}

		/**
		 * Computes applicable proposals for the replace field.
		 * @return the proposals
		 */
		public IContentProposal[] computeReplaceProposals() {
			if (fDocumentOffset > 0 && '$' == fExpression.charAt(fDocumentOffset - 1)) {
				addProposal("", RegExMessages.displayString_dollar, RegExMessages.additionalInfo_dollar); //$NON-NLS-1$
			} else {
				addProposal("$", RegExMessages.displayString_dollar, RegExMessages.additionalInfo_dollar); //$NON-NLS-1$
				addBsProposal("\\", RegExMessages.displayString_replace_bs, RegExMessages.additionalInfo_replace_bs); //$NON-NLS-1$
				addProposal("\t", RegExMessages.displayString_tab, RegExMessages.additionalInfo_tab); //$NON-NLS-1$
			}
			return (IContentProposal[]) fProposals.toArray(new IContentProposal[fProposals.size()]);
		}
		
		/**
		 * Adds a proposal.
		 * 
		 * @param proposal the string to be inserted
		 * @param displayString the proposal's label
		 * @param additionalInfo the additional information
		 */
		private void addProposal(String proposal, String displayString, String additionalInfo) {
			fProposals.add(new Proposal(proposal, displayString, additionalInfo, proposal.length()));
		}

		/**
		 * Adds a proposal.
		 * 
		 * @param proposal the string to be inserted
		 * @param cursorPosition the cursor position after insertion,
		 * 		relative to the start of the proposal
		 * @param displayString the proposal's label
		 * @param additionalInfo the additional information
		 */
		private void addProposal(String proposal, int cursorPosition, String displayString, String additionalInfo) {
			fProposals.add(new Proposal(proposal, displayString, additionalInfo, cursorPosition));
		}

		/**
		 * Adds a proposal to the priority proposals list.
		 * 
		 * @param proposal the string to be inserted
		 * @param displayString the proposal's label
		 * @param additionalInfo the additional information
		 */
		private void addPriorityProposal(String proposal, String displayString, String additionalInfo) {
			fPriorityProposals.add(new Proposal(proposal, displayString, additionalInfo, proposal.length()));
		}
		
		/**
		 * Adds a proposal. Ensures that existing pre- and postfixes are not duplicated.
		 * 
		 * @param proposal the string to be inserted
		 * @param cursorPosition the cursor position after insertion,
		 * 		relative to the start of the proposal
		 * @param displayString the proposal's label
		 * @param additionalInfo the additional information
		 */
		private void addBracketProposal(String proposal, int cursorPosition, String displayString, String additionalInfo) {
			String prolog= fExpression.substring(0, fDocumentOffset);
			if (! fIsEscape && prolog.endsWith("\\") && proposal.startsWith("\\")) { //$NON-NLS-1$//$NON-NLS-2$
				fProposals.add(new Proposal(proposal, displayString, additionalInfo, cursorPosition));
				return;
			}
			for (int i= 1; i <= cursorPosition; i++) {
				String prefix= proposal.substring(0, i);
				if (prolog.endsWith(prefix)) {
					String postfix= proposal.substring(cursorPosition);
					String epilog= fExpression.substring(fDocumentOffset);
					if (epilog.startsWith(postfix)) {
						fPriorityProposals.add(new Proposal(proposal.substring(i, cursorPosition), displayString, additionalInfo, cursorPosition-i));
					} else {
						fPriorityProposals.add(new Proposal(proposal.substring(i), displayString, additionalInfo, cursorPosition-i));
					}
					return;
				}
			}
			fProposals.add(new Proposal(proposal, displayString, additionalInfo, cursorPosition));
		}

		/**
		 * Adds a proposal that starts with a backslash.
		 * Ensures that the backslash is not repeated if already typed.
		 * 
		 * @param proposal the string to be inserted
		 * @param displayString the proposal's label
		 * @param additionalInfo the additional information
		 */
		private void addBsProposal(String proposal, String displayString, String additionalInfo) {
			String prolog= fExpression.substring(0, fDocumentOffset);
			int position= proposal.length();
			// If the string already contains the backslash, do not include in the proposal
			if (prolog.endsWith("\\")) { //$NON-NLS-1$
				position--;
				proposal= proposal.substring(1);
			}

			if (fIsEscape) {
				fPriorityProposals.add(new Proposal(proposal, displayString, additionalInfo, position));
			} else {
				addProposal(proposal, position, displayString, additionalInfo);
			}
		}
	}
	
	/**
	 * <code>true</code> iff the processor is for the find field.
	 * <code>false</code> iff the processor is for the replace field.
	 */
	private final boolean fIsFind;
	

	/**
	 * Creates a new completion proposal provider.
	 * 
	 * @param isFind <code>true</code> if the provider is used for the 'find' field
	 * 					<code>false</code> if the provider is used for the 'reaplce' field
	 */
	public RegExContentProposalProvider(boolean isFind) {
		fIsFind= isFind;
	}
	
	/*
	 * @see org.eclipse.jface.fieldassist.IContentProposalProvider#getProposals(java.lang.String, int)
	 */
	public IContentProposal [] getProposals(String contents, int position) {
		if (fIsFind)
			return new ProposalComputer(contents, position).computeFindProposals();
		return new ProposalComputer(contents, position).computeReplaceProposals();
	}
}
