package de.ugoe.cs.swe.bnftools.ui.formatter;

import java.util.ArrayList;
import java.util.Stack;

import org.eclipse.emf.ecore.EObject;
import org.eclipse.xtext.parsetree.AbstractNode;
import org.eclipse.xtext.parsetree.CompositeNode;
import org.eclipse.xtext.parsetree.LeafNode;
import org.eclipse.xtext.parsetree.NodeUtil;

import de.ugoe.cs.swe.bnftools.ebnf.Atom;
import de.ugoe.cs.swe.bnftools.ebnf.BnfEntry;
import de.ugoe.cs.swe.bnftools.ebnf.DefinitionList;
import de.ugoe.cs.swe.bnftools.ebnf.DeltaEntry;
import de.ugoe.cs.swe.bnftools.ebnf.EtsiBnf;
import de.ugoe.cs.swe.bnftools.ebnf.ExtRule;
import de.ugoe.cs.swe.bnftools.ebnf.GlobalCombinator;
import de.ugoe.cs.swe.bnftools.ebnf.GroupedSequence;
import de.ugoe.cs.swe.bnftools.ebnf.HookCombinator;
import de.ugoe.cs.swe.bnftools.ebnf.Import;
import de.ugoe.cs.swe.bnftools.ebnf.ImportSection;
import de.ugoe.cs.swe.bnftools.ebnf.MergeEntry;
import de.ugoe.cs.swe.bnftools.ebnf.MergeRule;
import de.ugoe.cs.swe.bnftools.ebnf.OptionalSequence;
import de.ugoe.cs.swe.bnftools.ebnf.RepeatedSequence;
import de.ugoe.cs.swe.bnftools.ebnf.Rule;
import de.ugoe.cs.swe.bnftools.ebnf.RuleCombinator;
import de.ugoe.cs.swe.bnftools.ebnf.RuleReference;
import de.ugoe.cs.swe.bnftools.ebnf.SectionHeading;
import de.ugoe.cs.swe.bnftools.ebnf.SingleDefinition;
import de.ugoe.cs.swe.bnftools.ebnf.StringRule;
import de.ugoe.cs.swe.bnftools.ebnf.Term;
import de.ugoe.cs.swe.bnftools.visitor.EbnfVisitor;

public class EbnfFormatterVisitor extends EbnfVisitor {
	protected StringBuffer buf;
	protected FormatterConfig config;
	protected int bufferPositionFormattedTextNoWhitespaces = 0;
	protected int bufferPositionOriginalText = 0;
	protected int allCommentsPosition = 0;
	protected ArrayList<LeafNode> allComments = new ArrayList<LeafNode>();
	
	protected boolean lastWasSectionHeading=false;
	protected CompositeNode parserEtsiBnfNode;
	protected String originalText;
	protected int bufferPositionFormattedText;
	protected String formattedText;
	protected String formattedTextNoWhitespaces;
	protected String originalTextNoWhitespaces;
	protected int newLineOffsetCounter = 0;
	protected int rightHandSideRuleOffset = 0;
	protected Stack<Integer> ruleSpacingStack = new Stack<Integer>();
	protected Double averageSingleDefinitionLength;
	
	public EbnfFormatterVisitor(EObject rootNode, FormatterConfig config) {
		super(rootNode);
		this.config = config;
		buf = new StringBuffer();
	}

	public EbnfFormatterVisitor(FormatterConfig config) {
		this.config = config;
		buf = new StringBuffer();
	}

	public StringBuffer getBuf() {
		return buf;
	}

	protected boolean isCommentNode(LeafNode node) {
		if ((node.getText().trim().startsWith("//") || node.getText().trim().startsWith("/*")) && (node.isHidden()))
			return true;
		return false;
	}
	
	protected void collectAllComments(CompositeNode node) {
		for (int i=0; i < node.getChildren().size(); i++) {
			AbstractNode currentNode = node.getChildren().get(i);
			if (currentNode instanceof LeafNode) {
				LeafNode leafNode = (LeafNode) currentNode;
				if (isCommentNode(leafNode)) {
					allComments.add(leafNode);
				} 
			}
			
			if (currentNode instanceof CompositeNode) {
				collectAllComments((CompositeNode) currentNode);
			}
		}
	}

	protected boolean isSingleLineComment(String str) {
		if (str.startsWith("//"))
			return true;
		return false;
	}
	
	protected boolean isMultiLineComment(String str) {
		if (str.startsWith("/*"))
			return true;
		return false;
	}

	protected boolean isWhitespace(char ch) {
		if ((ch==' ') || (ch == '\t') || (ch == '\n') || (ch == '\r'))
			return true;
		return false;
	}
	
	protected void skipWhitespacesOriginalText() {
		while (bufferPositionOriginalText < originalText.length() && isWhitespace(originalText.charAt(bufferPositionOriginalText))) {
			bufferPositionOriginalText++;
		}
	}

	protected void skipWhitespacesFormattedText(StringBuffer result) {
		while (bufferPositionFormattedText < formattedText.length() && isWhitespace(formattedText.charAt(bufferPositionFormattedText))) {
			result.append(formattedText.substring(bufferPositionFormattedText, bufferPositionFormattedText+1));
			bufferPositionFormattedText++;
		}
	}

	protected boolean isSingleLineCommentNext(String str, int position) {
		if ((str.charAt(position) == '/') && (str.charAt(position) == '/'))
			return true;
		return false;
	}
	
	protected boolean isMultiLineCommentNext(String str, int position) {
		if ((str.charAt(position) == '/') && (str.charAt(position) == '*'))
			return true;
		return false;
	}
		
	protected boolean isCommentNext(String str, int position) {
		if (isSingleLineCommentNext(str, position) || isMultiLineCommentNext(str, position))
			return true;
		else
			return false;
	}
	
	protected String scanBackWhitespaces(String str, int position) {
		StringBuffer whiteSpaces = new StringBuffer();
		int currentPosition = position;
		if (currentPosition >= str.length() || currentPosition < 0)
			return "";
		char ch;
		ch = str.charAt(currentPosition);
		while (isWhitespace(ch)) {
			whiteSpaces.append(str.charAt(currentPosition));
			currentPosition--;
			if (currentPosition < 0)
				break;
			ch = str.charAt(currentPosition);
		}
		return whiteSpaces.toString();
	}
	
	protected String stripEndingNewline(String str) {
		int position = str.length() - 1;
		while ((str.charAt(position) == '\n') || (str.charAt(position) == '\r')) {
			position--;
		}
		return str.substring(0, position + 1);
	}
	
	protected int scanBackNewlinesCount(String str, int position) {
		int newLinesCount = 0;
		int currentPosition = position;
		while ((str.charAt(currentPosition) == '\n') || (str.charAt(currentPosition) == '\r')) {
			if (str.charAt(currentPosition) == '\n') {
				if (str.charAt(currentPosition - 1) == '\r') {
					currentPosition -= 2;
				} else {
					currentPosition -= 1;
				}
				newLinesCount++;
			} else if (str.charAt(currentPosition) == '\r') {
				currentPosition -= 1;
				newLinesCount++;
			}
		}
		
		return newLinesCount;
	}
	
	protected void weaveComments() {
		bufferPositionOriginalText = 0;
		bufferPositionFormattedTextNoWhitespaces = 0;
		bufferPositionFormattedText = 0;
		
		StringBuffer result = new StringBuffer();
		formattedTextNoWhitespaces = buf.toString().replaceAll("[ \t\n\r]", "");
		formattedText = buf.toString();
		
		while (bufferPositionFormattedTextNoWhitespaces <= formattedTextNoWhitespaces.length()) {
			skipWhitespacesOriginalText();
			skipWhitespacesFormattedText(result);
			
			if (!(bufferPositionOriginalText < originalText.length()))
				break;
			
			char formattedPositionNoWhitespaces;
			if (bufferPositionFormattedTextNoWhitespaces == formattedTextNoWhitespaces.length()) {
				formattedPositionNoWhitespaces = ' ';
			} else {
				formattedPositionNoWhitespaces = formattedTextNoWhitespaces.charAt(bufferPositionFormattedTextNoWhitespaces);
			}
			char originalPosition = originalText.charAt(bufferPositionOriginalText);

			if (formattedPositionNoWhitespaces != originalPosition) {
				if (formattedPositionNoWhitespaces == ';') { // formatted text always outputs the optional semicolon, skip it if necessary
					bufferPositionFormattedTextNoWhitespaces++;
					bufferPositionFormattedText++;
				} else if (isCommentNext(originalText, bufferPositionOriginalText)) {
					LeafNode currentComment = allComments.get(allCommentsPosition); 
					if (currentComment.getTotalOffset() == bufferPositionOriginalText) {
						if (isMultiLineComment(currentComment.getText())) {
							int newLinesCount = scanBackNewlinesCount(originalText, bufferPositionOriginalText-1);
							if (newLinesCount > 0) {
								if (scanBackNewlinesCount(result.toString(), result.toString().length()-1) == 0) {
									result.append("\n\n");
								}
								
								result.append(currentComment.getText());
								result.append("\n");
							} else {
								String lastWhiteSpaces = scanBackWhitespaces(result.toString(), result.toString().length()-1);
								result.delete(result.toString().length() - lastWhiteSpaces.length(), result.toString().length());
								result.append(" " + stripEndingNewline(currentComment.getText()));
								result.append(lastWhiteSpaces);
							}
						} else if (isSingleLineComment(currentComment.getText())) {
							int newLinesCount = scanBackNewlinesCount(originalText, bufferPositionOriginalText-1);
							String lastWhiteSpaces = scanBackWhitespaces(result.toString(), result.toString().length()-1);
							result.delete(result.toString().length() - lastWhiteSpaces.length(), result.toString().length());
							if (newLinesCount > 0) {
								result.append("\n\n" + stripEndingNewline(currentComment.getText()));
							} else {
								result.append(" " + stripEndingNewline(currentComment.getText()));
							}
							result.append(lastWhiteSpaces);
						}
						bufferPositionOriginalText+=currentComment.getLength();
						allCommentsPosition++;
					}
				} else { // disaster handling: return original unformatted text!
					System.err.println("Disaster Recovery: returning original text!!");
					buf = new StringBuffer();
					buf.append(originalText);
					return;
				}
			} else {
				result.append(formattedText.substring(bufferPositionFormattedText, bufferPositionFormattedText+1));
				bufferPositionOriginalText++;
				bufferPositionFormattedText++;
				bufferPositionFormattedTextNoWhitespaces++;
			}
		}
		buf = result;
	}

	protected void newLine() {
		buf.append("\n");
		if ((ruleSpacingStack != null) && (!ruleSpacingStack.empty())) {
			newLineOffsetCounter = ruleSpacingStack.peek();
		} else {
			newLineOffsetCounter = 0;
		}
	}
	
	protected void text(String str) {
		buf.append(str);
		newLineOffsetCounter += str.length();
	}

	protected void space() {
		buf.append(" ");
		newLineOffsetCounter++;
	}
	
	protected void spaces(int count) {
		for (int i=0; i < count; i++) {
			buf.append(" ");
		}
	}

	protected boolean lastIsClosingParentheses() {
		char ch = buf.toString().charAt(buf.toString().length()-1);
		if ((ch == ')') || (ch == ']') || (ch == '}'))
			return true;
		return false;
	}

	protected void wrap() {
		if ((config.isWrapAfterThreshold()) && (newLineOffsetCounter > config.getWrapThreshold())) {
			char last = buf.toString().charAt(buf.toString().length()-1);
			if (!((last == '(' || last == '[' || last == '{' ))) {
				newLine();
				if (ruleSpacingStack.size() > 1)
					spaces(ruleSpacingStack.peek() + 1);
				else
					spaces(ruleSpacingStack.peek());
			}
		}
	}

	// -----------------------------------------------------------------------------

	protected void visitBefore(EtsiBnf node) {
		parserEtsiBnfNode = NodeUtil.getNodeAdapter(node).getParserNode();
		collectAllComments(parserEtsiBnfNode);
		originalText = NodeUtil.getNodeAdapter(node).getParserNode().serialize();
		originalTextNoWhitespaces = originalText.replaceAll("[ \t\n\r]", "");
		
		text("grammar " + node.getName());
		if (node.getType() != null)
			text(node.getType());
		text(";");

		newLine();
		newLine();
	}

	protected void visitAfter(EtsiBnf node) {
		weaveComments();
	}

	protected void visitBefore(ImportSection node) {
	}

	protected void visitAfter(ImportSection node) {
		newLine();
	}

	protected void visitBefore(BnfEntry node) {
	}

	protected void visitAfter(BnfEntry node) {
	}
	
	protected void visitBefore(DeltaEntry node) {
	}

	protected void visitAfter(DeltaEntry node) {
	}
	
	protected void visitBefore(MergeEntry node) {
	}

	protected void visitAfter(MergeEntry node) {
	}
	
	protected void visitBefore(Atom node) {
	}

	protected void visitAfter(Atom node) {
	}

	protected void visitBefore(Term node) {
	}

	protected void visitAfter(Term node) {
		if (!isLastElement())
			space();
	}

	protected void visitBefore(DefinitionList node) {
		averageSingleDefinitionLength = null;
		int totalLength = 0;
		for (int i=0; i < node.eContents().size(); i++) {
			CompositeNode parseNode = NodeUtil.getNodeAdapter(node.eContents().get(i)).getParserNode();
			totalLength += parseNode.serialize().trim().length();
		}
		averageSingleDefinitionLength = (double) totalLength / (double) node.eContents().size();
	}

	protected void visitAfter(DefinitionList node) {
	}

	protected void visitBefore(ExtRule node) {
	}

	protected void visitAfter(ExtRule node) {
	}

	protected void visitBefore(GlobalCombinator node) {
	}

	protected void visitAfter(GlobalCombinator node) {
	}

	protected void visitBefore(HookCombinator node) {
	}

	protected void visitAfter(HookCombinator node) {
	}

	protected void visitBefore(Import node) {
		text("import \"" + node.getImportURI() + "\"");
		if (node.getGrammarType() != null) {
			text("/" + node.getGrammarType());
		}
		if (node.getLabel() != null) {
			space();
			text("label: " + node.getLabel());
		}
		text(";");
		newLine();
	}

	protected void visitAfter(Import node) {
	}

	protected void visitBefore(MergeRule node) {
	}

	protected void visitAfter(MergeRule node) {
	}

	protected void visitBefore(GroupedSequence node) {
		wrap();
		text("(");
		ruleSpacingStack.push(newLineOffsetCounter-1);
	}

	protected void visitAfter(GroupedSequence node) {
//		if ((config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) || (lastIsClosingParentheses())) {
		if (config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) {
			newLine();
			spaces(ruleSpacingStack.peek());
		}
		
		text(")");
		ruleSpacingStack.pop();
	}

	protected void visitBefore(OptionalSequence node) {
		wrap();
		text("[");
		ruleSpacingStack.push(newLineOffsetCounter-1);
	}

	protected void visitAfter(OptionalSequence node) {
//		if ((config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) || (lastIsClosingParentheses())) {
		if (config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) {
			newLine();
			spaces(ruleSpacingStack.peek());
		}

		text("]");
		ruleSpacingStack.pop();
	}

	protected void visitBefore(RepeatedSequence node) {
		wrap();
		text("{");
		ruleSpacingStack.push(newLineOffsetCounter-1);
	}

	protected void visitAfter(RepeatedSequence node) {
//		if ((config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) || (lastIsClosingParentheses())) {
		if (config.isAlignParentheses() && (node.eContents().get(0).eContents().size() >= config.getAlignParenthesesElementCountThreshold())) {
			newLine();
			spaces(ruleSpacingStack.peek());
		}

		text("}");
		if (node.isMorethanonce())
			text("+");
		ruleSpacingStack.pop();
	}

	protected void visitBefore(Rule node) {
		if (lastWasSectionHeading)
			newLine();
		
		lastWasSectionHeading=false;

		newLineOffsetCounter = 0;

		if (node.getRulenumber() > 0)
			text(node.getRulenumber() + ". ");
		
		text(node.getName() + " ::= ");
		
		rightHandSideRuleOffset = newLineOffsetCounter;
		ruleSpacingStack.push(newLineOffsetCounter);
	}

	protected void visitAfter(Rule node) {
		text(";");
		newLine();
		ruleSpacingStack.pop();
	}

	protected void visitBefore(RuleCombinator node) {
	}

	protected void visitAfter(RuleCombinator node) {
	}

	protected void visitBefore(RuleReference node) {
		wrap();
		text(node.getRuleref().getName());
	}

	protected void visitAfter(RuleReference node) {
	}

	protected void visitBefore(SectionHeading node) {
		if (!lastWasSectionHeading && !buf.substring(buf.length()-2).equals("\n\n"))
			newLine();
		
		lastWasSectionHeading=true;
		
		text(node.getSectionHeader());
	}

	protected void visitAfter(SectionHeading node) {
	}

	protected void visitBefore(SingleDefinition node) {
	}

	protected void visitAfter(SingleDefinition node) {
		boolean preventAlternativeBreakShortAlternatives = config.isPreventNewLineAfterAlternativeOnShortAlternatives() && (averageSingleDefinitionLength <= config.getShortAlternativeThreshold());
		if (!isLastElement()) {
			text(" | ");
			if (config.isNewLineAfterAlternative()) {
				if (config.isPreventNewLineAfterAlternativeOnLessThanThreeElements()) {
					DefinitionList definitionList = (DefinitionList) node.eContainer();
					if ((definitionList.eContents().size() > 2) && (!preventAlternativeBreakShortAlternatives)) {
						newLine();
						if (ruleSpacingStack.size() > 1)
							spaces(ruleSpacingStack.peek() + 1);
						else
							spaces(ruleSpacingStack.peek());
					}
				} else {
					if (!preventAlternativeBreakShortAlternatives) {
						newLine();
						if (ruleSpacingStack.size() > 1)
							spaces(ruleSpacingStack.peek() + 1);
						else
							spaces(ruleSpacingStack.peek());
					}
				}
			}
		}
	}

	protected void visitBefore(StringRule node) {
		wrap();
		if (node.getLiteral() != null)
			text("\"" + node.getLiteral() + "\"");
		else if (node.getColon() != null)
			text("\"\"\"");
	}

	protected void visitAfter(StringRule node) {
	}
	
}