package org.simantics.scl.compiler.internal.parsing.parser;

import java.io.IOException;
import java.util.Arrays;

import org.simantics.scl.compiler.errors.Locations;
import org.simantics.scl.compiler.internal.parsing.Token;
import org.simantics.scl.compiler.internal.parsing.exceptions.SCLSyntaxErrorException;

import gnu.trove.list.array.TIntArrayList;
import gnu.trove.set.hash.TIntHashSet;

/**
 * 
 * <http://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-17800010.3>
 * @author Hannu Niemistö
 */
public class SCLPostLexer {
        
    public static TIntHashSet INDENTABLE = new TIntHashSet();
    public static TIntHashSet NO_SEMICOLON_BEFORE = new TIntHashSet();
    public static TIntHashSet NO_SEMICOLON_AFTER = new TIntHashSet();
    static {
        INDENTABLE.add(SCLTerminals.WHERE);
        INDENTABLE.add(SCLTerminals.QUERY_OP);
        INDENTABLE.add(SCLTerminals.WITH);
        INDENTABLE.add(SCLTerminals.DO);
        INDENTABLE.add(SCLTerminals.MDO);
        INDENTABLE.add(SCLTerminals.LET);
        INDENTABLE.add(SCLTerminals.ENFORCE);
        INDENTABLE.add(SCLTerminals.WHEN);
        INDENTABLE.add(SCLTerminals.FOLLOWS);
        INDENTABLE.add(SCLTerminals.EQ);
        
        NO_SEMICOLON_BEFORE.add(SCLTerminals.EOF);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.SYMBOL);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.THEN);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.ELSE);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.IN);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.RBRACE);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.RBRACKET);
        NO_SEMICOLON_BEFORE.add(SCLTerminals.RPAREN);
        
        NO_SEMICOLON_AFTER.add(SCLTerminals.EOF);
        NO_SEMICOLON_AFTER.add(SCLTerminals.SYMBOL);
    }
    
    SCLLexer lexer;
    Token[] queue = new Token[16];
    int queuePos=0, queueSize=0;
    TIntArrayList indentations = new TIntArrayList();
    Token curToken = null;
    int lineStart = 0;
    boolean firstTokenOfLine = true;
    private SCLParserOptions options;
            
    {
        indentations.add(0);
    }
    
    public SCLPostLexer(SCLLexer lexer) {
        this.lexer = lexer;
    }
    
    public SCLPostLexer(java.io.Reader in) {
        this(new SCLLexer(in));
    }

    public Token nextToken() throws Exception {
        while(queuePos == queueSize)
            fillQueue();
        return queue[queuePos++];
    }
    
    public Token peekToken() throws Exception {
        while(queuePos == queueSize)
            fillQueue();
        return queue[queuePos];
    }
    
    private void push(Token symbol) {
        /*System.out.println("TOKEN " + symbol.text + " (" + SCLParser.TERMINAL_NAMES[symbol.id] + ")" +
                " [" 
                + Locations.beginOf(symbol.location) + ".." 
                + Locations.endOf(symbol.location) + "]");*/
        if(queueSize == queue.length)
            queue = Arrays.copyOf(queue, queueSize*2);
        queue[queueSize++] = symbol;
    }
    
    private void fillQueue() throws Exception {
        queuePos = 0;
        queueSize = 0;
        
        for(int i=0;i<8;++i)
            handleToken(lexer.nextToken());
    }
    
    private SCLSyntaxErrorException error(int start, int end, String description) {
        return new SCLSyntaxErrorException(Locations.location(start, end), description);
    }
    
    private void handleToken(Token symbol) throws IOException {
        int symbolId = symbol.id;
        if(symbolId == SCLTerminals.EOL) {
            lineStart = Locations.endOf(symbol.location);
            firstTokenOfLine = true;
            return;
        }
        
        if(symbolId == SCLTerminals.COMMENT) {
            firstTokenOfLine = false;
            return;
        }
        
        Token prevToken = curToken;
        int prevTokenId = prevToken == null ? SCLTerminals.EOF : prevToken.id;
        curToken = symbol;
        
        int symbolStart = Locations.beginOf(symbol.location);
        int symbolEnd = Locations.endOf(symbol.location);
        
        if(INDENTABLE.contains(prevTokenId) && symbolId != SCLTerminals.LBRACE) {
            push(new Token(SCLTerminals.LBRACE, symbolStart, symbolStart, "implicit {"));
            int symbolIndentation = symbolStart-lineStart;
            //System.out.println("symbolIndentation = " + symbolIndentation);
            indentations.add(symbolIndentation);
            firstTokenOfLine = false;
        }
        else if(firstTokenOfLine) {
            if(NO_SEMICOLON_AFTER.contains(prevTokenId) || NO_SEMICOLON_BEFORE.contains(symbolId))
                ;
            else {
                int level = symbolStart - lineStart;
                //System.out.println("level = " + level);
                if(indentations.get(indentations.size()-1) >= level) {
                    while(indentations.get(indentations.size()-1) > level) {
                        indentations.removeAt(indentations.size()-1);
                        int loc = Locations.endOf(prevToken.location);
                        push(new Token(SCLTerminals.RBRACE, loc, loc, "implicit }"));
                    }
                    if(indentations.get(indentations.size()-1) == level)
                        push(new Token(SCLTerminals.SEMICOLON, symbolStart, symbolStart, "implicit ;"));
                }
            }
            firstTokenOfLine = false;
        }
        
        switch(symbolId) {
        case SCLTerminals.LBRACE:
        case SCLTerminals.LPAREN:
        case SCLTerminals.LBRACKET:
        case SCLTerminals.IF:
        case SCLTerminals.LET:
            indentations.add(-1);
            push(symbol);
            return;
        case SCLTerminals.RBRACE:
        case SCLTerminals.RPAREN:
        case SCLTerminals.RBRACKET:
        case SCLTerminals.ELSE:
        case SCLTerminals.IN:
            while(!indentations.isEmpty() && indentations.removeAt(indentations.size()-1) >= 0) {
                int loc = Locations.endOf(prevToken.location);
                push(new Token(SCLTerminals.RBRACE, loc, loc, "implicit }"));
            }
            if(indentations.isEmpty())
                throw error(symbolStart, symbolEnd, "No corresponding opening parenthesis for '" + symbol.text + "'.");
            push(symbol);
            return;
        case SCLTerminals.THEN: // 'then' both closes and opens a block
            while(!indentations.isEmpty() && indentations.removeAt(indentations.size()-1) >= 0) {
                int loc = Locations.endOf(prevToken.location);
                push(new Token(SCLTerminals.RBRACE, loc, loc, "implicit }"));
            }
            if(indentations.isEmpty())
                throw error(symbolStart, symbolEnd, "No corresponding opening parenthesis for '" + symbol.text + "'.");
            push(symbol);
            indentations.add(-1);
            return;
        case SCLTerminals.EOF:
            while(indentations.size() > 1 && indentations.get(indentations.size()-1) >= 0) {
                int loc = Locations.endOf(prevToken.location);
                push(new Token(SCLTerminals.RBRACE, loc, loc, "implicit }"));
                indentations.removeAt(indentations.size()-1);
            }
            if(indentations.size() > 1)
                throw error(symbolStart, symbolEnd, "Unclosed parentheses.");
            push(symbol);
            return;
        default:
            push(symbol);
            return;
        }
    }

    public void setParserOptions(SCLParserOptions options) {
        this.options = options;
        lexer.options = options;
    }

}