package org.simantics.scl.compiler.elaboration.expressions;

import org.simantics.scl.compiler.elaboration.contexts.ReplaceContext;
import org.simantics.scl.compiler.elaboration.contexts.SimplificationContext;
import org.simantics.scl.compiler.elaboration.contexts.TranslationContext;
import org.simantics.scl.compiler.elaboration.contexts.TypingContext;
import org.simantics.scl.compiler.elaboration.query.QExists;
import org.simantics.scl.compiler.elaboration.query.Query;
import org.simantics.scl.compiler.elaboration.query.compilation.QueryCompilationContext;
import org.simantics.scl.compiler.elaboration.query.compilation.QueryCompilationMode;
import org.simantics.scl.compiler.elaboration.query.compilation.UnsolvableQueryException;
import org.simantics.scl.compiler.errors.Locations;
import org.simantics.scl.compiler.types.Type;
import org.simantics.scl.compiler.types.Types;
import org.simantics.scl.compiler.types.exceptions.MatchException;
import org.simantics.scl.compiler.types.exceptions.UnificationException;
import org.simantics.scl.compiler.types.kinds.Kinds;

public class EWhen extends SimplifiableExpression {

    public Query query;
    public Expression action;
    public Variable[] variables;
    
    public EWhen(Query query, Expression action) {
        this.query = query;
        this.action = action;
    }
    
    public EWhen(long location, Query query, Expression action, Variable[] variables) {
        if(variables == null)
            throw new NullPointerException();
        if(location == Locations.NO_LOCATION)
            new Exception().printStackTrace();
        this.location = location;
        this.query = query;
        this.action = action;
        this.variables = variables;
    }

    @Override
    protected void updateType() throws MatchException {
        setType(Types.UNIT);
    }
    
    @Override
    public Expression checkBasicType(TypingContext context, Type requiredType) {
        try {
            Types.unify(requiredType, Types.UNIT);
        } catch (UnificationException e) {
            context.typeError(location, requiredType, Types.UNIT);
            return this;
        }
        for(Variable variable : variables)
            variable.setType(Types.metaVar(Kinds.STAR));
        query.checkType(context);
        action.checkIgnoredType(context);
        
        // Compile query
        return compile(context);
    }
    
    public Expression compile(TypingContext context) {
        try {
            QueryCompilationContext queryCompilationContext =
                    new QueryCompilationContext(context, QueryCompilationMode.ITERATE, null, action);
            new QExists(variables, query).generate(queryCompilationContext);
            return queryCompilationContext.getContinuation();
        } catch(UnsolvableQueryException e) {
            context.getErrorLog().log(getLocation(), "Failed to compile the query.\n" +  e.getMessage());
            return new EError(getLocation());
        }
    }

    @Override
    public Expression resolve(TranslationContext context) {
        context.pushExistentialFrame();
        query = query.resolve(context);
        action = action.resolve(context);
        variables = context.popExistentialFrame();
        return this;
    }
    
    @Override
    public Expression replace(ReplaceContext context) {
        Variable[] newVariables = new Variable[variables.length];
        for(int i=0;i<variables.length;++i) {
            Variable variable = variables[i];
            Variable newVariable = new Variable(variable.name, variable.getType());
            newVariables[i] = newVariable;
            context.varMap.put(variable, new EVariable(newVariable));
        }
        EWhen result = new EWhen(location, query.replace(context), action.replace(context), newVariables);
        for(int i=0;i<variables.length;++i)
            context.varMap.remove(variables[i]);
        return result;
    }

    @Override
    public void setLocationDeep(long loc) {
        if(location == Locations.NO_LOCATION) {
            location = loc;
            query.setLocationDeep(loc);
            action.setLocationDeep(loc);
        }
    }
    
    @Override
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }
    
    public Query getQuery() {
        return query;
    }
    
    public Expression getAction() {
        return action;
    }
    
    @Override
    public Expression simplify(SimplificationContext context) {
        throw new UnsupportedOperationException();
    }
    
    @Override
    public Expression accept(ExpressionTransformer transformer) {
        return transformer.transform(this);
    }

}