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

import static org.simantics.scl.compiler.elaboration.expressions.Expressions.Just;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.apply;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.let;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.loc;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.newVar;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.seq;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.tuple;
import static org.simantics.scl.compiler.elaboration.expressions.Expressions.var;

import org.simantics.scl.compiler.common.exceptions.InternalCompilerError;
import org.simantics.scl.compiler.common.names.Names;
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.internal.parsing.parser.SCLTerminals;
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.kinds.Kinds;

public class ESelect extends SimplifiableExpression {

    private final Type ARRAY_LIST = Types.con("ArrayList", "T"); 
    
    int selectVariant;
    public Expression expression;
    public Query query;
    public Variable[] variables;
    
    public ESelect(int selectVariant, Expression expression, Query query) {
        this.selectVariant = selectVariant;
        this.expression = expression;
        this.query = query;
    }

    @Override
    protected void updateType() throws MatchException {
        setType(selectVariant==SCLTerminals.SELECT_FIRST 
                ? Types.apply(Types.MAYBE, expression.getType()) 
                : Types.list(expression.getType()));
    }
    
    @Override
    public Expression checkBasicType(TypingContext context, Type requiredType) {
        Type componentType;
        switch(selectVariant) {
        case SCLTerminals.SELECT:
        case SCLTerminals.SELECT_DISTINCT:
            try {
                componentType = Types.unifyApply(Types.LIST, requiredType);
            } catch (MatchException e) {
                context.getErrorLog().log(location, "Select expression produces a list of values.");
                return new EError(location);
            }
            break;
        case SCLTerminals.SELECT_FIRST:
            try {
                componentType = Types.unifyApply(Types.MAYBE, requiredType);
            } catch (MatchException e) {
                context.getErrorLog().log(location, "Select first expression produces an optional value.");
                return new EError(location);
            }
            break;
        default: throw new InternalCompilerError();
        }
        for(Variable variable : variables)
            variable.setType(Types.metaVar(Kinds.STAR));
        expression.checkType(context, componentType);
        query.checkType(context);
        
        // Compile query
        Type elType = expression.getType();
        Expression result;
        if(selectVariant == SCLTerminals.SELECT_FIRST) {
            QueryCompilationContext queryCompilationContext =
                    new QueryCompilationContext(context, QueryCompilationMode.GET_FIRST,
                            expression.getType(),
                            Just(expression));
            try {
                new QExists(variables, query).generate(queryCompilationContext);
            } catch (UnsolvableQueryException e) {
                context.getErrorLog().log(getLocation(), "Failed to compile the query.\n" + e.getMessage());
                return new EError(getLocation());
            }
            result = queryCompilationContext.getContinuation();
        }
        else {
            Variable accumulator = newVar("accum", Types.apply(ARRAY_LIST, elType));
            result =
                    apply(context.getCompilationContext(), Types.PROC, Names.ArrayList_freeze, elType,
                            var(accumulator));
            Expression innerExpression = 
                    apply(context.getCompilationContext(), Types.PROC, Names.ArrayList_add, elType,
                            var(accumulator), expression);
            try {
                QueryCompilationContext queryCompilationContext =
                        new QueryCompilationContext(context, QueryCompilationMode.ITERATE, null, innerExpression);
                new QExists(variables, query).generate(queryCompilationContext);
                result = seq(queryCompilationContext.getContinuation(), result);
            } catch(UnsolvableQueryException e) {
                context.getErrorLog().log(getLocation(), "Failed to compile the query.\n" + e.getMessage());
                return new EError(getLocation());
            }
            result = let(accumulator,
                    apply(context.getCompilationContext(), Types.PROC, Names.ArrayList_new, elType, tuple()),
                    result
                    );
        }
        return loc(location, result);
    }

    @Override
    public Expression resolve(TranslationContext context) {
        context.pushExistentialFrame();
        expression = expression.resolve(context);
        query = query.resolve(context);
        variables = context.popExistentialFrame();
        return this;
    }
    
    @Override
    public void setLocationDeep(long loc) {
        if(location == Locations.NO_LOCATION) {
            location = loc;
            expression.setLocationDeep(loc);
            query.setLocationDeep(loc);
        }
    }
    
    @Override
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }
    
    @Override
    public Expression simplify(SimplificationContext context) {
        throw new UnsupportedOperationException();
    }
    
    @Override
    public Expression accept(ExpressionTransformer transformer) {
        return transformer.transform(this);
    }

}