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core module for querydsl
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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.mysema.query.support;

import javax.annotation.Nullable;

import com.mysema.query.Detachable;
import com.mysema.query.QueryMetadata;
import com.mysema.query.Tuple;
import com.mysema.query.types.*;
import com.mysema.query.types.expr.*;
import com.mysema.query.types.query.*;

/**
 * Mixin style implementation of the Detachable interface
 *
 * @author tiwe
 *
 */
public class DetachableMixin implements Detachable {

    private final QueryMixin queryMixin;

    public DetachableMixin(QueryMixin queryMixin) {
        this.queryMixin = queryMixin;
    }

    @Override
    public NumberSubQuery count() {
        return new NumberSubQuery(Long.class, projection(Wildcard.count));
    }

    @Override
    public BooleanExpression exists() {
        if (queryMixin.getMetadata().getJoins().isEmpty()) {
            throw new IllegalArgumentException("No sources given");
        }
        Expression expr = queryMixin.getMetadata().getJoins().get(0).getTarget();
        if (expr instanceof Operation && ((Operation)expr).getOperator() == Ops.ALIAS) {
            expr = ((Operation)expr).getArg(1);
        }
        return unique(expr).exists();
    }

    @Override
    public ListSubQuery list(Expression... args) {
        return new ListSubQuery(Tuple.class, projection(args));
    }

    @SuppressWarnings("unchecked")
    @Override
    public  ListSubQuery list(Expression projection) {
        return new ListSubQuery((Class)projection.getType(), projection(projection));
    }

    public ListSubQuery list(Object arg) {
        return list((Expression)convert(arg));
    }

    @Override
    public ListSubQuery list(Object... args) {
        return list(convert(args));
    }

    @Override
    public SimpleSubQuery unique(Object... args) {
        return unique(convert(args));
    }

    private Expression convert(Object arg) {
        if (arg instanceof Expression) {
            return (Expression)arg;
        } else if (arg instanceof ProjectionRole) {
            return ((ProjectionRole)arg).getProjection();
        } else if (arg != null) {
            return ConstantImpl.create(arg);
        } else {
            return NullExpression.DEFAULT;
        }
    }

    private Expression[] convert(Object... args) {
        final Expression[] exprs = new Expression[args.length];
        for (int i = 0; i < exprs.length; i++) {
            exprs[i] = convert(args[i]);
        }
        return exprs;
    }

    @Override
    public BooleanExpression notExists() {
        return exists().not();
    }

    private QueryMetadata projection(Expression... projection) {
        QueryMetadata metadata = queryMixin.getMetadata().clone();
        for (Expression expr : projection) {
            expr = queryMixin.convert(expr, false);
            metadata.addProjection(nullAsTemplate(expr));
        }
        return metadata;
    }

    private Expression nullAsTemplate(@Nullable Expression expr) {
        return expr != null ? expr : NullExpression.DEFAULT;
    }

    @SuppressWarnings("unchecked")
    @Override
    public > ComparableSubQuery unique(ComparableExpression projection) {
        return new ComparableSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    @SuppressWarnings("unchecked")
    @Override
    public > DateSubQuery unique(DateExpression projection) {
        return new DateSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    @SuppressWarnings("unchecked")
    @Override
    public > DateTimeSubQuery unique(DateTimeExpression projection) {
        return new DateTimeSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    @Override
    public SimpleSubQuery unique(Expression... args) {
        return new SimpleSubQuery(Tuple.class, uniqueProjection(args));
    }


    @SuppressWarnings("unchecked")
    @Override
    public  SimpleSubQuery unique(Expression projection) {
        return new SimpleSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    @SuppressWarnings("unchecked")
    @Override
    public > NumberSubQuery unique(NumberExpression projection) {
        return new NumberSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    @Override
    public BooleanSubQuery unique(Predicate projection) {
        return new BooleanSubQuery(uniqueProjection(projection));
    }

    @Override
    public StringSubQuery unique(StringExpression projection) {
        return new StringSubQuery(uniqueProjection(projection));
    }

    @SuppressWarnings("unchecked")
    @Override
    public > TimeSubQuery unique(TimeExpression projection) {
        return new TimeSubQuery((Class)projection.getType(), uniqueProjection(projection));
    }

    private QueryMetadata uniqueProjection(Expression... projection) {
        QueryMetadata metadata = projection(projection);
        metadata.setUnique(true);
        return metadata;
    }

}