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Object mapper for the DataStax CQL Java Driver.
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/*
 * Copyright (C) 2012-2017 DataStax Inc.
 *
 * 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.datastax.driver.mapping;

import com.datastax.driver.core.*;
import com.datastax.driver.mapping.annotations.Defaults;
import com.google.common.collect.Sets;
import com.google.common.reflect.TypeToken;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;

import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Set;

class MethodMapper {

    final Method method;
    final String queryString;
    private final ParamMapper[] paramMappers;

    private final ConsistencyLevel consistency;
    private final int fetchSize;
    private final boolean tracing;
    private final Boolean idempotent;

    private Session session;
    private PreparedStatement statement;

    private boolean returnStatement;
    private Mapper returnMapper;
    private boolean mapOne;
    private boolean async;

    MethodMapper(Method method, String queryString, ParamMapper[] paramMappers, ConsistencyLevel consistency, int fetchSize, boolean enableTracing, Boolean idempotent) {
        this.method = method;
        this.queryString = queryString;
        this.paramMappers = paramMappers;
        this.consistency = consistency;
        this.fetchSize = fetchSize;
        this.tracing = enableTracing;
        this.idempotent = idempotent;
    }

    public void prepare(MappingManager manager, PreparedStatement ps) {
        this.session = manager.getSession();
        this.statement = ps;

        validateParameters();

        Class returnType = method.getReturnType();
        if (Void.TYPE.isAssignableFrom(returnType) || ResultSet.class.isAssignableFrom(returnType))
            return;

        if (Statement.class.isAssignableFrom(returnType)) {
            returnStatement = true;
            return;
        }

        if (ResultSetFuture.class.isAssignableFrom(returnType)) {
            this.async = true;
            return;
        }

        if (ListenableFuture.class.isAssignableFrom(returnType)) {
            this.async = true;
            Type k = ((ParameterizedType) method.getGenericReturnType()).getActualTypeArguments()[0];
            if (k instanceof Class && ResultSet.class.isAssignableFrom((Class) k))
                return;

            mapType(manager, returnType, k);
        } else {
            mapType(manager, returnType, method.getGenericReturnType());
        }
    }

    // Checks the method parameters against the query's bind variables
    private void validateParameters() {
        if (method.isVarArgs())
            throw new IllegalArgumentException(String.format("Invalid varargs method %s in @Accessor interface", method.getName()));

        ColumnDefinitions variables = statement.getVariables();
        Set names = Sets.newHashSet();
        for (ColumnDefinitions.Definition variable : variables) {
            names.add(variable.getName());
        }

        if (method.getParameterTypes().length < names.size())
            throw new IllegalArgumentException(String.format("Not enough arguments for method %s, "
                            + "found %d but it should be at least the number of unique bind parameter names in the @Query (%d)",
                    method.getName(), method.getParameterTypes().length, names.size()));

        if (method.getParameterTypes().length > variables.size())
            throw new IllegalArgumentException(String.format("Too many arguments for method %s, "
                            + "found %d but it should be at most the number of bind parameters in the @Query (%d)",
                    method.getName(), method.getParameterTypes().length, variables.size()));

        // TODO could go further, e.g. check that the types match, inspect @Param annotations to check that all names are bound...
    }

    @SuppressWarnings("rawtypes")
    private void mapType(MappingManager manager, Class fullReturnType, Type type) {

        if (type instanceof ParameterizedType) {
            ParameterizedType pt = (ParameterizedType) type;
            Type raw = pt.getRawType();
            if (raw instanceof Class && Result.class.isAssignableFrom((Class) raw)) {
                type = pt.getActualTypeArguments()[0];
            } else {
                mapOne = true;
            }
        } else {
            mapOne = true;
        }

        if (!(type instanceof Class))
            throw new RuntimeException(String.format("Cannot map return of method %s to unsupported type %s", method, type));

        try {
            this.returnMapper = manager.mapper((Class) type);
        } catch (Exception e) {
            throw new RuntimeException("Cannot map return to class " + fullReturnType, e);
        }
    }

    Object invoke(Object[] args) {

        BoundStatement bs = statement.bind();

        for (int i = 0; i < args.length; i++) {
            paramMappers[i].setValue(bs, args[i]);
        }

        if (consistency != null)
            bs.setConsistencyLevel(consistency);
        if (fetchSize > 0)
            bs.setFetchSize(fetchSize);
        if (tracing)
            bs.enableTracing();
        if (idempotent != null)
            bs.setIdempotent(idempotent);

        if (returnStatement)
            return bs;

        if (async) {
            ListenableFuture future = session.executeAsync(bs);
            if (returnMapper == null)
                return future;

            return mapOne
                    ? Futures.transform(future, returnMapper.mapOneFunctionWithoutAliases)
                    : Futures.transform(future, returnMapper.mapAllFunctionWithoutAliases);
        } else {
            ResultSet rs = session.execute(bs);
            if (returnMapper == null)
                return rs;

            Result result = returnMapper.map(rs);
            return mapOne ? result.one() : result;
        }
    }

    static class ParamMapper {
        // We'll only set one or the other. If paramName is null, then paramIdx is used.
        private final String paramName;
        private final int paramIdx;
        private final TypeToken