#include <memory>

#include <boost/range/join.hpp>

#include <Poco/File.h>
#include <Poco/FileStream.h>

#include <Common/escapeForFileName.h>

#include <IO/WriteBufferFromFile.h>
#include <IO/WriteHelpers.h>

#include <Parsers/ASTColumnDeclaration.h>
#include <Parsers/ASTCreateQuery.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTNameTypePair.h>
#include <Parsers/ASTInsertQuery.h>
#include <Parsers/ParserCreateQuery.h>
#include <Parsers/formatAST.h>
#include <Parsers/parseQuery.h>

#include <Storages/StorageFactory.h>
#include <Storages/StorageLog.h>

#include <Interpreters/Context.h>
#include <Interpreters/DDLWorker.h>
#include <Interpreters/ExpressionAnalyzer.h>
#include <Interpreters/InterpreterCreateQuery.h>
#include <Interpreters/InterpreterSelectWithUnionQuery.h>
#include <Interpreters/InterpreterInsertQuery.h>
#include <Interpreters/ExpressionActions.h>

#include <DataTypes/DataTypeFactory.h>
#include <DataTypes/NestedUtils.h>
#include <DataTypes/DataTypesNumber.h>
#include <DataTypes/DataTypesDecimal.h>

#include <Databases/DatabaseFactory.h>
#include <Databases/IDatabase.h>

#include <Common/ZooKeeper/ZooKeeper.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int TABLE_ALREADY_EXISTS;
    extern const int EMPTY_LIST_OF_COLUMNS_PASSED;
    extern const int INCORRECT_QUERY;
    extern const int ENGINE_REQUIRED;
    extern const int UNKNOWN_DATABASE_ENGINE;
    extern const int DUPLICATE_COLUMN;
    extern const int READONLY;
    extern const int ILLEGAL_COLUMN;
    extern const int DATABASE_ALREADY_EXISTS;
    extern const int QUERY_IS_PROHIBITED;
}


InterpreterCreateQuery::InterpreterCreateQuery(const ASTPtr & query_ptr_, Context & context_)
    : query_ptr(query_ptr_), context(context_)
{
}


BlockIO InterpreterCreateQuery::createDatabase(ASTCreateQuery & create)
{
    if (!create.cluster.empty())
        return executeDDLQueryOnCluster(query_ptr, context, {create.database});

    String database_name = create.database;

    auto guard = context.getDDLGuard(database_name, "");

    /// Database can be created before or it can be created concurrently in another thread, while we were waiting in DDLGuard
    if (context.isDatabaseExist(database_name))
    {
        if (create.if_not_exists)
            return {};
        else
            throw Exception("Database " + database_name + " already exists.", ErrorCodes::DATABASE_ALREADY_EXISTS);
    }

    String database_engine_name;
    if (!create.storage)
    {
        database_engine_name = "Ordinary"; /// Default database engine.
        auto engine = std::make_shared<ASTFunction>();
        engine->name = database_engine_name;
        auto storage = std::make_shared<ASTStorage>();
        storage->set(storage->engine, engine);
        create.set(create.storage, storage);
    }
    else
    {
        const ASTStorage & storage = *create.storage;
        const ASTFunction & engine = *storage.engine;
        /// Currently, there are no database engines, that support any arguments.
        if (engine.arguments || engine.parameters || storage.partition_by || storage.order_by || storage.sample_by || storage.settings)
        {
            std::stringstream ostr;
            formatAST(storage, ostr, false, false);
            throw Exception("Unknown database engine: " + ostr.str(), ErrorCodes::UNKNOWN_DATABASE_ENGINE);
        }

        database_engine_name = engine.name;
    }

    String database_name_escaped = escapeForFileName(database_name);

    /// Create directories for tables metadata.
    String path = context.getPath();
    String metadata_path = path + "metadata/" + database_name_escaped + "/";
    Poco::File(metadata_path).createDirectory();

    DatabasePtr database = DatabaseFactory::get(database_engine_name, database_name, metadata_path, context);

    /// Will write file with database metadata, if needed.
    String metadata_file_tmp_path = path + "metadata/" + database_name_escaped + ".sql.tmp";
    String metadata_file_path = path + "metadata/" + database_name_escaped + ".sql";

    bool need_write_metadata = !create.attach;

    if (need_write_metadata)
    {
        create.attach = true;
        create.if_not_exists = false;

        std::ostringstream statement_stream;
        formatAST(create, statement_stream, false);
        statement_stream << '\n';
        String statement = statement_stream.str();

        /// Exclusive flag guarantees, that database is not created right now in another thread.
        WriteBufferFromFile out(metadata_file_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
        writeString(statement, out);

        out.next();
        if (context.getSettingsRef().fsync_metadata)
            out.sync();
        out.close();
    }

    try
    {
        context.addDatabase(database_name, database);

        if (need_write_metadata)
            Poco::File(metadata_file_tmp_path).renameTo(metadata_file_path);

        database->loadTables(context, thread_pool, has_force_restore_data_flag);
    }
    catch (...)
    {
        if (need_write_metadata)
            Poco::File(metadata_file_tmp_path).remove();

        throw;
    }

    return {};
}


using ColumnsAndDefaults = std::pair<NamesAndTypesList, ColumnDefaults>;

/// AST to the list of columns with types. Columns of Nested type are expanded into a list of real columns.
static ColumnsAndDefaults parseColumns(const ASTExpressionList & column_list_ast, const Context & context)
{
    /// list of table columns in correct order
    NamesAndTypesList columns{};
    ColumnDefaults defaults{};

    /// Columns requiring type-deduction or default_expression type-check
    std::vector<std::pair<NameAndTypePair *, ASTColumnDeclaration *>> defaulted_columns{};

    /** all default_expressions as a single expression list,
     *  mixed with conversion-columns for each explicitly specified type */
    ASTPtr default_expr_list = std::make_shared<ASTExpressionList>();
    default_expr_list->children.reserve(column_list_ast.children.size());

    for (const auto & ast : column_list_ast.children)
    {
        auto & col_decl = typeid_cast<ASTColumnDeclaration &>(*ast);

        if (col_decl.type)
        {
            columns.emplace_back(col_decl.name, DataTypeFactory::instance().get(col_decl.type));
        }
        else
            /// we're creating dummy DataTypeUInt8 in order to prevent the NullPointerException in ExpressionActions
            columns.emplace_back(col_decl.name, std::make_shared<DataTypeUInt8>());

        /// add column to postprocessing if there is a default_expression specified
        if (col_decl.default_expression)
        {
            defaulted_columns.emplace_back(&columns.back(), &col_decl);

            /** for columns with explicitly-specified type create two expressions:
             *    1. default_expression aliased as column name with _tmp suffix
             *    2. conversion of expression (1) to explicitly-specified type alias as column name */
            if (col_decl.type)
            {
                const auto & final_column_name = col_decl.name;
                const auto tmp_column_name = final_column_name + "_tmp";
                const auto data_type_ptr = columns.back().type.get();

                default_expr_list->children.emplace_back(setAlias(
                    makeASTFunction("CAST", std::make_shared<ASTIdentifier>(tmp_column_name),
                        std::make_shared<ASTLiteral>(Field(data_type_ptr->getName()))), final_column_name));
                default_expr_list->children.emplace_back(setAlias(col_decl.default_expression->clone(), tmp_column_name));
            }
            else
                default_expr_list->children.emplace_back(setAlias(col_decl.default_expression->clone(), col_decl.name));
        }
    }

    /// set missing types and wrap default_expression's in a conversion-function if necessary
    if (!defaulted_columns.empty())
    {
        const auto actions = ExpressionAnalyzer{default_expr_list, context, {}, columns}.getActions(true);
        const auto block = actions->getSampleBlock();

        for (auto & column : defaulted_columns)
        {
            const auto name_and_type_ptr = column.first;
            const auto col_decl_ptr = column.second;

            const auto & column_name = col_decl_ptr->name;
            const auto has_explicit_type = nullptr != col_decl_ptr->type;
            auto & explicit_type = name_and_type_ptr->type;

            /// if column declaration contains explicit type, name_and_type_ptr->type is not null
            if (has_explicit_type)
            {
                const auto & tmp_column = block.getByName(column_name + "_tmp");
                const auto & deduced_type = tmp_column.type;

                /// type mismatch between explicitly specified and deduced type, add conversion for non-array types
                if (!explicit_type->equals(*deduced_type))
                {
                    col_decl_ptr->default_expression = makeASTFunction("CAST", col_decl_ptr->default_expression,
                        std::make_shared<ASTLiteral>(explicit_type->getName()));

                    col_decl_ptr->children.clear();
                    col_decl_ptr->children.push_back(col_decl_ptr->type);
                    col_decl_ptr->children.push_back(col_decl_ptr->default_expression);
                }
            }
            else
                /// no explicit type, name_and_type_ptr->type is null, set to deduced type
                explicit_type = block.getByName(column_name).type;

            defaults.emplace(column_name, ColumnDefault{
                columnDefaultKindFromString(col_decl_ptr->default_specifier),
                col_decl_ptr->default_expression
            });
        }
    }

    return {Nested::flatten(columns), defaults};
}


static NamesAndTypesList removeAndReturnColumns(ColumnsAndDefaults & columns_and_defaults, const ColumnDefaultKind kind)
{
    auto & columns = columns_and_defaults.first;
    auto & defaults = columns_and_defaults.second;

    NamesAndTypesList removed{};

    for (auto it = std::begin(columns); it != std::end(columns);)
    {
        const auto jt = defaults.find(it->name);
        if (jt != std::end(defaults) && jt->second.kind == kind)
        {
            removed.push_back(*it);
            it = columns.erase(it);
        }
        else
            ++it;
    }

    return removed;
}


ASTPtr InterpreterCreateQuery::formatColumns(const NamesAndTypesList & columns)
{
    auto columns_list = std::make_shared<ASTExpressionList>();

    for (const auto & column : columns)
    {
        const auto column_declaration = std::make_shared<ASTColumnDeclaration>();
        column_declaration->name = column.name;

        StringPtr type_name = std::make_shared<String>(column.type->getName());
        auto pos = type_name->data();
        const auto end = pos + type_name->size();

        ParserIdentifierWithOptionalParameters storage_p;
        column_declaration->type = parseQuery(storage_p, pos, end, "data type", 0);
        column_declaration->type->owned_string = type_name;
        columns_list->children.emplace_back(column_declaration);
    }

    return columns_list;
}

ASTPtr InterpreterCreateQuery::formatColumns(const ColumnsDescription & columns)
{
    auto columns_list = std::make_shared<ASTExpressionList>();

    for (const auto & column : columns.getAll())
    {
        const auto column_declaration = std::make_shared<ASTColumnDeclaration>();
        ASTPtr column_declaration_ptr{column_declaration};

        column_declaration->name = column.name;

        StringPtr type_name = std::make_shared<String>(column.type->getName());
        auto pos = type_name->data();
        const auto end = pos + type_name->size();

        ParserIdentifierWithOptionalParameters storage_p;
        column_declaration->type = parseQuery(storage_p, pos, end, "data type", 0);
        column_declaration->type->owned_string = type_name;

        const auto it = columns.defaults.find(column.name);
        if (it != std::end(columns.defaults))
        {
            column_declaration->default_specifier = toString(it->second.kind);
            column_declaration->default_expression = it->second.expression->clone();
        }

        columns_list->children.push_back(column_declaration_ptr);
    }

    return columns_list;
}


ColumnsDescription InterpreterCreateQuery::getColumnsDescription(const ASTExpressionList & columns, const Context & context)
{
    ColumnsDescription res;

    auto && columns_and_defaults = parseColumns(columns, context);
    res.materialized = removeAndReturnColumns(columns_and_defaults, ColumnDefaultKind::Materialized);
    res.aliases = removeAndReturnColumns(columns_and_defaults, ColumnDefaultKind::Alias);
    res.ordinary = std::move(columns_and_defaults.first);
    res.defaults = std::move(columns_and_defaults.second);

    if (res.ordinary.size() + res.materialized.size() == 0)
        throw Exception{"Cannot CREATE table without physical columns", ErrorCodes::EMPTY_LIST_OF_COLUMNS_PASSED};

    return res;
}


void InterpreterCreateQuery::checkSupportedTypes(const ColumnsDescription & columns, const Context & context)
{
    const auto & settings = context.getSettingsRef();
    bool allow_low_cardinality = settings.allow_experimental_low_cardinality_type != 0;
    bool allow_decimal = settings.allow_experimental_decimal_type;

    if (allow_low_cardinality && allow_decimal)
        return;

    auto check_types = [&](const NamesAndTypesList & list)
    {
        for (const auto & column : list)
        {
            if (!allow_low_cardinality && column.type && column.type->lowCardinality())
            {
                String message = "Cannot create table with column '" + column.name + "' which type is '"
                                 + column.type->getName() + "' because LowCardinality type is not allowed. "
                                 + "Set setting allow_experimental_low_cardinality_type = 1 in order to allow it.";
                throw Exception(message, ErrorCodes::ILLEGAL_COLUMN);
            }
            if (!allow_decimal && column.type && isDecimal(column.type))
            {
                String message = "Cannot create table with column '" + column.name + "' which type is '" + column.type->getName()
                                 + "'. Set setting allow_experimental_decimal_type = 1 in order to allow it.";
                throw Exception(message, ErrorCodes::ILLEGAL_COLUMN);
            }
        }
    };

    check_types(columns.ordinary);
    check_types(columns.materialized);
}


ColumnsDescription InterpreterCreateQuery::setColumns(
    ASTCreateQuery & create, const Block & as_select_sample, const StoragePtr & as_storage) const
{
    ColumnsDescription res;

    if (create.columns)
    {
        res = getColumnsDescription(*create.columns, context);
    }
    else if (!create.as_table.empty())
    {
        res = as_storage->getColumns();
    }
    else if (create.select)
    {
        for (size_t i = 0; i < as_select_sample.columns(); ++i)
            res.ordinary.emplace_back(as_select_sample.safeGetByPosition(i).name, as_select_sample.safeGetByPosition(i).type);
    }
    else
        throw Exception("Incorrect CREATE query: required list of column descriptions or AS section or SELECT.", ErrorCodes::INCORRECT_QUERY);

    /// Even if query has list of columns, canonicalize it (unfold Nested columns).
    ASTPtr new_columns = formatColumns(res);
    if (create.columns)
        create.replace(create.columns, new_columns);
    else
        create.set(create.columns, new_columns);

    /// Check for duplicates
    std::set<String> all_columns;
    auto check_column_already_exists = [&all_columns](const NameAndTypePair & column_name_and_type)
    {
        if (!all_columns.emplace(column_name_and_type.name).second)
            throw Exception("Column " + backQuoteIfNeed(column_name_and_type.name) + " already exists", ErrorCodes::DUPLICATE_COLUMN);
    };

    for (const auto & elem : res.ordinary)
        check_column_already_exists(elem);
    for (const auto & elem : res.materialized)
        check_column_already_exists(elem);
    for (const auto & elem : res.aliases)
        check_column_already_exists(elem);

    return res;
}


void InterpreterCreateQuery::setEngine(ASTCreateQuery & create) const
{
    if (create.storage)
    {
        if (create.is_temporary && create.storage->engine->name != "Memory")
            throw Exception(
                "Temporary tables can only be created with ENGINE = Memory, not " + create.storage->engine->name,
                ErrorCodes::INCORRECT_QUERY);

        return;
    }

    if (create.is_temporary)
    {
        auto engine_ast = std::make_shared<ASTFunction>();
        engine_ast->name = "Memory";
        auto storage_ast = std::make_shared<ASTStorage>();
        storage_ast->set(storage_ast->engine, engine_ast);
        create.set(create.storage, storage_ast);
    }
    else if (!create.as_table.empty())
    {
        /// NOTE Getting the structure from the table specified in the AS is done not atomically with the creation of the table.

        String as_database_name = create.as_database.empty() ? context.getCurrentDatabase() : create.as_database;
        String as_table_name = create.as_table;

        ASTPtr as_create_ptr = context.getCreateTableQuery(as_database_name, as_table_name);
        const auto & as_create = typeid_cast<const ASTCreateQuery &>(*as_create_ptr);

        if (as_create.is_view)
            throw Exception(
                "Cannot CREATE a table AS " + as_database_name + "." + as_table_name + ", it is a View",
                ErrorCodes::INCORRECT_QUERY);

        create.set(create.storage, as_create.storage->ptr());
    }
}


BlockIO InterpreterCreateQuery::createTable(ASTCreateQuery & create)
{
    if (!create.cluster.empty())
    {
        NameSet databases{create.database};
        if (!create.to_table.empty())
            databases.emplace(create.to_database);

        return executeDDLQueryOnCluster(query_ptr, context, databases);
    }

    String path = context.getPath();
    String current_database = context.getCurrentDatabase();

    String database_name = create.database.empty() ? current_database : create.database;
    String table_name = create.table;
    String table_name_escaped = escapeForFileName(table_name);

    // If this is a stub ATTACH query, read the query definition from the database
    if (create.attach && !create.storage && !create.columns)
    {
        // Table SQL definition is available even if the table is detached
        auto query = context.getCreateTableQuery(database_name, table_name);
        auto & as_create = typeid_cast<const ASTCreateQuery &>(*query);
        create = as_create; // Copy the saved create query, but use ATTACH instead of CREATE
        create.attach = true;
    }

    if (create.to_database.empty())
        create.to_database = current_database;

    if (create.select && (create.is_view || create.is_materialized_view))
        create.select->setDatabaseIfNeeded(current_database);

    Block as_select_sample;
    if (create.select && (!create.attach || !create.columns))
        as_select_sample = InterpreterSelectWithUnionQuery::getSampleBlock(create.select->clone(), context);

    String as_database_name = create.as_database.empty() ? current_database : create.as_database;
    String as_table_name = create.as_table;

    StoragePtr as_storage;
    TableStructureReadLockPtr as_storage_lock;
    if (!as_table_name.empty())
    {
        as_storage = context.getTable(as_database_name, as_table_name);
        as_storage_lock = as_storage->lockStructure(false, __PRETTY_FUNCTION__);
    }

    /// Set and retrieve list of columns.
    ColumnsDescription columns = setColumns(create, as_select_sample, as_storage);

    /// Some column types may be not allowed according to settings.
    if (!create.attach)
        checkSupportedTypes(columns, context);

    /// Set the table engine if it was not specified explicitly.
    setEngine(create);

    StoragePtr res;

    {
        std::unique_ptr<DDLGuard> guard;

        String data_path;
        DatabasePtr database;

        if (!create.is_temporary)
        {
            database = context.getDatabase(database_name);
            data_path = database->getDataPath();

            /** If the request specifies IF NOT EXISTS, we allow concurrent CREATE queries (which do nothing).
              * If table doesnt exist, one thread is creating table, while others wait in DDLGuard.
              */
            guard = context.getDDLGuard(database_name, table_name);

            /// Table can be created before or it can be created concurrently in another thread, while we were waiting in DDLGuard.
            if (database->isTableExist(context, table_name))
            {
                if (create.if_not_exists)
                    return {};
                else
                    throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
            }
        }
        else if (context.tryGetExternalTable(table_name) && create.if_not_exists)
             return {};

        res = StorageFactory::instance().get(create,
            data_path,
            table_name,
            database_name,
            context,
            context.getGlobalContext(),
            columns,
            create.attach,
            false);

        if (create.is_temporary)
            context.getSessionContext().addExternalTable(table_name, res, query_ptr);
        else
            database->createTable(context, table_name, res, query_ptr);

        /// We must call "startup" and "shutdown" while holding DDLGuard.
        /// Because otherwise method "shutdown" (from InterpreterDropQuery) can be called before startup
        /// (in case when table was created and instantly dropped before started up)
        ///
        /// Method "startup" may create background tasks and method "shutdown" will wait for them.
        /// But if "shutdown" is called before "startup", it will exit early, because there are no background tasks to wait.
        /// Then background task is created by "startup" method. And when destructor of a table object is called, background task is still active,
        /// and the task will use references to freed data.

        res->startup();
    }

    /// If the query is a CREATE SELECT, insert the data into the table.
    if (create.select && !create.attach
        && !create.is_view && (!create.is_materialized_view || create.is_populate))
    {
        auto insert = std::make_shared<ASTInsertQuery>();

        if (!create.is_temporary)
            insert->database = database_name;

        insert->table = table_name;
        insert->select = create.select->clone();

        if (create.is_temporary && !context.getSessionContext().hasQueryContext())
            context.getSessionContext().setQueryContext(context.getSessionContext());

        return InterpreterInsertQuery(insert,
            create.is_temporary ? context.getSessionContext() : context,
            context.getSettingsRef().insert_allow_materialized_columns).execute();
    }

    return {};
}


BlockIO InterpreterCreateQuery::execute()
{
    ASTCreateQuery & create = typeid_cast<ASTCreateQuery &>(*query_ptr);
    checkAccess(create);
    ASTQueryWithOutput::resetOutputASTIfExist(create);

    /// CREATE|ATTACH DATABASE
    if (!create.database.empty() && create.table.empty())
    {
        return createDatabase(create);
    }
    else
        return createTable(create);
}


void InterpreterCreateQuery::checkAccess(const ASTCreateQuery & create)
{
    /// Internal queries (initiated by the server itself) always have access to everything.
    if (internal)
        return;

    const Settings & settings = context.getSettingsRef();
    auto readonly = settings.readonly;
    auto allow_ddl = settings.allow_ddl;

    if (!readonly && allow_ddl)
        return;

    /// CREATE|ATTACH DATABASE
    if (!create.database.empty() && create.table.empty())
    {
        if (readonly)
            throw Exception("Cannot create database in readonly mode", ErrorCodes::READONLY);

        throw Exception("Cannot create database. DDL queries are prohibited for the user", ErrorCodes::QUERY_IS_PROHIBITED);
    }

    if (create.is_temporary && readonly >= 2)
        return;

    if (readonly)
        throw Exception("Cannot create table in readonly mode", ErrorCodes::READONLY);

    throw Exception("Cannot create table. DDL queries are prohibited for the user", ErrorCodes::QUERY_IS_PROHIBITED);
}
}