ClickHouse/src/Functions/FunctionsStringSearchToString.h

#pragma once

#include <Columns/ColumnArray.h>
#include <Columns/ColumnConst.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnFixedString.h>
#include <Columns/ColumnVector.h>
#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypesNumber.h>
#include <Functions/FunctionHelpers.h>
#include <Functions/IFunctionImpl.h>
#include <IO/WriteHelpers.h>
#include <Interpreters/Context.h>
#include <common/StringRef.h>


namespace DB
{
/** Applies regexp re2 and extracts:
  * - the first subpattern, if the regexp has a subpattern;
  * - the zero subpattern (the match part, otherwise);
  * - if not match - an empty string.
  * extract(haystack, pattern)
  */

namespace ErrorCodes
{
    extern const int ILLEGAL_TYPE_OF_ARGUMENT;
    extern const int ILLEGAL_COLUMN;
}


template <typename Impl, typename Name>
class FunctionsStringSearchToString : public IFunction
{
public:
    static constexpr auto name = Name::name;
    static FunctionPtr create(const Context &) { return std::make_shared<FunctionsStringSearchToString>(); }

    String getName() const override { return name; }

    size_t getNumberOfArguments() const override { return 2; }

    bool useDefaultImplementationForConstants() const override { return true; }
    ColumnNumbers getArgumentsThatAreAlwaysConstant() const override { return {1}; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        if (!isString(arguments[0]))
            throw Exception(
                "Illegal type " + arguments[0]->getName() + " of argument of function " + getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

        if (!isString(arguments[1]))
            throw Exception(
                "Illegal type " + arguments[1]->getName() + " of argument of function " + getName(), ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT);

        return std::make_shared<DataTypeString>();
    }

    ColumnPtr executeImpl(ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t /*input_rows_count*/) const override
    {
        const ColumnPtr column = arguments[0].column;
        const ColumnPtr column_needle = arguments[1].column;

        const ColumnConst * col_needle = typeid_cast<const ColumnConst *>(&*column_needle);
        if (!col_needle)
            throw Exception("Second argument of function " + getName() + " must be constant string", ErrorCodes::ILLEGAL_COLUMN);

        if (const ColumnString * col = checkAndGetColumn<ColumnString>(column.get()))
        {
            auto col_res = ColumnString::create();

            ColumnString::Chars & vec_res = col_res->getChars();
            ColumnString::Offsets & offsets_res = col_res->getOffsets();
            Impl::vector(col->getChars(), col->getOffsets(), col_needle->getValue<String>(), vec_res, offsets_res);

            return col_res;
        }
        else
            throw Exception(
                "Illegal column " + arguments[0].column->getName() + " of argument of function " + getName(),
                ErrorCodes::ILLEGAL_COLUMN);
    }
};

}