ClickHouse/src/Processors/Formats/Impl/JSONAsStringRowInputFormat.h

#pragma once

#include <Processors/Formats/IRowInputFormat.h>
#include <Processors/Formats/ISchemaReader.h>
#include <Formats/FormatFactory.h>
#include <IO/PeekableReadBuffer.h>
#include <DataTypes/DataTypeString.h>

namespace DB
{

class ReadBuffer;

/// This format parses a sequence of JSON objects separated by newlines, spaces and/or comma.
class JSONAsRowInputFormat : public IRowInputFormat
{
public:
    JSONAsRowInputFormat(const Block & header_, ReadBuffer & in_, Params params_);

    void resetParser() override;
    void setReadBuffer(ReadBuffer & in_) override;

private:
    JSONAsRowInputFormat(const Block & header_, std::unique_ptr<PeekableReadBuffer> buf_, Params params_);

    bool readRow(MutableColumns & columns, RowReadExtension & ext) override;

    void readPrefix() override;
    void readSuffix() override;

protected:
    virtual void readJSONObject(IColumn & column) = 0;
    std::unique_ptr<PeekableReadBuffer> buf;

private:
    /// This flag is needed to know if data is in square brackets.
    bool data_in_square_brackets = false;
    bool allow_new_rows = true;
};

/// Each JSON object is parsed as a whole to string.
/// This format can only parse a table with single field of type String.
class JSONAsStringRowInputFormat final : public JSONAsRowInputFormat
{
public:
    JSONAsStringRowInputFormat(const Block & header_, ReadBuffer & in_, Params params_);
    String getName() const override { return "JSONAsStringRowInputFormat"; }

private:
    void readJSONObject(IColumn & column) override;
};


/// Each JSON object is parsed as a whole to object.
/// This format can only parse a table with single field of type Object.
class JSONAsObjectRowInputFormat final : public JSONAsRowInputFormat
{
public:
    JSONAsObjectRowInputFormat(const Block & header_, ReadBuffer & in_, Params params_, const FormatSettings & format_settings_);
    String getName() const override { return "JSONAsObjectRowInputFormat"; }

private:
    void readJSONObject(IColumn & column) override;
    const FormatSettings format_settings;
};

class JSONAsStringExternalSchemaReader : public IExternalSchemaReader
{
public:
    NamesAndTypesList readSchema() override
    {
        return {{"json", std::make_shared<DataTypeString>()}};
    }
};

}