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/**
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* Relational pipes
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* Copyright © 2019 František Kučera (Frantovo.cz, GlobalCode.info)
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include <vector>
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#include <filesystem>
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#include <relpipe/writer/typedefs.h>
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#include <relpipe/writer/AttributeMetadata.h>
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#include <relpipe/writer/RelationalWriter.h>
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#include "RequestedField.h"
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namespace relpipe {
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namespace in {
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namespace filesystem {
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namespace fs = std::filesystem;
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using namespace relpipe::writer;
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class AttributeFinder {
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public:
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/**
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* Single requested fields might generate multiple attributes in the relation.
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* But usually it is 1:1.
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* @param field requested field from the user (usually from CLI arguments)
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* @return attribute metadata to be used in the RelationalWriter.startRelation()
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*/
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virtual vector<AttributeMetadata> toMetadata(const RequestedField& field) = 0;
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/**
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* Writing of the record for current file is starting.
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* Following writeField() calls are related to this file.
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* @param file
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*/
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virtual void startFile(const fs::path& file) = 0;
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/**
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* Writing of the record for current file is finished. All resources linked to this file should be released.
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*/
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virtual void endFile() = 0;
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/**
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* Writes field attribute(s). The attribute count must match with count of AttributeMetadata returned in toMetadata().
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* @param writer
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* @param field
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*/
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virtual void writeField(RelationalWriter* writer, const RequestedField& field) = 0;
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/**
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* Writes empty attribute(s) in case of non-existent file or an error.
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* The attribute count must match with count of AttributeMetadata returned in toMetadata().
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* @param writer
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* @param field
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*/
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virtual void writeEmptyField(RelationalWriter* writer, const RequestedField& field) {
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// TODO: better handling of null values (when null values are supported by the format specification)
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for (AttributeMetadata m : toMetadata(field)) {
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switch (m.typeId) {
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case TypeId::BOOLEAN:
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writer->writeAttribute(L"false");
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break;
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case TypeId::INTEGER:
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writer->writeAttribute(L"0");
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break;
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case TypeId::STRING:
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writer->writeAttribute(L"");
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break;
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default:
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throw RelpipeWriterException(L"Unsupported attribute type in writeEmptyField().");
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}
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}
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}
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virtual ~AttributeFinder() {
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}
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};
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}
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}
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} |