rather fail-fast than hide mistakes (might be e.g. a typo in the source YAML file)
/**
* Relational pipes
* Copyright © 2020 František Kučera (Frantovo.cz, GlobalCode.info)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, version 3 of the License.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <cstdlib>
#include <iostream>
#include <memory>
#include <vector>
#include <yaml.h>
#include <relpipe/writer/RelationalWriter.h>
#include <relpipe/writer/typedefs.h>
namespace relpipe {
namespace in {
namespace yaml {
class YAMLCommand {
private:
using string_t = relpipe::writer::string_t;
using RelpipeWriterException = relpipe::writer::RelpipeWriterException;
std::wstring_convert<codecvt_utf8<wchar_t>> convertor; // YAML strings are in UTF-8
class YAMLEvent {
private:
yaml_event_t event;
public:
YAMLEvent(yaml_event_t event) : event(event) {
}
virtual ~YAMLEvent() {
yaml_event_delete(&event);
}
const yaml_event_type_t getType() const {
return event.type;
}
const string_t getTypeName() const {
return findTypeName(event.type);
}
/** Just for debugging and error handling */
static const string_t findTypeName(const yaml_event_type_t eventType) {
if (eventType == YAML_NO_EVENT) return L"NO";
else if (eventType == YAML_STREAM_START_EVENT) return L"STREAM_START";
else if (eventType == YAML_STREAM_END_EVENT) return L"STREAM_END";
else if (eventType == YAML_DOCUMENT_START_EVENT) return L"DOCUMENT_START";
else if (eventType == YAML_DOCUMENT_END_EVENT) return L"DOCUMENT_END";
else if (eventType == YAML_ALIAS_EVENT) return L"ALIAS";
else if (eventType == YAML_SCALAR_EVENT) return L"SCALAR";
else if (eventType == YAML_SEQUENCE_START_EVENT) return L"SEQUENCE_START";
else if (eventType == YAML_SEQUENCE_END_EVENT) return L"SEQUENCE_END";
else if (eventType == YAML_MAPPING_START_EVENT) return L"MAPPING_START";
else if (eventType == YAML_MAPPING_END_EVENT) return L"MAPPING_END";
else return L"UNKNOWN";
}
const yaml_event_t* getEvent() const {
return &event;
}
YAMLEvent(const YAMLEvent&) = delete;
YAMLEvent& operator=(const YAMLEvent&) = delete;
};
class YAMLParser {
private:
yaml_parser_t yamlParser;
std::istream* input = nullptr;
static int readFromInput(void* instance, unsigned char* buffer, size_t size, size_t* length) {
std::istream* input = ((YAMLParser*) instance)->input;
input->read((char*) buffer, size);
*length = input->gcount();
return (input->good() || input->eof()) ? 1 : 0;
}
public:
YAMLParser() {
yaml_parser_initialize(&yamlParser);
}
virtual ~YAMLParser() {
yaml_parser_delete(&yamlParser);
}
YAMLParser(const YAMLParser&) = delete;
YAMLParser& operator=(const YAMLParser&) = delete;
void setInput(std::istream* input) {
this->input = input;
yaml_parser_set_input(&yamlParser, readFromInput, (void*) this);
}
YAMLEvent* next() {
yaml_event_t event;
int result = yaml_parser_parse(&yamlParser, &event);
return result == 1 && event.type != yaml_event_type_e::YAML_NO_EVENT ? new YAMLEvent(event) : nullptr; // 1 = OK in yaml.h; YAML_NO_EVENT = end
}
};
using YAMLEvent_p = std::shared_ptr<YAMLEvent>;
YAMLParser parser;
std::shared_ptr<relpipe::writer::RelationalWriter> writer;
string_t relationName;
std::vector<string_t> record;
std::vector<relpipe::writer::AttributeMetadata> attributesMetadata;
string_t y2s(const yaml_char_t* value) {
return value ? convertor.from_bytes((const char*) value) : L"";
}
string_t fetchScalarValue(YAMLEvent_p event) {
if (event->getType() == YAML_SCALAR_EVENT) return y2s(event->getEvent()->data.scalar.value);
else throw RelpipeWriterException(L"Invalid YAML structure: expected SCALAR but got: " + event->getTypeName());
}
void consumeEvent(const yaml_event_type_t expectedEventType, string_t expectedScalarValue = L"") {
YAMLEvent_p event = YAMLEvent_p(parser.next());
if (!event) throw RelpipeWriterException(L"Invalid YAML structure: missing event: " + YAMLEvent::findTypeName(expectedEventType));
if (event->getType() != expectedEventType) throw RelpipeWriterException(L"Invalid YAML structure: expected event: " + YAMLEvent::findTypeName(expectedEventType) + L", but got: " + event->getTypeName());
if (expectedEventType == YAML_SCALAR_EVENT && expectedScalarValue.size() && expectedScalarValue != fetchScalarValue(event)) throw RelpipeWriterException(L"Invalid YAML structure: expected scalar value: „" + expectedScalarValue + L"“, but got „" + fetchScalarValue(event) + L"“");
}
string_t consumeScalarEvent() {
YAMLEvent_p event = YAMLEvent_p(parser.next());
if (event && event->getType() == YAML_SCALAR_EVENT) return fetchScalarValue(event);
else throw RelpipeWriterException(L"Invalid YAML structure: expected SCALAR, but got: " + event->getTypeName());
}
bool until(const yaml_event_type_t until, YAMLEvent_p& event) {
event = YAMLEvent_p(parser.next());
return event && event->getType() != until;
}
void processRelation() {
YAMLEvent_p event = YAMLEvent_p(parser.next());
if (event->getType() == YAML_MAPPING_START_EVENT) processRelationWithMetadata();
else if (event->getType() == YAML_SEQUENCE_START_EVENT)processRelationWithoutMetadata();
else throw RelpipeWriterException(L"Invalid YAML structure: expected MAPPING or SEQUENCE, but got: " + event->getTypeName());
}
void processRelationWithMetadata() {
consumeEvent(YAML_SCALAR_EVENT, L"attribute-metadata");
consumeEvent(YAML_SEQUENCE_START_EVENT);
for (YAMLEvent_p event; until(YAML_SEQUENCE_END_EVENT, event);) {
if (event->getType() != YAML_MAPPING_START_EVENT) throw RelpipeWriterException(L"Invalid YAML structure: expected MAPPING (attribute-metadata), but got: " + event->getTypeName());
string_t name;
string_t type = L"string";
for (YAMLEvent_p event; until(YAML_MAPPING_END_EVENT, event);) {
auto key = fetchScalarValue(event);
auto value = consumeScalarEvent();
if (key == L"name") name = value;
else if (key == L"type") type = value;
else throw RelpipeWriterException(L"Invalid YAML structure: expected „name“ or „type“ but got: " + key);
}
attributesMetadata.push_back({name, writer->toTypeId(type)});
}
writer->startRelation(relationName, attributesMetadata, true);
YAMLEvent_p event = YAMLEvent_p(parser.next());
if (event->getType() == YAML_SCALAR_EVENT && fetchScalarValue(event) == L"record") {
consumeEvent(YAML_SEQUENCE_START_EVENT);
processRecords();
consumeEvent(YAML_MAPPING_END_EVENT);
} else if (event->getType() == YAML_MAPPING_END_EVENT) {
// empty relation, no records
} else {
RelpipeWriterException(L"Invalid YAML structure: expected „record“ or MAPPING_END, but got: " + event->getTypeName());
}
}
void processRelationWithoutMetadata() {
// First record:
consumeEvent(YAML_MAPPING_START_EVENT);
record.clear();
for (YAMLEvent_p event; until(YAML_MAPPING_END_EVENT, event);) {
auto name = fetchScalarValue(event);
auto value = consumeScalarEvent();
attributesMetadata.push_back({name, relpipe::writer::TypeId::STRING});
record.push_back(value);
}
writer->startRelation(relationName, attributesMetadata, true);
for (auto value : record) writer->writeAttribute(value);
// Following records:
processRecords();
}
void processRecords() {
for (YAMLEvent_p event; until(YAML_SEQUENCE_END_EVENT, event);) {
if (event->getType() != YAML_MAPPING_START_EVENT) throw RelpipeWriterException(L"Invalid YAML structure: expected MAPPING (record), but got: " + event->getTypeName());
record.clear();
record.resize(attributesMetadata.size());
for (YAMLEvent_p event; until(YAML_MAPPING_END_EVENT, event);) {
auto name = fetchScalarValue(event);
auto value = consumeScalarEvent();
for (int i = 0; i < attributesMetadata.size(); i++) {
if (name == attributesMetadata[i].attributeName) {
record[i] = value;
break;
}
}
}
for (auto value : record) writer->writeAttribute(value);
}
}
public:
YAMLCommand() {
}
virtual ~YAMLCommand() {
}
void process(std::istream& input, std::shared_ptr<relpipe::writer::RelationalWriter> writer) {
parser.setInput(&input);
this->writer = writer;
consumeEvent(YAML_STREAM_START_EVENT);
consumeEvent(YAML_DOCUMENT_START_EVENT);
consumeEvent(YAML_MAPPING_START_EVENT);
for (YAMLEvent_p event; until(YAML_MAPPING_END_EVENT, event);) {
relationName = fetchScalarValue(event);
attributesMetadata.clear();
processRelation();
}
consumeEvent(YAML_DOCUMENT_END_EVENT);
consumeEvent(YAML_STREAM_END_EVENT);
}
};
}
}
}