/**
 * Relational pipes
 * Copyright © 2022 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 <memory>
#include <string>
#include <vector>
#include <iostream>
#include <sstream>
#include <locale>
#include <codecvt>

#include <relpipe/reader/typedefs.h>
#include <relpipe/reader/TypeId.h>
#include <relpipe/reader/handlers/RelationalReaderStringHandler.h>
#include <relpipe/reader/handlers/AttributeMetadata.h>

#include "Configuration.h"
#include "RelpipeSQLWriterException.h"

namespace relpipe {
namespace out {
namespace sql {

using namespace relpipe;
using namespace relpipe::reader;
using namespace relpipe::reader::handlers;

class SQLHandler : public RelationalReaderStringHandler {
private:
	std::ostream& output;
	Configuration& configuration;
	std::wstring_convert<std::codecvt_utf8<wchar_t>> convertor; // generate SQL always in UTF-8
	std::vector<AttributeMetadata> currentAttributes;
	integer_t valueCount = 0;
	integer_t recordCount = 0;
	string_t currentTable;

	/**
	 * @param a
	 * @param b
	 * @return true if relations have same number and types of attributes (names may differ)
	 */
	bool matches(const std::vector<AttributeMetadata>& a, const std::vector<AttributeMetadata>& b) {
		if (a.size() != b.size()) return false;
		for (int i = 0, limit = a.size(); i < limit; i++) if (a[i].getTypeId() != b[i].getTypeId()) return false;
		return true;
	}

	static void writeIdentifier(std::ostream& output, std::string identifier) {
		output << '"';
		for (auto & ch : identifier) {
			if (ch == '"') output << "\"\"";
			else output << ch;
		}
		output << '"';
	}

	static void writeValue(std::ostream& output, std::string value) {
		output << '\'';
		for (auto & ch : value) {
			if (ch == '\'') output << "''";
			else output << ch;
		}
		output << '\'';
	}

	void writeRecordCount() {
		// currently disabled due to relpipe-in-sql parser issues with last comment without any following expression
		// output << "-- Record count: " << recordCount << std::endl;
	}

	void endRelation() {

		if (configuration.insertMode == Configuration::InsertMode::MULTI) {
			output << std::endl << ";" << std::endl;
		}

		writeRecordCount();
	}

public:

	SQLHandler(std::ostream& output, Configuration& configuration) : output(output), configuration(configuration) {
	}

	void startRelation(string_t name, std::vector<AttributeMetadata> attributes) override {
		// TODO: ALTER TABLE / add columns on duplicate relation name
		// TODO: optionally omit CREATE/ALTER table (just INSERT)
		// TODO: optional transformation to upper/lower case
		// TODO: custom data type mapping
		// TODO: custom primary key or other column properties
		// TODO: custom table properties
		// TODO: custom SQL script before/after stream/relation/record
		// TODO: comments and/or custom comments + record count of each table as a comment
		// TODO: optional transactions: BEGIN/COMMIT/ROLLBACK for stream/relation/record
		// TODO: optional wrapping at certain width (like 80 characters)?
		// TODO: optional syntax highlighting?
		// TODO: share code/behavior with relpipe-tr-sql (but it uses parametrized statements)

		if (currentTable.size()) {
			endRelation();
			output << std::endl;
		}

		currentTable = name;
		currentAttributes = attributes;
		recordCount = 0;
		valueCount = 0;

		output << "CREATE TABLE ";
		writeIdentifier(output, convertor.to_bytes(currentTable));
		output << " (" << std::endl;
		for (size_t i = 0, limit = attributes.size(); i < limit; i++) {
			auto attribute = attributes[i];
			output << "\t";
			writeIdentifier(output, convertor.to_bytes(attribute.getAttributeName()));
			// TODO: support all data types + implement RelationalReaderValueHandler
			output << " TEXT";
			if (i < (limit - 1)) output << ",";
			output << std::endl;

		}
		output << ");" << std::endl << std::endl;

		if (currentAttributes.empty()) {
			//if (configuration.writeHeader) for (auto attr : attributes) attribute(configuration.writeTypes ? attr.getAttributeName() + L"::" + attr.getTypeName() : attr.getAttributeName());
		} else if (matches(currentAttributes, attributes)) {
			// do UNION ALL – just append the records
		} else {
			// throw RelpipeSQLWriterException(L"To the SQL format we can convert only one relation or multiple relations that have same number of attributes of same types (relation and attribute names may differ – result is named after the first one).");
		}
	}

	void attribute(const string_t& value) override {

		if (valueCount % currentAttributes.size() == 0) {
			// TODO: optional use of function/procedure instead of INSERT
			// TODO: optional INSERT of multiple records
			// TODO: custom line-ends + indentation
			// TODO: optionally write also the column names
			recordCount++;

			if (configuration.insertMode == Configuration::InsertMode::SINGLE) {
				output << "INSERT INTO ";
				writeIdentifier(output, convertor.to_bytes(currentTable));

				output << " (";
				for (size_t i = 0, limit = currentAttributes.size(); i < limit; i++) {
					writeIdentifier(output, convertor.to_bytes(currentAttributes[i].getAttributeName()));
					if (i < (limit - 1)) output << ", ";
				}
				output << ")";

				output << " VALUES (";
			} else if (configuration.insertMode == Configuration::InsertMode::MULTI) {
				if (recordCount == 1) {
					// --------
					output << "INSERT INTO ";
					writeIdentifier(output, convertor.to_bytes(currentTable));

					output << "\n\t(";
					for (size_t i = 0, limit = currentAttributes.size(); i < limit; i++) {
						writeIdentifier(output, convertor.to_bytes(currentAttributes[i].getAttributeName()));
						if (i < (limit - 1)) output << ", ";
					}
					output << ")";
					// --------

					output << std::endl << "VALUES" << std::endl;
				} else {
					output << "," << std::endl;
				}
				output << "\t(";
			} else {
				throw RelpipeSQLWriterException(L"Unsupported InsertMode: " + std::to_wstring((int) configuration.insertMode));
			}
		}

		valueCount++;

		if (value.size() > 0) {
			// TODO: support all data types + implement RelationalReaderValueHandler
			writeValue(output, convertor.to_bytes(value));
		} else {
			// TODO: support actual nulls when supported in the relpipe data format + just optional conversion from empty strings to NULLs
			output << "NULL";
		}

		if (valueCount % currentAttributes.size()) {
			output << ", ";
		} else {
			if (configuration.insertMode == Configuration::InsertMode::SINGLE) {
				output << ");" << std::endl;
			} else if (configuration.insertMode == Configuration::InsertMode::MULTI) {
				output << ")";
			} else {
				throw RelpipeSQLWriterException(L"Unsupported InsertMode: " + std::to_wstring((int) configuration.insertMode));
			}
			valueCount = 0;
		}
	}

	void endOfPipe() {
		if (currentTable.size()) {
			endRelation();
		}
		output.flush();
	}

};

}
}
}