/**
 * Relational pipes
 * Copyright © 2018 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 <regex>

#include <Python.h>

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

#include <relpipe/writer/Factory.h>

#include <relpipe/cli/RelpipeCLIException.h>

namespace relpipe {
namespace tr {
namespace python {

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

class PythonHandler : public RelationalReaderStringHandler {
private:
	const wregex ATTRIBUTE_NAMES_ALLOWED = wregex(L"[a-zA-Z0-9_]+");
	const wregex ATTRIBUTE_NAMES_DISALLOWED = wregex(L"WHERE|[0-9_].*|False|None|True|and|as|assert|break|class|continue|def|del|elif|else|except|finally|for|from|global|if|import|in|is|lambda|nonlocal|not|or|pass|raise|return|try|while|with|yield"); // Python keywords from: import keyword; keyword.kwlist

	shared_ptr<writer::RelationalWriter> relationalWriter;

	wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
	wchar_t* pythonProgramName;

	wregex relationNameRegEx;
	string_t pythonCode;

	vector<writer::AttributeMetadata> currentWriterMetadata;
	vector<string_t> currentRecord;
	integer_t currentAttributeIndex = 0;
	boolean_t includeCurrentRecord = true;
	boolean_t filterCurrentRelation = false;

public:

	PythonHandler(ostream& output, const vector<string_t>& arguments) {
		relationalWriter.reset(writer::Factory::create(output));

		pythonProgramName = Py_DecodeLocale("relpipe-tr-python", NULL);
		Py_SetProgramName(pythonProgramName);
		Py_Initialize();

		if (arguments.size() == 2) {
			relationNameRegEx = wregex(arguments[0]);
			pythonCode = arguments[1];
			// TODO: allow relation structure changes: if there are more arguments, the describe the output relation
			// TODO: allow also other modes:
			//	- insert additional records
			//	- process whole relation at once (can do e.g. some aggregations)
			//	- process whole stream at once (can do e.g. some joins or unions)
		} else {
			PyMem_RawFree(pythonProgramName);
			throw cli::RelpipeCLIException(L"Usage: relpipe-tr-python <relationNameRegExp> <pythonCode>", cli::CLI::EXIT_CODE_UNKNOWN_COMMAND);
		}
	}

	virtual ~PythonHandler() {
		Py_FinalizeEx();
		PyMem_RawFree(pythonProgramName);
	}

	void startRelation(string_t name, vector<AttributeMetadata> attributes) override {
		// TODO: move to a reusable method (or use same metadata on both reader and writer side?)
		currentWriterMetadata.clear();
		for (AttributeMetadata readerMetadata : attributes) {
			currentWriterMetadata.push_back({readerMetadata.getAttributeName(), relationalWriter->toTypeId(readerMetadata.getTypeName())});
		}


		currentRecord.resize(attributes.size());
		filterCurrentRelation = regex_match(name, relationNameRegEx);
		relationalWriter->startRelation(name, currentWriterMetadata, true);
	}

	void attribute(const string_t& value) override {
		if (filterCurrentRelation) {
			currentRecord[currentAttributeIndex] = value;
			currentAttributeIndex++;

			if (currentAttributeIndex > 0 && currentAttributeIndex % currentRecord.size() == 0) {

				PyObject* pyModule;
				PyObject* pyDict;
				PyObject* pyWhere;
				PyObject* pyRecord = PyList_New(currentRecord.size());

				//PyUnicode_FromWideChar()

				pyModule = PyImport_AddModule((char*) "__main__"); // FIXME: variable and Py_DecodeLocale ?
				pyDict = PyModule_GetDict(pyModule);

				for (int i = 0; i < currentRecord.size(); i++) {
					// TODO: pass particular data-types to Python, not only strings
					PyObject* pyValue = PyUnicode_FromString(convertor.to_bytes(currentRecord[i]).c_str());
					PyList_SetItem(pyRecord, i, pyValue);
					string_t attributeName = currentWriterMetadata[i].attributeName;
					if (regex_match(attributeName, ATTRIBUTE_NAMES_ALLOWED)) {
						if (regex_match(attributeName, ATTRIBUTE_NAMES_DISALLOWED)) attributeName = L"a_" + attributeName;
						PyDict_SetItemString(pyDict, convertor.to_bytes(attributeName).c_str(), pyValue);
					}
				}

				PyDict_SetItemString(pyDict, "r", pyRecord);

				PyRun_SimpleString(convertor.to_bytes(pythonCode).c_str());

				// FIXME: check Python error and throw exception
				// if (PyErr_Occurred()) throw cli::RelpipeCLIException(L"Python code failed.", cli::CLI::EXIT_CODE_UNEXPECTED_ERROR); // TODO: review exit code
				// if (PyErr_Occurred()) { PyErr_Print(); PyErr_Clear(); }


				pyWhere = PyDict_GetItemString(pyDict, "WHERE");

				if (pyWhere) includeCurrentRecord = PyLong_AsLong(pyWhere);


				if (includeCurrentRecord) {
					for (int i = 0; i < currentRecord.size(); i++) {
						Py_ssize_t l;
						currentRecord[i] = wstring(PyUnicode_AsWideCharString(PyList_GetItem(pyRecord, i), &l));
					}
				}


				if (includeCurrentRecord) for (string_t v : currentRecord) relationalWriter->writeAttribute(v);
				includeCurrentRecord = true;
			}

			currentAttributeIndex = currentAttributeIndex % currentRecord.size();
		} else {
			relationalWriter->writeAttribute(value);
		}
	}

	void endOfPipe() {

	}

};

}
}
}