{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "\"\"\"\n",
    "The module optimize_query contains a function which sends the query\n",
    "to Optimizer to be optimized and returns the optimized query back.\n",
    "\"\"\"\n",
    "import asyncio\n",
    "import nest_asyncio\n",
    "nest_asyncio.apply()\n",
    "\n",
    "from libs_pkg.exception_handler import *\n",
    "\n",
    "async def opt_comm_exec(reader, writer, query, db_name, flag):\n",
    "    \"\"\"\n",
    "    This function  sends the query to Optimizer to be optimized and returns the optimized query back.\n",
    "    \n",
    "    :param reader: The stream reader of the connection to Optimizer.\n",
    "    :param writer: The stream writer of the connection to Optimizer.\n",
    "    :param query: The query to be optimized given as string.\n",
    "    :param db_name: The The currently open database related to the given query.\n",
    "    :param flag: The boolean value that shows if the command should be executed by optimizer (True) or should be optimized (False).\n",
    "    \n",
    "    :return: The optimized query as string.\n",
    "    \"\"\"\n",
    "    \n",
    "    if reader == None or writer == None:\n",
    "        raise SecondoAPI_Error('Connection to Optimizer reset.')\n",
    "    else:\n",
    "        \n",
    "        #execute query\n",
    "        if flag:\n",
    "            writer.write(b'<execute>\\n')\n",
    "        \n",
    "        #optimize query\n",
    "        else: \n",
    "            writer.write(b'<optimize>\\n')\n",
    "    \n",
    "        writer.write(b'<database>\\n')\n",
    "        db_name += \"\\n\"\n",
    "        writer.write(db_name.encode())\n",
    "    \n",
    "        writer.write(b'</database>\\n')\n",
    "    \n",
    "        writer.write(b'<query>\\n')\n",
    "        query += \"\\n\"\n",
    "        writer.write(query.encode())\n",
    "    \n",
    "        writer.write(b'</query>\\n')\n",
    "    \n",
    "        if flag:\n",
    "            writer.write(b'</execute>\\n')\n",
    "        \n",
    "        else: \n",
    "            writer.write(b'</optimize>\\n')\n",
    "    \n",
    "        await writer.drain()\n",
    "    \n",
    "        res = await reader.readline()\n",
    "        res = res.decode()\n",
    "        if not res:\n",
    "            raise SecondoAPI_Error(\"Connection to Optimizer is broken.\")\n",
    "        if res != \"<answer>\\n\":\n",
    "            raise SecondoError(\"Wrong Data received from Optimizer.\")\n",
    "        res = await reader.readline()\n",
    "        res = res.decode()\n",
    "        if not res:\n",
    "            raise SecondoAPI_Error('Connection to Optimizer is broken.')\n",
    "        opt_res = \"\"\n",
    "        count = 3\n",
    "        while res != \"</answer>\\n\":\n",
    "            if flag:\n",
    "                opt_res += res\n",
    "            else:\n",
    "                opt_res += res.replace(\" \\n\", \"\")\n",
    "            res = await reader.readline()\n",
    "            res = res.decode()\n",
    "            count += 1\n",
    "            if not res:\n",
    "                raise SecondoAPI_Error('Connection to Optimizer is broken.')\n",
    "        \n",
    "        if opt_res == \"\":\n",
    "            raise SecondoAPI_Error('Optimization failed due to some Errors in the query.')\n",
    "        return opt_res"
   ]
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.7.4"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}