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Add Call Center solution
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‎solutions/object_oriented_design/call_center/__init__.py‎

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‎solutions/object_oriented_design/call_center/call_center.ipynb‎

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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# Design a call center"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Constraints and assumptions\n",
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"\n",
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"* What levels of employees are in the call center?\n",
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" * Operator, supervisor, director\n",
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"* Can we assume operators always get the initial calls?\n",
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" * Yes\n",
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"* If there is no free operators or the operator can't handle the call, does the call go to the supervisors?\n",
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" * Yes\n",
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"* If there is no free supervisors or the supervisor can't handle the call, does the call go to the directors?\n",
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" * Yes\n",
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"* Can we assume the directors can handle all calls?\n",
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" * Yes\n",
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"* What happens if nobody can answer the call?\n",
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" * It gets queued\n",
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"* Do we need to handle 'VIP' calls where we put someone to the front of the line?\n",
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" * No\n",
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"* Can we assume inputs are valid or do we have to validate them?\n",
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" * Assume they're valid"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Solution"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting call_center.py\n"
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]
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}
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],
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"source": [
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"%%writefile call_center.py\n",
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"from abc import ABCMeta, abstractmethod\n",
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"from collections import deque\n",
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"from enum import Enum\n",
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"\n",
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"\n",
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"class Rank(Enum):\n",
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"\n",
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" OPERATOR = 0\n",
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" SUPERVISOR = 1\n",
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" DIRECTOR = 2\n",
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"\n",
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"\n",
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"class Employee(metaclass=ABCMeta):\n",
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"\n",
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" def __init__(self, employee_id, name, rank, call_center):\n",
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" self.employee_id = employee_id\n",
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" self.name = name\n",
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" self.rank = rank\n",
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" self.call = None\n",
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" self.call_center = call_center\n",
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"\n",
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" def take_call(self, call):\n",
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" \"\"\"Assume the employee will always successfully take the call.\"\"\"\n",
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" self.call = call\n",
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" self.call.employee = self\n",
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" self.call.state = CallState.IN_PROGRESS\n",
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"\n",
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" def complete_call(self):\n",
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" self.call.state = CallState.COMPLETE\n",
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" self.call_center.notify_call_completed(self.call)\n",
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"\n",
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" @abstractmethod\n",
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" def escalate_call(self):\n",
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" pass\n",
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"\n",
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" def _escalate_call(self):\n",
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" self.call.state = CallState.READY\n",
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" call = self.call\n",
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" self.call = None\n",
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" self.call_center.notify_call_escalated(call)\n",
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"\n",
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"\n",
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"class Operator(Employee):\n",
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"\n",
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" def __init__(self, employee_id, name):\n",
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" super(Operator, self).__init__(employee_id, name, Rank.OPERATOR)\n",
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"\n",
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" def escalate_call(self):\n",
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" self.call.level = Rank.SUPERVISOR\n",
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" self._escalate_call()\n",
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"\n",
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"\n",
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"class Supervisor(Employee):\n",
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"\n",
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" def __init__(self, employee_id, name):\n",
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" super(Operator, self).__init__(employee_id, name, Rank.SUPERVISOR)\n",
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"\n",
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" def escalate_call(self):\n",
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" self.call.level = Rank.DIRECTOR\n",
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" self._escalate_call()\n",
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"\n",
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"\n",
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"class Director(Employee):\n",
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"\n",
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" def __init__(self, employee_id, name):\n",
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" super(Operator, self).__init__(employee_id, name, Rank.DIRECTOR)\n",
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"\n",
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" def escalate_call(self):\n",
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" raise NotImplemented('Directors must be able to handle any call')\n",
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"\n",
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"\n",
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"class CallState(Enum):\n",
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"\n",
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" READY = 0\n",
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" IN_PROGRESS = 1\n",
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" COMPLETE = 2\n",
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"\n",
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"\n",
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"class Call(object):\n",
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"\n",
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" def __init__(self, rank):\n",
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" self.state = CallState.READY\n",
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" self.rank = rank\n",
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" self.employee = None\n",
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"\n",
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"\n",
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"class CallCenter(object):\n",
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"\n",
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" def __init__(self, operators, supervisors, directors):\n",
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" self.operators = operators\n",
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" self.supervisors = supervisors\n",
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" self.directors = directors\n",
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" self.queued_calls = deque()\n",
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"\n",
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" def dispatch_call(self, call):\n",
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" if call.rank not in (Rank.OPERATOR, Rank.SUPERVISOR, Rank.DIRECTOR):\n",
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" raise ValueError('Invalid call rank: {}'.format(call.rank))\n",
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" employee = None\n",
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" if call.rank == Rank.OPERATOR:\n",
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" employee = self._dispatch_call(call, self.operators)\n",
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" if call.rank == Rank.SUPERVISOR or employee is None:\n",
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" employee = self._dispatch_call(call, self.supervisors)\n",
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" if call.rank == Rank.DIRECTOR or employee is None:\n",
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" employee = self._dispatch_call(call, self.directors)\n",
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" if employee is None:\n",
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" self.queued_calls.append(call)\n",
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"\n",
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" def _dispatch_call(self, call, employees):\n",
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" for employee in employees:\n",
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" if employee.call is None:\n",
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" employee.take_call(call)\n",
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" return employee\n",
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" return None\n",
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"\n",
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" def notify_call_escalated(self, call): # ...\n",
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" def notify_call_completed(self, call): # ...\n",
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" def dispatch_queued_call_to_newly_freed_employee(self, call, employee): # ..."
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.4.3"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}

‎solutions/object_oriented_design/call_center/call_center.py‎

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from abc import ABCMeta, abstractmethod
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from collections import deque
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from enum import Enum
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class Rank(Enum):
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OPERATOR = 0
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SUPERVISOR = 1
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DIRECTOR = 2
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class Employee(metaclass=ABCMeta):
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def __init__(self, employee_id, name, rank, call_center):
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self.employee_id = employee_id
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self.name = name
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self.rank = rank
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self.call = None
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self.call_center = call_center
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def take_call(self, call):
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"""Assume the employee will always successfully take the call."""
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self.call = call
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self.call.employee = self
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self.call.state = CallState.IN_PROGRESS
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def complete_call(self):
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self.call.state = CallState.COMPLETE
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self.call_center.notify_call_completed(self.call)
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@abstractmethod
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def escalate_call(self):
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pass
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def _escalate_call(self):
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self.call.state = CallState.READY
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call = self.call
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self.call = None
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self.call_center.notify_call_escalated(call)
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class Operator(Employee):
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def __init__(self, employee_id, name):
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super(Operator, self).__init__(employee_id, name, Rank.OPERATOR)
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def escalate_call(self):
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self.call.level = Rank.SUPERVISOR
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self._escalate_call()
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class Supervisor(Employee):
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def __init__(self, employee_id, name):
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super(Operator, self).__init__(employee_id, name, Rank.SUPERVISOR)
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def escalate_call(self):
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self.call.level = Rank.DIRECTOR
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self._escalate_call()
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class Director(Employee):
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def __init__(self, employee_id, name):
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super(Operator, self).__init__(employee_id, name, Rank.DIRECTOR)
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def escalate_call(self):
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raise NotImplemented('Directors must be able to handle any call')
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class CallState(Enum):
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READY = 0
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IN_PROGRESS = 1
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COMPLETE = 2
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class Call(object):
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def __init__(self, rank):
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self.state = CallState.READY
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self.rank = rank
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self.employee = None
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class CallCenter(object):
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def __init__(self, operators, supervisors, directors):
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self.operators = operators
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self.supervisors = supervisors
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self.directors = directors
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self.queued_calls = deque()
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def dispatch_call(self, call):
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if call.rank not in (Rank.OPERATOR, Rank.SUPERVISOR, Rank.DIRECTOR):
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raise ValueError('Invalid call rank: {}'.format(call.rank))
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employee = None
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if call.rank == Rank.OPERATOR:
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employee = self._dispatch_call(call, self.operators)
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if call.rank == Rank.SUPERVISOR or employee is None:
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employee = self._dispatch_call(call, self.supervisors)
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if call.rank == Rank.DIRECTOR or employee is None:
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employee = self._dispatch_call(call, self.directors)
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if employee is None:
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self.queued_calls.append(call)
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def _dispatch_call(self, call, employees):
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for employee in employees:
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if employee.call is None:
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employee.take_call(call)
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return employee
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return None
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def notify_call_escalated(self, call): # ...
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def notify_call_completed(self, call): # ...
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def dispatch_queued_call_to_newly_freed_employee(self, call, employee): # ...

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