#!/usr/bin/env python3

from collections import defaultdict
from datetime import datetime
from random import choices
from os import listdir
from csv import DictReader

import os.path
import re
import json

class ColdCall():
    def __init__ (self, record_attendance=True):
        with open("configuration.json") as config_file:
            config = json.loads(config_file.read())

        self.today = str(datetime.date(datetime.now()))
        # how much less likely should it be that a student is called upon?
        self.weight = 2
        self.record_attendance = record_attendance

        # filenames
        self.__fn_studentinfo = config["student_info_file"]
        self.__fn_daily_calllist = config["daily_calllist_file"].format(date=self.today)
        self.__fn_daily_attendance = config["daily_attendance"].format(date=self.today)

        self.unique_row = config["unique_name_rowname"]
        self.preferred_row = config["preferred_name_rowname"]

        self.preferred_names = self.__get_preferred_names()
        
    def __load_prev_questions(self):
        previous_questions = defaultdict(int)

        for fn in listdir("./data/"):
            if re.match("call_list-\d{4}-\d{2}-\d{2}.tsv", fn):
                with open(f"./data/{fn}", 'r') as f:
                    for row in DictReader(f, delimiter="\t"):
                        if not row["answered"] == "FALSE":
                            previous_questions[row[self.unique_row]] += 1

        return previous_questions

    def __get_preferred_names(self):
        # translate the unique name into the preferred students name,
        # if possible, otherwise return the unique name

        preferred_names = {}
        with open(self.__fn_studentinfo, 'r') as f:
            for row in DictReader(f, delimiter="\t"):
                preferred_names[row[self.unique_row]] = row[self.preferred_row]

        return(preferred_names)
        
    def __get_preferred_name(self, selected_student):
        if selected_student in self.preferred_names:
            return self.preferred_names[selected_student]
        else:
            return None

    def __select_student_from_list (self, students_present):
        prev_questions = self.__load_prev_questions()
        
        # created a weighted list by starting out with everybody 1
        weights = {s : 1 for s in students_present}
        
        for s in students_present:
            for i in range(0, prev_questions[s]):
                # reduce the weight by a factor of 1/weight each time the student has been called upon
                weights[s] = weights[s] / self.weight

        # choose one student from the weighted list
        # print(weights) # DEBUG LINE
        return choices(list(weights.keys()), weights=list(weights.values()), k=1)[0]

    def __record_attendance(self, students_present):
        # if it's the first one of the day, write it out
        if not os.path.exists(self.__fn_daily_attendance):
            with open(self.__fn_daily_attendance, "w") as f:
                print("\t".join(["timestamp", "attendance_list"]), file=f)

        # open for appending the student
        with open(self.__fn_daily_attendance, "a") as f:
            print("\t".join([str(datetime.now()),
                             ",".join(students_present)]),
                  file=f)

    def __record_coldcall(self, selected_student):
        # if it's the first one of the day, write it out
        if not os.path.exists(self.__fn_daily_calllist):
            with open(self.__fn_daily_calllist, "w") as f:
                print("\t".join([self.unique_row, self.preferred_row, "answered", "assessment", "timestamp"]), file=f)

        preferred_name = self.__get_preferred_name(selected_student)

        # open for appending the student
        with open(self.__fn_daily_calllist, "a") as f:
            print("\t".join([selected_student, preferred_name,
                             "MISSING", "MISSING", str(datetime.now())]), file=f)

    def coldcall(self, students_present):
        selected_student = self.__select_student_from_list(students_present)

        # record the called-upon student in the right place
        if self.record_attendance:
            self.__record_attendance(students_present)
        self.__record_coldcall(selected_student)

        preferred_name = self.__get_preferred_name(selected_student)
        if preferred_name:
            coldcall_message = f"{preferred_name} (@{selected_student}), you're up!"
        else:
            coldcall_message = f"@{selected_student}, you're up!"
        return coldcall_message