#!/bin/env python
# Example of dictionaries and JSON files

import random
import sys
import json

def mkTelDict(n,names):
    """Build a dictionary of <n> random telephone numbers for <n> random first-names taken from <names>."""
    tel_dict = dict();
    for i in range(n):
        no = random.randint(1000,9999)
        name = names[random.randint(0,99)]
        tel_dict[name]=no

    return tel_dict

def ppTelDict(tel):
    """Pretty print a phone dictionary."""
    for k, v in tel.items():
        print(k, " -> ", v)

def printNoOf(name,tel):
  """Print phone number of <name> in dictionary <tel>, or sorry message."""
  if name in tel:
      print("The tel no. of "+name+" is ", tel[name])
  else:
      print("No phone number for "+name+", sorry!")

def readFile(fname):
    """Read contents of a file, and put each line of the file into an element of a list."""
    fd = open(fname,'r')
    names = []
    for line in fd:
        names.append(line[0:-1])
    return names

# -----------------------------------------------------------------------------
# Constants
fname = 'names.txt'
jfile = 'tel.json'

# -----------------------------------------------------------------------------
# main

if (len(sys.argv) != 2): # expect 1 args: n
  print("Usage: dict3.py <int>\n build a phone dictionary with <n> entries and write it to a JSON file")
else:
  n = int(sys.argv[1])   # read from command-line
  names = readFile(fname)
  tel = mkTelDict(n, names)
  ppTelDict(tel)
  
  json.dump(tel, fp=open(jfile,'w'), indent=2)
  print("Data has been written to file ", jfile);

  tel_new = json.loads(open(jfile,'r').read())
  ppTelDict(tel_new)

  the_name = "Billy"
  printNoOf(the_name,tel_new);
  the_name = names[random.randint(0,99)];
  printNoOf(the_name,tel_new);