#!/usr/bin/env python3

def process_csv_line( line ):
    # We want to remove empty spaces and line breaks from the
    # beginning and end of each line
    line = line.strip()
    # We want to remove double quotes '"' from the text, for
    # that we use the "replace" function which takes here two
    # parameters, the first one is the character to replace
    # and the second one is the replacement.
    line = line.replace( '"', '' )
    # We want to split each line based on the separator ";".
    line = line.split( ";" )
    return line

# Here I define a function that loads the content
# of a file in memory, given a filename.
# It takes a parameter, the variable "filename",
# it returns a list containing the content of
# the file corresponding to "filename".
def load_content_of_file_in_list( filename ):
    # here is a declared variable, of type list
    # for the moment this variable is empty
    content_file = []
    # Here I open the file with the filename given
    # as parameter and with the mode "r" which means
    # read only. I declare the variable "file_csv" as
    # my file handler (or wrapper).
    with open( filename, mode = "r" ) as file_csv:
        for line in file_csv:
            # Here i call the function "process_csv_line"
            # which contains all the code dedicated to
            # processing one line at a time from my file.
            line = process_csv_line( line )
            # Here I add the content of the variable "line" to the variable
            # "content_file"
            content_file.append( line )
    return content_file

# This function is dedicated to testing the size (or length)
# of a list.
# It receives a list "my_list" as parameter and
# it returns a string "message".
def test_length_list( my_list ):
    if len( my_list ) <= 0:
        message = "Error: the file is empty!"
    else:
        message = "Success: the file was loaded in memory!"
    return message

def get_column_position( name, column_names ):
    return column_names.index( name )

# Here is the function answering question 1
# it takes a parameter, the variable "filename"
# it returns a list containing the content of
# the file corresponding to "filename".
def question_1_function( filename ):
    content_file = load_content_of_file_in_list( filename )
    # Here I test the length of the list "content_file"
    # and print two different messages corresponding to
    # an empty or non empty list situation respectively.
    print( test_length_list( content_file ) )
    # Here I return, as the result of the function, the variable
    # "content_file", if it is empty or not.
    return content_file

# Here is the function answering question 2
# it takes two parameters: the content of a file
# processed according to question 1 and a country
# name,
# it returns the population for the country name
# given as parameter.
def question_2_function( content, country_name ):
    # First, we loop over the countries contained
    # in the list "content".
    for country in content:
        # Second, we temporarily store the first element
        # of every list "country" in a variable "temporary_
        # countr_name".
        temporary_country_name = country[ 0 ]
        # Third, we compare the temporary country name to
        # the country name give as function parameter.
        if country_name == temporary_country_name:
            # If the country names match, we return the third
            # element of the list "country", which is the population.
            return country[ 2 ]

# Here is the function answering question 3.
# It takes two parameters, the first one is the content
# of the file to process, the second one is the name of the
# column we want to extract.
# It returns the extracted column as a list.
def question_3_function( content, column_name ):
    # First, we store the header of the file in a variable
    # called "header".
    header = content[ 0 ]
    # Second, we retrieve the position of the column we
    # want to extract based on the column name.
    position = get_column_position( column_name, header )
    column = []
    # Third, we loop over each list "country", extract the
    # element at the wanted "position" and store it in the
    # list "column".
    for country in content:
        column.append( country[ position ] )
    return column

# Here I declared a variable which contains the absolute
# path of the CSV file I want to process.
file_absolute_path = "/home/student/Documents/20190114/eu_countries.csv"

# Here I call the function answering Question 1
# I give a parameter which is the absolute file path to process
content_file_csv = question_1_function( file_absolute_path )
print( content_file_csv )

population = question_2_function( content_file_csv, "Germany" )
print( population )

#'Country', 'Capital', 'Population (approx.)', 'Official Language(s)'
column = question_3_function( content_file_csv, "Official Language(s)" )
print( column )

user_input = input( "Enter a country name: " )
print( "The population for the country", user_input, "is: ", question_2_function( content_file_csv, user_input ) )