#!/usr/bin/env python
# coding: utf-8

# ## ``Q6.`` ##  
# 
# ## ```Perform the following file operations using Python```##    
# 
# ## ```a) Traverse a path and display all the files and subdirectories in each level till the deepest level for a given path. Also, display the total number of files and subdirectories.```    
# 
# ## ```b) Read a file contents and copy only the contents at odd lines into a new file.```  ##

# ## -----------------------------------------------------------------------------------------------------------------------------

# **Approach to displaying the files and subdirectories in each level**  
# 
# 1. Get path information from the user. <br><br>  
# 
# 2. Check whether the path exists or not.<br><br>   
# 
# 3. If the path exists, then walk through all the file and subdirectories (including root directory) using os.walk() function.<br><br>  
# 
# 4. Normalize the paths and count the number of subdirectories and files in each of those subdirectories. <br><br>  
# 
# 5. Display the names of subdirectories and files in subdirectories (including root directory). <br><br>  
# 
# 
# **Below functions are used in the program**
# 
# `os.path.exists(path)`  
# 
# Return ```True``` if path refers to an existing path. Returns ```False``` for broken symbolic links. On some platforms, this function may return ```False``` if permission is not granted to access the requested file, even if the path physically exists.  
# 
# `os.path.normpath(path)`  
#   
# Normalize a pathname by collapsing redundant separators and up-level references so that A//B, A/B/, A/./B and A/foo/../B all become A/B. On Windows, it converts forward slashes to backward slashes.  
# 
# `os.walk(topdir[, topdown=True])`    
# 
# Generate the file names in a directory tree by walking the tree either top-down (default) or bottom-up (topdown = False). Specifying argument `topdown` is optional. For each directory in the tree rooted at directory `topdir` (including topdir itself), it yields a 3-tuple (`dirpath,` `dirnames,` `filenames`). 
#     
# 1. `dirpath` is a string, the path to the directory.<br><br>  
# 
# 2. `dirnames` is a list of the names of the subdirectories in dirpath (excluding '.' and '..').<br><br>
# 
# 3. `filenames` is a list of the names of the non-directory files in dirpath. Note that the names in the lists contain no path components. To get a full path (which begins with top) to a file or directory in dirpath, do os.path.join(dirpath, name).<br><br>
# 

# ## -----------------------------------------------------------------------------------------------------------------------------

# **Approach to copy the contents from one file to another file at odd lines**  
# 
# 1. Open a file source_file as in_file in read mode. <br><br>    
# 
# 2. Open a file destination_file as out_file in write mode. <br><br>    
# 
# 3. To read all the lines of a file use `f.readlines().`<br><br>    
# 
# 4. Obtain the total number of lines in the file. <br><br>  
# 
# 5. Check the line number which is not divisible by 2 and then write the contents to out_file else pass. <br><br>  

# ## ------------------------------------------------------------------------------------------------------------------------

# In[1]:


import os


def display_files():
    # Set the directory to start from
    print("Enter path to traverse: ")
    root_dir = input()
    if os.path.exists(root_dir):
        dir_count = 0
        file_count = 0
        for dir_name, sub_dir_list, file_list in os.walk(root_dir):
            print(f"Found directory: {dir_name} \n")
            # check to ignore starting directory while taking directory count
            # normpath returns the normalized path eliminating double slashes etc.
            if os.path.normpath(root_dir) != os.path.normpath(dir_name):
                dir_count += 1
            for each_file_name in file_list:
                file_count += 1
                print(f"File name(s) {each_file_name} \n")
        print(f"Number of subdirectories are {dir_count} \n")
        print(f"Number of files are {file_count} \n")
        display_menu()
    else:
        print("Entered path doesn't exist")
        display_menu()


def copy_contents_to_file():
    source_file = input("Enter the Source file name: ")
    print("\n")
    destination_file = input("Enter the Destination file name: ")
    print("\n")
    try:
        with open(source_file) as in_file, open(destination_file, "w") as out_file:
            list_of_lines = in_file.readlines()
            for i in range(0, len(list_of_lines)):
                if i % 2 != 0:
                    out_file.write(list_of_lines[i])
    except IOError:
        print("Error in file names")

    print("File contents at odd lines copied to destination file \n")
    display_menu()


def display_menu():
    print("Enter your choice")
    print("Press 1 --> Display files and directories for a given path and their count")
    print("Press 2 --> Copy the contents present at odd lines to another file")
    print("Press 3 --> Exit the program")
    choice = int(input())

    if choice == 1:
        display_files()
    elif choice == 2:
        copy_contents_to_file()
    else:
        exit()


if __name__ == "__main__":
    display_menu()