import hashlib

import os

import shutil

from pathlib import Path

def sync(source, dest):

# imperative shell step 1, gather inputs

source_hashes = read_paths_and_hashes(source)

dest_hashes = read_paths_and_hashes(dest)

# step 2: call functional core

actions = determine_actions(source_hashes, dest_hashes, source, dest)

# imperative shell step 3, apply outputs

for action, *paths in actions:

if action == "COPY":

shutil.copyfile(*paths)

if action == "MOVE":

shutil.move(*paths)

if action == "DELETE":

os.remove(paths[0])

BLOCKSIZE = 65536

def hash_file(path):

hasher = hashlib.sha1()

with path.open("rb") as file:

buf = file.read(BLOCKSIZE)

while buf:

hasher.update(buf)

buf = file.read(BLOCKSIZE)

return hasher.hexdigest()

def read_paths_and_hashes(root):

hashes = {}

for folder, _, files in os.walk(root):

for fn in files:

hashes[hash_file(Path(folder) / fn)] = fn

return hashes

def determine_actions(source_hashes, dest_hashes, source_folder, dest_folder):

for sha, filename in source_hashes.items():

if sha not in dest_hashes:

sourcepath = Path(source_folder) / filename

destpath = Path(dest_folder) / filename

yield "COPY", sourcepath, destpath

elif dest_hashes[sha] != filename:

olddestpath = Path(dest_folder) / dest_hashes[sha]

newdestpath = Path(dest_folder) / filename

yield "MOVE", olddestpath, newdestpath

for sha, filename in dest_hashes.items():

if sha not in source_hashes:

yield "DELETE", dest_folder / filename