feat(main): refactored apt download implementation

main.py

@@ -0,0 +1,147 @@
+import logging
+import os
+import shutil
+import lzma
+import pickle
+import re
+import tarfile
+
+import urllib.request
+from pathlib import Path
+
+from src.update import *
+from src.packages import *
+from src.install import *
+
+DEFAULT_ARCHITECTURE = 'amd64'
+TEMP_FOLDER_NAME = 'temp_apt'
+
+
+def get(url):
+    '''
+    send a get request to the specified url and return the response
+    '''
+    with urllib.request.urlopen(url) as response:
+        if response.status == 200:
+            return response.read()
+        else:
+            return ''
+
+
+def tar_dir(path, name):
+    with tarfile.open(name, 'w:gz') as tar:
+        for root, dirs, files in os.walk(path):
+            for f in files:
+                tar.add(os.path.join(root, f))
+
+
+def save_update_file(name, data):
+    '''
+    save a file to a subdirectory 'update' in the temp directory 
+    '''
+    # create directory if it doesn't exist
+    update_directory = os.path.join(TEMP_FOLDER_NAME, 'update')
+    Path(update_directory).mkdir(parents=True, exist_ok=True)
+
+    path = os.path.join(update_directory, name)
+    with open(path, 'wb') as update_file:
+        update_file.write(data)
+
+    return path
+
+
+def save_package_file(name, data):
+    '''
+    save a file to a subdirectory 'packages' in the temp directory 
+    '''
+    # create directory if it doesn't exist
+    update_directory = os.path.join(TEMP_FOLDER_NAME, 'packages')
+    Path(update_directory).mkdir(parents=True, exist_ok=True)
+
+    path = os.path.join(update_directory, name)
+    with open(path, 'wb') as update_file:
+        update_file.write(data)
+
+    return name
+
+
+def read_lzma(path):
+    '''
+    read a file from disk and decompress it using lzma
+    '''
+    with open(path, 'rb') as index_file:
+        data = index_file.read()
+
+    return lzma.decompress(data).decode('utf-8')
+
+
+def apt_update(sources_list_path):
+    '''
+    retrieve the required files and create an index of the packages
+    '''
+    with open(sources_list_path, 'r') as sources_list:
+        data = sources_list.read()
+
+    # generate urls from sources list
+    parts = parse_sources_list(data)
+    urls = get_release_urls(parts)
+    urls.extend(get_index_urls(parts, architecture=DEFAULT_ARCHITECTURE))
+
+    # download index files and save them
+    filenames = (url_into_saved_file_name(url) for url in urls)
+    downloads = (get(url) for url in urls)
+    saved = (save_update_file(name, data)
+             for name, data in zip(filenames, downloads))
+
+    # create an index dictionary from the index files
+    index_files = (path for path in saved if path.endswith('Packages.xz'))
+    decompressed = (read_lzma(path) for path in index_files)
+    indexes = (generate_index_dictionary(data) for data in decompressed)
+
+    # add an 'Apt-Source' key to all packages in the index, used later in order to download package
+    sources = (get_apt_sources(url)
+               for url in urls if url.endswith('Packages.xz'))
+    indexes = (add_apt_source_field(index, source)
+               for index, source in zip(indexes, sources))
+
+    # combine all indexes into one and add virtual packages
+    full_index = {}
+    [full_index.update(index) for index in indexes]
+    full_index = add_virtual_indexes(full_index)
+
+    return full_index
+
+
+def download_package(name, index, with_dependencies=True, with_recommended=True, with_pre_dependencies=True):
+    '''
+    download a package with all it's dependencies
+    '''
+    packages = get_package_dependencies(
+        name, index, with_dependencies, with_recommended, with_pre_dependencies)
+
+    urls = [get_package_url(name, index) for name in packages]
+    filenames = (os.path.basename(url) for url in urls)
+    downloads = (get(url) for url in urls)
+    save = (save_package_file(name, data)
+            for name, data in zip(filenames, downloads))
+
+    return list(save)
+
+
+def write_install_script(filenames):
+    data = create_install_script(filenames)
+    with open(f'{TEMP_FOLDER_NAME}/install.sh', 'w', newline='\n') as install:
+        install.write(data)
+
+
+def main():
+    index = apt_update('sources.list')
+    name = 'git'
+
+    filenames = download_package(name, index)
+    write_install_script(filenames)
+    tar_dir(TEMP_FOLDER_NAME, f'{name}.tar.gz')
+
+
+if __name__ == '__main__':
+    main()