Simplify README, fix some flows and output

- Simplify README and better keywords
- Fix the verbosity
- Better docstrings
- Client flow for init and main are clear

Signed-off-by: Kairo de Araujo <[email protected]>

Author: Kairo de Araujo

examples/client_example/README.md

@@ -1,24 +1,15 @@
-# Python Client Example
+# TUF Client Example
 
-Introduction
-============
 
-Python Client Example, using ``python-tuf``.
+TUF Client Example, using ``python-tuf``.
 
-This Python Client Example implements the following actions:
+This TUF Client Example implements the following actions:
    - Client Infrastructure Initialization
    - Download target files from TUF Repository
 
-
-Repository
-==========
-
-This example demonstrates how to use the ``python-tuf`` to build a client
-application.
-
-The repository will use static files.
-The static files are available in the ``python-tuf`` source code repository in
-``tests/repository_data/repository``.
+The example client expects to find a TUF repository running on localhost. We
+can use the static metadata files in ``tests/repository_data/repository``
+to set one up.
 
 Run the repository using the Python3 built-in HTTP module, and keep this
 session running.
@@ -28,30 +19,8 @@ session running.
    Serving HTTP on :: port 8000 (http://[::]:8000/) ...
 ```
 
-Client Example
-==============
-
-The [Client Example source code](./client_example.py>) is available entirely
-in this source code repository.
-
-How to use the Client Example:
-
+How to use the TUF Client Example to download a target file.
 
-1. Download the ``file1.txt``
-
-   ```console
-   $ ./client_example.py download file1.txt
-   Download directory [./downloads] was created
-   Metadata folder [<metadata dir>] was created
-   Added trusted root in /Users/kdearaujo/.local/share/python-tuf-client-example
-   Found trusted root in <metadata dir>
-   Target downloaded and available in ./downloads/file1.txt
-   ```
-
-2. Download again ``file1.txt``
-
-   ```console
-   $ ./client_example.py download file1.txt
-   Found trusted root in <metadata dir>
-   Target is available in ./downloads/file1.txt
-   ```
+```console
+$ ./client_example.py download file1.txt
+```

examples/client_example/client_example.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-"""Python Client Example."""
+"""TUF Client Example"""
 
 # Copyright 2012 - 2017, New York University and the TUF contributors
 # SPDX-License-Identifier: MIT OR Apache-2.0
@@ -20,20 +20,14 @@
 CLIENT_EXAMPLE_DIR = os.path.dirname(os.path.abspath(__file__))
 
 
-def init():
-    """
-    The function that initializes the TUF client infrastructure.
-
-    It creates the metadata directory and adds a trusted ``root.json``.
-    """
+def init() -> None:
+    """Initialize local trusted metadata and create a directory for downloads"""
 
     if not os.path.isdir(DOWNLOAD_DIR):
         os.mkdir(DOWNLOAD_DIR)
-        print(f"Download directory [{DOWNLOAD_DIR}] was created")
 
     if not os.path.isdir(METADATA_DIR):
         os.makedirs(METADATA_DIR)
-        print(f"Metadata folder [{METADATA_DIR}] was created")
 
     if not os.path.isfile(f"{METADATA_DIR}/root.json"):
         shutil.copy(
@@ -45,10 +39,9 @@ def init():
         print(f"Found trusted root in {METADATA_DIR}")
 
 
-def download(target):
+def download(target: str) -> bool:
     """
-    The function that downloads the target file using the TUF ``nglcient``
-    Updater.
+    Download the target file using ``ngclient`` Updater.
 
     The Updater refreshes the top-level metadata, get the target information,
     verifies if the target is already cached, and in case it is not cached,
@@ -74,27 +67,23 @@ def download(target):
 
         path = updater.find_cached_target(info)
         if path:
-            print(f"Target is available in {DOWNLOAD_DIR}/{info.path}")
+            print(f"Target is available in {path}")
             return True
 
         path = updater.download_target(info)
-        print(f"Target downloaded and available in {DOWNLOAD_DIR}/{info.path}")
+        print(f"Target downloaded and available in {path}")
 
-    except (FileNotFoundError, RepositoryError) as e:
+    except (OSError, RepositoryError) as e:
         print(str(e))
         return False
 
     return True
 
 
-if __name__ == "__main__":
-
-    # initialize the Python Client Example infrastructure
-    init()
+def main() -> None:
+    """Main TUF Client Example function"""
 
-    client_args = argparse.ArgumentParser(
-        description="TUF Python Client Example"
-    )
+    client_args = argparse.ArgumentParser(description="TUF Client Example")
 
     # Global arguments
     client_args.add_argument(
@@ -122,7 +111,7 @@ def download(target):
 
     command_args = client_args.parse_args()
 
-    if command_args.verbose <= 1:
+    if command_args.verbose == 1:
         loglevel = logging.ERROR
     elif command_args.verbose == 2:
         loglevel = logging.WARNING
@@ -133,8 +122,15 @@ def download(target):
 
     logging.basicConfig(level=loglevel)
 
+    # initialize the TUF Client Example infrastructure
+    init()
+
     if command_args.sub_command == "download":
         download(command_args.target)
 
     else:
         client_args.print_help()
+
+
+if __name__ == "__main__":
+    main()