Rudimentary Command Line Interface (#25)

* Add a rudamentary CLI

* Update README to prefer CLI for generating stubs.

README.md

@@ -20,11 +20,11 @@ uStubby is targeted to run on Python 3.7, but should run on versions 3.6 or grea
 ### Installing
 
 Currently, there are no external dependencies for running uStubby.
-Clone the repository using git and just put it on the path to install.
-Alternatively, install from PyPI with 
+Install from PyPI with:
 ```bash
 pip install ustubby
 ```
+Alternatively, clone the repository using git and just put it on the path to install.
 
 ## Usage
 This example follows generating the template as shown [here](http://docs.micropython.org/en/latest/develop/cmodules.html#basic-example)
@@ -39,7 +39,14 @@ def add_ints(a: int, b: int) -> int:
     :param b:
     :return:a + b"""
 ```
-We can then convert this into the appropriate c stub by running
+We can then convert this into the appropriate c stub via the CLI:
+```bash
+# This will generate the file "example.c"
+ustubby example.py
+```
+
+Alternatively, you can invoke the python interface in a script:
+
 ```python
 import ustubby
 import example
@@ -150,13 +157,7 @@ def foo(*args, **kwargs):
 MP_DEFINE_CONST_FUN_OBJ_KW
 ```
 Each successively increasing the boiler plate to conveniently accessing the variables.
-Using the same code to parse it
-```python
-import ustubby
-import example
 
-print(ustubby.stub_module(example))
-```
 <details><summary>Output</summary><p>
 
 ```c

setup.py

@@ -58,6 +58,11 @@ def get_dependencies():
     long_description_content_type="text/markdown",
     package_dir={'': 'src'},
     packages=find_packages('src'),
+    entry_points={
+        'console_scripts': [
+            'ustubby = ustubby.__main__:main'
+        ]
+    },
     url="https://github.com/pazzarpj/micropython-ustubby",
     version=get_version(),
     python_requires='>=3.6',

src/ustubby/__init__.py

@@ -414,7 +414,6 @@ def ret_val_init(ret_type):
 
 
 def ret_val_return(ret_type):
-    print('ret_type', ret_type)
     return return_handler[ret_type]
 
 

src/ustubby/__main__.py

@@ -0,0 +1,58 @@
+import argparse
+import importlib
+import sys
+from pathlib import Path
+
+import ustubby
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Converts a python file into micropython c extension stubs.")
+    parser.add_argument("input", type=Path,
+                        help="Python file to convert.")
+    parser.add_argument("-o", "--output", type=Path, default=None,
+                        help="Output C file. Defaults to \"${input}.c\".")
+    parser.add_argument("--overwrite", action="store_true",
+                        help="Overwrite output file if it already exists.")
+    args = parser.parse_args()
+
+    ########################################
+    # Preprocess and error-check arguments #
+    ########################################
+    if not args.input.exists():
+        print(f"{args.input} does not exist.")
+        return 1
+
+    if args.input.suffix != ".py":
+        print(f"{args.input} is not a \".py\" file.")
+        return 1
+
+    args.input = args.input.expanduser().resolve()
+
+    if args.output is None:
+        args.output = args.input.with_suffix(".c")
+
+    if args.output.suffix != ".c":
+        print(f"{args.output} is not a \".c\" file.")
+        return 1
+
+    if args.output.exists() and not args.overwrite:
+        print(f"{args.output} already exists.")
+        return 1
+
+    ###################
+    # Execute ustubby #
+    ###################
+    sys.path.insert(0, str(args.input.parent))
+
+    module = importlib.import_module(args.input.stem)
+
+    c_output = ustubby.stub_module(module)
+
+    args.output.parent.mkdir(exist_ok=True, parents=True)
+    args.output.write_text(c_output)
+
+    return 0
+
+if __name__ == "__main__":
+    sys.exit(main())