FastAPI support for React ( with working react-router )

fastapi_react.py

"""
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serve react app via fastapi, complete with working react-router
 
How to use ?
-------
it's actually very simple. 
create your fastapi app like you'd normally do
but you have to use this as your VERY LAST mount to your main app

example
----

```
    # regular fastapi setup 
    root = fastapi.FastAPI()
    @root.get('/some/path')
    ...
    ...code...
    ...
    @root.get('/some/other/path')
    ...
    ...code...
    ...
    ... some static files maybe ?
    root.mount('/some/staticfiles')
    ...
    ...code...
    ...
    
    # moment of truth 
 
    from fastapi_react import frontend
    root.mount('/', frontend(build_dir='build'))  # we are MOUNTING it!
    ...
    ...
    uvicorn.run(root, port=8080) # maybe ?
```
"""

def frontend(build_dir="./build"):
    """
     FASTAPI ROUTER FOR REACT FRONTEND

    :param build_dir: the path to your build folder for react
            we are assuming the "static" folder lives within your build folder
            if not, change it some lines below
    :return: fastapi.FastAPI
    """

    import pathlib
    import fastapi.exceptions
    from fastapi import FastAPI, Request, Response
    from fastapi.staticfiles import StaticFiles

    build_dir = pathlib.Path(build_dir)

    react = FastAPI(openapi_url="")
    react.mount('/static', StaticFiles(directory=build_dir / "static"))

    @react.get('/{path:path}')
    async def handle_catch_all(request: Request, path):

        if path and path != "/":
            disk_path = build_dir / path
            if disk_path.exists():
                return Response(disk_path.read_bytes(), 200)
            else:
                if disk_path.is_file():
                    raise fastapi.exceptions.HTTPException(404)

        return Response((build_dir / "index.html").read_bytes(), 200)

    return react