"""
Main function to control the simulator flow by selecting which preprocess function to run.

Users should fill in the "pre_type" field in the input JSON with the preprocess
function that they wish to run. The value in the field should be in a format similar to a Python
import. For example, if your function is called "my_func" in the Python file "my_file", you should
put "my_file.my_func" in the "pre_type" field in the JSON. The function should be in your app
folder: app/user_app/my_file.

The preprocess function should return a list of numpy arrays in channel last format (1, h, w, c)
and a dictionary of values to pass to the postprocess.
"""
import importlib
import sys
import traceback

import python_flow.common.directory_manager as dm

def preprocess_main(config, prev_output=None):
    """Main function that calls the appropriate preprocess function.

    Arguments:
        config: TestConfig class that holds the user's input config and options
        prev_output: Output passed in from a previous stage needed for this preprocess
    """
    if config["pre"]["pre_bypass"]:
        print("Bypassing preprocess")
        return None, None

    try:
        # Get function in python import format (with dots)
        function = config["pre"]["pre_type"].replace("/", ".")
        module, function_name = function.rsplit(".", 1)
        preprocess = importlib.import_module(module)
        pre_func = getattr(preprocess, function_name)
        with dm.DirectoryManager("bin"):
            results = pre_func(config, prev_output)
    except (ModuleNotFoundError, AttributeError) as error:
        traceback.print_exc()
        sys.exit(f"\n{error}. Please check {function} in your input JSON "
                 f"{config['flow']['input_json']}.")

    return results