"""
Improve the standard Python REPL.

This module attempts to emulate the workflow of ghci or lisp repls. It uses
importlib to load a namespace from the provided path, typechecks it with mypy,
and provides some tools for improving repl-driven development.

This module is called in Biz/Ide/repl.sh like so:

    python -i Biz/Repl.py NS PATH

where NS is the dot-partitioned namespace of the main module, and PATH is the
path to the same file. In the future this could be expanded to be a list of
additional files to load.
"""

import importlib
import importlib.util
import logging
import os
import sys

import mypy.api

from Biz import Log


def use(ns: str, path: str) -> None:
    """
    Load or reload the module named 'ns' from 'path'.

    Like `use` in the Guile Scheme repl.
    """
    logging.info("loading %s from %s", ns, path)
    spec = importlib.util.spec_from_file_location(ns, path)
    module = importlib.util.module_from_spec(spec)
    # delete module and its imported names if its already loaded
    if ns in sys.modules:
        del sys.modules[ns]
        for name in module.__dict__:
            if name in globals():
                del globals()[name]
    sys.modules[ns] = module
    spec.loader.exec_module(module)
    names = list(module.__dict__)
    globals().update({k: getattr(module, k) for k in names})


def typecheck(path: str) -> None:
    """Typecheck this namespace."""
    # this envvar is undocumented, but it works
    # https://github.com/python/mypy/issues/13815
    os.environ["MYPY_FORCE_COLOR"] = "1"
    logging.info("typechecking %s", path)
    stdout, stderr, _ = mypy.api.run([path])
    sys.stdout.write(stdout)
    sys.stdout.flush()
    sys.stderr.write(stderr)
    sys.stderr.flush()


if __name__ == "__main__":
    Log.setup()
    NS = sys.argv[1]
    PATH = sys.argv[2]
    use(NS, PATH)
    typecheck(PATH)

    logging.info("use reload() after making changes")
    sys.ps1 = f"{NS}> "
    sys.ps2 = f"{NS}| "

    def reload() -> None:
        """Reload the namespace."""
        use(NS, PATH)
        typecheck(PATH)