#!/usr/bin/env python3
"""
Dotfile setup utility.

Syncronizes dotfiles from a source dir that mimics a homedir tree to a homedir,
removing old symlinks as necessary as well as optionally files.
"""

import inspect
import os  # Needed for os.walk til Py3.12
import sys
from pathlib import Path

FORCE = False
HOMEDIR = Path("~").expanduser()
SOURCEDIR = Path(str(inspect.getsourcefile(lambda: False))).parent
EXCLUSIONS = [".git", "setup_dotfiles.py", "README.md"]


def check_and_remove(source: Path, destination: Path, *, force: bool = False) -> bool:
    """
    Check if a file exists and remove it if appropriate.

    If it's a symlink we check it points the right place and remove it if not.

    If it's a file, we remove it if --force is provided, or error if not.

    If we need to re-deploy the symlink, return True, else return False.
    """
    Path(destination).parent.mkdir(parents=True, exist_ok=True)

    # Destination exists as a symlink
    if Path(destination).is_symlink():
        # Symlink is correct, return
        # This is the only function that bumps our requirement to py3.9, lol
        if Path(destination).readlink() == source:
            return False
        # Symlink is incorrect, remove it
        Path(destination).unlink()
    # Destination exists as a file
    elif Path(destination).exists():
        # Force mode enabled, remove it (Data loss risk!!)
        if force:
            Path(destination).unlink()
        # Force mode disabled, skip this file
        else:
            print(f"{destination!s} exists as a file and --force not provided")
            return False

    # File doesn't exist or undefined "thing" happened, return True to try to
    # write, and if something goes wrong, we'll see the OSError
    return True


def install_dotfiles(source_dir: Path, dest_dir: Path, exclusions: list, *, force: bool = False) -> None:
    """
    Iterate files in SOURCEDIR and create symlinks to them in HOMEDIR.

    We also exclude files noted in exclusions, and will remove files in the way
    if "force" is true.
    """
    for root, dir_names, file_names in os.walk(source_dir):
        # Remove exclusions from the walk list so we don't touch them
        for exclusion in exclusions:
            if exclusion in dir_names:
                dir_names.remove(exclusion)
            if exclusion in file_names:
                file_names.remove(exclusion)

        for file_name in file_names:
            # Get the full path for the source file
            source = Path(root) / file_name

            # Get the full path for where the symlink should go
            # We remove the source_dir to get a dotfile dir relative path
            destination = dest_dir / source.relative_to(source_dir)

            # Check for and remove the destination file if it exists
            # If a removal occurs, catch True and deploy the symlink
            if check_and_remove(source, destination, force=force):
                print(f"Symlinking {source} => {destination}")
                os.symlink(source, destination)


if __name__ == "__main__":
    force = "--force" in sys.argv

    if force:
        print("--force enabled, will remove files to create symlinks")

    install_dotfiles(SOURCEDIR, HOMEDIR, EXCLUSIONS, force=force)