import shelve
from os import access, X_OK
from pathlib import Path
from collections import UserDict
from functools import reduce
from operator import or_


class DictSetMerge(UserDict):
    def __or__(self, other):
        results = self.copy()
        for key, paths in other.items():
            if key in results:
                results[key] |= paths
            else:
                results[key] = paths
                
        return results
                
    def __getitem__(self, key):
        if key not in self:
            paths = set()
            self[key] = paths
            return paths
        else:    
            return super().__getitem__(key)
            
    def add(self, key: str | Path, paths: set[Path] | None = None):
        """
        Add a single Path if key is a Path object.
        Otherwise add values to the set.
        """
        if not isinstance(key, Path) and paths is None:
            raise ValueError("Values allowed only to be None, if key is a Path")
            
        if not paths:
            paths = [key]
            key = key.name
            
        if key in self:
            self[key] |= set(paths)
        else:
            self[key] = set(paths)


def make_db(root) -> DictListMerge:
    
    results = DictSetMerge()
    
    for file in Path(root).rglob("*"):
        
        if file.is_file() and access(file, X_OK):
            results.add(file)
        
    return results

db_file = Path("db.shelve")
if db_file.exists():
    with shelve.open(db_file) as sh:
        db = DictListMerge(sh)
else:
    paths = ["/bin","/sbin","/usr/sbin","/usr/lib","/home/deadeye/.local/"]
    db = reduce(or_, map(make_db, paths))
    with shelve.open(db_file) as sh:
        sh.update(db)