from migrate.versioning.base import *
from migrate.versioning.util import KeyedInstance
import os,shutil
from migrate.versioning import exceptions

class Pathed(KeyedInstance):
    """A class associated with a path/directory tree
    Only one instance of this class may exist for a particular file; 
    __new__ will return an existing instance if possible
    """
    parent=None

    @classmethod
    def _key(cls,path):
        return str(path)

    def __init__(self,path):
        self.path=path
        if self.__class__.parent is not None:
            self._init_parent(path)

    def _init_parent(self,path):
        """Try to initialize this object's parent, if it has one"""
        parent_path=self.__class__._parent_path(path)
        self.parent=self.__class__.parent(parent_path)
        log.info("Getting parent %r:%r"%(self.__class__.parent,parent_path))
        self.parent._init_child(path,self)
    
    def _init_child(self,child,path):
        """Run when a child of this object is initialized
        Parameters: the child object; the path to this object (its parent)
        """
        pass
    
    @classmethod
    def _parent_path(cls,path):
        """Fetch the path of this object's parent from this object's path
        """
        # os.path.dirname(), but strip directories like files (like unix basename)
        # Treat directories like files...
        if path[-1]=='/':
            path=path[:-1]
        ret = os.path.dirname(path)
        return ret

    @classmethod
    def require_notfound(cls,path):
        """Ensures a given path does not already exist"""
        if os.path.exists(path):
            raise exceptions.PathFoundError(path)
    
    @classmethod
    def require_found(cls,path):
        """Ensures a given path already exists"""
        if not os.path.exists(path):
            raise exceptions.PathNotFoundError(path)

    def __str__(self):
        return self.path