import struct
import base64
import shelve
import os.path

from log import index

def int2key (id) :
    """
        Turn an integer into a short-as-possible url-safe string
    """
    for type in ('B', 'H', 'I') :
        try :
            return base64.b64encode(struct.pack(type, id), '-_').rstrip('=')
        except struct.error :
            continue

    raise Exception("ID overflow: %s" % id)

def updateDB (root) :
    """
        DeGAL <= 0.2 used a simple key => path mapping, but now we use
        something more structured, key => (type, dirpath, fname), where

        type    - one of 'img', 'dir'
        dirpath - the path to the directory, e.g. '.', './foobar', './foobar/quux'
        fname   - the filename, one of '', 'DSC9839.JPG', 'this.png', etc.
    """

    db = shelve.open('shorturls2', 'c', writeback=True)
    
    id = db.get('_id', 1)

    dirqueue = [root]

    # dict of path -> obj
    paths = {}

    index.info("Processing ShortURLs...")

    while dirqueue :
        dir = dirqueue.pop(0)

        dirqueue.extend(dir.subdirs.itervalues())

        if dir.alive :
            paths[dir.path] = dir

        for img in dir.images.itervalues() :
            paths[img.path] = img

    for key in db.keys() :
        if key.startswith('_') :
            continue

        type, dirpath, fname = db[key]
        
        path = os.path.join(dirpath, fname).rstrip(os.sep)

        try :
            paths.pop(path).shorturl_code = key
            index.debug("Code for `%s' is %s", path, key)

        except KeyError :
            index.debug("Path `%s' in DB does not exist?", path)

    for obj in paths.itervalues() :
        key = int2key(id)
        id += 1
        
        index.info("Alloc code `%s' for `%s'", key, obj.html_path)

        obj.shorturl_code = key

        db[key] = obj.getObjInfo()

    db['_id'] = id
    db.close()