0bin/zerobin/paste.py

# -*- coding: utf-8 -*-

import os
import fcntl
import sys
import hashlib


from datetime import datetime, timedelta

from utils import settings


class Paste(object):
    """
        A paste objet to deal with the file opening/parsing/saving and the
        calculation of the expiration date.
    """

    DIR_CACHE = set()

    DURATIONS = {
        u'1_day': 24 * 3600,
        u'1_month': 30 * 24 * 3600,
        u'never': 365 * 24 * 3600 * 100,
    }


    def __init__(self, uuid=None, content=None,
                 expiration=None):

        self.content = content
        self.expiration = expiration

        if isinstance(self.content, unicode):
            self.content = self.content.encode('utf8')

        self.expiration = self.get_expiration(expiration)

        self.uuid = uuid or hashlib.sha1(self.content).hexdigest()


    def get_expiration(self, expiration):
        """
            Return a tuple with the date at which the Paste will expire
            or if it should be destroyed after first reading.

            Do not modify the value if it's already a date object or
            if it's burn_after_reading
        """

        if (isinstance(expiration, datetime) or
            'burn_after_reading' in str(expiration)):
            return expiration

        try:
            return datetime.now() + timedelta(seconds=self.DURATIONS[expiration])
        except KeyError:
            return u'burn_after_reading'


    @classmethod
    def build_path(cls, *dirs):
        """
            Generic static content path builder. Return a path to
            a location in the static content file dir.
        """
        return os.path.join(settings.PASTE_FILES_ROOT, *dirs)


    @classmethod
    def get_path(cls, uuid):
        """
            Return the file path of a paste given uuid
        """
        return cls.build_path(uuid[:2], uuid[2:4], uuid)


    @property
    def path(self):
        """
            Return the file path for this path. Use get_path().
        """
        return self.get_path(self.uuid)


    @classmethod
    def load_from_file(cls, path):
        """
            Return an instance of the paste object with the content of the
            given file.
        """
        try:
            paste = open(path)
            uuid = os.path.basename(path)
            expiration = paste.next().strip()
            content = paste.next().strip()
            if "burn_after_reading" not in str(expiration):
                expiration = datetime.strptime(expiration, '%Y-%m-%d %H:%M:%S.%f')

        except StopIteration:
            raise TypeError(u'File %s is malformed' % path)
        except (IOError, OSError):
            raise ValueError(u'Can not open paste from file %s' % path)

        return Paste(uuid=uuid, expiration=expiration, content=content)


    @classmethod
    def load(cls, uuid):
        """
            Return an instance of the paste object with the content of the
            file matching this uuid. Use load_from_file() and get_path()
        """
        return cls.load_from_file(cls.get_path(uuid))


    
    def increment_counter(self):
        """
            Increment pastes counter 
        """

        # simple counter incrementation
        # using lock file to prevent multi access to the file
        # could be improved.


        path = settings.PASTE_FILES_ROOT
        counter_file = os.path.join(path, 'counter') 

        fd = os.open(counter_file, os.O_RDWR | os.O_CREAT)
        fcntl.lockf(fd, fcntl.LOCK_EX)
        s = os.read(fd, 4096)
        try:
            n = long(float(s))
        except ValueError:
            raise ValueError(u"Couldn't read value from counter file " + counter_file + ", assuming 0")
            n = 0
        fnn = counter_file + ".new"
        f = open(fnn, "w")
        f.write(str(n + 1))
        f.close()
        os.rename(fnn, counter_file)
        os.close(fd)


    def save(self):
        """
            Save the content of this paste to a file.
        """
        head, tail = self.uuid[:2], self.uuid[2:4]

        # the static files are saved in project_dir/static/xx/yy/uuid
        # xx and yy are generated from the uuid (see get_path())
        # we need to check if they are created before writting
        # but since we want to prevent to many writes, we create
        # an in memory cache that will hold the result of this check fo
        # each worker. If the dir is not in cache, we check the FS, and
        # if the dir is not in there, we create the dir
        if head not in self.DIR_CACHE:

            self.DIR_CACHE.add(head)

            if not os.path.isdir(self.build_path(head)):
                os.makedirs(self.build_path(head, tail))
                self.DIR_CACHE.add((head, tail))

        if (head, tail) not in self.DIR_CACHE:
            path = self.build_path(head, tail)
            self.DIR_CACHE.add((head, tail))
            if not os.path.isdir(path):
                os.mkdir(path)

        # add a timestamp to burn after reading to allow
        # a quick period of time where you can redirect to the page without
        # deleting the paste
        if self.expiration == "burn_after_reading":
            self.expiration = self.expiration + '#%s' % datetime.now()

        # write the paste
        with open(self.path, 'w') as f:
            f.write(unicode(self.expiration) + '\n')
            f.write(self.content + '\n')

        return self


    def delete(self):
        """
            Delete the paste file.
        """
        os.remove(self.path)