#!/usr/bin/env python
import apt_pkg, apt_inst, sys, os, stat
from os.path import dirname, basename
import re, shelve, shutil, fcntl
import copy, UserDict, tempfile
from time import sleep

import os

###############
# Memory usage pasted from python cookbook
_proc_status = '/proc/%d/status' % os.getpid()

_scale = {'kB': 1024.0, 'mB': 1024.0*1024.0,
          'KB': 1024.0, 'MB': 1024.0*1024.0}

def _VmB(VmKey):
    '''Private.
    '''
    global _proc_status, _scale
     # get pseudo file  /proc/<pid>/status
    try:
        t = open(_proc_status)
        v = t.read()
        t.close()
    except:
        return 0.0  # non-Linux?
     # get VmKey line e.g. 'VmRSS:  9999  kB\n ...'
    i = v.index(VmKey)
    v = v[i:].split(None, 3)  # whitespace
    if len(v) < 3:
        return 0.0  # invalid format?
     # convert Vm value to bytes
    return float(v[1]) * _scale[v[2]]


def memory(since=0.0):
    '''Return memory usage in bytes.
    '''
    return _VmB('VmSize:') - since


def resident(since=0.0):
    '''Return resident memory usage in bytes.
    '''
    return _VmB('VmRSS:') - since


def stacksize(since=0.0):
    '''Return stack size in bytes.
    '''
    return _VmB('VmStk:') - since
###################

class AptPackages:
    """
    Uses AptPackagesServer to answer queries about packages.

    Makes a fake configuration for python-apt for each backend.

    self.packages: a list of files which should go in the fake source.list
    along with their mtime.
    """
    local_config = {
        #'APT' : '',
        'APT::Architecture' : apt_pkg.CPU,
        #'APT::Default-Release' : 'unstable',
   
        'Dir':'/home/ranty/work/apt-proxy/twisted/cache/', # /
        'Dir::State' : 'apt/', # var/lib/apt/
        'Dir::State::Lists': 'lists/', # lists/
        #'Dir::State::cdroms' : 'cdroms.list',
        #'Dir::State::userstatus' : 'status.user',
        'Dir::State::status': 'dpkg/status', # '/var/lib/dpkg/status'
        'Dir::Cache' : '.apt/cache/', # var/cache/apt/
        #'Dir::Cache::archives' : 'archives/',
        'Dir::Cache::srcpkgcache' : 'srcpkgcache.bin',
        'Dir::Cache::pkgcache' : 'pkgcache.bin',
        'Dir::Etc' : 'apt/etc/', # etc/apt/
        'Dir::Etc::sourcelist' : 'sources.list',
        'Dir::Etc::vendorlist' : 'vendors.list',
        'Dir::Etc::vendorparts' : 'vendors.list.d',
        #'Dir::Etc::main' : 'apt.conf',
        #'Dir::Etc::parts' : 'apt.conf.d',
        #'Dir::Etc::preferences' : 'preferences',
        #'Dir::Bin' : '',
        #'Dir::Bin::methods' : '', #'/usr/lib/apt/methods'
        #'Dir::Bin::dpkg' : '/usr/bin/dpkg',
        #'DPkg' : '',
        #'DPkg::Pre-Install-Pkgs' : '',
        #'DPkg::Tools' : '',
        #'DPkg::Tools::Options' : '',
        #'DPkg::Tools::Options::/usr/bin/apt-listchanges' : '',
        #'DPkg::Tools::Options::/usr/bin/apt-listchanges::Version' : '2',
        #'DPkg::Post-Invoke' : '',
        }
    essential_dirs = ('apt', 'apt/cache', 'apt/dpkg', 'apt/etc', 'apt/lists',
                      'apt/lists/partial')
    essential_files = ('apt/dpkg/status', 'apt/etc/sources.list',)
        
    def __init__(self, path):
        self.local_config = copy.copy(self.local_config)

        self.status_dir = path

        for dir in self.essential_dirs:
            path = self.status_dir+'/'+dir
            if not os.path.exists(path):
                os.makedirs(path)
        for file in self.essential_files:
            path = self.status_dir+'/'+file
            if not os.path.exists(path):
                f = open(path,'w')
                f.close()
                del f

        self.local_config['Dir'] = self.status_dir

    def load(self):
        """
        Regenerates the fake configuration and load the packages server.
        """
        shutil.rmtree(self.status_dir+'/apt/lists/')
        os.makedirs(self.status_dir+'/apt/lists/partial')
        sources = open(self.status_dir+'/'+'apt/etc/sources.list', 'w')
        sources.close()

        for key, value in self.local_config.items():
            apt_pkg.Config[key] = value
        apt_pkg.InitSystem()

        self.cache = apt_pkg.GetCache()

        self.records = apt_pkg.GetPkgRecords(self.cache)

    def cleanup(self):
        del self.cache
        del self.records

if __name__ == '__main__':
    tmpdir = tempfile.mkdtemp('.aptproxy')
    print "start:",resident()
    tester = AptPackages(tmpdir)
    print "AptPackages:",resident()
    tester.load()
    print "load:",resident()
    tester.cleanup()
    print "cleanup:",resident()
    del tester
    os.removedirs(tmpdir)
    print "del:",resident()