'''Bcfg2.Server.Core provides the runtime support for bcfg2 modules'''
__revision__ = '$Revision$'

from os import stat
from stat import ST_MODE, S_ISDIR
from syslog import syslog, LOG_ERR
from time import time

import _fam

class GeneratorError(Exception):
    '''This error is raised upon generator failures'''
    pass

class PublishError(Exception):
    '''This error is raised upon publication failures'''
    pass

class fam(object):
    '''The fam object is a set of callbacks for file alteration events'''
    
    def __init__(self):
        object.__init__(self)
        self.fm = _fam.open()
        self.users = {}
        self.handles = {}

    def fileno(self):
        '''return fam file handle number'''
        return self.fm.fileno()

    def AddMonitor(self, path, obj=None):
        '''add a monitor to path, installing a callback to obj.HandleEvent'''
        mode = stat(path)[ST_MODE]
        if S_ISDIR(mode):
            handle = self.fm.monitorDirectory(path, None)
        else:
            handle = self.fm.monitorFile(path, None)
        self.handles[handle.requestID()] = handle
        if obj != None:
            self.users[handle.requestID()] = obj
        return handle.requestID()

    def HandleEvent(self):
        '''Route a fam event to the proper callback'''
        event = self.fm.nextEvent()
        reqid = event.requestID
        if self.users.has_key(reqid):
            self.users[reqid].HandleEvent(event)

class PublishedValue(object):
    '''This is for data shared between generators'''
    def __init__(self, owner, key, value):
        object.__init__(self)
        self.owner = owner
        self.key = key
        self.value = value

    def Update(self, owner, value):
        '''Update the value after an ownership check succeeds'''
        if owner != self.owner:
            raise PublishError, (self.key, owner)
        self.value = value

class Core(object):
    '''The Core object is the container for all Bcfg2 Server logic, and modules'''
    def __init__(self, repository, structures, generators):
        object.__init__(self)
        self.datastore = repository
        self.fam = fam()
        self.pubspace = {}
        self.structures = []
        self.cron = {}
        for structure in structures:
            try:
                mod = getattr(__import__("Bcfg2.Server.Structures.%s" %
                                         (structure)).Server.Structures, structure)
            except ImportError:
                syslog(LOG_ERR, "Failed to load structure %s" % (structure))
                continue
            struct = getattr(mod, structure)
            self.structures.append(struct(self, self.datastore))
        self.generators = []
        for generator in generators:
            try:
                mod = getattr(__import__("Bcfg2.Server.Generators.%s" %
                                         (generator)).Server.Generators, generator)
            except ImportError:
                syslog(LOG_ERR, 'Failed to load generator %s' % (generator))
                continue
            gen = getattr(mod, generator)
            self.generators.append(gen(self, self.datastore))
        # we need to inventory and setup generators
        # Process generator requirements
        for gen in self.generators:
            for prq in gen.__requires__:
                if not self.pubspace.has_key(prq):
                    raise GeneratorError, (gen.name, prq)
            gen.CompleteSetup()

    def PublishValue(self, owner, key, value):
        '''Publish a shared generator value'''
        if not self.pubspace.has_key(key):
            # This is a new entry
            self.pubspace[key] = PublishedValue(owner, key, value)
        else:
            # This is an old entry. Update can fai
            try:
                self.pubspace[key].Update(owner, value)
            except PublishError:
                syslog(LOG_ERR, "Publish conflict for %s. Owner %s, Modifier %s"%
                       (key, self.pubspace[key].owner, owner))

    def ReadValue(self, key):
        '''Read a value published by another generator'''
        if self.pubspace.has_key(key):
            return self.pubspace[key].value
        raise KeyError, key

    def GetStructures(self, metadata):
        '''Get all structures for client specified by metadata'''
        return reduce(lambda x, y:x+y,
                      [struct.Construct(metadata) for struct in self.structures])

    def BindStructure(self, structure, metadata):
        '''Bind a complete structure'''
        for entry in [child for child in structure.getchildren() if child.tag not in ['SymLink', 'Directory']]:
            try:
                self.Bind(entry, metadata)
            except KeyError, key:
                syslog(LOG_ERR, "Unable to locate %s" % key)

    def Bind(self, entry, metadata):
        '''Bind an entry using the appropriate generator'''
        glist = [gen for gen in self.generators if
                 gen.__provides__.get(entry.tag, {}).has_key(entry.get('name'))]
        if len(glist) == 1:
            return glist[0].__provides__[entry.tag][entry.get('name')](entry, metadata)
        elif len(glist) > 1:
            print "Data Integrity error for %s %s" % (entry.tag, entry.get('name'))
        else:
            for gen in self.generators:
                if hasattr(gen, "FindHandler"):
                    try:
                        return gen.FindHandler(entry)(entry, metadata)
                    except:
                        print gen, "failed"
            raise KeyError, (entry.tag, entry.get('name'))
                
    def RunCronTasks(self):
        '''Run periodic tasks for generators'''
        generators = [gen for gen in self.generators if gen.__croninterval__]
        for generator in generators:
            current = time()
            if ((current - self.cron.get(generator, 0)) > generator.__croninterval__):
                generator.Cron()
                self.cron[generator] = current