import os
import re
import sys
import copy
import logging
import lxml.etree
import Bcfg2.Server.Plugin
try:
    from Bcfg2.Encryption import ssl_decrypt, EVPError
    have_crypto = True
except ImportError:
    have_crypto = False

logger = logging.getLogger(__name__)

SETUP = None

def passphrases():
    section = "encryption"
    if SETUP.cfp.has_section(section):
        return dict([(o, SETUP.cfp.get(section, o))
                     for o in SETUP.cfp.options(section)])
    else:
        return dict()


class PropertyFile(Bcfg2.Server.Plugin.StructFile):
    """Class for properties files."""
    def write(self):
        """ Write the data in this data structure back to the property
        file """
        if not SETUP.cfp.getboolean("properties", "writes_enabled",
                                    default=True):
            msg = "Properties files write-back is disabled in the configuration"
            logger.error(msg)
            raise Bcfg2.Server.Plugin.PluginExecutionError(msg)
        try:
            self.validate_data()
        except Bcfg2.Server.Plugin.PluginExecutionError:
            msg = "Cannot write %s: %s" % (self.name, sys.exc_info()[1])
            logger.error(msg)
            raise Bcfg2.Server.Plugin.PluginExecutionError(msg)

        try:
            open(self.name, "wb").write(lxml.etree.tostring(self.xdata,
                                                            pretty_print=True))
            return True
        except IOError:
            err = sys.exc_info()[1]
            msg = "Failed to write %s: %s" % (self.name, err)
            logger.error(msg)
            raise Bcfg2.Server.Plugin.PluginExecutionError(msg)

    def validate_data(self):
        """ ensure that the data in this object validates against the
        XML schema for this property file (if a schema exists) """
        schemafile = self.name.replace(".xml", ".xsd")
        if os.path.exists(schemafile):
            try:
                schema = lxml.etree.XMLSchema(file=schemafile)
            except:
                err = sys.exc_info()[1]
                raise Bcfg2.Server.Plugin.PluginExecutionError("Failed to process schema for %s: %s" % (self.name, err))
        else:
            # no schema exists
            return True

        if not schema.validate(self.xdata):
            raise Bcfg2.Server.Plugin.PluginExecutionError("Data for %s fails to validate; run bcfg2-lint for more details" % self.name)
        else:
            return True

    def Index(self):
        Bcfg2.Server.Plugin.StructFile.Index(self)
        if self.xdata.get("encryption", "false").lower() != "false":
            if not have_crypto:
                msg = "Properties: M2Crypto is not available: %s" % self.name
                logger.error(msg)
                raise Bcfg2.Server.Plugin.PluginExecutionError(msg)
            for el in self.xdata.xpath("*[@encrypted]"):
                try:
                    el.text = self._decrypt(el)
                except EVPError:
                    msg = "Failed to decrypt %s element in %s" % (el.tag,
                                                                  self.name)
                    logger.error(msg)
                    raise Bcfg2.Server.PluginExecutionError(msg)

    def _decrypt(self, element):
        if not element.text.strip():
            return
        passes = passphrases()
        try:
            passphrase = passes[element.get("encrypted")]
            try:
                return ssl_decrypt(element.text, passphrase)
            except EVPError:
                # error is raised below
                pass
        except KeyError:
            for passwd in passes.values():
                try:
                    return ssl_decrypt(element.text, passwd)
                except EVPError:
                    pass
        raise EVPError("Failed to decrypt")

class PropDirectoryBacked(Bcfg2.Server.Plugin.DirectoryBacked):
    __child__ = PropertyFile
    patterns = re.compile(r'.*\.xml$')


class Properties(Bcfg2.Server.Plugin.Plugin,
                 Bcfg2.Server.Plugin.Connector):
    """
       The properties plugin maps property
       files into client metadata instances.
    """
    name = 'Properties'

    def __init__(self, core, datastore):
        global SETUP
        Bcfg2.Server.Plugin.Plugin.__init__(self, core, datastore)
        Bcfg2.Server.Plugin.Connector.__init__(self)
        try:
            self.store = PropDirectoryBacked(self.data, core.fam)
        except OSError:
            e = sys.exc_info()[1]
            self.logger.error("Error while creating Properties store: %s %s" %
                              (e.strerror, e.filename))
            raise Bcfg2.Server.Plugin.PluginInitError

        SETUP = core.setup

    def get_additional_data(self, metadata):
        autowatch = self.core.setup.cfp.getboolean("properties", "automatch",
                                                   default=False)
        rv = dict()
        for fname, pfile in self.store.entries.items():
            if (autowatch or
                pfile.xdata.get("automatch", "false").lower() == "true"):
                rv[fname] = pfile.XMLMatch(metadata)
            else:
                rv[fname] = copy.copy(pfile)
        return rv