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# Copyright (C) 2012  Codethink Limited
# 

import json
import logging
import re
import glob
import os

default_values = [
    ( u'serial', 0 ),
    ( u'create', u'never' ),
    ( u'destroy', u'never' ),
    ( u'interval', u'1m' ),
    ( u'stagger', False ),
    ( u'type', u'invalid_type' ),
]

valid_whens = set(["always", "never", "unchanged"])
valid_interval = re.compile(r"^([1-9][0-9]*)([mhd])?$")
interval_mults = {
    None: 1,
    'm': 60,
    'h': 60 * 60,
    'd': 60 * 60 * 24,
}
class LorryControllerConfig(object):
    '''This encapsulates the configuration for lorry-controller.'''

    def __init__(self, settings, confpath):
        self.settings = settings
        self.lorries = {}
        confpath = os.path.join(settings['work-area'], confpath)
        logging.debug("Parsing configuration: %s" % confpath)
        with open(confpath, "r") as fh:
            self._raw_conf = json.load(fh)
        logging.debug("Validating configuration semantics")
        self._validate__raw_conf()
        logging.debug("Configuration loaded")

    def _validate__raw_conf(self):
        '''Validate the entire raw config.'''
        if type(self._raw_conf) != list:
            self._give_up("Configuration was not a list.")
        for entry in self._raw_conf:
            if type(entry) != dict:
                self._give_up("Configuration entry was not a dict.")
            if type(entry.get('type', None)) != unicode:
                self._give_up("Configuration entry lacked a suitable 'type' "
                             "field.")
            # Set the defaults
            for key, defval in default_values:
                entry[key] = entry.get(key, defval)
            # And validate the generic values such as serial
            self._validate__generics(entry)
            # Now validate the rest
            validator = getattr(self, '_validate_' + entry['type'], None)
            if validator is None:
                self._give_up("Configuration entry had unknown type: %s" %
                             entry['type'])
            validator(entry)

    def _validate__generics(self, entry):
        '''Validate the generic entries such as 'serial'.'''
        for key, defval in default_values:
            if type(defval) != type(entry[key]):
                self._give_up("Invalid type for '%s': %r" % (key, entry[key]))
        self._validate__when(entry, 'create')
        if entry['create'] == "unchanged":
            self._give_up("Invalid value for create: unchanged")
        self._validate__when(entry, 'destroy')
        entry['interval-parsed'] = self._parse_interval(entry['interval'])

    def _validate__when(self, entry, key):
        if entry[key] not in valid_whens:
            self._give_up("Invalid value for %s: %s" % (key, entry[key]))

    def _parse_interval(self, interval):
        m = valid_interval.match(interval.lower())
        if m is None:
            self._give_up("Unable to parse '%s' as an interval" % interval)
        num, mult = m.groups()
        num = int(num)
        mult = interval_mults.get(mult, None)
        if mult is None:
            self._give_up("Somehow, '%s' managed to appear as a multiplier!" %
                         m.group(2))
        logging.debug("Converted interval %r to %r", interval, (num * mult))
        return num * mult

    def _validate_lorries(self, entry):
        '''Validate a 'lorries' stanza.'''
        if type(entry.get('globs', None)) != list:
            self._give_up("Lorries stanzas need lists for their 'globs'")
        if entry.get('prefix', None) is None:
            entry['prefix'] = u""
        if type(entry['prefix']) != unicode:
            self._give_up("Lorry prefixes should be strings.")
        my_lorries = set()
        git_base = os.path.join(self.settings['work-area'], 'git')
        for glob_entry in entry['globs']:
            if type(glob_entry) != unicode:
                self._give_up("Lorries globs should be strings")
            fullglob = os.path.join(git_base, glob_entry)
            my_lorries = my_lorries.union(set(glob.iglob(fullglob)))
        for lorry in my_lorries:
            if not lorry.startswith(git_base):
                self._give_up("Glob found %s which is outside the git base")

        logging.debug("Expanded globs in entry to %d lorry files" % 
                      len(my_lorries))
        logging.debug("Loading lorries into memory, please wait...")

        for lorry in my_lorries:
            try:
                with open(lorry, "r") as fh:
                    lorry_json = json.load(fh)
                    for name, content in lorry_json.iteritems():
                        fullname = os.path.join(entry['prefix'], name)
                        if self.lorries.get(fullname, None) is not None:
                            self._give_up("Lorry repeated: %s" % fullname)
                        logging.debug("[%r]=%r" % (fullname, content))
                        self.lorries[fullname] = content
            except Exception, e:
                logging.debug("Unable to parse %s, because of %s. Moving on" %
                              (lorry, e))

        logging.debug("Now loaded %d lorries" % len(self.lorries.keys()))
            
    def _give_up(self, *args, **kwargs):
        logging.error(*args, **kwargs)
        raise SystemExit(5)