# (c) 2014, Brian Coca, Josh Drake, et al
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import os
import time
import errno
import codecs

try:
    import simplejson as json
except ImportError:
    import json

from ansible import constants as C
from ansible.errors import AnsibleError
from ansible.parsing.utils.jsonify import jsonify
from ansible.plugins.cache.base import BaseCacheModule
from ansible.utils.unicode import to_bytes

try:
    from __main__ import display
except ImportError:
    from ansible.utils.display import Display
    display = Display()


class CacheModule(BaseCacheModule):
    """
    A caching module backed by json files.
    """
    def __init__(self, *args, **kwargs):

        self._timeout = float(C.CACHE_PLUGIN_TIMEOUT)
        self._cache = {}
        self._cache_dir = os.path.expanduser(os.path.expandvars(C.CACHE_PLUGIN_CONNECTION)) # expects a dir path
        if not self._cache_dir:
            raise AnsibleError("error, fact_caching_connection is not set, cannot use fact cache")

        if not os.path.exists(self._cache_dir):
            try:
                os.makedirs(self._cache_dir)
            except (OSError,IOError) as e:
                display.warning("error while trying to create cache dir %s : %s" % (self._cache_dir, to_bytes(e)))
                return None

    def get(self, key):
        """ This checks the in memory cache first as the fact was not expired at 'gather time'
        and it would be problematic if the key did expire after some long running tasks and
        user gets 'undefined' error in the same play """

        if key in self._cache:
            return self._cache.get(key)

        if self.has_expired(key) or key == "":
            raise KeyError

        cachefile = "%s/%s" % (self._cache_dir, key)
        try:
            with codecs.open(cachefile, 'r', encoding='utf-8') as f:
                try:
                    value = json.load(f)
                    self._cache[key] = value
                    return value
                except ValueError as e:
                    display.warning("error while trying to read %s : %s. Most likely a corrupt file, so erasing and failing." % (cachefile, to_bytes(e)))
                    self.delete(key)
                    raise AnsibleError("The JSON cache file %s was corrupt, or did not otherwise contain valid JSON data."
                            " It has been removed, so you can re-run your command now." % cachefile)
        except (OSError,IOError) as e:
            display.warning("error while trying to read %s : %s" % (cachefile, to_bytes(e)))
            raise KeyError

    def set(self, key, value):

        self._cache[key] = value

        cachefile = "%s/%s" % (self._cache_dir, key)
        try:
            f = codecs.open(cachefile, 'w', encoding='utf-8')
        except (OSError,IOError) as e:
            display.warning("error while trying to write to %s : %s" % (cachefile, to_bytes(e)))
            pass
        else:
            f.write(jsonify(value))
        finally:
            f.close()

    def has_expired(self, key):

        cachefile = "%s/%s" % (self._cache_dir, key)
        try:
            st = os.stat(cachefile)
        except (OSError,IOError) as e:
            if e.errno == errno.ENOENT:
                return False
            else:
                display.warning("error while trying to stat %s : %s" % (cachefile, to_bytes(e)))
                pass

        if time.time() - st.st_mtime <= self._timeout:
            return False

        if key in self._cache:
            del self._cache[key]
        return True

    def keys(self):
        keys = []
        for k in os.listdir(self._cache_dir):
            if not (k.startswith('.') or self.has_expired(k)):
                keys.append(k)
        return keys

    def contains(self, key):
        cachefile = "%s/%s" % (self._cache_dir, key)

        if key in self._cache:
            return True

        if self.has_expired(key):
            return False
        try:
            os.stat(cachefile)
            return True
        except (OSError,IOError) as e:
            if e.errno == errno.ENOENT:
                return False
            else:
                display.warning("error while trying to stat %s : %s" % (cachefile, to_bytes(e)))
                pass

    def delete(self, key):
        try:
            del self._cache[key]
        except KeyError:
            pass
        try:
            os.remove("%s/%s" % (self._cache_dir, key))
        except (OSError, IOError):
            pass #TODO: only pass on non existing?

    def flush(self):
        self._cache = {}
        for key in self.keys():
            self.delete(key)

    def copy(self):
        ret = dict()
        for key in self.keys():
            ret[key] = self.get(key)
        return ret
