# -*- coding: utf-8 -*-
'''
Minion data cache plugin for Consul key/value data store.

.. versionadded:: 2016.11.2

:depends: python-consul >= 0.2.0

It is up to the system administrator to set up and configure the Consul
infrastructure. All is needed for this plugin is a working Consul agent
with a read-write access to the key-value store.

The related documentation can be found in the `Consul documentation`_.

To enable this cache plugin, the master will need the python client for
Consul installed. This can be easily installed with pip:

.. code-block: bash

    pip install python-consul

Optionally, depending on the Consul agent configuration, the following values
could be set in the master config. These are the defaults:

.. code-block:: yaml

    consul.host: 127.0.0.1
    consul.port: 8500
    consul.token: None
    consul.scheme: http
    consul.consistency: default
    consul.dc: dc1
    consul.verify: True

Related docs could be found in the `python-consul documentation`_.

To use the consul as a minion data cache backend, set the master ``cache`` config
value to ``consul``:

.. code-block:: yaml

    cache: consul


.. _`Consul documentation`: https://www.consul.io/docs/index.html
.. _`python-consul documentation`: https://python-consul.readthedocs.io/en/latest/#consul

'''
from __future__ import absolute_import, print_function, unicode_literals
import logging
try:
    import consul
    HAS_CONSUL = True
except ImportError:
    HAS_CONSUL = False

from salt.exceptions import SaltCacheError

log = logging.getLogger(__name__)
api = None


# Define the module's virtual name
__virtualname__ = 'consul'

__func_alias__ = {'list_': 'list'}


def __virtual__():
    '''
    Confirm this python-consul package is installed
    '''
    if not HAS_CONSUL:
        return (False, "Please install python-consul package to use consul data cache driver")

    consul_kwargs = {
            'host': __opts__.get('consul.host', '127.0.0.1'),
            'port': __opts__.get('consul.port', 8500),
            'token': __opts__.get('consul.token', None),
            'scheme': __opts__.get('consul.scheme', 'http'),
            'consistency': __opts__.get('consul.consistency', 'default'),
            'dc': __opts__.get('consul.dc', None),
            'verify': __opts__.get('consul.verify', True),
            }

    try:
        global api
        api = consul.Consul(**consul_kwargs)
    except AttributeError:
        return (False, "Failed to invoke consul.Consul, please make sure you have python-consul >= 0.2.0 installed")

    return __virtualname__


def store(bank, key, data):
    '''
    Store a key value.
    '''
    c_key = '{0}/{1}'.format(bank, key)
    try:
        c_data = __context__['serial'].dumps(data)
        api.kv.put(c_key, c_data)
    except Exception as exc:
        raise SaltCacheError(
            'There was an error writing the key, {0}: {1}'.format(
                c_key, exc
            )
        )


def fetch(bank, key):
    '''
    Fetch a key value.
    '''
    c_key = '{0}/{1}'.format(bank, key)
    try:
        _, value = api.kv.get(c_key)
        if value is None:
            return {}
        return __context__['serial'].loads(value['Value'])
    except Exception as exc:
        raise SaltCacheError(
            'There was an error reading the key, {0}: {1}'.format(
                c_key, exc
            )
        )


def flush(bank, key=None):
    '''
    Remove the key from the cache bank with all the key content.
    '''
    if key is None:
        c_key = bank
    else:
        c_key = '{0}/{1}'.format(bank, key)
    try:
        return api.kv.delete(c_key, recurse=key is None)
    except Exception as exc:
        raise SaltCacheError(
            'There was an error removing the key, {0}: {1}'.format(
                c_key, exc
            )
        )


def list_(bank):
    '''
    Return an iterable object containing all entries stored in the specified bank.
    '''
    try:
        _, keys = api.kv.get(bank + '/', keys=True, separator='/')
    except Exception as exc:
        raise SaltCacheError(
            'There was an error getting the key "{0}": {1}'.format(
                bank, exc
            )
        )
    if keys is None:
        keys = []
    else:
        # Any key could be a branch and a leaf at the same time in Consul
        # so we have to return a list of unique names only.
        out = set()
        for key in keys:
            out.add(key[len(bank) + 1:].rstrip('/'))
        keys = list(out)
    return keys


def contains(bank, key):
    '''
    Checks if the specified bank contains the specified key.
    '''
    if key is None:
        return True  # any key could be a branch and a leaf at the same time in Consul
    else:
        try:
            c_key = '{0}/{1}'.format(bank, key)
            _, value = api.kv.get(c_key)
        except Exception as exc:
            raise SaltCacheError(
                'There was an error getting the key, {0}: {1}'.format(
                    c_key, exc
                )
            )
        return value is not None
