#!/usr/bin/python
#
# (c) 2015, Steve Gargan <steve.gargan@gmail.com>
# (c) 2018 Genome Research Ltd.
# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)

from __future__ import absolute_import, division, print_function
__metaclass__ = type


ANSIBLE_METADATA = {'metadata_version': '1.1',
                    'status': ['preview'],
                    'supported_by': 'community'}


DOCUMENTATION = """
module: consul_kv
short_description: Manipulate entries in the key/value store of a consul cluster
description:
  - Allows the retrieval, addition, modification and deletion of key/value entries in a
    consul cluster via the agent. The entire contents of the record, including
    the indices, flags and session are returned as 'value'.
  - If the key represents a prefix then Note that when a value is removed, the existing
    value if any is returned as part of the results.
  - See http://www.consul.io/docs/agent/http.html#kv for more details.
requirements:
  - python >= 2.6
  - python-consul
  - requests
version_added: "2.0"
author:
  - Steve Gargan (@sgargan)
  - Colin Nolan (@colin-nolan)
options:
    state:
        description:
          - The action to take with the supplied key and value. If the state is 'present' and `value` is set, the key
            contents will be set to the value supplied and `changed` will be set to `true` only if the value was
            different to the current contents. If the state is 'present' and `value` is not set, the existing value
            associated to the key will be returned. The state 'absent' will remove the key/value pair,
            again 'changed' will be set to true only if the key actually existed
            prior to the removal. An attempt can be made to obtain or free the
            lock associated with a key/value pair with the states 'acquire' or
            'release' respectively. a valid session must be supplied to make the
            attempt changed will be true if the attempt is successful, false
            otherwise.
        choices: [ absent, acquire, present, release ]
        default: present
    key:
        description:
          - The key at which the value should be stored.
        required: yes
    value:
        description:
          - The value should be associated with the given key, required if C(state)
            is C(present).
        required: yes
    recurse:
        description:
          - If the key represents a prefix, each entry with the prefix can be
            retrieved by setting this to C(yes).
        type: bool
        default: 'no'
    session:
        description:
          - The session that should be used to acquire or release a lock
            associated with a key/value pair.
    token:
        description:
          - The token key indentifying an ACL rule set that controls access to
            the key value pair
    cas:
        description:
          - Used when acquiring a lock with a session. If the C(cas) is C(0), then
            Consul will only put the key if it does not already exist. If the
            C(cas) value is non-zero, then the key is only set if the index matches
            the ModifyIndex of that key.
    flags:
        description:
          - Opaque integer value that can be passed when setting a value.
    host:
        description:
          - Host of the consul agent.
        default: localhost
    port:
        description:
          - The port on which the consul agent is running.
        default: 8500
    scheme:
        description:
          - The protocol scheme on which the consul agent is running.
        default: http
        version_added: "2.1"
    validate_certs:
        description:
          - Whether to verify the tls certificate of the consul agent.
        type: bool
        default: 'yes'
        version_added: "2.1"
"""


EXAMPLES = '''
# If the key does not exist, the value associated to the "data" property in `retrieved_key` will be `None`
# If the key value is empty string, `retrieved_key["data"]["Value"]` will be `None`
- name: retrieve a value from the key/value store
  consul_kv:
    key: somekey
  register: retrieved_key

- name: Add or update the value associated with a key in the key/value store
  consul_kv:
    key: somekey
    value: somevalue

- name: Remove a key from the store
  consul_kv:
    key: somekey
    state: absent

- name: Add a node to an arbitrary group via consul inventory (see consul.ini)
  consul_kv:
    key: ansible/groups/dc1/somenode
    value: top_secret

- name: Register a key/value pair with an associated session
  consul_kv:
    key: stg/node/server_birthday
    value: 20160509
    session: "{{ sessionid }}"
    state: acquire
'''

from ansible.module_utils._text import to_text

try:
    import consul
    from requests.exceptions import ConnectionError
    python_consul_installed = True
except ImportError:
    python_consul_installed = False

from ansible.module_utils.basic import AnsibleModule

# Note: although the python-consul documentation implies that using a key with a value of `None` with `put` has a
# special meaning (https://python-consul.readthedocs.io/en/latest/#consul-kv), if not set in the subsequently API call,
# the value just defaults to an empty string (https://www.consul.io/api/kv.html#create-update-key)
NOT_SET = None


def _has_value_changed(consul_client, key, target_value):
    """
    Uses the given Consul client to determine if the value associated to the given key is different to the given target
    value.
    :param consul_client: Consul connected client
    :param key: key in Consul
    :param target_value: value to be associated to the key
    :return: tuple where the first element is the value of the "X-Consul-Index" header and the second is `True` if the
    value has changed (i.e. the stored value is not the target value)
    """
    index, existing = consul_client.kv.get(key)
    if not existing:
        return index, True
    try:
        changed = to_text(existing['Value'], errors='surrogate_or_strict') != target_value
        return index, changed
    except UnicodeError:
        # Existing value was not decodable but all values we set are valid utf-8
        return index, True


def execute(module):
    state = module.params.get('state')

    if state == 'acquire' or state == 'release':
        lock(module, state)
    elif state == 'present':
        if module.params.get('value') is NOT_SET:
            get_value(module)
        else:
            set_value(module)
    elif state == 'absent':
        remove_value(module)
    else:
        module.exit_json(msg="Unsupported state: %s" % (state, ))


def lock(module, state):

    consul_api = get_consul_api(module)

    session = module.params.get('session')
    key = module.params.get('key')
    value = module.params.get('value')

    if not session:
        module.fail(
            msg='%s of lock for %s requested but no session supplied' %
            (state, key))

    index, changed = _has_value_changed(consul_api, key, value)

    if changed and not module.check_mode:
        if state == 'acquire':
            changed = consul_api.kv.put(key, value,
                                        cas=module.params.get('cas'),
                                        acquire=session,
                                        flags=module.params.get('flags'))
        else:
            changed = consul_api.kv.put(key, value,
                                        cas=module.params.get('cas'),
                                        release=session,
                                        flags=module.params.get('flags'))

    module.exit_json(changed=changed,
                     index=index,
                     key=key)


def get_value(module):
    consul_api = get_consul_api(module)
    key = module.params.get('key')

    index, existing_value = consul_api.kv.get(key, recurse=module.params.get('recurse'))

    module.exit_json(changed=False, index=index, data=existing_value)


def set_value(module):
    consul_api = get_consul_api(module)

    key = module.params.get('key')
    value = module.params.get('value')

    if value is NOT_SET:
        raise AssertionError('Cannot set value of "%s" to `NOT_SET`' % key)

    index, changed = _has_value_changed(consul_api, key, value)

    if changed and not module.check_mode:
        changed = consul_api.kv.put(key, value,
                                    cas=module.params.get('cas'),
                                    flags=module.params.get('flags'))

    stored = None
    if module.params.get('retrieve'):
        index, stored = consul_api.kv.get(key)

    module.exit_json(changed=changed,
                     index=index,
                     key=key,
                     data=stored)


def remove_value(module):
    ''' remove the value associated with the given key. if the recurse parameter
     is set then any key prefixed with the given key will be removed. '''
    consul_api = get_consul_api(module)

    key = module.params.get('key')

    index, existing = consul_api.kv.get(
        key, recurse=module.params.get('recurse'))

    changed = existing is not None
    if changed and not module.check_mode:
        consul_api.kv.delete(key, module.params.get('recurse'))

    module.exit_json(changed=changed,
                     index=index,
                     key=key,
                     data=existing)


def get_consul_api(module, token=None):
    return consul.Consul(host=module.params.get('host'),
                         port=module.params.get('port'),
                         scheme=module.params.get('scheme'),
                         verify=module.params.get('validate_certs'),
                         token=module.params.get('token'))


def test_dependencies(module):
    if not python_consul_installed:
        module.fail_json(msg="python-consul required for this module. "
                             "see https://python-consul.readthedocs.io/en/latest/#installation")


def main():

    module = AnsibleModule(
        argument_spec=dict(
            cas=dict(type='str'),
            flags=dict(type='str'),
            key=dict(type='str', required=True),
            host=dict(type='str', default='localhost'),
            scheme=dict(type='str', default='http'),
            validate_certs=dict(type='bool', default=True),
            port=dict(type='int', default=8500),
            recurse=dict(type='bool'),
            retrieve=dict(type='bool', default=True),
            state=dict(type='str', default='present', choices=['absent', 'acquire', 'present', 'release']),
            token=dict(type='str', no_log=True),
            value=dict(type='str', default=NOT_SET),
            session=dict(type='str'),
        ),
        supports_check_mode=False
    )

    test_dependencies(module)

    try:
        execute(module)
    except ConnectionError as e:
        module.fail_json(msg='Could not connect to consul agent at %s:%s, error was %s' % (
            module.params.get('host'), module.params.get('port'), e))
    except Exception as e:
        module.fail_json(msg=str(e))


if __name__ == '__main__':
    main()
