Mini Shell

"""
Module for Management of Memcached Keys

.. versionadded:: 2014.1.0
"""

import logging

import salt.utils.functools
from salt.exceptions import CommandExecutionError, SaltInvocationError

# TODO: use salt.utils.memcache


try:
    import memcache

    HAS_MEMCACHE = True
except ImportError:
    HAS_MEMCACHE = False

DEFAULT_HOST = "127.0.0.1"
DEFAULT_PORT = 11211
DEFAULT_TIME = 0
DEFAULT_MIN_COMPRESS_LEN = 0

log = logging.getLogger(__name__)

# Don't shadow built-ins
__func_alias__ = {"set_": "set"}

__virtualname__ = "memcached"


def __virtual__():
    """
    Only load if python-memcache is installed
    """
    if HAS_MEMCACHE:
        return __virtualname__
    return (
        False,
        "The memcached execution module cannot be loaded: "
        "python memcache library not available.",
    )


def _connect(host=DEFAULT_HOST, port=DEFAULT_PORT):
    """
    Returns a tuple of (user, host, port) with config, pillar, or default
    values assigned to missing values.
    """
    if str(port).isdigit():
        return memcache.Client([f"{host}:{port}"], debug=0)
    raise SaltInvocationError("port must be an integer")


def _check_stats(conn):
    """
    Helper function to check the stats data passed into it, and raise an
    exception if none are returned. Otherwise, the stats are returned.
    """
    stats = conn.get_stats()
    if not stats:
        raise CommandExecutionError("memcached server is down or does not exist")
    return stats


def status(host=DEFAULT_HOST, port=DEFAULT_PORT):
    """
    Get memcached status

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.status
    """
    conn = _connect(host, port)
    try:
        stats = _check_stats(conn)[0]
    except (CommandExecutionError, IndexError):
        return False
    else:
        return {stats[0]: stats[1]}


def get(key, host=DEFAULT_HOST, port=DEFAULT_PORT):
    """
    Retrieve value for a key

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.get <key>
    """
    conn = _connect(host, port)
    _check_stats(conn)
    return conn.get(key)


def set_(
    key,
    value,
    host=DEFAULT_HOST,
    port=DEFAULT_PORT,
    time=DEFAULT_TIME,
    min_compress_len=DEFAULT_MIN_COMPRESS_LEN,
):
    """
    Set a key on the memcached server, overwriting the value if it exists.

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.set <key> <value>
    """
    if not isinstance(time, int):
        raise SaltInvocationError("'time' must be an integer")
    if not isinstance(min_compress_len, int):
        raise SaltInvocationError("'min_compress_len' must be an integer")
    conn = _connect(host, port)
    _check_stats(conn)
    return conn.set(key, value, time, min_compress_len)


def delete(key, host=DEFAULT_HOST, port=DEFAULT_PORT, time=DEFAULT_TIME):
    """
    Delete a key from memcache server

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.delete <key>
    """
    if not isinstance(time, int):
        raise SaltInvocationError("'time' must be an integer")
    conn = _connect(host, port)
    _check_stats(conn)
    return bool(conn.delete(key, time))


def add(
    key,
    value,
    host=DEFAULT_HOST,
    port=DEFAULT_PORT,
    time=DEFAULT_TIME,
    min_compress_len=DEFAULT_MIN_COMPRESS_LEN,
):
    """
    Add a key to the memcached server, but only if it does not exist. Returns
    False if the key already exists.

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.add <key> <value>
    """
    if not isinstance(time, int):
        raise SaltInvocationError("'time' must be an integer")
    if not isinstance(min_compress_len, int):
        raise SaltInvocationError("'min_compress_len' must be an integer")
    conn = _connect(host, port)
    _check_stats(conn)
    return conn.add(key, value, time=time, min_compress_len=min_compress_len)


def replace(
    key,
    value,
    host=DEFAULT_HOST,
    port=DEFAULT_PORT,
    time=DEFAULT_TIME,
    min_compress_len=DEFAULT_MIN_COMPRESS_LEN,
):
    """
    Replace a key on the memcached server. This only succeeds if the key
    already exists. This is the opposite of :mod:`memcached.add
    <salt.modules.memcached.add>`

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.replace <key> <value>
    """
    if not isinstance(time, int):
        raise SaltInvocationError("'time' must be an integer")
    if not isinstance(min_compress_len, int):
        raise SaltInvocationError("'min_compress_len' must be an integer")
    conn = _connect(host, port)
    stats = conn.get_stats()
    return conn.replace(key, value, time=time, min_compress_len=min_compress_len)


def increment(key, delta=1, host=DEFAULT_HOST, port=DEFAULT_PORT):
    """
    Increment the value of a key

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.increment <key>
        salt '*' memcached.increment <key> 2
    """
    conn = _connect(host, port)
    _check_stats(conn)
    cur = get(key)

    if cur is None:
        raise CommandExecutionError(f"Key '{key}' does not exist")
    elif not isinstance(cur, int):
        raise CommandExecutionError(
            f"Value for key '{key}' must be an integer to be incremented"
        )

    try:
        return conn.incr(key, delta)
    except ValueError:
        raise SaltInvocationError("Delta value must be an integer")


incr = salt.utils.functools.alias_function(increment, "incr")


def decrement(key, delta=1, host=DEFAULT_HOST, port=DEFAULT_PORT):
    """
    Decrement the value of a key

    CLI Example:

    .. code-block:: bash

        salt '*' memcached.decrement <key>
        salt '*' memcached.decrement <key> 2
    """
    conn = _connect(host, port)
    _check_stats(conn)

    cur = get(key)
    if cur is None:
        raise CommandExecutionError(f"Key '{key}' does not exist")
    elif not isinstance(cur, int):
        raise CommandExecutionError(
            f"Value for key '{key}' must be an integer to be decremented"
        )

    try:
        return conn.decr(key, delta)
    except ValueError:
        raise SaltInvocationError("Delta value must be an integer")


decr = salt.utils.functools.alias_function(decrement, "decr")