import asyncio
import json
import os
from enum import Enum
from typing import List

from defence360agent.contracts.config import Core as CoreConfig


class MessageNotFoundError(Exception):
    pass


class UnknownMessage:
    """
    Used as stub for MessageType
    """

    def __init__(self):
        raise MessageNotFoundError("Message class is not found.")

    def __getattr__(self, name):
        return "Unknown"  # pragma: no cover


class MessageT:
    _subclasses = []

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls._subclasses.append(cls)

    @classmethod
    def get_subclasses(cls):
        return tuple(cls._subclasses)


class _MessageType:
    """
    Used to get specific message class. For example,
    >>> _MessageType().ConfigUpdate
    <class 'defence360agent.contracts.messages.ConfigUpdate'>
    >>> _MessageType().NotExistMessage
    <class 'defence360agent.contracts.messages.UnknownMessage'>
    >>>
    """

    def __getattr__(self, name):
        for subcls in Message.get_subclasses():
            # is is supposed that all subclasses have different names
            if subcls.__name__ == name:
                return subcls
        return UnknownMessage


MessageType = _MessageType()


class ReportTarget(Enum):
    API = "api"
    PERSISTENT_CONNECTION = "conn"


class Reportable(MessageT):
    """
    Mixin class for messages that should be sent to the server
    """

    TARGET = ReportTarget.PERSISTENT_CONNECTION

    @classmethod
    def get_subclass_with_method(cls, method: str):
        """
        Return a subclass with the same DEFAULT_METHOD as *method*.
        It can be used to detect report target from message method.
        NOTE: it is not guaranteed that the class with the *method* is unique,
              in this case the first subclass found is returned, but
              it is tested that all such subclasses have the same TARGET.
        """
        for subclass in cls.__subclasses__():
            if method == getattr(subclass, "DEFAULT_METHOD"):
                return subclass
        return None  # pragma: no cover


class Received(MessageT):
    """
    Mixin class for messages received from the server.

    These messages are created in the client360 plugin when receiving a
    request from imunify360.cloudlinux.com.
    """

    @classmethod
    def get_subclass_with_action(cls, action: str):
        for subclass in cls.__subclasses__():
            received_actions = getattr(subclass, "RECEIVED_ACTIONS", []) or [
                getattr(subclass, "DEFAULT_METHOD")
            ]
            if action in received_actions:
                return subclass
        raise MessageNotFoundError(
            'Message class is not found for "{}" action'.format(action)
        )


class Lockable(MessageT):
    _lock = None

    @classmethod
    async def acquire(cls) -> None:
        if cls._lock is None:
            cls._lock = asyncio.Lock()
        await cls._lock.acquire()

    @classmethod
    def locked(cls) -> bool:
        return cls._lock is not None and cls._lock.locked()

    @classmethod
    def release(cls) -> None:
        if cls._lock is not None:
            cls._lock.release()


class Message(dict, MessageT):
    """
    Base class for messages to be passed as
    a parameter to plugins.MessageSink.process_message()
    """

    # Default method='...' to send to the Server
    DEFAULT_METHOD = ""
    PRIORITY = 10
    PROCESSING_TIME_THRESHOLD = 60  # 1 min
    #: fold collections' repr with more than the threshold number of items
    _FOLD_LIST_THRESHOLD = 100
    #: shorten strings longer than the threshold characters
    _SHORTEN_STR_THRESHOLD = 320

    def __init__(self, *args, **kwargs) -> None:
        if self.DEFAULT_METHOD:
            self["method"] = self.DEFAULT_METHOD
        super(Message, self).__init__(*args, **kwargs)

    @property
    def payload(self):
        return {k: v for k, v in self.items() if k != "method"}

    def __getattr__(self, name):
        """
        Called when an attribute lookup has not found the attribute
        in the usual places

        A shortcut to access an item from dict
        """
        try:
            return self[name]
        except KeyError as exc:
            raise AttributeError(name) from exc

    def __repr__(self):
        """Render for logs: collections with more than _FOLD_LIST_THRESHOLD
        items are collapsed to a count and strings longer than
        _SHORTEN_STR_THRESHOLD are shortened, recursively through nested
        payloads, so a single message cannot flood the log."""
        folded_msg = {
            k: _fold_repr_value(
                v,
                fold_limit=self._FOLD_LIST_THRESHOLD,
                str_limit=self._SHORTEN_STR_THRESHOLD,
            )
            for k, v in self.items()
        }
        return "{}({})".format(self.__class__.__qualname__, folded_msg)

    def __str__(self):
        return self.__repr__()


class MessageList(Message):
    def __init__(self, msg_list):
        super().__init__(list=msg_list)

    @property
    def payload(self):
        return self.list


class ShortenReprListMixin:
    """
    Do not flood console.log with large sequences
    The method collapses messages that are a list.
    Instead of showing all the elements of the message,
    their number will be displayed.
    """

    def __repr__(self: dict):  # type: ignore
        return "{}({})".format(
            self.__class__.__qualname__,
            "<{} item(s)>".format(len(self.get("items", []))),
        )


class Accumulatable(Message):
    """Messages of this class will be grouped into a list of LIST_CLASS
    message instance by Accumulate plugin.  Messages whose do_accumulate()
    call returns False will not be added to list."""

    LIST_CLASS = MessageList

    def do_accumulate(self) -> bool:
        """Return True if this message is worth collecting, False otherwise."""
        return True


class ServerConnected(Message):
    pass


# alias (for better client code readability)
class ServerReconnected(ServerConnected):
    pass


class Ping(Message, Reportable):
    """
    Will send this message on connected, reconnected events
    to provide central server with agent version
    """

    DEFAULT_METHOD = "PING"
    PRIORITY = 0

    def __init__(self):
        super().__init__()
        self["version"] = CoreConfig.VERSION


class Ack(Message, Reportable):
    """
    Notify Server that a persistent message with *seq_number* has been
    received by Agent.

    """

    DEFAULT_METHOD = "ACK"

    def __init__(self, seq_number, **kwargs):
        super().__init__(**kwargs)
        self["_meta"] = dict(per_seq=seq_number)


class Noop(Message):
    """
    Sending NOOP to the agent to track the message in agent logs.
    """

    DEFAULT_METHOD = "NOOP"


class ServerConfig(Message, Reportable):
    """
    Information about server environment
    """

    DEFAULT_METHOD = "SERVER_CONFIG"
    TARGET = ReportTarget.API

    def __repr__(self):
        return "{}()".format(self.__class__.__qualname__)


class WpSecurityPluginStats(Message, Reportable):
    DEFAULT_METHOD = "WP_SECURITY_PLUGIN_STATS"
    TARGET = ReportTarget.API


class DomainList(Message, Reportable):
    """
    Information about server domains
    """

    DEFAULT_METHOD = "DOMAIN_LIST"
    TARGET = ReportTarget.API

    def __repr__(self):
        return "{}()".format(self.__class__.__qualname__)


class FilesUpdated(Message):
    """
    To consume products of files.update()
    """

    def __init__(self, files_type, files_index):
        """
        :param files_type: files.Type
        :param files_index: files.LocalIndex
        """
        # explicit is better than implicit
        self["files_type"] = files_type
        self["files_index"] = files_index

    def __repr__(self):
        """
        Do not flood console.log with large sequences
        """
        return "{}({{'files_type':'{}', 'files_index':{}}})".format(
            self.__class__.__qualname__,
            self["files_type"],
            self["files_index"],
        )


class UpdateFiles(Message, Received):
    """
    Update files by getting message from the server
    """

    DEFAULT_METHOD = "UPDATE"


class ConfigUpdate(Message):
    DEFAULT_METHOD = "CONFIG_UPDATE"


class Reject(Exception):
    """
    Kinda message filtering facility.
    Raised in order to stop message processing through plugins.
    Takes reason of reject as argument.
    """

    pass


class Health(Message):
    DEFAULT_METHOD = "HEALTH"


class CommandInvoke(Message, Reportable):
    DEFAULT_METHOD = "COMMAND_INVOKE"


class ScanFailed(Message, Reportable):
    DEFAULT_METHOD = "SCAN_FAILED"


class CleanupFailed(Message, Reportable):
    DEFAULT_METHOD = "CLEANUP_FAILED"


class RestoreFromBackupTask(Message):
    """
    Creates a task to restore files from backup
    """

    DEFAULT_METHOD = "MALWARE_RESTORE_FROM_BACKUP"


class cPanelEvent(Message):
    DEFAULT_METHOD = "PANEL_EVENT"
    ALLOWED_FIELDS = {
        "new_pkg",
        "plan",
        "exclude",
        "imunify360_proactive",
        "imunify360_av",
    }

    @classmethod
    def from_hook_event(
        cls, username: str, hook: str, ts: float, fields: dict
    ):
        data = {
            k.lower(): v
            for k, v in fields.items()
            if k.lower() in cls.ALLOWED_FIELDS
        }
        # Check for user rename
        if (
            hook == "Modify"
            and "user" in fields
            and "newuser" in fields
            and fields["user"] != fields["newuser"]
        ):
            data["old_username"] = fields["user"]
        return cls(
            {
                "username": username,
                "hook": hook,
                "data": data,
                "timestamp": ts,
            }
        )


class IContactSent(Message, Reportable):
    DEFAULT_METHOD = "ICONTACT_SENT"


def _shorten_str(s: str, limit: int) -> str:
    """Shorten *s* string if its length exceeds *limit*."""
    assert limit > 4
    return (
        f"{s[: limit // 2 - 1]}...{s[-limit // 2 + 2 :]}"
        if len(s) > limit
        else s
    )


def _fold_repr_value(value, *, fold_limit: int, str_limit: int):
    if isinstance(value, str):
        return _shorten_str(value, str_limit)
    if isinstance(value, dict):
        if len(value) > fold_limit:
            return "<{} item(s)>".format(len(value))
        return {
            k: _fold_repr_value(v, fold_limit=fold_limit, str_limit=str_limit)
            for k, v in value.items()
        }
    if isinstance(value, (list, tuple, set, frozenset)):
        if len(value) > fold_limit:
            return "<{} item(s)>".format(len(value))
        return type(value)(
            _fold_repr_value(v, fold_limit=fold_limit, str_limit=str_limit)
            for v in value
        )
    return value


class BackupInfo(Message, Reportable):
    """Information about enabled backup backend"""

    DEFAULT_METHOD = "BACKUP_INFO"


class MDSReportList(ShortenReprListMixin, Message, Reportable):
    DEFAULT_METHOD = "MDS_SCAN_LIST"


class MDSReport(Accumulatable):
    LIST_CLASS = MDSReportList


# Target serialized size per outgoing message chunk. Kept far below the
# 10 MB NATS max_payload so envelope overhead and size-estimate drift cannot
# push a chunk over the transport limit; the transport keeps a split-on-
# overflow safety net for the rare cases this estimate misses.
MAX_MESSAGE_SIZE = int(
    os.environ.get("IMUNIFY360_MAX_MESSAGE_SIZE", 1024 * 1024)
)


def serialized_size(obj) -> int:
    from defence360agent.utils.json import ServerJSONEncoder

    try:
        return len(json.dumps(obj, cls=ServerJSONEncoder).encode())
    except (TypeError, ValueError):
        return len(repr(obj).encode())


def estimate_size(obj) -> int:
    """Upper bound on obj's JSON byte size as sent on the wire (ensure_ascii),
    biased to never undercount. Far cheaper than a full ``serialized_size`` per
    call on big scans: JSON-native values are measured structurally without
    building the encoded string, and printable-ASCII strings (the common path
    for file paths/snippets) are counted with C-level ``str`` ops. Non-native
    values (peewee Models, IPs, ...) fall back to the exact ``serialized_size``
    — their ``repr`` would wildly undercount the ServerJSONEncoder output. The
    transport keeps a split-on-overflow net for the rare drift this leaves."""
    if obj is None:
        return 4
    if isinstance(obj, bool):
        return 5
    if isinstance(obj, int):
        return max(20, len(str(obj)) + 1)
    if isinstance(obj, float):
        return 24
    if isinstance(obj, str):
        if obj.isascii() and obj.isprintable():
            return len(obj) + 2 + obj.count('"') + obj.count("\\")
        return len(json.dumps(obj))
    if isinstance(obj, (list, tuple)):
        return 2 + sum(estimate_size(v) + 1 for v in obj)
    if isinstance(obj, dict):
        return 2 + sum(
            estimate_size(k if isinstance(k, str) else str(k))
            + 1
            + estimate_size(v)
            + 1
            for k, v in obj.items()
        )
    return serialized_size(obj)


class Splittable:
    """
    A message list could be split into multiple batches.
    The split is possible for a list itself along with internal resources.
    """

    LIST_SIZE = None

    BATCH_SIZE = None
    BATCH_FIELD = None

    @classmethod
    def _max_message_size(cls) -> int:
        return MAX_MESSAGE_SIZE

    @classmethod
    def _split_items(cls, messages: List[Accumulatable]):
        """
        Split messages' internal lists of things into batches.
        A field that is meant to split is defined by `BATCH_FIELD`.
        """
        if cls.BATCH_FIELD and cls.BATCH_SIZE:
            for message in messages:
                if (items := message.get(cls.BATCH_FIELD)) is None:
                    yield message
                else:
                    message_class = type(message)
                    for batch in cls._size_bounded_batches(items, message):
                        data = message.copy()
                        data[cls.BATCH_FIELD] = batch
                        new_message = message_class(data)
                        yield new_message
        else:
            yield from iter(messages)

    @classmethod
    def _unit_size(cls, unit, is_dict: bool, message) -> int:
        """Serialized byte cost of one BATCH_FIELD unit. Subclasses override
        to also count data paired with the unit in sibling fields of the
        message (e.g. a per-hit cleanup result), so those bytes are not
        excluded from the byte budget."""
        return estimate_size({unit[0]: unit[1]} if is_dict else unit)

    @classmethod
    def _size_bounded_batches(cls, items, message):
        """Pack `items` into batches bounded by both the byte budget and the
        `BATCH_SIZE` count. A single element larger than the budget is emitted
        alone rather than dropped."""
        budget = cls._max_message_size()
        is_dict = isinstance(items, dict)
        units = list(items.items()) if is_dict else items

        def build(buffer):
            return dict(buffer) if is_dict else list(buffer)

        buffer = []
        size = 0
        for unit in units:
            unit_size = cls._unit_size(unit, is_dict, message)
            if buffer and (
                size + unit_size > budget or len(buffer) >= cls.BATCH_SIZE
            ):
                yield build(buffer)
                buffer, size = [], 0
            buffer.append(unit)
            size += unit_size
        if buffer:
            yield build(buffer)

    @classmethod
    def batched(cls, messages: List[Accumulatable]):
        list_size = cls.LIST_SIZE or len(messages)
        budget = cls._max_message_size()
        buffer = []
        size = 0
        for message in cls._split_items(messages):
            message_size = estimate_size(message)
            if buffer and (
                size + message_size > budget or len(buffer) >= list_size
            ):
                yield buffer
                buffer, size = [], 0
            buffer.append(message)
            size += message_size
        if buffer:
            yield buffer


class EnsureServiceState(Message):
    """Ensure the service has the appropriate status"""

    DEFAULT_METHOD = "ENSURE_SERVICE_STATE"


class SensorWordpressIncidentList(MessageList, Reportable):
    """Aggregated incident list"""

    DEFAULT_METHOD = "INCIDENT_LIST"


class WordpressPluginAction(Message):
    DEFAULT_METHOD = "WP_SECURITY_PLUGIN_ACTION"


class WordpressPluginTelemetry(Message, Reportable):
    """
    Information about telemetry event related to Imunify Security WordPress plugin
    """

    DEFAULT_METHOD = "WP_SECURITY_PLUGIN_EVENT"
    TARGET = ReportTarget.API

    def __repr__(self):
        return "{}()".format(self.__class__.__qualname__)


class WPRuleDisabled(Message, Reportable):
    """WordPress protection rule disabled."""

    DEFAULT_METHOD = "RULE_DISABLED"


class WPRuleEnabled(Message, Reportable):
    """WordPress protection rule re-enabled."""

    DEFAULT_METHOD = "RULE_ENABLED"


class GeneralMetrics(MessageList, Reportable):
    DEFAULT_METHOD = "GENERAL_METRICS"