"""Message templates for websocket commands."""
from __future__ import annotations

from functools import lru_cache
import logging
from typing import TYPE_CHECKING, Any, Final, cast

import voluptuous as vol

from homeassistant.const import (
    COMPRESSED_STATE_ATTRIBUTES,
    COMPRESSED_STATE_CONTEXT,
    COMPRESSED_STATE_LAST_CHANGED,
    COMPRESSED_STATE_LAST_UPDATED,
    COMPRESSED_STATE_STATE,
)
from homeassistant.core import Event, State
from homeassistant.helpers import config_validation as cv
from homeassistant.helpers.json import JSON_DUMP, find_paths_unserializable_data
from homeassistant.util.json import format_unserializable_data

from . import const

_LOGGER: Final = logging.getLogger(__name__)

# Minimal requirements of a message
MINIMAL_MESSAGE_SCHEMA: Final = vol.Schema(
    {vol.Required("id"): cv.positive_int, vol.Required("type"): cv.string},
    extra=vol.ALLOW_EXTRA,
)

# Base schema to extend by message handlers
BASE_COMMAND_MESSAGE_SCHEMA: Final = vol.Schema({vol.Required("id"): cv.positive_int})

IDEN_TEMPLATE: Final = "__IDEN__"
IDEN_JSON_TEMPLATE: Final = '"__IDEN__"'

STATE_DIFF_ADDITIONS = "+"
STATE_DIFF_REMOVALS = "-"

ENTITY_EVENT_ADD = "a"
ENTITY_EVENT_REMOVE = "r"
ENTITY_EVENT_CHANGE = "c"


def result_message(iden: int, result: Any = None) -> dict[str, Any]:
    """Return a success result message."""
    return {"id": iden, "type": const.TYPE_RESULT, "success": True, "result": result}


def construct_result_message(iden: int, payload: str) -> str:
    """Construct a success result message JSON."""
    iden_str = str(iden)
    return f'{{"id":{iden_str},"type":"result","success":true,"result":{payload}}}'


def error_message(iden: int | None, code: str, message: str) -> dict[str, Any]:
    """Return an error result message."""
    return {
        "id": iden,
        "type": const.TYPE_RESULT,
        "success": False,
        "error": {"code": code, "message": message},
    }


def construct_event_message(iden: int, payload: str) -> str:
    """Construct an event message JSON."""
    iden_str = str(iden)
    return f'{{"id":{iden_str},"type":"event","event":{payload}}}'


def event_message(iden: int, event: Any) -> dict[str, Any]:
    """Return an event message."""
    return {"id": iden, "type": "event", "event": event}


def cached_event_message(iden: int, event: Event) -> str:
    """Return an event message.

    Serialize to json once per message.

    Since we can have many clients connected that are
    all getting many of the same events (mostly state changed)
    we can avoid serializing the same data for each connection.
    """
    return _cached_event_message(event).replace(IDEN_JSON_TEMPLATE, str(iden), 1)


@lru_cache(maxsize=128)
def _cached_event_message(event: Event) -> str:
    """Cache and serialize the event to json.

    The IDEN_TEMPLATE is used which will be replaced
    with the actual iden in cached_event_message
    """
    return message_to_json({"id": IDEN_TEMPLATE, "type": "event", "event": event})


def cached_state_diff_message(iden: int, event: Event) -> str:
    """Return an event message.

    Serialize to json once per message.

    Since we can have many clients connected that are
    all getting many of the same events (mostly state changed)
    we can avoid serializing the same data for each connection.
    """
    return _cached_state_diff_message(event).replace(IDEN_JSON_TEMPLATE, str(iden), 1)


@lru_cache(maxsize=128)
def _cached_state_diff_message(event: Event) -> str:
    """Cache and serialize the event to json.

    The IDEN_TEMPLATE is used which will be replaced
    with the actual iden in cached_event_message
    """
    return message_to_json(
        {"id": IDEN_TEMPLATE, "type": "event", "event": _state_diff_event(event)}
    )


def _state_diff_event(event: Event) -> dict:
    """Convert a state_changed event to the minimal version.

    State update example

    {
        "a": {entity_id: compressed_state,…}
        "c": {entity_id: diff,…}
        "r": [entity_id,…]
    }
    """
    if (event_new_state := event.data["new_state"]) is None:
        return {ENTITY_EVENT_REMOVE: [event.data["entity_id"]]}
    if TYPE_CHECKING:
        event_new_state = cast(State, event_new_state)
    if (event_old_state := event.data["old_state"]) is None:
        return {
            ENTITY_EVENT_ADD: {
                event_new_state.entity_id: event_new_state.as_compressed_state()
            }
        }
    if TYPE_CHECKING:
        event_old_state = cast(State, event_old_state)
    return _state_diff(event_old_state, event_new_state)


def _state_diff(
    old_state: State, new_state: State
) -> dict[str, dict[str, dict[str, dict[str, str | list[str]]]]]:
    """Create a diff dict that can be used to overlay changes."""
    additions: dict[str, Any] = {}
    diff: dict[str, dict[str, Any]] = {STATE_DIFF_ADDITIONS: additions}
    new_state_context = new_state.context
    old_state_context = old_state.context
    if old_state.state != new_state.state:
        additions[COMPRESSED_STATE_STATE] = new_state.state
    if old_state.last_changed != new_state.last_changed:
        additions[COMPRESSED_STATE_LAST_CHANGED] = new_state.last_changed.timestamp()
    elif old_state.last_updated != new_state.last_updated:
        additions[COMPRESSED_STATE_LAST_UPDATED] = new_state.last_updated.timestamp()
    if old_state_context.parent_id != new_state_context.parent_id:
        additions[COMPRESSED_STATE_CONTEXT] = {"parent_id": new_state_context.parent_id}
    if old_state_context.user_id != new_state_context.user_id:
        if COMPRESSED_STATE_CONTEXT in additions:
            additions[COMPRESSED_STATE_CONTEXT]["user_id"] = new_state_context.user_id
        else:
            additions[COMPRESSED_STATE_CONTEXT] = {"user_id": new_state_context.user_id}
    if old_state_context.id != new_state_context.id:
        if COMPRESSED_STATE_CONTEXT in additions:
            additions[COMPRESSED_STATE_CONTEXT]["id"] = new_state_context.id
        else:
            additions[COMPRESSED_STATE_CONTEXT] = new_state_context.id
    if (old_attributes := old_state.attributes) != (
        new_attributes := new_state.attributes
    ):
        for key, value in new_attributes.items():
            if old_attributes.get(key) != value:
                additions.setdefault(COMPRESSED_STATE_ATTRIBUTES, {})[key] = value
        if removed := set(old_attributes).difference(new_attributes):
            # sets are not JSON serializable by default so we convert to list
            # here if there are any values to avoid jumping into the json_encoder_default
            # for every state diff with a removed attribute
            diff[STATE_DIFF_REMOVALS] = {COMPRESSED_STATE_ATTRIBUTES: list(removed)}
    return {ENTITY_EVENT_CHANGE: {new_state.entity_id: diff}}


def message_to_json(message: dict[str, Any]) -> str:
    """Serialize a websocket message to json."""
    try:
        return JSON_DUMP(message)
    except (ValueError, TypeError):
        _LOGGER.error(
            "Unable to serialize to JSON. Bad data found at %s",
            format_unserializable_data(
                find_paths_unserializable_data(message, dump=JSON_DUMP)
            ),
        )
        return JSON_DUMP(
            error_message(
                message["id"], const.ERR_UNKNOWN_ERROR, "Invalid JSON in response"
            )
        )
