"""Live ``slack_sdk``-backed Slack poster (design §3.3.1, §7.1 P1 — Slack first).

The :mod:`agent_team.transport.slack_adapter` module ships the §3.3.1 transport
contract with a dependency-injected ``poster`` seam: the adapter renders the
question-set into a message dict and hands it to a
``SlackPoster = Callable[[dict[str, Any]], Mapping[str, Any]]`` whose job is to
perform the real ``chat.postMessage`` and return a response carrying the message
``ts``. The foundation's default poster refuses the network so nothing ships
provisioned; this module supplies the **production** poster, backed by
``slack_sdk.WebClient``, that the P1 (Slack first) live wiring injects.

Deferred import (mirrors :func:`agent_team.graph.build_sqlite_checkpointer`):
``slack_sdk`` is an optional dependency that may be absent in pre-deploy /
test environments, so this module imports cleanly without it. The import is
deferred to the moment a live client is actually constructed, and a missing
package raises a clear :class:`RuntimeError` so a misconfigured deploy fails
loudly rather than silently.

Message-dict to ``chat.postMessage`` mapping
--------------------------------------------
The adapter's message dict (see ``SlackTransport.post_question``) carries
``channel``, ``callback_id``, ``text``, ``blocks`` and ``metadata``. Slack's
``chat.postMessage`` Web API method does **not** accept a top-level
``callback_id`` keyword argument (``callback_id`` is a legacy attachment /
interactive-component field, not a message-post parameter), so passing it
through verbatim would raise a ``TypeError`` / Slack ``invalid_arguments``.

The durable inbound key is therefore carried by ``metadata`` instead: the
adapter embeds ``question_id`` under ``metadata.event_payload.question_id``, and
``slack_adapter._extract_question_id`` reads exactly that path off an inbound
message. ``chat.postMessage`` *does* accept ``metadata``, so forwarding it
preserves the inbound mapping. The poster consequently **drops** ``callback_id``
from the postMessage kwargs and forwards only the parameters the Web API
accepts (``channel``, ``text``, ``blocks``, ``metadata``), letting ``metadata``
do the question-id round-trip the adapter relies on.
"""

from __future__ import annotations

import os
from collections.abc import Mapping
from typing import Any

from agent_team.transport.slack_adapter import SlackPoster, SlackTransport

__all__ = [
    "build_live_slack_transport",
    "build_slack_poster",
]

# Top-level ``chat.postMessage`` keyword arguments the live poster forwards.
# ``callback_id`` is deliberately excluded: it is not a postMessage parameter,
# and the durable inbound key lives in ``metadata.event_payload`` instead.
_POST_MESSAGE_KEYS = ("channel", "text", "blocks", "metadata")


def build_slack_poster(token: str | None = None, *, client: Any = None) -> SlackPoster:
    """Build a live ``slack_sdk``-backed :data:`SlackPoster` (§3.3.1, P1).

    The returned callable accepts the adapter's rendered message dict, performs
    a ``chat.postMessage``, and returns the response as a mapping carrying the
    message ``ts`` so ``SlackTransport._extract_ts`` can record the
    ``channel_ref``.

    ``client`` (optional) injects a pre-built Slack client for testability; any
    object exposing ``chat_postMessage(**kwargs)`` works. When omitted, a
    ``slack_sdk.WebClient`` is constructed lazily from ``token`` (falling back to
    the ``SLACK_BOT_TOKEN`` environment variable). The ``slack_sdk`` import is
    deferred so this module imports cleanly without the optional package; a
    missing package or a missing token raises a clear :class:`RuntimeError`.

    The poster maps the adapter's message dict to the Web API's accepted
    parameters: it forwards ``channel``, ``text``, ``blocks`` and ``metadata``
    and **drops** ``callback_id`` (not a ``chat.postMessage`` parameter — the
    ``question_id`` round-trips via ``metadata.event_payload`` instead). See the
    module docstring for the full rationale.
    """
    if client is None:
        client = _build_web_client(token)

    def _poster(message: dict[str, Any]) -> Mapping[str, Any]:
        kwargs = {key: message[key] for key in _POST_MESSAGE_KEYS if key in message}
        response = client.chat_postMessage(**kwargs)
        return _as_mapping(response)

    return _poster


def build_live_slack_transport(
    channel: str, token: str | None = None, *, client: Any = None
) -> SlackTransport:
    """Build a :class:`SlackTransport` wired to a live ``slack_sdk`` poster.

    Convenience constructor for the P1 live coordinator: equivalent to
    ``SlackTransport(channel, poster=build_slack_poster(token, client=client))``.
    See :func:`build_slack_poster` for the token / client / deferred-import
    semantics.
    """
    return SlackTransport(channel, poster=build_slack_poster(token, client=client))


def _build_web_client(token: str | None) -> Any:
    """Lazily construct a ``slack_sdk.WebClient`` (deferred optional import).

    Raises a clear :class:`RuntimeError` if ``slack_sdk`` is not installed or no
    token is resolvable (neither ``token`` nor ``SLACK_BOT_TOKEN``), so a
    misconfigured deploy fails loudly rather than silently.
    """
    try:
        from slack_sdk import WebClient
    except ImportError as exc:  # pragma: no cover - depends on optional dep
        raise RuntimeError(
            "slack_sdk is unavailable; install the 'slack_sdk' package to build "
            "a live Slack poster (P1), or inject a 'client' for testing."
        ) from exc

    resolved = token or os.environ.get("SLACK_BOT_TOKEN")
    if not resolved:
        raise RuntimeError(
            "No Slack bot token available; pass 'token' or set the "
            "SLACK_BOT_TOKEN environment variable to build a live Slack poster."
        )
    return WebClient(token=resolved)


def _as_mapping(response: Any) -> Mapping[str, Any]:
    """Coerce a ``chat_postMessage`` response to a plain mapping.

    ``slack_sdk`` returns a ``SlackResponse`` exposing the payload via ``.data``;
    if a test injects a client returning a bare mapping, accept it as-is. The
    result must carry ``ts`` so ``SlackTransport._extract_ts`` recovers the
    ``channel_ref``.
    """
    if isinstance(response, Mapping):
        return response
    data = getattr(response, "data", None)
    if isinstance(data, Mapping):
        return data
    raise TypeError(
        "Slack chat_postMessage returned an unsupported response; expected a "
        f"mapping or an object with a mapping '.data', got {type(response)!r}"
    )