"""Dispatch participant client (D4 / 08_DECISIONS D3-D4, INTER_MODULE_CONTRACT §2).

LegacyHUB joins the shared platform bus as participant ``legacyhub``. This module
publishes events (``LegacyhubDocumentIndexed``, ``AssetDerivativeReady``) to the
``dispatch-api`` over HTTP with an ``X-API-Key``, and handles inbound command
events delivered to the module's HTTP inbox.

Design notes:
- Publishing is best-effort and happens AFTER the DB commit; a dispatch outage
  never fails document processing. Event ids are deterministic (uuid5 over the
  business key) so re-emits are idempotent for downstream consumers.
- The body carries JSON only - asset ids and object-storage refs, never binary
  payloads, presigned URLs, or local filesystem paths (10 §7).
- Internal Celery+Redis stays the intra-module queue; this is the inter-module
  channel and the two are not conflated (D3).
"""

from __future__ import annotations

import time
import uuid
from datetime import UTC, datetime
from typing import Any

import httpx

from app import __version__
from app.config import settings
from app.logging_config import get_logger

logger = get_logger(__name__)

# Stable namespace for deterministic (idempotent) event ids.
_DISPATCH_NAMESPACE = uuid.UUID("6f1c8d2e-2a4b-5c6d-8e9f-0a1b2c3d4e5f")

EVENT_DOCUMENT_INDEXED = "LegacyhubDocumentIndexed"
EVENT_ASSET_DERIVATIVE_READY = "AssetDerivativeReady"


def deterministic_event_id(*parts: Any) -> str:
    return str(uuid.uuid5(_DISPATCH_NAMESPACE, ":".join(str(p) for p in parts)))


def _card_uid(value: str) -> str:
    """Envelope card_uid must be a UUID (dispatch_api/models.py). Business ids
    that are already UUIDs pass through; ULID-style asset ids map to a stable
    uuid5 so re-emits keep the same card."""
    try:
        return str(uuid.UUID(str(value)))
    except ValueError:
        return str(uuid.uuid5(_DISPATCH_NAMESPACE, str(value)))


def build_envelope(
    message_type: str,
    card_uid: str,
    body: dict[str, Any],
    *,
    event_id: str | None = None,
    message_id: str | None = None,
    created_at: str | None = None,
) -> dict[str, Any]:
    """Build the dispatch JSON envelope (02 §2.4 + platform doc 23 profile).

    The card block mirrors the mandatory DispatchCard fields of the platform
    pydantic model (dispatch_api/models.py): int schema_version/state_code,
    task_id 0 for out-of-ticket events, int4-safe epoch-second
    sequence_number; the event payload nests under card.event untouched.
    """
    now = created_at or datetime.now(tz=UTC).isoformat()
    uid = _card_uid(card_uid)
    return {
        "message_id": message_id or str(uuid.uuid4()),
        "event_id": event_id or str(uuid.uuid4()),
        "card_uid": uid,
        "task_id": 0,
        "message_type": message_type,
        "participant_code": settings.dispatch_participant_code,
        "created_at": now,
        "card": {
            "schema_version": 1,
            "card_uid": uid,
            "task_id": 0,
            "sequence_number": int(time.time()),
            "created_at": now,
            "updated_at": now,
            "state_code": 0,
            "specialist_status": "n/a",
            "event": body,
        },
        "media_files": [],
        "media_file_count": 0,
        "local_delivery_status": {},
    }


def publish(
    message_type: str,
    card_uid: str,
    body: dict[str, Any],
    *,
    event_id: str | None = None,
) -> dict[str, Any] | None:
    """Publish one envelope to dispatch-api. Best-effort; returns the envelope on
    success, ``None`` when disabled or on a (logged) transport failure."""
    if not settings.dispatch_enabled:
        logger.info("dispatch.disabled", message_type=message_type, card_uid=str(card_uid))
        return None
    if not settings.dispatch_api_url:
        logger.warning("dispatch.no_url", message_type=message_type)
        return None

    envelope = build_envelope(message_type, card_uid, body, event_id=event_id)
    try:
        res = httpx.post(
            f"{settings.dispatch_api_url.rstrip('/')}/dispatch/envelopes",
            json=envelope,
            headers={"X-API-Key": settings.dispatch_api_key},
            timeout=settings.dispatch_timeout_seconds,
        )
        res.raise_for_status()
    except Exception as exc:  # noqa: BLE001 - dispatch must never break ingestion
        logger.warning("dispatch.publish_failed", message_type=message_type, error=str(exc))
        return None

    logger.info("dispatch.published", message_type=message_type, event_id=envelope["event_id"])
    return envelope


def publish_document_indexed(
    document_id: uuid.UUID | str, *, asset_metadata: dict[str, Any] | None = None
) -> dict[str, Any] | None:
    body: dict[str, Any] = {"document_id": str(document_id)}
    card_uid = str(document_id)
    if asset_metadata:
        for key in ("asset_id", "owner_module", "owner_record_type", "owner_record_id", "manifest_version"):
            if asset_metadata.get(key):
                body[key] = asset_metadata[key]
        if asset_metadata.get("asset_id"):
            card_uid = str(asset_metadata["asset_id"])
    event_id = deterministic_event_id(EVENT_DOCUMENT_INDEXED, card_uid)
    return publish(EVENT_DOCUMENT_INDEXED, card_uid, body, event_id=event_id)


def publish_derivative_ready(
    asset_metadata: dict[str, Any],
    *,
    derivative_type: str = "ocr_markdown",
    content_type: str = "text/markdown",
) -> dict[str, Any] | None:
    asset_id = asset_metadata.get("asset_id")
    if not asset_id:
        return None
    body = {
        "event_type": EVENT_ASSET_DERIVATIVE_READY,  # canonical body-level type (10 §7)
        "asset_id": asset_id,
        "owner_module": asset_metadata.get("owner_module"),
        "owner_record_type": asset_metadata.get("owner_record_type"),
        "owner_record_id": asset_metadata.get("owner_record_id"),
        "derivative_type": derivative_type,
        "content_type": content_type,
        "source_asset_sha256": asset_metadata.get("sha256"),
        "generator": {"pipeline": "legacyhub", "version": __version__},
    }
    event_id = deterministic_event_id(EVENT_ASSET_DERIVATIVE_READY, asset_id, derivative_type)
    return publish(EVENT_ASSET_DERIVATIVE_READY, str(asset_id), body, event_id=event_id)


def emit_after_indexing(document_id: uuid.UUID) -> None:
    """Emit indexing events after a document reaches INDEXING_COMPLETED.

    Called at the tail of the pipeline (after commit). No-op when dispatch is
    disabled. Always best-effort.
    """
    if not settings.dispatch_enabled:
        return
    from app.ingestion.knowledge_ingest import (  # noqa: PLC0415
        load_asset_ingest_options,
        load_asset_metadata_for_document,
    )

    meta = load_asset_metadata_for_document(document_id) or {}
    publish_document_indexed(document_id, asset_metadata=meta or None)

    if meta.get("asset_id"):
        options = load_asset_ingest_options(document_id)
        if options.get("emit_events", True):
            publish_derivative_ready(meta)


# ---- Inbound (HTTP inbox) ----

def handle_inbox_message(envelope: dict[str, Any]) -> dict[str, Any]:
    """Process one inbound dispatch envelope idempotently.

    Idempotency: an ``audit_log`` row keyed on ``event_id`` marks a processed
    event; a repeat delivery is acknowledged without reprocessing (at-least-once
    delivery, 10 §7).
    """
    from sqlalchemy import select  # noqa: PLC0415

    from app.db.audit import record_audit  # noqa: PLC0415
    from app.db.models import AuditLog  # noqa: PLC0415
    from app.db.session import session_scope  # noqa: PLC0415

    event_id = str(envelope.get("event_id") or "")
    message_type = str(envelope.get("message_type") or "")
    # Doc 23 profile nests the payload under card.event; legacy senders used a
    # root-level body. Accept both at this external boundary.
    card = envelope.get("card") or {}
    body = card.get("event") or envelope.get("body") or {}

    with session_scope() as db:
        already = db.execute(
            select(AuditLog).where(
                AuditLog.action == "dispatch.inbox.processed",
                AuditLog.entity_id == event_id,
            )
        ).first()
        if already is not None:
            return {"status": "confirmed", "event_id": event_id, "duplicate": True}

        handled = _handle_inbox(message_type, body)
        record_audit(
            db,
            action="dispatch.inbox.processed",
            actor=f"participant:{envelope.get('participant_code')}",
            entity_type="dispatch_event",
            entity_id=event_id,
            details={"message_type": message_type, "handled": handled},
        )
    return {"status": "confirmed", "event_id": event_id, "handled": handled}


def _handle_inbox(message_type: str, body: dict[str, Any]) -> bool:
    """Return True if the message triggered an action."""
    if message_type in ("ReindexRequested", "LegacyhubReindexRequested"):
        return _enqueue_reindex(body)
    if message_type in ("AssetTombstoned", "AssetDeleted"):
        return _purge_projection(body)
    logger.info("dispatch.inbox.ignored", message_type=message_type)
    return False


def _purge_projection(body: dict[str, Any]) -> bool:
    asset_id = body.get("asset_id")
    if not asset_id:
        logger.warning("dispatch.tombstone.no_asset_id")
        return False
    from app.indexing.projection import purge_projection_by_asset_id  # noqa: PLC0415

    result = purge_projection_by_asset_id(str(asset_id))
    return bool(result.get("purged"))


def _enqueue_reindex(body: dict[str, Any]) -> bool:
    from sqlalchemy import select  # noqa: PLC0415

    from app.db.models import AssetIngestJob  # noqa: PLC0415
    from app.db.session import session_scope  # noqa: PLC0415

    document_id = body.get("document_id")
    asset_id = body.get("asset_id")
    if document_id is None and asset_id is not None:
        with session_scope() as db:
            job = (
                db.execute(
                    select(AssetIngestJob)
                    .where(AssetIngestJob.asset_id == str(asset_id))
                    .order_by(AssetIngestJob.created_at.desc())
                )
                .scalars()
                .first()
            )
            document_id = str(job.document_id) if job is not None else None
    if document_id is None:
        logger.warning("dispatch.reindex.unresolved", asset_id=asset_id)
        return False

    from app.db.audit import record_audit  # noqa: PLC0415
    from app.db.session import session_scope  # noqa: PLC0415

    with session_scope() as db:
        record_audit(
            db,
            action="asset.reindex",
            actor="dispatch",
            entity_type="document",
            entity_id=str(document_id),
            details={"asset_id": asset_id},
        )

    from app.workers.tasks import process_document  # noqa: PLC0415

    process_document.delay(str(document_id), str(uuid.uuid4()))
    logger.info("dispatch.reindex.enqueued", document_id=str(document_id))
    return True


__all__ = [
    "EVENT_ASSET_DERIVATIVE_READY",
    "EVENT_DOCUMENT_INDEXED",
    "build_envelope",
    "deterministic_event_id",
    "emit_after_indexing",
    "handle_inbox_message",
    "publish",
    "publish_derivative_ready",
    "publish_document_indexed",
]