"""Workflow-aware render dispatch service.

C2: extends the legacy dispatch_render path with WorkflowDefinition support.

If an OutputType has workflow_definition_id set:
  - Loads the WorkflowDefinition
  - Calls dispatch_workflow() to build + submit a Celery Canvas
  - Creates a WorkflowRun record tracking the submission

If no workflow_definition_id is set, falls back to the existing direct
task-dispatch logic in app.services.render_dispatcher (legacy path).
"""
from __future__ import annotations

import logging
from datetime import datetime

logger = logging.getLogger(__name__)


def dispatch_render_with_workflow(order_line_id: str) -> dict:
    """Dispatch a render for the given order line.

    Checks whether the associated OutputType has a WorkflowDefinition linked.
    If yes, uses the Celery Canvas workflow builder.
    If no, falls back to the legacy direct-dispatch logic.

    This function is synchronous (Celery-task-safe).
    """
    from sqlalchemy import create_engine, select
    from sqlalchemy.orm import Session, selectinload

    from app.config import settings
    from app.domains.orders.models import OrderLine
    from app.domains.rendering.models import OutputType, WorkflowDefinition, WorkflowRun

    engine = create_engine(
        settings.database_url.replace("+asyncpg", ""),
        pool_pre_ping=True,
    )

    with Session(engine) as session:
        # Load order line with its output_type
        line = session.execute(
            select(OrderLine)
            .where(OrderLine.id == order_line_id)
            .options(selectinload(OrderLine.output_type))
        ).scalar_one_or_none()

        if not line:
            raise ValueError(f"OrderLine {order_line_id} not found")

        output_type: OutputType | None = line.output_type

        if output_type is None or output_type.workflow_definition_id is None:
            # Legacy path — no workflow definition linked
            logger.info(
                "order_line %s: no workflow_definition_id, using legacy dispatch",
                order_line_id,
            )
            return _legacy_dispatch(order_line_id)

        # Load the linked WorkflowDefinition
        wf_def: WorkflowDefinition | None = session.execute(
            select(WorkflowDefinition).where(
                WorkflowDefinition.id == output_type.workflow_definition_id,
                WorkflowDefinition.is_active.is_(True),
            )
        ).scalar_one_or_none()

        if wf_def is None:
            logger.warning(
                "order_line %s: workflow_definition_id %s not found or inactive, "
                "falling back to legacy dispatch",
                order_line_id,
                output_type.workflow_definition_id,
            )
            return _legacy_dispatch(order_line_id)

        workflow_type = wf_def.config.get("type")
        params = wf_def.config.get("params", {})

        logger.info(
            "order_line %s: dispatching via WorkflowDefinition %s (type=%s)",
            order_line_id,
            wf_def.id,
            workflow_type,
        )

        from app.domains.rendering.workflow_builder import dispatch_workflow
        celery_task_id = dispatch_workflow(workflow_type, order_line_id, params)

        # Persist a WorkflowRun record
        run = WorkflowRun(
            workflow_def_id=wf_def.id,
            order_line_id=line.id,
            celery_task_id=celery_task_id,
            status="pending",
            started_at=datetime.utcnow(),
        )
        session.add(run)
        session.commit()

        return {
            "backend": "workflow",
            "workflow_type": workflow_type,
            "workflow_run_id": str(run.id),
            "celery_task_id": celery_task_id,
        }


def _legacy_dispatch(order_line_id: str) -> dict:
    """Queue render_order_line_task (the working Celery render implementation)."""
    from app.tasks.step_tasks import render_order_line_task
    render_order_line_task.delay(order_line_id)
    return {"backend": "celery", "queued": True}