from __future__ import annotations

from sqlalchemy import case, or_, select
from sqlalchemy.orm import Session

from govoplan_core.auth import ApiPrincipal
from govoplan_core.core.workflows import (
    WorkflowCurrentStepResolution,
    WorkflowInstanceRef,
    WorkflowStandardStartRequest,
)
from govoplan_workflow_engine.backend.db.models import (
    WorkflowDefinition,
    WorkflowDefinitionRevision,
    WorkflowInstance,
    WorkflowInstanceStep,
)
from govoplan_workflow_engine.backend.instance_service import (
    get_instance as get_workflow_instance,
    resolve_step,
    start_instance,
)
from govoplan_workflow_engine.backend.schemas import (
    WorkflowInstanceStartRequest,
    WorkflowStepActionRequest,
)


class SqlWorkflowOrchestrationProvider:
    def __init__(self, *, registry: object | None = None) -> None:
        self._registry = registry

    def start_standard(
        self,
        session: object,
        principal: object,
        *,
        request: WorkflowStandardStartRequest,
    ) -> WorkflowInstanceRef:
        sql_session = _session(session)
        api_principal = _principal(principal)
        definition = _active_standard(
            sql_session,
            tenant_id=request.tenant_id,
            origin_module_id=request.origin_module_id,
            definition_key=request.definition_key,
        )
        instance, replayed = start_instance(
            sql_session,
            tenant_id=request.tenant_id,
            definition_id=definition.id,
            actor_id=request.actor_id,
            principal=api_principal,
            registry=self._registry,
            payload=WorkflowInstanceStartRequest(
                idempotency_key=request.idempotency_key,
                input=dict(request.input),
                correlation_id=request.correlation_id,
            ),
            start_origin=request.start_origin,
        )
        return _instance_ref(sql_session, instance, replayed=replayed)

    def resolve_current_step(
        self,
        session: object,
        principal: object,
        *,
        tenant_id: str,
        instance_id: str,
        resolution: WorkflowCurrentStepResolution,
    ) -> WorkflowInstanceRef:
        sql_session = _session(session)
        api_principal = _principal(principal)
        instance = get_workflow_instance(
            sql_session,
            tenant_id=tenant_id,
            instance_id=instance_id,
        )
        step_id = instance.current_step_id
        if step_id is None:
            raise ValueError("Workflow instance has no current waiting step.")
        if (
            resolution.expected_step_id is not None
            and resolution.expected_step_id != step_id
        ):
            raise ValueError("Workflow current step changed; reload and retry.")
        resolved = resolve_step(
            sql_session,
            tenant_id=tenant_id,
            instance_id=instance_id,
            step_id=step_id,
            actor_id=resolution.actor_id,
            principal=api_principal,
            registry=self._registry,
            payload=WorkflowStepActionRequest(
                action=resolution.action,  # type: ignore[arg-type]
                output=dict(resolution.output),
                evidence=list(resolution.evidence),
                comment=resolution.comment,
            ),
        )
        return _instance_ref(sql_session, resolved)

    def get_instance(
        self,
        session: object,
        *,
        tenant_id: str,
        instance_id: str,
    ) -> WorkflowInstanceRef:
        sql_session = _session(session)
        instance = get_workflow_instance(
            sql_session,
            tenant_id=tenant_id,
            instance_id=instance_id,
        )
        return _instance_ref(sql_session, instance)


def _active_standard(
    session: Session,
    *,
    tenant_id: str,
    origin_module_id: str,
    definition_key: str,
) -> WorkflowDefinition:
    definition = session.scalar(
        select(WorkflowDefinition)
        .where(
            or_(
                WorkflowDefinition.tenant_id == tenant_id,
                WorkflowDefinition.tenant_id.is_(None),
            ),
            WorkflowDefinition.standard_origin_module_id == origin_module_id,
            WorkflowDefinition.standard_definition_key == definition_key,
            WorkflowDefinition.status == "active",
            WorkflowDefinition.active_revision.is_not(None),
            WorkflowDefinition.deleted_at.is_(None),
        )
        .order_by(
            case(
                (WorkflowDefinition.tenant_id == tenant_id, 0),
                else_=1,
            ),
            WorkflowDefinition.updated_at.desc(),
        )
    )
    if definition is None:
        raise ValueError(
            f"Active Workflow standard is unavailable: "
            f"{origin_module_id}/{definition_key}."
        )
    return definition


def _instance_ref(
    session: Session,
    instance: WorkflowInstance,
    *,
    replayed: bool = False,
) -> WorkflowInstanceRef:
    revision = session.get(
        WorkflowDefinitionRevision,
        instance.definition_revision_id,
    )
    if revision is None:
        raise ValueError("Workflow instance revision is unavailable.")
    step = (
        session.get(WorkflowInstanceStep, instance.current_step_id)
        if instance.current_step_id
        else None
    )
    return WorkflowInstanceRef(
        id=instance.id,
        tenant_id=instance.tenant_id,
        definition_id=instance.definition_id,
        definition_revision_id=instance.definition_revision_id,
        definition_revision=revision.revision,
        definition_hash=revision.content_hash,
        status=instance.status,
        current_step_id=instance.current_step_id,
        current_node_id=step.node_id if step is not None else None,
        replayed=replayed,
    )


def _session(value: object) -> Session:
    if not isinstance(value, Session):
        raise TypeError("Workflow orchestration requires a SQLAlchemy Session.")
    return value


def _principal(value: object) -> ApiPrincipal:
    if not isinstance(value, ApiPrincipal):
        raise TypeError("Workflow orchestration requires an API principal.")
    return value


__all__ = ["SqlWorkflowOrchestrationProvider"]