from __future__ import annotations

from datetime import UTC, datetime
from typing import Any, Mapping, Sequence

from sqlalchemy.orm import Session

from govoplan_core.core.institutional import (
    InstitutionalContextError,
    InstitutionalReference,
    ServiceAvailabilityAssessment,
    ServiceDefinition,
    TemporalRevision,
)
from govoplan_core.core.temporal import TemporalDataContext
from govoplan_core.db.temporal import apply_temporal_revision_filter
from govoplan_services.backend.db.models import ServiceDefinitionRevision


_PUBLICATION_TRANSITIONS: dict[str, frozenset[str]] = {
    "draft": frozenset({"draft", "published", "retired"}),
    "published": frozenset({"published", "suspended", "retired"}),
    "suspended": frozenset({"suspended", "published", "retired"}),
    "retired": frozenset(),
}


class ServiceStoreError(ValueError):
    pass


def record_service_definition(
    session: Session,
    principal: object,
    *,
    definition: ServiceDefinition,
    expected_revision: str | None = None,
) -> ServiceDefinition:
    tenant_id = _principal_tenant(principal)
    _validate_definition(definition, tenant_id=tenant_id)
    payload = definition.to_dict(include_inspection=True)
    replay = (
        session.query(ServiceDefinitionRevision)
        .filter(
            ServiceDefinitionRevision.tenant_id == tenant_id,
            ServiceDefinitionRevision.service_id == definition.reference.object_id,
            ServiceDefinitionRevision.revision == definition.temporal.revision,
        )
        .one_or_none()
    )
    if replay is not None:
        if replay.payload != payload:
            raise ServiceStoreError(
                "A different Service payload already uses this revision."
            )
        return _definition_from_row(replay)

    current = _current_row(
        session,
        tenant_id=tenant_id,
        service_id=definition.reference.object_id,
        lock=True,
    )
    _validate_temporal(definition.temporal)
    if current is None:
        if expected_revision is not None:
            raise ServiceStoreError(
                "Service revision conflict: no current revision exists."
            )
        collision = (
            session.query(ServiceDefinitionRevision.id)
            .filter(
                ServiceDefinitionRevision.tenant_id == tenant_id,
                ServiceDefinitionRevision.service_key == definition.key,
                ServiceDefinitionRevision.superseded_at.is_(None),
            )
            .first()
        )
        if collision is not None:
            raise ServiceStoreError("Service key is already in use in this tenant.")
    else:
        current_definition = _definition_from_row(current)
        if expected_revision != current.revision:
            raise ServiceStoreError(
                "Service revision conflict: the expected revision is stale."
            )
        if definition.key != current_definition.key:
            raise ServiceStoreError("A Service key cannot change across revisions.")
        if definition.publication_state not in _PUBLICATION_TRANSITIONS[current.publication_state]:
            raise ServiceStoreError(
                f"Service publication transition {current.publication_state!r} to "
                f"{definition.publication_state!r} is not allowed."
            )
        current.superseded_at = definition.temporal.recorded_at

    row = ServiceDefinitionRevision(
        tenant_id=tenant_id,
        service_id=definition.reference.object_id,
        service_key=definition.key,
        revision=definition.temporal.revision,
        previous_revision_id=current.id if current is not None else None,
        publication_state=definition.publication_state,
        valid_from=definition.temporal.valid_from,
        valid_to=definition.temporal.valid_to,
        recorded_at=_recorded_at(definition.temporal),
        search_text=f"{definition.key} {definition.title}".casefold(),
        payload=payload,
        created_by=_principal_actor(principal),
    )
    session.add(row)
    session.flush()
    return _definition_from_row(row)


def get_service_definition(
    session: Session,
    principal: object,
    *,
    service_id: str,
    revision: str | None = None,
    temporal_context: TemporalDataContext | None = None,
) -> ServiceDefinition | None:
    tenant_id = _principal_tenant(principal)
    query = session.query(ServiceDefinitionRevision).filter(
        ServiceDefinitionRevision.tenant_id == tenant_id,
        ServiceDefinitionRevision.service_id == service_id,
    )
    if revision is None:
        query = apply_temporal_revision_filter(
            query,
            ServiceDefinitionRevision,
            context=temporal_context,
        )
    else:
        query = query.filter(ServiceDefinitionRevision.revision == revision)
    row = query.order_by(ServiceDefinitionRevision.recorded_at.desc()).first()
    return _definition_from_row(row) if row is not None else None


def list_service_definitions(
    session: Session,
    principal: object,
    *,
    query: str = "",
    publication_states: Sequence[str] | None = None,
    limit: int = 100,
) -> tuple[ServiceDefinition, ...]:
    tenant_id = _principal_tenant(principal)
    if not 1 <= limit <= 200:
        raise ServiceStoreError("Service list limit must be between 1 and 200.")
    statement = session.query(ServiceDefinitionRevision).filter(
        ServiceDefinitionRevision.tenant_id == tenant_id,
    )
    statement = apply_temporal_revision_filter(
        statement,
        ServiceDefinitionRevision,
    )
    if publication_states is not None:
        statement = statement.filter(
            ServiceDefinitionRevision.publication_state.in_(tuple(publication_states))
        )
    clean_query = query.strip().casefold()
    if clean_query:
        statement = statement.filter(
            ServiceDefinitionRevision.search_text.contains(clean_query)
        )
    rows = statement.order_by(
        ServiceDefinitionRevision.service_key.asc(),
        ServiceDefinitionRevision.recorded_at.desc(),
    ).limit(limit).all()
    return tuple(_definition_from_row(row) for row in rows)


class SqlServiceDefinitionProvider:
    def get_service_definition(
        self,
        session: object,
        principal: object,
        *,
        reference: InstitutionalReference,
        effective_at: datetime | None = None,
    ) -> ServiceDefinition | None:
        tenant_id = _principal_tenant(principal)
        if reference.kind != "service" or reference.tenant_id != tenant_id:
            raise InstitutionalContextError(
                "Service definition lookup requires a same-tenant Service reference."
            )
        item = get_service_definition(
            _session(session),
            principal,
            service_id=reference.object_id,
            revision=reference.version,
            temporal_context=(
                TemporalDataContext(validity_mode="at", valid_at=effective_at)
                if effective_at is not None and reference.version is None
                else None
            ),
        )
        if item is None or (effective_at is not None and reference.version is not None and not item.temporal.effective_at(effective_at)):
            return None
        return item

    def list_service_definitions(
        self,
        session: object,
        principal: object,
        *,
        tenant_id: str,
        query: str = "",
        limit: int = 100,
    ) -> Sequence[ServiceDefinition]:
        if tenant_id != _principal_tenant(principal):
            raise InstitutionalContextError(
                "Service catalogue lookup cannot cross tenants."
            )
        return list_service_definitions(
            _session(session),
            principal,
            query=query,
            publication_states=("published", "suspended"),
            limit=limit,
        )


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

    def evaluate_service_availability(
        self,
        session: object,
        principal: object,
        *,
        definition: ServiceDefinition,
        effective_at: datetime,
    ) -> ServiceAvailabilityAssessment:
        del session
        tenant_id = _principal_tenant(principal)
        if definition.reference.tenant_id != tenant_id:
            raise InstitutionalContextError(
                "Service availability cannot be evaluated across tenants."
            )
        states: dict[str, bool] = {}
        reasons: list[str] = []
        if not definition.temporal.effective_at(effective_at):
            reasons.append("service.outside_effective_interval")
        if definition.publication_state != "published":
            reasons.append(f"service.publication.{definition.publication_state}")
        for requirement in definition.availability_requirements:
            if requirement.kind == "module":
                states[requirement.key] = _registry_has(self._registry, requirement.reference)
            elif requirement.kind == "capability":
                states[requirement.key] = _registry_has_capability(
                    self._registry,
                    requirement.reference,
                )
        return ServiceAvailabilityAssessment(
            requirement_states=states,
            reason_codes=tuple(reasons),
        )


def definition_from_mapping(value: Mapping[str, object]) -> ServiceDefinition:
    try:
        return ServiceDefinition.from_mapping(value)
    except InstitutionalContextError as exc:
        raise ServiceStoreError(str(exc)) from exc


def _current_row(
    session: Session,
    *,
    tenant_id: str,
    service_id: str,
    lock: bool,
) -> ServiceDefinitionRevision | None:
    query = session.query(ServiceDefinitionRevision).filter(
        ServiceDefinitionRevision.tenant_id == tenant_id,
        ServiceDefinitionRevision.service_id == service_id,
        ServiceDefinitionRevision.superseded_at.is_(None),
    )
    if lock:
        query = query.with_for_update()
    return query.one_or_none()


def _definition_from_row(row: ServiceDefinitionRevision) -> ServiceDefinition:
    payload: dict[str, Any] = dict(row.payload)
    temporal = dict(payload.get("temporal") or {})
    temporal["superseded_at"] = _datetime_text(row.superseded_at)
    payload["temporal"] = temporal
    return ServiceDefinition.from_mapping(payload)


def _validate_definition(definition: ServiceDefinition, *, tenant_id: str) -> None:
    if definition.reference.owner_module != "services":
        raise ServiceStoreError("Service definitions must be owned by Services.")
    if definition.reference.tenant_id != tenant_id:
        raise ServiceStoreError("Service definitions cannot cross tenants.")
    if definition.reference.version != definition.temporal.revision:
        raise ServiceStoreError(
            "Service reference version must match its temporal revision."
        )
    if definition.temporal.superseded_at is not None:
        raise ServiceStoreError("Clients cannot set Service superseded_at.")


def _validate_temporal(temporal: TemporalRevision) -> None:
    _recorded_at(temporal)
    if not str(temporal.change_reason or "").strip():
        raise ServiceStoreError(
            "A Service revision requires recorded_at and change_reason."
        )


def _recorded_at(temporal: TemporalRevision) -> datetime:
    if temporal.recorded_at is None:
        raise ServiceStoreError("A Service revision requires recorded_at.")
    return temporal.recorded_at


def _principal_tenant(principal: object) -> str:
    tenant_id = str(getattr(principal, "tenant_id", "") or "").strip()
    if not tenant_id:
        raise InstitutionalContextError(
            "Service operations require a tenant-bound principal."
        )
    return tenant_id


def _principal_actor(principal: object) -> str | None:
    for name in ("account_id", "identity_id", "membership_id"):
        value = str(getattr(principal, name, "") or "").strip()
        if value:
            return value
    return None


def _session(value: object) -> Session:
    if not hasattr(value, "query"):
        raise InstitutionalContextError("Service provider requires a database session.")
    return value  # type: ignore[return-value]


def _registry_has(registry: object | None, module_id: str) -> bool:
    return bool(registry is not None and hasattr(registry, "has") and registry.has(module_id))


def _registry_has_capability(registry: object | None, capability: str) -> bool:
    return bool(
        registry is not None
        and hasattr(registry, "has_capability")
        and registry.has_capability(capability)
    )


def _datetime_text(value: datetime | None) -> str | None:
    if value is None:
        return None
    if value.tzinfo is None:
        value = value.replace(tzinfo=UTC)
    return value.isoformat()


__all__ = [
    "RegistryServiceAvailabilityEvaluator",
    "ServiceStoreError",
    "SqlServiceDefinitionProvider",
    "definition_from_mapping",
    "get_service_definition",
    "list_service_definitions",
    "record_service_definition",
]