from __future__ import annotations

from .enums import MigrationStatus, ModelLifecycle, UpgradeClass, VerificationStatus


class InvalidTransition(ValueError):
    pass


MODEL_TRANSITIONS: dict[ModelLifecycle, frozenset[ModelLifecycle]] = {
    ModelLifecycle.DISCOVERED: frozenset(
        {ModelLifecycle.CANDIDATE, ModelLifecycle.REJECTED, ModelLifecycle.DEPRECATED}
    ),
    ModelLifecycle.CANDIDATE: frozenset(
        {ModelLifecycle.DOWNLOADING, ModelLifecycle.REJECTED, ModelLifecycle.DEPRECATED}
    ),
    ModelLifecycle.DOWNLOADING: frozenset({ModelLifecycle.QUARANTINED, ModelLifecycle.REJECTED}),
    ModelLifecycle.QUARANTINED: frozenset(
        {ModelLifecycle.VERIFIED, ModelLifecycle.SECURITY_BLOCKED, ModelLifecycle.LICENSE_BLOCKED}
    ),
    ModelLifecycle.VERIFIED: frozenset({ModelLifecycle.TESTING, ModelLifecycle.INCOMPATIBLE}),
    ModelLifecycle.TESTING: frozenset(
        {ModelLifecycle.APPROVED, ModelLifecycle.INCOMPATIBLE, ModelLifecycle.REJECTED}
    ),
    ModelLifecycle.APPROVED: frozenset(
        {ModelLifecycle.STANDBY, ModelLifecycle.ACTIVE, ModelLifecycle.DEPRECATED}
    ),
    ModelLifecycle.STANDBY: frozenset({ModelLifecycle.ACTIVE, ModelLifecycle.DEPRECATED}),
    ModelLifecycle.ACTIVE: frozenset({ModelLifecycle.STANDBY, ModelLifecycle.DEPRECATED}),
    ModelLifecycle.DEPRECATED: frozenset({ModelLifecycle.ARCHIVED, ModelLifecycle.ACTIVE}),
    ModelLifecycle.ARCHIVED: frozenset(),
    ModelLifecycle.REJECTED: frozenset(),
    ModelLifecycle.INCOMPATIBLE: frozenset({ModelLifecycle.CANDIDATE}),
    ModelLifecycle.SECURITY_BLOCKED: frozenset(
        {ModelLifecycle.QUARANTINED, ModelLifecycle.REJECTED}
    ),
    ModelLifecycle.LICENSE_BLOCKED: frozenset(
        {ModelLifecycle.QUARANTINED, ModelLifecycle.REJECTED}
    ),
}


def assert_model_transition(current: ModelLifecycle, target: ModelLifecycle) -> None:
    if target not in MODEL_TRANSITIONS[current]:
        raise InvalidTransition(f"model lifecycle transition {current} -> {target} is not allowed")


def assert_promotion_allowed(
    *,
    upgrade_class: UpgradeClass,
    verification_status: VerificationStatus,
    local_benchmark_ids: list[str],
    project_benchmark_ids: list[str],
    operator_approval_id: str | None,
    rollback_deployment_id: str | None,
    migration_status: MigrationStatus | None = None,
) -> None:
    blockers: list[str] = []
    if verification_status is not VerificationStatus.VERIFIED:
        blockers.append("artifact is not verified")
    if not local_benchmark_ids:
        blockers.append("local benchmark evidence is missing")
    if not project_benchmark_ids:
        blockers.append("project benchmark evidence is missing")
    if not operator_approval_id:
        blockers.append("operator approval is missing")
    if not rollback_deployment_id:
        blockers.append("rollback target is missing")
    if (
        upgrade_class is UpgradeClass.REQUIRES_REINDEX
        and migration_status is not MigrationStatus.READY
    ):
        blockers.append("ready migration is required for reindexing change")
    if blockers:
        raise InvalidTransition("promotion blocked: " + "; ".join(blockers))