import { ExportStatus, Prisma } from "@prisma/client";
import { PipelineError } from "./errors";

/**
 * Export lifecycle state machine (RenderPipeline2 §4).
 * The server is the sole authority on state; workers *request* transitions.
 *
 * NOTE (Phase 2 interim): RENDERING → READY_FOR_QC is temporarily legal.
 * Phase 3 inserts VALIDATING between them (§17.3) — remove READY_FOR_QC from
 * RENDERING's list when the validation engine ships.
 */
export const EXPORT_TRANSITIONS: Record<ExportStatus, ExportStatus[]> = {
  QUEUED: ["RENDERING", "CANCELLED", "SUPERSEDED", "READY_FOR_QC"], // READY_FOR_QC: manual mark-done only
  RENDERING: [
    "VALIDATING",
    "GENERATING_PREVIEW", // interim: preview stage runs before validation exists
    "RENDER_FAILED",
    "QUEUED", // lease expiry / retryable fail with attempts remaining (T5)
    "CANCELLED",
    "READY_FOR_QC", // preview disabled / manual mark-done
  ],
  RENDER_FAILED: ["QUEUED", "SUPERSEDED"],
  VALIDATING: ["VALIDATION_FAILED", "GENERATING_PREVIEW"],
  VALIDATION_FAILED: ["QUEUED", "SUPERSEDED"],
  GENERATING_PREVIEW: ["PREVIEW_FAILED", "READY_FOR_QC"],
  PREVIEW_FAILED: ["GENERATING_PREVIEW", "SUPERSEDED"],
  READY_FOR_QC: ["QC_FAILED", "READY_FOR_DELIVERY", "SUPERSEDED"],
  QC_FAILED: ["SUPERSEDED"],
  READY_FOR_DELIVERY: ["PACKAGED", "SUPERSEDED"],
  PACKAGED: ["DELIVERED"],
  DELIVERED: ["ARCHIVED"],
  SUPERSEDED: [],
  ARCHIVED: [],
  CANCELLED: [],
};

export type TransitionActor = {
  type: "WORKER" | "USER" | "SYSTEM";
  id?: string | null;
  note?: string | null;
};

export function isTransitionAllowed(from: ExportStatus, to: ExportStatus): boolean {
  return EXPORT_TRANSITIONS[from]?.includes(to) ?? false;
}

/**
 * Applies a state transition inside an existing transaction: validates
 * legality, stamps statusChangedAt, appends the ExportEvent audit row.
 * Throws PipelineError(409) on an illegal transition (§4.2 rules).
 */
export async function applyTransition(
  tx: Prisma.TransactionClient,
  exportRow: { id: string; status: ExportStatus },
  to: ExportStatus,
  actor: TransitionActor,
  extraData: Prisma.ExportUpdateInput = {}
) {
  if (!isTransitionAllowed(exportRow.status, to)) {
    throw new PipelineError(409, `Invalid transition ${exportRow.status} → ${to}`);
  }
  const updated = await tx.export.update({
    where: { id: exportRow.id },
    data: { status: to, statusChangedAt: new Date(), ...extraData },
  });
  await tx.exportEvent.create({
    data: {
      exportId: exportRow.id,
      fromStatus: exportRow.status,
      toStatus: to,
      actorType: actor.type,
      actorId: actor.id ?? null,
      note: actor.note ?? null,
    },
  });
  return updated;
}