import type { TaskEnvelope } from "../types.js";

export function estimateTokens(value: unknown): number {
  return Math.ceil(JSON.stringify(value).length / 4);
}

export function fitEnvelope(envelope: TaskEnvelope, hardCapTokens = 8000): TaskEnvelope {
  const fitted: TaskEnvelope = structuredClone(envelope);
  while (estimateTokens(fitted) > hardCapTokens && fitted.knownFacts.length > 0) fitted.knownFacts.pop();
  while (estimateTokens(fitted) > hardCapTokens && fitted.openQuestions.length > 1) fitted.openQuestions.pop();
  while (estimateTokens(fitted) > hardCapTokens && fitted.constraints.length > 1) fitted.constraints.pop();
  if (estimateTokens(fitted) > hardCapTokens) throw new Error("Task Envelope exceeds hard cap; narrow scope before spawn");
  if ((fitted.declaredArtifacts?.length ?? 0) !== (envelope.declaredArtifacts?.length ?? 0)) throw new Error("Task Envelope must not drop declared artifacts");
  return fitted;
}

export function envelopePrompt(envelope: TaskEnvelope): string {
  const fitted = fitEnvelope(envelope);
  return [
    "Work only within the declared scope. Do not delegate. Return exactly one JSON AgentResult and no prose.",
    `Fact IDs must use F:${fitted.trace.runId}:${fitted.trace.nodeId}:<positive sequence>.`,
    JSON.stringify(fitted),
  ].join("\n\n");
}