export type ExperimentStopReason = "verified-success-drop" | "rework-increase" | "cost-increase-without-quality-benefit" | "safety-incident" | "sample-corruption" | "provider-drift" | "model-drift" | "manual" | "completed";

export interface StopLossInput {
  successDrop: number;
  reworkIncrease: number;
  costIncrease: number;
  qualityBenefit?: boolean;
  safetyIncident: boolean;
  sampleCorruption: boolean;
  providerDrift?: boolean;
  modelDrift?: boolean;
}

export function experimentStopReason(input: StopLossInput, thresholds = { successDrop: 0.05, costIncrease: 0.2 }): ExperimentStopReason | undefined {
  if (input.safetyIncident) return "safety-incident";
  if (input.sampleCorruption || ![input.successDrop, input.reworkIncrease, input.costIncrease].every(Number.isFinite)) return "sample-corruption";
  if (input.providerDrift) return "provider-drift";
  if (input.modelDrift) return "model-drift";
  if (input.successDrop > thresholds.successDrop) return "verified-success-drop";
  if (input.reworkIncrease > 0) return "rework-increase";
  if (input.costIncrease > thresholds.costIncrease && !input.qualityBenefit) return "cost-increase-without-quality-benefit";
  return undefined;
}

export function shouldStopExperiment(input: StopLossInput, thresholds = { successDrop: 0.05, costIncrease: 0.2 }): boolean {
  return experimentStopReason(input, thresholds) !== undefined;
}