import type { ContextUsage } from "@earendil-works/pi-coding-agent";
import type {
  ThresholdEvaluation,
  TriggerSnapshot,
  UsableContextUsage,
} from "./types.ts";

export function normalizeContextUsage(usage: ContextUsage | undefined): UsableContextUsage | undefined {
  if (!usage) return undefined;
  if (usage.tokens === null || usage.percent === null) return undefined;
  if (!Number.isFinite(usage.tokens) || usage.tokens < 0) return undefined;
  if (!Number.isFinite(usage.percent) || usage.percent < 0) return undefined;
  if (!Number.isFinite(usage.contextWindow) || usage.contextWindow <= 0) return undefined;

  return {
    tokens: usage.tokens,
    contextWindow: usage.contextWindow,
    percent: usage.percent,
  };
}

export function evaluateThreshold(
  usage: ContextUsage | undefined,
  thresholdPercent: number,
): ThresholdEvaluation | undefined {
  const normalized = normalizeContextUsage(usage);
  if (!normalized || normalized.percent < thresholdPercent) return undefined;

  const trigger: TriggerSnapshot = {
    tokens: normalized.tokens,
    contextWindow: normalized.contextWindow,
    percent: normalized.percent,
    thresholdPercent,
  };
  return { usage: normalized, trigger };
}

export function buildFailureKey(sessionId: string, usage: UsableContextUsage): string {
  return `${sessionId}:${usage.contextWindow}:${Math.floor(usage.tokens / 1000)}`;
}