// Safe harbor recommender — client-side wrapper around
// GET /api/v1/fcc/safe-harbor-recommendation.
//
// Consumed by RevenueStep to display a contextual recommendation next
// to the method dropdown. The server does the actual comparison against
// the customer's CDR traffic study — this is just a thin fetch wrapper.

export type Recommendation =
  | "safe_harbor_okay"
  | "use_actual_saves"
  | "use_actual_required"
  | "no_actual_data"
  | "not_allowed"
  | "no_safe_harbor_for_category";

export interface SafeHarborRecommendation {
  recommendation: Recommendation;
  category: string;
  year: number;
  safe_harbor_pct: number | null;
  actual_interstate_pct: number | null;
  delta_percentage_points?: number;
  estimated_usf_delta_cents?: number;
  total_revenue_cents?: number;
  study_methodology?: string | null;
  total_classified_calls?: number;
  message: string;
}

export async function fetchSafeHarborRecommendation(opts: {
  profile_id?: number | null;
  year: number;
  category: string;
  total_revenue_cents?: number;
}): Promise<SafeHarborRecommendation | null> {
  const params = new URLSearchParams({
    year: String(opts.year),
    category: opts.category,
  });
  if (opts.profile_id) params.set("profile_id", String(opts.profile_id));
  if (opts.total_revenue_cents) {
    params.set("total_revenue_cents", String(opts.total_revenue_cents));
  }
  try {
    const r = await fetch(`/api/v1/fcc/safe-harbor-recommendation?${params.toString()}`);
    if (!r.ok) return null;
    return await r.json();
  } catch {
    return null;
  }
}

/** UI hint: banner color + preferred method for a recommendation. */
export function recommendationBadge(rec: Recommendation): {
  tone: "ok" | "info" | "warn" | "danger";
  suggest: "safe_harbor" | "actual_data" | "traffic_study" | null;
  headline: string;
} {
  switch (rec) {
    case "safe_harbor_okay":
      return { tone: "ok", suggest: "safe_harbor",
        headline: "Safe harbor is a good choice here." };
    case "use_actual_saves":
      return { tone: "info", suggest: "actual_data",
        headline: "Using actual data would save you money." };
    case "use_actual_required":
      return { tone: "warn", suggest: "traffic_study",
        headline: "Safe harbor would under-report — switch to traffic study." };
    case "no_actual_data":
      return { tone: "info", suggest: "safe_harbor",
        headline: "No traffic study — safe harbor is the sensible default." };
    case "not_allowed":
      return { tone: "danger", suggest: "traffic_study",
        headline: "Safe harbor not allowed for this category." };
    case "no_safe_harbor_for_category":
      return { tone: "danger", suggest: "actual_data",
        headline: "No safe harbor defined for this category / year." };
  }
}