import { formatQuantity, roundToThousandths } from "@/lib/medicines/format";
import type { LotView } from "@/lib/medicines/types";

const SEPARATOR = " · ";

/** "2027-03-31" as "03/2027", read as written. */
function monthYear(day: string): string {
  const [year, month] = day.split("-");
  return `${month}/${year}`;
}

/** "Ch.-B. 4711 · Rest 180 ml · verw. bis 03/2027" */
export function lotLabel(lot: LotView): string {
  const parts = [
    lot.batchNumber ? `Ch.-B. ${lot.batchNumber}` : "Ohne Ch.-B.",
    `Rest ${formatQuantity(lot.remaining, lot.unit)}`,
  ];
  if (lot.expiresOn) parts.push(`verw. bis ${monthYear(lot.expiresOn)}`);
  return parts.join(SEPARATOR);
}

/** What the pack supplies instead of the typed fields, e.g. "aus Packung: Ch.-B. 4711 · Lieferant X". */
export function lotSourceLine(lot: LotView): string {
  const parts = [
    lot.batchNumber ? `Ch.-B. ${lot.batchNumber}` : null,
    lot.supplier ? `Lieferant ${lot.supplier}` : null,
    lot.purchaseProof ? `Beleg ${lot.purchaseProof}` : null,
    lot.prescribingVet ? `Tierarzt ${lot.prescribingVet}` : null,
  ].filter((part): part is string => part !== null);
  return parts.length > 0 ? `aus Packung: ${parts.join(SEPARATOR)}` : "aus Packung";
}

/**
 * What speaks against taking from this pack: expired on the treatment day, or
 * too little left for the dose of all colonies. Only warnings - the server
 * books anyway and the readiness check reports a negative rest.
 */
export function lotWarnings(
  lot: LotView,
  dose: number | null,
  colonyCount: number,
  treatmentDay: string,
): string[] {
  const warnings: string[] = [];
  if (lot.expiresOn && treatmentDay && lot.expiresOn < treatmentDay) {
    warnings.push(`Die Packung ist abgelaufen (verw. bis ${monthYear(lot.expiresOn)}).`);
  }
  if (dose !== null && Number.isFinite(dose) && dose > 0) {
    const needed = roundToThousandths(dose * Math.max(colonyCount, 1));
    if (needed > lot.remaining) {
      warnings.push(
        `Die Packung reicht nicht: Rest ${formatQuantity(lot.remaining, lot.unit)}, gebraucht ${formatQuantity(needed, lot.unit)}.`,
      );
    }
  } else if (lot.remaining <= 0) {
    warnings.push("Die Packung ist leer.");
  }
  return warnings;
}