import type { StockItem } from "./types";

/**
 * Stock status levels — used by the /stock list to render the
 * reorder-alert badge and by the API to flag low-stock rows.
 *
 * The "inactive" state is orthogonal: an inactive item is always
 * surfaced as `inactive` regardless of its current/min qty, so
 * the operator can spot soft-deleted items that the rest of the
 * app would otherwise treat as "low stock" or "out".
 */
export type StockStatus = "ok" | "low" | "out" | "inactive";

/**
 * Reorder-alert thresholds.
 *
 *   current_qty === 0            → "out"     (red)
 *   0 < current_qty <= min_qty   → "low"     (amber)
 *   current_qty  > min_qty       → "ok"      (green)
 *   current_qty <  0             → "out"     (red; treat as a bug
 *                                            rather than clamp)
 *   is_active === false          → "inactive" (grey overlay)
 *
 * Pure, no side effects. Called by both the list page (to pick the
 * badge colour) and the API filter (to gate `?low_stock=true`).
 */
export function getStockStatus(
  currentQty: number | null | undefined,
  minQty: number | null | undefined,
  isActive: boolean | null | undefined,
): StockStatus {
  if (isActive === false) return "inactive";
  const current = Number(currentQty ?? 0);
  const min = Number(minQty ?? 0);
  if (current <= 0) return "out";
  if (current <= min) return "low";
  return "ok";
}

/**
 * Tailwind-friendly colour tokens for each status. Centralised so
 * the list table, the detail header, and the badge helper all
 * render the same palette — the operator's eye learns one set of
 * cues.
 */
export const STOCK_STATUS_STYLES: Record<
  StockStatus,
  { label: string; hex: string; ring: string; text: string }
> = {
  ok: {
    label: "In stock",
    hex: "#047857", // emerald-700 — matches CompleteBadge
    ring: "rgba(4, 120, 87, 0.30)",
    text: "text-emerald-700 dark:text-emerald-400",
  },
  low: {
    label: "Low stock",
    hex: "#b45309", // amber-700 — high contrast on light surfaces
    ring: "rgba(180, 83, 9, 0.30)",
    text: "text-amber-700 dark:text-amber-400",
  },
  out: {
    label: "Out of stock",
    hex: "#b91c1c", // red-700
    ring: "rgba(185, 28, 28, 0.30)",
    text: "text-red-700 dark:text-red-400",
  },
  inactive: {
    label: "Inactive",
    hex: "#475569", // slate-600
    ring: "rgba(71, 85, 105, 0.30)",
    text: "text-slate-600 dark:text-slate-400",
  },
};

/**
 * Convenience helper for the list-page filter: true when the row
 * should be surfaced by `?low_stock=true`. Mirrors the list badge
 * (red + amber), but EXCLUDES inactive rows — the operator asked
 * "what needs reordering" not "what's soft-deleted".
 */
export function isLowStock(
  currentQty: number | null | undefined,
  minQty: number | null | undefined,
  isActive: boolean | null | undefined,
): boolean {
  if (isActive === false) return false;
  return getStockStatus(currentQty, minQty, isActive) !== "ok";
}

/**
 * Apply `?low_stock=true` semantics to a StockItem record. Used by
 * the list API as the gate after the PB fetch.
 */
export function isLowStockItem(item: Pick<StockItem, "current_qty" | "min_qty" | "is_active">): boolean {
  return isLowStock(item.current_qty, item.min_qty, item.is_active);
}