import type { OilItem, OilMovement } from "./data";
// From the NEUTRAL module, not from purchase-parser: this file is imported by a
// client component, and the parser pulls in pdfjs and `node:module`.
import { normaliseCostCode } from "./cost-code";

/**
 * Oil stock is the SUM of what came IN minus what went OUT. Every movement is kept, so
 * the first usage is a subtraction from a real history rather than a guess about what
 * it removed.
 *
 * `litresOnHand` is a number, and an empty drum is genuinely R0 of oil — unlike every
 * other "unknown" in this project, a drained drum is not missing data, it is the state.
 * Where nothing has EVER been received, that is different: it means nobody has entered
 * a delivery, so `known` is false and the page says so rather than drawing a full drum.
 */

export type OilStock = {
  item: OilItem;
  litres: number;
  /** False when the item has no movement history at all — "not entered", not "empty". */
  known: boolean;
  /** 0–1. A drum is FULL at 1, and stock above one drum's worth simply reads full. */
  fillRatio: number;
  /** True once a drum's worth is on hand or more. */
  isFull: boolean;
  isEmpty: boolean;
  /** Whole drums held, for the "2 drums" reading next to the graphic. */
  drumsHeld: number;
};

/** Diesel sits in a tank, not a drum. Derived from the code so no schema change is needed. */
export function isTank(item: Pick<OilItem, "code">): boolean {
  return (item.code || "").startsWith("FUEL");
}

export function oilStock(item: OilItem, movements: OilMovement[]): OilStock {
  const mine = movements.filter((m) => m.item === item.id);
  const litres = mine.reduce(
    // "adjusted" carries a SIGNED litres figure (opening stock, or a manual overwrite).
    (sum, m) => sum + (m.kind === "used" ? -(m.litres || 0) : m.litres || 0),
    0,
  );
  const known = mine.length > 0;
  const capacity = item.drum_litres || 210;
  const fillRatio = known ? Math.max(0, Math.min(1, litres / capacity)) : 0;
  return {
    item,
    litres,
    known,
    fillRatio,
    isFull: known && litres >= capacity,
    isEmpty: known && litres <= 0,
    drumsHeld: known ? Math.max(0, Math.floor(litres / capacity)) : 0,
  };
}

/** Does this purchase-order cost code name an oil store rather than a machine? */
export function storeCodeOf(costCode: string, items: OilItem[]): OilItem | null {
  const wanted = normaliseCostCode(costCode);
  if (!wanted) return null;
  return items.find((i) => normaliseCostCode(i.store_cost_code || "") === wanted) ?? null;
}

/** What the drum's QR encodes: the oil name and its item code. */
export function oilQrPayload(item: Pick<OilItem, "name" | "code">): string {
  return `${(item.name || "").trim()} | ${(item.code || "").trim()}`;
}