/**
 * order-delivery-note-link-service — detects when a new order is an
 * exact repeat of a past delivery note's items, scoped to the same
 * company (not customer — a different person at the same company can
 * place the repeat order).
 *
 * Visibility only. Nothing downstream reads this to drive pricing,
 * supplier assignment, or processing — a wrong flag costs nothing, the
 * operator just ignores the pill. That's what justifies writing the
 * match automatically with no human confirmation step, unlike the
 * order↔quote matcher's deliberately conservative suggest-only policy
 * (see order-quote-link-service.ts) — that policy exists because a
 * wrong quote link puts wrong prices in front of a buyer.
 *
 * Called from inside createOrder's existing after()/E468 guard
 * (orders-service.ts) — this function lets errors propagate to that
 * caller rather than double-guarding.
 */

import { getAdminPocketBase } from "@/lib/server/pocketbase-admin";
import { isExactItemMatch, type DeliveryLine } from "@/lib/server/delivery-note-order-match";

export type DeliveryNoteMatchMethod = "exact_items" | "no_match";

export interface SuggestDeliveryNoteResult {
  orderId: string;
  best: { deliveryNoteId: string; deliveryNoteNumber: string } | null;
  method: DeliveryNoteMatchMethod;
}

const ORDER_COLLECTION = "orders";
const ORDER_ITEMS_COLLECTION = "order_items";
const DELIVERY_NOTES_COLLECTION = "delivery_notes";
const QUOTES_COLLECTION = "quotes";
const QUOTE_ITEMS_COLLECTION = "quote_items";

/** Maximum age (in days) of a delivery-note candidate considered for
 *  repeat matching. Beyond this window, even an exact-line match is
 *  treated as a coincidence, not a repeat order. */
const WINDOW_DAYS = 60;

/** PB rejects filter expressions longer than ~8 KB (HTTP 400 "Something
 *  went wrong while processing your request."). Each candidate adds
 *  roughly 40 chars (`delivery_note_number = "<up-to-20-char-no>" || `),
 *  so 200 candidates keeps the filter at ~8 KB — at the limit. Using
 *  200 still collapses ~190 individual fetches per chunk while keeping
 *  every individual filter comfortably parseable. */
const BULK_FILTER_CHUNK_SIZE = 100;

// Per 2026-08-30 business decision: match against a DN of ANY status,
// including `cancelled` (previously excluded along with a hardcoded
// allowlist of "active" statuses — see git history) — the prior
// exclusion missed real repeat orders where the original delivery's DN
// had been cancelled for reasons unrelated to whether goods went out.
// A 60-day candidate window (computed below) bounds the search space
// instead.

function esc(s: string): string {
  return (s || "").replace(/"/g, '\\"');
}

interface DnCandidate {
  id: string;
  delivery_note_number: string;
  company?: string;
  status: string;
  created: string;
  /** The order this DN's items originated from (Path A). Empty for
   *  ad-hoc counter DNs and for combined DNs spanning several orders.
   *  Read solely to skip an order's own delivery note — see the guard
   *  in the candidate loop. */
  order?: string;
}

export async function suggestDeliveryNoteForOrder(
  orderId: string,
): Promise<SuggestDeliveryNoteResult> {
  const pb = await getAdminPocketBase();
  pb.autoCancellation(false);

  const order = await pb
    .collection(ORDER_COLLECTION)
    .getOne<{ id: string; company?: string }>(orderId);

  if (!order.company) {
    // No signal to match on — deliberately does not write
    // `delivery_note_matching_attempted`, unlike the quote matcher's
    // "no_match" path. A never-attempted order (no company at all) is
    // a different state from "we looked and found nothing," and a
    // company gets added later, so leaving `attempted: false` lets a
    // future sweep (out of scope for this iteration) reconsider it.
    return { orderId, best: null, method: "no_match" };
  }

  const orderItemRows = await pb
    .collection(ORDER_ITEMS_COLLECTION)
    .getFullList<{
      id: string;
      description?: string;
      quantity?: number;
      selling_price?: number;
    }>({
      filter: `order = "${esc(orderId)}"`,
      fields: "id,description,quantity,selling_price",
      batch: 1000,
    });
  const orderLines: DeliveryLine[] = orderItemRows.map((r) => ({
    description: r.description || "",
    quantity: Number(r.quantity) || 0,
  }));

  const WINDOW_MS = WINDOW_DAYS * 24 * 60 * 60 * 1000;
  const cutoff = new Date(Date.now() - WINDOW_MS);
  const cutoffStr = cutoff.toISOString().replace("T", " ");

  const candidates = await pb
    .collection(DELIVERY_NOTES_COLLECTION)
    .getFullList<DnCandidate>({
      filter: `company = "${esc(order.company)}" && created >= "${cutoffStr}"`,
      fields: "id,delivery_note_number,company,status,created,order",
      batch: 1000,
    });

  // Self-skip DNs that belong to the order being matched — both the
  // `dn.order === orderId` direct case and the combined-DN case where
  // any of the DN's items point back to this order. Both checks need
  // the DN's items, which we fetch ONCE below.
  const candidatesToFetch = candidates.filter((dn) => !(dn.order && dn.order === orderId));

  let matched: DnCandidate[] = [];

  if (candidatesToFetch.length > 0) {
    // Bulk-fetch ALL items for ALL candidate DNs, chunked to stay under
    // PB's filter-expression length limit. The chunked query still
    // collapses N per-candidate getFullList calls into ceil(N/200) —
    // ~190x faster than the old N+1 loop, while never producing a single
    // filter larger than ~8 KB. delivery_note_number is the join key —
    // group rows by it.
    const itemsByDn = new Map<string, Array<{ order?: string; description?: string; quantity?: number }>>();
    for (let i = 0; i < candidatesToFetch.length; i += BULK_FILTER_CHUNK_SIZE) {
      const chunk = candidatesToFetch.slice(i, i + BULK_FILTER_CHUNK_SIZE);
      const chunkItems = await pb
        .collection(ORDER_ITEMS_COLLECTION)
        .getFullList<{ order?: string; delivery_note_number?: string; description?: string; quantity?: number }>({
          filter: chunk.map((d) => `delivery_note_number = "${esc(d.delivery_note_number)}"`).join(" || "),
          fields: "order,delivery_note_number,description,quantity",
          batch: 5000,
        });
      for (const row of chunkItems) {
        if (!row.delivery_note_number) continue;
        const bucket = itemsByDn.get(row.delivery_note_number);
        if (bucket) bucket.push(row);
        else itemsByDn.set(row.delivery_note_number, [row]);
      }
    }

    for (const dn of candidatesToFetch) {
      const dnItemRows = itemsByDn.get(dn.delivery_note_number) ?? [];

      // Second half of the self-skip: a combined DN (see
      // `combineDeliveryNotes`) has `dn.order` empty because its items
      // span several orders. The id check above can't catch those, so
      // fall back to checking whether any of the DN's rows belong to the
      // order we're matching.
      if (dnItemRows.some((r) => r.order && r.order === orderId)) continue;

      const dnLines: DeliveryLine[] = dnItemRows.map((r) => ({
        description: r.description || "",
        quantity: Number(r.quantity) || 0,
      }));
      if (isExactItemMatch(orderLines, dnLines)) matched.push(dn);
    }
  }

  let best: DnCandidate | null = null;
  if (matched.length === 1) {
    best = matched[0];
  } else if (matched.length > 1) {
    best = (await breakTieByQuotePrice(pb, matched, orderItemRows)) ?? mostRecent(matched);
  }

  await pb.collection(ORDER_COLLECTION).update(orderId, {
    potential_delivery_note: best ? best.id : null,
    potential_delivery_note_number: best ? best.delivery_note_number : "",
    delivery_note_match_confidence: best ? 1 : 0,
    delivery_note_match_method: best ? "exact_items" : "no_match",
    delivery_note_matching_attempted: true,
  });

  return {
    orderId,
    best: best
      ? { deliveryNoteId: best.id, deliveryNoteNumber: best.delivery_note_number }
      : null,
    method: best ? "exact_items" : "no_match",
  };
}

function mostRecent(candidates: DnCandidate[]): DnCandidate {
  return [...candidates].sort((a, b) =>
    (b.created || "").localeCompare(a.created || ""),
  )[0];
}

/** Among tied exact-item-match candidates, prefer the one whose priced
 *  quote (status="delivery_note") also matches the order's line
 *  prices. Returns null if no candidate's quote prices match — caller
 *  falls back to most-recent. */
async function breakTieByQuotePrice(
  pb: Awaited<ReturnType<typeof getAdminPocketBase>>,
  candidates: DnCandidate[],
  orderItemRows: Array<{ description?: string; selling_price?: number }>,
): Promise<DnCandidate | null> {
  const priceByDesc = new Map<string, number>();
  for (const r of orderItemRows) {
    priceByDesc.set(
      (r.description || "").trim().toLowerCase(),
      Number(r.selling_price) || 0,
    );
  }

  for (const dn of candidates) {
    const quotes = await pb
      .collection(QUOTES_COLLECTION)
      .getFullList<{ id: string; delivery_note: string }>({
        filter: `delivery_note = "${esc(dn.id)}" && status = "delivery_note"`,
        fields: "id,delivery_note",
        batch: 5,
      });
    if (quotes.length === 0) continue;
    const quoteItems = await pb
      .collection(QUOTE_ITEMS_COLLECTION)
      .getFullList<{ description?: string; selling_price?: number }>({
        filter: `quote = "${esc(quotes[0].id)}"`,
        fields: "description,selling_price",
        batch: 1000,
      });
    const allPricesMatch = quoteItems.every((qi) => {
      const orderPrice = priceByDesc.get((qi.description || "").trim().toLowerCase());
      return orderPrice !== undefined && orderPrice === (Number(qi.selling_price) || 0);
    });
    if (allPricesMatch && quoteItems.length > 0) return dn;
  }
  return null;
}