/**
 * order-order-duplicate-link-service — detects when a new order's
 * line items (description + quantity, exact multiset match) exactly
 * repeat another order for the SAME company, created within the last
 * 60 days, REGARDLESS of either order's status.
 *
 * Visibility only — same reasoning as order-delivery-note-link-service
 * and order-number-duplicate-link-service. This is deliberately a
 * separate flag/pill from the delivery-note repeat check: this one
 * catches "we already have an ORDER for this," the DN check catches
 * "we already DELIVERED this" — different facts, different pills.
 *
 * PREREQUISITE: Before this code can run against a real PocketBase
 * instance, the operator must add five fields to the `orders`
 * collection in the PB admin UI (per the AGENTS.md convention — PB
 * schema is not self-service from code):
 *   - `potential_duplicate_order`  (Relation → orders, single)
 *   - `potential_duplicate_order_number`  (Text)
 *   - `duplicate_order_match_confidence`  (Number)
 *   - `duplicate_order_match_method`  (Text)
 *   - `duplicate_order_matching_attempted`  (Bool)
 * Without these fields, the `.update()` below will 500 in production.
 */

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

const ORDER_COLLECTION = "orders";
const ORDER_ITEMS_COLLECTION = "order_items";
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 30 chars (`order = "<15-char-id>" || `), so 200 candidates
 *  keeps the filter at ~6 KB — comfortably under the limit while still
 *  collapsing ~190 individual fetches per chunk. */
const BULK_FILTER_CHUNK_SIZE = 100;

export type OrderDuplicateMatchMethod = "exact_items_same_company" | "no_match";

export interface SuggestOrderDuplicateResult {
  orderId: string;
  duplicateOrderId: string | null;
  method: OrderDuplicateMatchMethod;
}

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

function pbDate(d: Date): string {
  return d.toISOString().replace("T", " ");
}

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

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

  if (!order.company) {
    // No signal to match on — same "leave attempted unset" reasoning
    // as the delivery-note matcher: a company gets added later and a
    // future sweep should reconsider it.
    return { orderId, duplicateOrderId: null, method: "no_match" };
  }

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

  const cutoff = new Date(Date.now() - WINDOW_DAYS * 24 * 60 * 60 * 1000);

  const candidates = await pb
    .collection(ORDER_COLLECTION)
    .getFullList<{ id: string; order_number: string; created: string }>({
      filter: `company = "${esc(order.company)}" && id != "${esc(orderId)}" && created >= "${pbDate(cutoff)}"`,
      fields: "id,order_number,created",
      sort: "created",
      batch: 500,
    });

  let match: { id: string; order_number: string } | null = null;

  // Bulk-fetch ALL items for ALL candidates, 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 ~6 KB. Group items by candidate order id so we can compare each
  // candidate's lines to the source order's lines in memory.
  if (candidates.length > 0) {
    const itemsByOrder = new Map<string, Array<{ description?: string; quantity?: number }>>();
    for (let i = 0; i < candidates.length; i += BULK_FILTER_CHUNK_SIZE) {
      const chunk = candidates.slice(i, i + BULK_FILTER_CHUNK_SIZE);
      const chunkItems = await pb
        .collection(ORDER_ITEMS_COLLECTION)
        .getFullList<{ order?: string; description?: string; quantity?: number }>({
          filter: chunk.map((c) => `order = "${esc(c.id)}"`).join(" || "),
          fields: "order,description,quantity",
          batch: 5000,
        });
      for (const row of chunkItems) {
        if (!row.order) continue;
        const bucket = itemsByOrder.get(row.order);
        if (bucket) bucket.push(row);
        else itemsByOrder.set(row.order, [row]);
      }
    }

    for (const candidate of candidates) {
      const candidateItemRows = itemsByOrder.get(candidate.id) ?? [];
      const candidateLines: DeliveryLine[] = candidateItemRows.map((r) => ({
        description: r.description || "",
        quantity: Number(r.quantity) || 0,
      }));
      if (isExactItemMatch(orderLines, candidateLines)) {
        match = candidate;
        break; // candidates sorted oldest-first — first hit is the original
      }
    }
  }

  await pb.collection(ORDER_COLLECTION).update(orderId, {
    potential_duplicate_order: match ? match.id : null,
    potential_duplicate_order_number: match ? match.order_number : "",
    duplicate_order_match_confidence: match ? 1 : 0,
    duplicate_order_match_method: match ? "exact_items_same_company" : "no_match",
    duplicate_order_matching_attempted: true,
  });

  return {
    orderId,
    duplicateOrderId: match ? match.id : null,
    method: match ? "exact_items_same_company" : "no_match",
  };
}