/**
 * Stock Quick-Draft service — backs the /stock-orders modal that lets
 * a buyer add items to draft stock_purchases in an item-first rhythm.
 *
 * Reuses `generateStockPurchaseNumber` from `stock-purchases-service.ts`
 * for the find-or-create open-draft step; no schema changes, no new
 * statuses. Admin PB only (consistent with the other service modules).
 */
import type PocketBase from "pocketbase";
import { getAdminPocketBase } from "./pocketbase-admin";
import { generateStockPurchaseNumber } from "./stock-purchases-service";

const STOCK_ITEMS = "stock_items";
const STOCK_PURCHASES = "stock_purchases";
const STOCK_PURCHASE_ITEMS = "stock_purchase_items";

const SEARCH_LIMIT_MAX = 25;
const SEARCH_LIMIT_DEFAULT = 10;

/* ============================================================================
 * Minimal PB client shape this module needs.
 *
 * The route passes in the real `getAdminPocketBase()`; the unit test
 * passes in a tiny mock. Only the methods we actually call are typed.
 * ========================================================================== */

export interface StockQuickDraftPb {
  collection: (name: string) => {
    getList: (
      page?: number,
      perPage?: number,
      opts?: { filter?: string; sort?: string; expand?: string }
    ) => Promise<{
      items: Array<Record<string, unknown>>;
      totalItems: number;
      page: number;
      perPage: number;
      totalPages: number;
    }>;
    getFullList: (opts?: { filter?: string }) => Promise<Array<Record<string, unknown>>>;
    getOne: (id: string, opts?: { expand?: string }) => Promise<Record<string, unknown>>;
    create: (data: Record<string, unknown>) => Promise<Record<string, unknown>>;
    update: (id: string, data: Record<string, unknown>) => Promise<Record<string, unknown>>;
    delete: (id: string) => Promise<Record<string, unknown>>;
  };
}

/* ============================================================================
 * Public types
 * ========================================================================== */

export interface StockItemSearchResult {
  id: string;
  sku: string;
  name: string;
  description: string;
  unit?: string;
}

export interface SupplierHistoryEntry {
  supplierId: string;
  supplierName: string;
  lastCost: number;
  lastDate: string;
  timesBought: number;
}

export interface AddQuickDraftLineNewStockItem {
  name: string;
  sku: string;
  description?: string;
  unit?: string;
}

export interface AddQuickDraftLineInput {
  supplierId: string;
  stockItemId?: string;
  quantity: number;
  costPrice: number;
  newStockItem?: AddQuickDraftLineNewStockItem;
}

export type AddQuickDraftLineResult =
  | { ok: true; purchaseId: string; purchaseNumber: string; lineId: string; createdDraft: boolean }
  | { ok: false; reason: string; message: string };

export type RemoveQuickDraftLineResult =
  | { ok: true }
  | { ok: false; reason: string; message: string };

/* ============================================================================
 * Helpers
 * ========================================================================== */

async function resolvePb(pb?: StockQuickDraftPb): Promise<StockQuickDraftPb> {
  if (pb) return pb;
  return (await getAdminPocketBase()) as unknown as StockQuickDraftPb;
}

/* ============================================================================
 * searchStockItemsForQuickDraft
 * ========================================================================== */

/**
 * Typeahead search over `stock_items`. Matches `sku` OR `name` with
 * PocketBase's `~` (contains, case-insensitive). Excludes inactive
 * items. Limit defaults to 10, clamped to a max of 25.
 *
 * Returns a narrow projection — only the fields the modal needs.
 */
export async function searchStockItemsForQuickDraft(
  pb: StockQuickDraftPb,
  q: string,
  limit?: number,
): Promise<StockItemSearchResult[]> {
  const safeLimit = Math.min(Math.max(limit ?? SEARCH_LIMIT_DEFAULT, 1), SEARCH_LIMIT_MAX);
  const escaped = q.replace(/"/g, '\\"');
  const filter = `is_active=true && (sku ~ "${escaped}" || name ~ "${escaped}")`;

  const result = await pb.collection(STOCK_ITEMS).getList(1, safeLimit, {
    filter,
    sort: "name",
  });

  return result.items.map((row) => ({
    id: String(row.id),
    sku: String(row.sku ?? ""),
    name: String(row.name ?? ""),
    description: String(row.description ?? ""),
    unit: row.unit ? String(row.unit) : undefined,
  }));
}

/* ============================================================================
 * getStockItemSupplierHistory
 * ========================================================================== */

/**
 * Returns the per-supplier purchase history for a `stock_item`.
 * Reads `stock_purchase_items` joined through `stock_purchases` so
 * we can aggregate by supplier. Filters to lines that have actually
 * been received (`quantity_received > 0`) so drafts don't pollute
 * the "we bought this from X before" list.
 *
 * The supplier is expanded via `purchase.supplier`; if the
 * `stock_purchases.supplier` row no longer exists in `suppliers`,
 * the line is silently skipped (we can't show a name for it).
 */
export async function getStockItemSupplierHistory(
  pb: StockQuickDraftPb,
  stockItemId: string,
): Promise<SupplierHistoryEntry[]> {
  const rows = await pb.collection(STOCK_PURCHASE_ITEMS).getFullList({
    filter: `stock_item = "${stockItemId}" && quantity_received > 0`,
  });

  const purchaseIds = Array.from(
    new Set(
      rows
        .map((r) => (r.purchase ? String(r.purchase) : null))
        .filter((id): id is string => id !== null),
    ),
  );
  if (purchaseIds.length === 0) return [];

  // Fetch purchases in one call (with supplier expanded). We use
  // a single getList rather than N getOnes — cheaper on PB.
  const purchasesResult = await pb
    .collection(STOCK_PURCHASES)
    .getList(1, purchaseIds.length, {
      filter: purchaseIds.map((id) => `id = "${id}"`).join(" || "),
      expand: "supplier",
    });

  const purchaseById = new Map<string, Record<string, unknown>>();
  for (const p of purchasesResult.items) purchaseById.set(String(p.id), p);

  type Agg = {
    supplierId: string;
    supplierName: string;
    lastCost: number;
    lastDate: string;
    timesBought: number;
  };
  const bySupplier = new Map<string, Agg>();

  for (const row of rows) {
    const purchaseId = row.purchase ? String(row.purchase) : null;
    if (!purchaseId) continue;
    const purchase = purchaseById.get(purchaseId);
    if (!purchase) continue;

    const expand = purchase.expand as
      | { supplier?: { id: string; suppliername: string } }
      | undefined;
    const supplier = expand?.supplier;
    if (!supplier) continue;

    const supplierId = String(supplier.id);
    const cost = typeof row.cost_price === "number" ? row.cost_price : 0;
    const created = String(purchase.created ?? "");

    const existing = bySupplier.get(supplierId);
    if (!existing) {
      bySupplier.set(supplierId, {
        supplierId,
        supplierName: String(supplier.suppliername ?? ""),
        lastCost: cost,
        lastDate: created,
        timesBought: 1,
      });
    } else {
      existing.timesBought += 1;
      if (created > existing.lastDate) {
        existing.lastDate = created;
        existing.lastCost = cost;
      }
    }
  }

  return Array.from(bySupplier.values()).sort((a, b) =>
    a.lastDate < b.lastDate ? 1 : a.lastDate > b.lastDate ? -1 : 0,
  );
}