import {
  ok,
  err,
  type ReadonlyDB,
  type PaginationInput,
  buildPaginatedResult,
  DEFAULT_PAGE_SIZE,
} from "@tailor-platform/erp-kit/core";
import { Decimal } from "decimal.js";
import type { DB } from "../generated/kysely-tailordb";
import { sumOpenStockReservationQuantity } from "../internal/stockReservation";
import { NoFilterProvidedError } from "../lib/errors.generated";

type OrderByField = "createdAt";

export interface ListStockLevelsInput extends PaginationInput<OrderByField> {
  itemId?: string;
  storageLocationId?: string;
  siteId?: string;
}

function reservationByItemLocation(
  reservations: Array<{
    itemId: string;
    storageLocationId: string | null;
    reservedQuantity: string;
    consumedQuantity: string;
  }>,
) {
  const byKey = new Map<string, Decimal>();
  for (const reservation of reservations) {
    if (!reservation.storageLocationId) {
      continue;
    }
    const key = `${reservation.itemId}:${reservation.storageLocationId}`;
    const openQuantity = sumOpenStockReservationQuantity([reservation]);
    byKey.set(key, (byKey.get(key) ?? new Decimal(0)).plus(openQuantity));
  }
  return byKey;
}

export async function run(db: ReadonlyDB<DB>, input: ListStockLevelsInput) {
  if (!input.itemId && !input.storageLocationId && !input.siteId) {
    return err(new NoFilterProvidedError("listStockLevels"));
  }

  const limit = input.limit ?? DEFAULT_PAGE_SIZE;
  const offset = input.offset ?? 0;
  const orderBy = input.orderBy ?? "createdAt";
  const orderDirection = input.orderDirection ?? "asc";

  if (input.siteId) {
    const locationIds = await db
      .selectFrom("StorageLocation")
      .select("id")
      .where("siteId", "=", input.siteId)
      .execute();

    if (locationIds.length === 0) {
      return ok(buildPaginatedResult([], limit));
    }

    let query = db
      .selectFrom("StockLevel")
      .selectAll()
      .where(
        "storageLocationId",
        "in",
        locationIds.map((l) => l.id),
      );

    if (input.itemId) {
      query = query.where("itemId", "=", input.itemId);
    }

    const stockLevels = await query
      .orderBy(orderBy, orderDirection)
      .limit(limit + 1)
      .offset(offset)
      .execute();
    let reservationQuery = db
      .selectFrom("StockReservation")
      .selectAll()
      .where(
        "storageLocationId",
        "in",
        locationIds.map((l) => l.id),
      )
      .where("status", "=", "OPEN");

    if (input.itemId) {
      reservationQuery = reservationQuery.where("itemId", "=", input.itemId);
    }

    const reservationsResult = await reservationQuery.execute();
    const reservations = Array.isArray(reservationsResult) ? reservationsResult : [];
    const reservedByKey = reservationByItemLocation(reservations);

    const items = stockLevels.map((row) => ({
      ...row,
      availableQuantity:
        row.stockType === "AVAILABLE"
          ? new Decimal(row.quantity)
              .minus(reservedByKey.get(`${row.itemId}:${row.storageLocationId}`) ?? 0)
              .toString()
          : "0",
    }));

    return ok(buildPaginatedResult(items, limit));
  }

  let query = db.selectFrom("StockLevel").selectAll();

  if (input.itemId) {
    query = query.where("itemId", "=", input.itemId);
  }
  if (input.storageLocationId) {
    query = query.where("storageLocationId", "=", input.storageLocationId);
  }

  const stockLevels = await query
    .orderBy(orderBy, orderDirection)
    .limit(limit + 1)
    .offset(offset)
    .execute();
  let reservationQuery = db.selectFrom("StockReservation").selectAll();

  if (input.itemId) {
    reservationQuery = reservationQuery.where("itemId", "=", input.itemId);
  }
  if (input.storageLocationId) {
    reservationQuery = reservationQuery.where("storageLocationId", "=", input.storageLocationId);
  }
  reservationQuery = reservationQuery.where("status", "=", "OPEN");

  const reservationsResult = await reservationQuery.execute();
  const reservations = Array.isArray(reservationsResult) ? reservationsResult : [];
  const reservedByKey = reservationByItemLocation(reservations);

  const items = stockLevels.map((row) => ({
    ...row,
    availableQuantity:
      row.stockType === "AVAILABLE"
        ? new Decimal(row.quantity)
            .minus(reservedByKey.get(`${row.itemId}:${row.storageLocationId}`) ?? 0)
            .toString()
        : "0",
  }));

  return ok(buildPaginatedResult(items, limit));
}