import { ok, err } from "@tailor-platform/erp-kit/core";
import type { Transaction } from "../generated/kysely-tailordb";
import {
  CategoryNotActiveError,
  DuplicateUnitSymbolError,
  InvalidConversionFactorError,
  InvalidRoundingPrecisionError,
  UomCategoryNotFoundError,
} from "../lib/errors.generated";

interface CreateUnitInput {
  categoryId: string;
  name: string;
  symbol: string;
  conversionFactor: number;
  roundingPrecision: number;
}

/**
 * Function: createUnit
 *
 * Adds a new unit of measure to an existing category with its symbol,
 * display name, and conversion factor relative to the reference unit.
 */
export async function run<CF extends Record<string, unknown>>(
  db: Transaction,
  input: CreateUnitInput & CF,
) {
  const { categoryId, name, symbol, conversionFactor, roundingPrecision, ...customFields } = input;

  // 1. Check category exists
  const uoMCategory = await db
    .selectFrom("UoMCategory")
    .selectAll()
    .where("id", "=", categoryId)
    .executeTakeFirst();

  if (!uoMCategory) {
    return err(new UomCategoryNotFoundError(categoryId));
  }

  // 2. Check category is active
  if (uoMCategory.status !== "ACTIVE") {
    return err(new CategoryNotActiveError(categoryId));
  }

  // 3. Check symbol uniqueness within category
  const existingUnit = await db
    .selectFrom("Unit")
    .selectAll()
    .where("categoryId", "=", categoryId)
    .where("symbol", "=", symbol)
    .forUpdate()
    .executeTakeFirst();

  if (existingUnit) {
    return err(new DuplicateUnitSymbolError(`${symbol} in ${categoryId}`));
  }

  // 4. Validate conversion factor
  if (conversionFactor <= 0) {
    return err(new InvalidConversionFactorError(String(conversionFactor)));
  }

  // 5. Validate rounding precision
  if (roundingPrecision < 0) {
    return err(new InvalidRoundingPrecisionError(String(roundingPrecision)));
  }

  // 6. Create unit
  const unit = await db
    .insertInto("Unit")
    .values({
      ...(customFields as Record<string, unknown>),
      name,
      symbol,
      categoryId,
      conversionFactor,
      roundingPrecision,
      status: "ACTIVE" as const,
    })
    .returningAll()
    .executeTakeFirstOrThrow();

  return ok({ unit });
}