import { BadRequestException } from "@nestjs/common";
import { EimsConfig } from "../../config/eims.config";
import { EimsSessionContext } from "./eims-auth.service";
import {
  EimsMapperContext,
  EimsMapperLine,
  EimsSellerDetails,
} from "../billing/eims-invoice.mapper";

/**
 * Turns configuration into the seller identity and mapper context that `toEimsInvoice` requires.
 *
 * Everything here is unavailable from the database by construction: EDR's own legal identity is not
 * modelled anywhere, and the application has no tax model at all (`invoice.taxAmount` is always 0,
 * `invoice_lines` and the rate catalogue carry no fiscal columns). Rather than defaulting any of it,
 * a missing value fails **here** — locally, before a single byte reaches the gateway — naming the
 * exact environment variables to set.
 */

interface RequiredSpec {
  env: string;
  value: string | number | null | undefined;
}

// `systemNumber` / `systemType` are absent by design: they come from the access token, which is
// MoR's own statement of who we are. See EimsAuthService.getSessionContext.
const REQUIRED = (invoice: EimsConfig["invoice"], tin: string): RequiredSpec[] => [
  { env: "EIMS_TIN", value: tin },
  { env: "EIMS_SELLER_LEGAL_NAME", value: invoice.sellerLegalName },
  { env: "EIMS_SELLER_VAT_NUMBER", value: invoice.sellerVatNumber },
  { env: "EIMS_SELLER_PHONE", value: invoice.sellerPhone },
  { env: "EIMS_SELLER_EMAIL", value: invoice.sellerEmail },
  { env: "EIMS_SELLER_REGION", value: invoice.sellerRegion },
  { env: "EIMS_SELLER_WEREDA", value: invoice.sellerWereda },
  { env: "EIMS_TAX_CODE", value: invoice.taxCode },
  { env: "EIMS_TAX_RATE_PERCENT", value: invoice.taxRatePercent },
  { env: "EIMS_INCOME_WITHHOLD_VALUE", value: invoice.incomeWithholdValue },
  { env: "EIMS_TRANSACTION_WITHHOLD_VALUE", value: invoice.transactionWithholdValue },
  { env: "EIMS_TRANSACTION_TYPE", value: invoice.transactionType },
  { env: "EIMS_NATURE_OF_SUPPLIES", value: invoice.natureOfSupplies },
  { env: "EIMS_PAYMENT_MODE", value: invoice.paymentMode },
  { env: "EIMS_PAYMENT_TERM", value: invoice.paymentTerm },
  { env: "EIMS_UNIT_DEFAULT", value: invoice.unitDefault },
];

/** Throws naming every unset variable at once, so one round trip fixes the whole configuration. */
export function assertEimsInvoiceConfig(config: EimsConfig): void {
  const missing = REQUIRED(config.invoice, config.tin)
    .filter(({ value }) => value === null || value === undefined || value === "")
    .map(({ env }) => env);

  if (missing.length > 0) {
    throw new BadRequestException({
      code: "EIMS_INVOICE_CONFIG_INCOMPLETE",
      message:
        "EIMS invoice registration is not configured. Set these environment variables " +
        `(tax values need finance sign-off — they are deliberately not defaulted): ${missing.join(", ")}`,
    });
  }

  assertSellerFormats(config.invoice);
}

/**
 * MoR's own patterns for the seller fields, checked here rather than at the gateway.
 *
 * A placeholder like `_` is "set" but unfilable, and finding that out costs a real request and a
 * consumed counter — these are the exact regexes its 400 SCHEMA ERROR quoted back at us.
 */
const SELLER_FORMATS: { env: string; value: (i: EimsConfig["invoice"]) => string; pattern: RegExp }[] = [
  { env: "EIMS_SELLER_PHONE", value: (i) => i.sellerPhone, pattern: /^\+?[0-9]{6,}$/ },
  {
    env: "EIMS_SELLER_EMAIL",
    value: (i) => i.sellerEmail,
    pattern: /^[a-zA-Z0-9+_.-]+@[a-zA-Z0-9.-]+$/,
  },
  { env: "EIMS_SELLER_REGION", value: (i) => i.sellerRegion, pattern: /^[0-9]{1,3}$/ },
  { env: "EIMS_SELLER_WEREDA", value: (i) => i.sellerWereda, pattern: /^[0-9A-Za-z]{1,10}$/ },
];

function assertSellerFormats(invoice: EimsConfig["invoice"]): void {
  const bad = SELLER_FORMATS.filter(({ value, pattern }) => !pattern.test(value(invoice))).map(
    ({ env, pattern }) => `${env} (must match ${pattern.source})`,
  );
  if (bad.length > 0) {
    throw new BadRequestException({
      code: "EIMS_INVOICE_CONFIG_INVALID",
      message: `EIMS seller details would be rejected by MoR: ${bad.join("; ")}`,
    });
  }
}

export function buildEimsSeller(config: EimsConfig): EimsSellerDetails {
  const { invoice } = config;
  return {
    City: invoice.sellerCity,
    Email: invoice.sellerEmail,
    HouseNumber: invoice.sellerHouseNumber,
    LegalName: invoice.sellerLegalName,
    Locality: invoice.sellerLocality,
    Phone: invoice.sellerPhone,
    Region: invoice.sellerRegion,
    SubCity: invoice.sellerSubCity,
    Tin: config.tin,
    VatNumber: invoice.sellerVatNumber,
    Wereda: invoice.sellerWereda,
  };
}

export interface EimsContextInput {
  /** `DocumentDetails.DocumentNumber`. The caller decides its source. */
  documentNumber: string;
  invoiceCounter: number;
  previousIrn: string | null;
  /** Source-system identity from the access token, never from configuration. */
  session: EimsSessionContext;
  /** Required when the invoice currency is not ETB. */
  exchangeRate?: number | null;
}

export function buildEimsContext(config: EimsConfig, input: EimsContextInput): EimsMapperContext {
  const { invoice } = config;
  // Validated by assertEimsInvoiceConfig; the non-null assertions below are safe after that call.
  const taxCode = invoice.taxCode;
  const ratePercent = invoice.taxRatePercent!;
  const exciseTaxValue = invoice.exciseTaxValue ?? 0;

  return {
    systemNumber: input.session.systemNumber,
    systemType: input.session.systemType,
    documentNumber: input.documentNumber,
    invoiceCounter: input.invoiceCounter,
    previousIrn: input.previousIrn,
    cashierName: invoice.cashierName,
    salesPersonName: invoice.salesPersonName,
    transactionType: invoice.transactionType,
    payment: { mode: invoice.paymentMode, term: invoice.paymentTerm },
    // One treatment for every line today. The mapper resolves tax per line, so a future
    // charge-type-specific rule slots in here without touching the mapper.
    taxForLine: (_line: EimsMapperLine) => ({ code: taxCode, ratePercent, exciseTaxValue }),
    natureOfSupplies: invoice.natureOfSupplies,
    unitDefault: invoice.unitDefault,
    incomeWithholdValue: invoice.incomeWithholdValue!,
    transactionWithholdValue: invoice.transactionWithholdValue!,
    buyerCountryCode: invoice.buyerCountryCode,
    buyerRegionCodes: invoice.buyerRegionCodes,
    exchangeRate: input.exchangeRate ?? null,
  };
}