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);
  assertChargeTypeOverrides(config.invoice);
}

/**
 * Per-`chargeType` tax overrides must be internally consistent before anything is filed:
 * `EIMS_TAX_CODE_BY_CHARGE_TYPE` and `EIMS_TAX_RATE_BY_CHARGE_TYPE` must name the same charge
 * types (a code with no rate, or vice versa, is a half-finished override), and every rate/excise/
 * discount value must parse as a number — checked once here rather than once per line at
 * registration time.
 */
function assertChargeTypeOverrides(invoice: EimsConfig["invoice"]): void {
  const codeKeys = Object.keys(invoice.taxCodeByChargeType);
  const rateKeys = Object.keys(invoice.taxRateByChargeType);
  const mismatched = [...new Set([...codeKeys, ...rateKeys])].filter(
    (k) => !(codeKeys.includes(k) && rateKeys.includes(k)),
  );
  if (mismatched.length > 0) {
    throw new BadRequestException({
      code: "EIMS_INVOICE_CONFIG_INVALID",
      message:
        `EIMS_TAX_CODE_BY_CHARGE_TYPE and EIMS_TAX_RATE_BY_CHARGE_TYPE must list the same charge ` +
        `types; mismatched: ${mismatched.join(", ")}`,
    });
  }

  const numericMaps: { env: string; map: Record<string, string> }[] = [
    { env: "EIMS_TAX_RATE_BY_CHARGE_TYPE", map: invoice.taxRateByChargeType },
    { env: "EIMS_EXCISE_BY_CHARGE_TYPE", map: invoice.exciseByChargeType },
    { env: "EIMS_DISCOUNT_BY_CHARGE_TYPE", map: invoice.discountByChargeType },
  ];
  const badNumbers = numericMaps.flatMap(({ env, map }) =>
    Object.entries(map)
      .filter(([, value]) => !Number.isFinite(Number(value)))
      .map(([chargeType]) => `${env}[${chargeType}]`),
  );
  if (badNumbers.length > 0) {
    throw new BadRequestException({
      code: "EIMS_INVOICE_CONFIG_INVALID",
      message: `EIMS charge-type overrides must be numbers: ${badNumbers.join(", ")}`,
    });
  }
}

/**
 * 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;
  /** `DocumentDetails.Type` — defaults to "INV" in the mapper when omitted. */
  documentType?: EimsMapperContext["documentType"];
  /** Required (by the mapper) when documentType is DEB/CRE. */
  reason?: string | null;
  /** `ReferenceDetails.RelatedDocument` — the original invoice's IRN, required for DEB/CRE. */
  relatedDocument?: string | 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 },
    // Per-`chargeType` override when one is configured (validated symmetric in
    // assertChargeTypeOverrides), else the single invoice-wide default.
    taxForLine: (line: EimsMapperLine) => {
      const { chargeType } = line;
      const code = invoice.taxCodeByChargeType[chargeType] ?? taxCode;
      const rate =
        chargeType in invoice.taxRateByChargeType
          ? Number(invoice.taxRateByChargeType[chargeType])
          : ratePercent;
      const excise =
        chargeType in invoice.exciseByChargeType
          ? Number(invoice.exciseByChargeType[chargeType])
          : exciseTaxValue;
      const discount =
        chargeType in invoice.discountByChargeType
          ? Number(invoice.discountByChargeType[chargeType])
          : 0;
      return { code, ratePercent: rate, exciseTaxValue: excise, discount };
    },
    natureOfSupplies: invoice.natureOfSupplies,
    unitDefault: invoice.unitDefault,
    incomeWithholdValue: invoice.incomeWithholdValue!,
    transactionWithholdValue: invoice.transactionWithholdValue!,
    buyerCountryCode: invoice.buyerCountryCode,
    buyerCountryCodes: invoice.buyerCountryCodes,
    buyerRegionCodes: invoice.buyerRegionCodes,
    buyerWeredaCodes: invoice.buyerWeredaCodes,
    buyerCityCodes: invoice.buyerCityCodes,
    // TEMPORARY — see EimsInvoiceConfig.buyerIdType.
    buyerIdType: invoice.buyerIdType,
    buyerIdNumber: invoice.buyerIdNumber,
    exchangeRate: input.exchangeRate ?? null,
    documentType: input.documentType,
    reason: input.reason ?? null,
    relatedDocument: input.relatedDocument ?? null,
  };
}