/**
 * Pure mapper from an EDR invoice onto the Ethiopian MoR EIMS registration document
 * (`POST https://core.mor.gov.et/v1/register`).
 *
 * Field names, casing and section layout are taken verbatim from the supplied
 * `EimsCoreApiMockCollection2.postman_collection.json`. Note the payload spells the district
 * `Wereda` even though the collection *variable* is named `sellerWoreda`.
 *
 * Scope: mapping only — no HTTP, no signing, no persistence, no counter allocation. Everything
 * that does not live on the invoice (document number, counters, previous IRN, seller identity,
 * tax treatment) is supplied by the caller and is never guessed here.
 *
 * Values that the collection only *demonstrates* by example — the date format, the meaning of an
 * empty `PreviousIrn`, the `SystemType` enum, `PaymentTerm` values — are treated as observed, not
 * authoritative: they are passed through or overridable rather than validated against a fixed set.
 */

import { round2 } from "./invoice-settlement.util";

/** Only proven-required constant: the 400 SCHEMA ERROR sample rejects a payload without it. */
const EIMS_VERSION = "1";

/** The only `DocumentDetails.Type` observed in the supplied material. */
const EIMS_DOCUMENT_TYPE = "INV";

export interface EimsBuyerDetails {
  City: string | null;
  Email: string | null;
  HouseNumber: string | null;
  IdNumber: string | null;
  IdType: string | null;
  Tin: string;
  LegalName: string;
  Phone: string | null;
  Region: string | null;
  Country: string | null;
  Zone: string | null;
  Kebele: string | null;
  VatNumber: string | null;
  Wereda: string | null;
}

export interface EimsSellerDetails {
  City: string | null;
  Email: string | null;
  HouseNumber: string | null;
  LegalName: string;
  Locality: string | null;
  Phone: string | null;
  /** MoR region *code* (e.g. "13"), not a region name. */
  Region: string | null;
  SubCity: string | null;
  Tin: string;
  VatNumber: string | null;
  /** MoR wereda *code* (e.g. "574"). */
  Wereda: string | null;
}

export interface EimsDocumentDetails {
  DocumentNumber: string;
  /** Observed format `dd-MM-yyyyTHH:mm:ss`. Rule seen in the collection: within 3 days of now. */
  Date: string;
  Type: string;
}

export interface EimsInvoiceItem {
  Discount: number;
  ExciseTaxValue: number;
  HarmonizationCode: string | null;
  NatureOfSupplies: string;
  ItemCode: string;
  ProductDescription: string;
  PreTaxValue: number;
  Quantity: number;
  LineNumber: number;
  TaxAmount: number;
  TaxCode: string;
  TotalLineAmount: number;
  Unit: string;
  UnitPrice: number;
}

export interface EimsPaymentDetails {
  Mode: string;
  PaymentTerm: string;
}

export interface EimsReferenceDetails {
  PreviousIrn: string | null;
  RelatedDocument: string | null;
}

export interface EimsSourceSystem {
  CashierName: string | null;
  InvoiceCounter: number;
  SalesPersonName: string | null;
  SystemNumber: string;
  SystemType: string;
}

export interface EimsValueDetails {
  Discount: number | null;
  ExciseValue: number;
  IncomeWithholdValue: number;
  TaxValue: number;
  TotalValue: number;
  TransactionWithholdValue: number;
  InvoiceCurrency: string;
  /** Absent from the register sample, present on the verify response. Emitted only when supplied. */
  ExchangeRate?: number;
}

export interface EimsInvoiceRequest {
  BuyerDetails: EimsBuyerDetails;
  DocumentDetails: EimsDocumentDetails;
  ItemList: EimsInvoiceItem[];
  PaymentDetails: EimsPaymentDetails;
  ReferenceDetails: EimsReferenceDetails;
  SellerDetails: EimsSellerDetails;
  SourceSystem: EimsSourceSystem;
  TransactionType: string;
  ValueDetails: EimsValueDetails;
  Version: string;
}

/** `body` of a successful `POST /v1/register`, as observed in the collection. */
export interface EimsRegisterResponseBody {
  irn: string;
  ackDate: string;
  signedQR: string;
  signedInvoice: string;
  status: string;
  documentNumber: string;
  errorMessage: string | null;
}

/** Numeric columns arrive from pg as strings; every money field is normalised through `num`. */
export interface EimsMapperLine {
  chargeType: string;
  description?: string | null;
  quantity: number | string;
  unitRate: number | string;
  amount: number | string;
  metadata?: Record<string, unknown> | null;
}

export interface EimsMapperCompany {
  name: string;
  tin: string;
  vatNumber?: string | null;
  phone?: string | null;
  email?: string | null;
  region?: string | null;
  zone?: string | null;
  woreda?: string | null;
  kebele?: string | null;
  houseNo?: string | null;
  country?: string | null;
}

/**
 * Structurally what `BillingService.findById` returns — the only read path that loads the header,
 * the buyer company and the lines together.
 */
export interface EimsMapperInvoice {
  invoiceNumber: string;
  currency: string;
  issuedAt?: Date | string | null;
  totalAmount: number | string;
  company?: EimsMapperCompany | null;
  lines: EimsMapperLine[];
}

/**
 * Tax treatment for a single line. EIMS models `TaxCode`/`TaxAmount`/`ExciseTaxValue` per item, and
 * different charge types may eventually be treated differently, so this is resolved per line.
 *
 * Nothing in this repo can supply it: `Invoice.taxAmount` is hardcoded to 0 with no caller ever
 * setting it, `invoice_lines` has no tax column, and the rate catalogue has no fiscal field. That
 * is the absence of a tax model, not evidence of zero-rating — hence no default here.
 */
export interface EimsLineTax {
  code: string;
  ratePercent: number;
  exciseTaxValue: number;
  /**
   * Line-level `Discount`. Its effect on `TotalLineAmount` has never been observed live (every
   * prior test ran it at 0), so the total below still sums PreTax + Tax + Excise only — do not
   * start subtracting this without a confirmed MoR example.
   */
  discount: number;
}

export interface EimsMapperContext {
  systemNumber: string;
  /** Observed values: POS, MAN, CRM, EFD, SYS (the collection prose also mentions ERP). */
  systemType: string;
  /** Caller decides the source — our own `invoiceNumber` or a dedicated EIMS sequence. */
  documentNumber: string;
  invoiceCounter: number;
  /** Passed through verbatim; the collection shows `""` used for an unchained document. */
  previousIrn: string | null;
  cashierName: string | null;
  salesPersonName: string | null;
  /** B2B / B2C — a tax classification, so the caller states it. */
  transactionType: string;
  payment: { mode: string; term: string };
  /** Must return a treatment for every line, or throw. */
  taxForLine: (line: EimsMapperLine, lineNumber: number) => EimsLineTax;
  natureOfSupplies: string;
  /** Used when a line carries no `metadata.unit`. */
  unitDefault: string;
  incomeWithholdValue: number;
  transactionWithholdValue: number;
  /** Null for an ordinary invoice; set only for a real related-document case. */
  relatedDocument?: string | null;
  /** MoR numeric country code for the buyer; our DB stores the country name. */
  buyerCountryCode?: string | null;
  /**
   * Region name → MoR numeric code, for buyers whose stored region is free text.
   *
   * `companies.region` holds names ("Addis Ababa") while MoR validates `BuyerDetails.Region`
   * against `^[0-9]{1,3}$`. A stored value that is already a code passes through; anything else
   * must be in this map or the mapping **fails locally** — sending a guessed region code onto a
   * tax document is worse than refusing to file.
   */
  buyerRegionCodes: Record<string, string>;
  /**
   * Wereda name → MoR code, same shape as `buyerRegionCodes`. `companies.woreda` holds names
   * ("Yeka") or codes inconsistently; unlike Region, MoR has never named a Wereda regex in an
   * error, so this is precautionary rather than confirmed — but the fix is identical either way:
   * fail locally on an unmapped name rather than file a guess.
   */
  buyerWeredaCodes: Record<string, string>;
  buyerIdType?: string | null;
  buyerIdNumber?: string | null;
  buyerCity?: string | null;
  /** Required when the invoice currency is not ETB. */
  exchangeRate?: number | null;
  invoiceDiscount?: number | null;
  /** Override while the observed `dd-MM-yyyyTHH:mm:ss` format is unconfirmed by MoR. */
  formatDate?: (issuedAt: Date) => string;
}

/**
 * MoR's own constraint on `Region`: one to three digits, confirmed by its 400 SCHEMA ERROR. Reused
 * as the pass-through test for `Wereda` too — every Wereda value MoR has actually shown us (seller
 * "12"/"13", the collection's "574") fits the same shape, though MoR has not named a Wereda regex
 * the way it named Region's.
 */
const LOCATION_CODE = /^[0-9]{1,3}$/;

/**
 * The only two values MoR accepts for `NatureOfSupplies`, lowercase.
 *
 * Its schema branches on this as a `oneOf` with a `const` per branch, so `"Service"` fails the
 * whole `ItemList` — the error reads "must be the constant value 'service'".
 */
const NATURE_OF_SUPPLIES = ["goods", "service"] as const;

const num = (v: number | string): number => {
  const n = Number(v);
  if (!Number.isFinite(n)) throw new Error(`EIMS mapping: expected a numeric value, got ${String(v)}`);
  return n;
};

const pad = (n: number, width = 2): string => String(n).padStart(width, "0");

/** Observed EIMS document-date format: `dd-MM-yyyyTHH:mm:ss`, no timezone marker. */
export const formatEimsDate = (issuedAt: Date): string =>
  `${pad(issuedAt.getDate())}-${pad(issuedAt.getMonth() + 1)}-${issuedAt.getFullYear()}` +
  `T${pad(issuedAt.getHours())}:${pad(issuedAt.getMinutes())}:${pad(issuedAt.getSeconds())}`;

/**
 * Map one loaded invoice onto an EIMS registration document.
 *
 * Throws rather than emitting a payload EIMS would reject opaquely: missing buyer TIN, no lines,
 * an unissued invoice, unresolved line tax, a line/total mismatch, or a non-ETB invoice with no
 * exchange rate.
 */
/**
 * A buyer's location value (Region or Wereda) as a MoR code: passed through when already numeric,
 * otherwise looked up by name (case- and space-insensitive). Throws when neither applies — sending
 * a guessed code onto a tax document is worse than refusing to file.
 */
function resolveLocationCode(
  field: "Region" | "Wereda",
  value: string | null | undefined,
  codes: Record<string, string>,
  envVar: string,
  invoiceNumber: string,
): string {
  const raw = (value ?? "").trim();
  if (LOCATION_CODE.test(raw)) return raw;

  const key = raw.toLowerCase().replace(/\s+/g, " ");
  const mapped = Object.entries(codes).find(
    ([name]) => name.trim().toLowerCase().replace(/\s+/g, " ") === key,
  )?.[1];
  if (mapped && LOCATION_CODE.test(mapped)) return mapped;

  throw new Error(
    `EIMS mapping: invoice ${invoiceNumber} has buyer ${field} ${raw ? `"${raw}"` : "(unset)"}, ` +
      `which is not a MoR ${field} code and has no mapping. Add it to ${envVar}.`,
  );
}

export function toEimsInvoice(
  invoice: EimsMapperInvoice,
  seller: EimsSellerDetails,
  context: EimsMapperContext,
): EimsInvoiceRequest {
  const company = invoice.company;
  if (!company || !company.tin?.trim()) {
    throw new Error(`EIMS mapping: invoice ${invoice.invoiceNumber} has no buyer company TIN`);
  }
  if (!invoice.lines?.length) {
    throw new Error(`EIMS mapping: invoice ${invoice.invoiceNumber} has no lines`);
  }
  if (!invoice.issuedAt) {
    throw new Error(`EIMS mapping: invoice ${invoice.invoiceNumber} is not issued (issuedAt is null)`);
  }
  if (invoice.currency !== "ETB" && context.exchangeRate == null) {
    throw new Error(
      `EIMS mapping: invoice ${invoice.invoiceNumber} is in ${invoice.currency} and needs an exchangeRate`,
    );
  }

  const issuedAt = invoice.issuedAt instanceof Date ? invoice.issuedAt : new Date(invoice.issuedAt);
  if (Number.isNaN(issuedAt.getTime())) {
    throw new Error(`EIMS mapping: invoice ${invoice.invoiceNumber} has an unparseable issuedAt`);
  }

  const natureOfSupplies = context.natureOfSupplies.trim().toLowerCase();
  if (!NATURE_OF_SUPPLIES.includes(natureOfSupplies as (typeof NATURE_OF_SUPPLIES)[number])) {
    throw new Error(
      `EIMS mapping: NatureOfSupplies must be one of ${NATURE_OF_SUPPLIES.join(", ")}, ` +
        `got "${context.natureOfSupplies}"`,
    );
  }

  const ItemList: EimsInvoiceItem[] = invoice.lines.map((line, index) => {
    const lineNumber = index + 1;
    const tax = context.taxForLine(line, lineNumber);
    if (
      !tax ||
      !tax.code ||
      !Number.isFinite(tax.ratePercent) ||
      !Number.isFinite(tax.exciseTaxValue) ||
      !Number.isFinite(tax.discount)
    ) {
      throw new Error(
        `EIMS mapping: unresolved tax treatment for line ${lineNumber} (${line.chargeType}) ` +
          `on invoice ${invoice.invoiceNumber}`,
      );
    }

    const PreTaxValue = round2(num(line.amount));
    const TaxAmount = round2((PreTaxValue * tax.ratePercent) / 100);
    const ExciseTaxValue = round2(tax.exciseTaxValue);
    const unit = typeof line.metadata?.unit === "string" ? line.metadata.unit : context.unitDefault;

    return {
      Discount: round2(tax.discount),
      ExciseTaxValue,
      HarmonizationCode: null,
      NatureOfSupplies: natureOfSupplies,
      ItemCode: line.chargeType,
      ProductDescription: line.description?.trim() || line.chargeType,
      PreTaxValue,
      Quantity: round2(num(line.quantity)),
      LineNumber: lineNumber,
      TaxAmount,
      TaxCode: tax.code,
      TotalLineAmount: round2(PreTaxValue + TaxAmount + ExciseTaxValue),
      Unit: unit,
      UnitPrice: round2(num(line.unitRate)),
    };
  });

  const preTaxTotal = round2(ItemList.reduce((sum, item) => sum + item.PreTaxValue, 0));
  const invoiceTotal = round2(num(invoice.totalAmount));
  if (Math.abs(preTaxTotal - invoiceTotal) > 0.01) {
    throw new Error(
      `EIMS mapping: invoice ${invoice.invoiceNumber} lines sum to ${preTaxTotal} ` +
        `but the invoice total is ${invoiceTotal}`,
    );
  }

  const ValueDetails: EimsValueDetails = {
    Discount: context.invoiceDiscount ?? null,
    ExciseValue: round2(ItemList.reduce((sum, item) => sum + item.ExciseTaxValue, 0)),
    IncomeWithholdValue: context.incomeWithholdValue,
    TaxValue: round2(ItemList.reduce((sum, item) => sum + item.TaxAmount, 0)),
    TotalValue: round2(ItemList.reduce((sum, item) => sum + item.TotalLineAmount, 0)),
    TransactionWithholdValue: context.transactionWithholdValue,
    InvoiceCurrency: invoice.currency,
  };
  if (context.exchangeRate != null) ValueDetails.ExchangeRate = context.exchangeRate;

  return {
    BuyerDetails: {
      City: context.buyerCity ?? null,
      Email: company.email ?? null,
      HouseNumber: company.houseNo ?? null,
      IdNumber: context.buyerIdNumber ?? null,
      IdType: context.buyerIdType ?? null,
      Tin: company.tin,
      LegalName: company.name,
      Phone: company.phone ?? null,
      Region: resolveLocationCode(
        "Region",
        company.region,
        context.buyerRegionCodes,
        "EIMS_BUYER_REGION_CODES",
        invoice.invoiceNumber,
      ),
      Country: context.buyerCountryCode ?? null,
      Zone: company.zone ?? null,
      Kebele: company.kebele ?? null,
      VatNumber: company.vatNumber ?? null,
      Wereda: resolveLocationCode(
        "Wereda",
        company.woreda,
        context.buyerWeredaCodes,
        "EIMS_BUYER_WEREDA_CODES",
        invoice.invoiceNumber,
      ),
    },
    DocumentDetails: {
      DocumentNumber: context.documentNumber,
      Date: (context.formatDate ?? formatEimsDate)(issuedAt),
      Type: EIMS_DOCUMENT_TYPE,
    },
    ItemList,
    PaymentDetails: { Mode: context.payment.mode, PaymentTerm: context.payment.term },
    ReferenceDetails: {
      PreviousIrn: context.previousIrn,
      RelatedDocument: context.relatedDocument ?? null,
    },
    SellerDetails: seller,
    SourceSystem: {
      CashierName: context.cashierName,
      InvoiceCounter: context.invoiceCounter,
      SalesPersonName: context.salesPersonName,
      SystemNumber: context.systemNumber,
      SystemType: context.systemType,
    },
    TransactionType: context.transactionType,
    ValueDetails,
    Version: EIMS_VERSION,
  };
}