import { Injectable } from "@nestjs/common";
import type { ServiceKind } from "@jorgecuadros/database";
import { PrismaService } from "../prisma/prisma.service";
import type { ParsedStatement } from "./parsers/statement-parser";

export interface MatchResult {
  propertyServiceId: string | null;
  customerId: string | null;
  /** Why it landed here — shown in the review queue verbatim. */
  note: string;
  /** True only for an unambiguous hit on the scoped field. */
  confident: boolean;
  /** Populated when more than one service claims the same number. */
  candidates: { propertyServiceId: string; customerId: string; customerName: string }[];
}

/**
 * Resolves a parsed statement to the customer who should be billed for it.
 *
 * Two rules govern everything here.
 *
 * **Match on one scoped field, never fuzzily across all identifiers.** Each
 * service kind has exactly one column its statements print, and only that
 * column is consulted. A blanket search over accountNumber/meterNumber/route
 * would let a water account number collide with an unrelated phone number, and
 * the resulting mis-post would look perfectly ordinary in the ledger.
 *
 * **Never match on the customer name.** The name on a utility bill is the
 * account's registrant, which drifts from the current owner and is often years
 * stale — one sample CESPT receipt is printed to "ARNAIZ ROSAS ELSA AURORA"
 * for an account this office holds under "CATT, RANDY", who is not the same
 * person. Names are displayed for the reviewer to sanity-check, and are never
 * an input to matching.
 */
/**
 * Which `PropertyService` column a given kind's statements actually print.
 *
 * Exported because the same answer governs three places that must agree: the
 * lookup here, the blank-service fill on review, and the write-back on confirm.
 * When they disagree, a reference gets learned into a column nothing searches,
 * and the same page returns to the review queue every month forever.
 *
 * `meterNumber` is doing double duty for the three kinds whose printed
 * reference DATMEX never held in `accountNumber`:
 *   - GAS, where the number lived in free-text notes,
 *   - PROPERTY_TAX, where `accountNumber` holds DATMEX.predial — a 3-4 digit
 *     office file number that is neither unique nor printed on any statement.
 *     The Tijuana municipal receipt prints an 8-digit account and no clave
 *     catastral at all, so it needs a column of its own; overwriting the legacy
 *     predial numbers to make room would destroy the only link back to the
 *     original records, and
 *   - FEDERAL_ZONE, where `accountNumber` holds DATMEX.zfed, which is not a
 *     reference of any kind but a peso amount: 3 of its 77 values carry cents
 *     (`246.06`, `2369.09`, `22653.94`) and one is negative. Searching it for
 *     the concession clave the receipt prints would never hit, and — worse —
 *     because every row already has a value, the `[field]: null` guards in
 *     `learnAccountRefs` and the blank-service fill would never fire either, so
 *     the same page would return to the review queue every bimester forever.
 */
export function scopedRefField(
  kind: ServiceKind,
): "accountNumber" | "meterNumber" | null {
  switch (kind) {
    case "ELECTRIC": // CFE "NO. DE SERVICIO" -> DATMEX.rpu
    case "WATER": // CESPT "Cuenta" / "No. DE CUENTA" -> DATMEX.agua
    case "TELEPHONE": // Telnor "Teléfono" (LADA stripped) -> DATMEX.telefono
    case "CABLE":
      return "accountNumber";
    case "GAS": // bajagas "Cuenta" -> recovered from notes into meterNumber
    case "PROPERTY_TAX": // Tijuana's 8-digit municipal account
    case "FEDERAL_ZONE": // ZOFEMAT concession clave, e.g. `12T012`
      return "meterNumber";
    default:
      return null;
  }
}

@Injectable()
export class StatementMatcherService {
  constructor(private readonly prisma: PrismaService) {}

  async match(parsed: ParsedStatement, expectedKind: ServiceKind): Promise<MatchResult> {
    const kind = parsed.serviceKind ?? expectedKind;

    // The uploader labels a batch with one service kind. If the parser reads a
    // page as a different provider, that is a mis-sorted page, not a match —
    // posting it would book a phone bill as a water charge.
    if (parsed.serviceKind && parsed.serviceKind !== expectedKind) {
      return this.unmatched(
        `la página parece de ${parsed.provider} (${parsed.serviceKind}) pero el lote es de ${expectedKind}`,
      );
    }

    const field = scopedRefField(kind);

    if (field && parsed.accountRef) {
      const hit = await this.byServiceField(kind, field, parsed.accountRef);
      if (hit) return hit;
    }

    // The clave catastral is printed on CESPT bills as well as predial ones, so
    // it rescues a page whose account number did not OCR — which happened on
    // real samples, where the clave read cleanly and the account number did
    // not. On the Rosarito and Ensenada predial layouts it is not a rescue at
    // all but the only identifier the receipt carries, so a unique hit there is
    // as good as any account-number match and is treated as one.
    if (parsed.cadastralKey) {
      const primary = kind === "PROPERTY_TAX" && !parsed.accountRef;
      const hit = await this.byCadastralKey(kind, parsed.cadastralKey, primary);
      if (hit) return hit;
    }

    if (!field && !parsed.cadastralKey) {
      return this.unmatched(`no hay campo de búsqueda definido para ${kind}`);
    }
    if (!parsed.accountRef && !parsed.cadastralKey) {
      return this.unmatched(
        kind === "PROPERTY_TAX"
          ? "no se leyó ni la clave catastral ni la cuenta municipal"
          : "no se pudo leer la referencia de la cuenta",
      );
    }
    return this.unmatched(
      parsed.accountRef
        ? `no se encontró ningún servicio de ${kind} con la referencia ${parsed.accountRef}`
        : `no se encontró ninguna propiedad con la clave catastral ${parsed.cadastralKey}`,
    );
  }

  private async byServiceField(
    kind: ServiceKind,
    field: "accountNumber" | "meterNumber",
    ref: string,
  ): Promise<MatchResult | null> {
    const rows = await this.prisma.propertyService.findMany({
      where: { kind, [field]: ref },
      select: {
        id: true,
        property: {
          select: { customerId: true, customer: { select: { name: true } } },
        },
      },
    });
    if (rows.length === 0) return null;

    const candidates = rows.map((r) => ({
      propertyServiceId: r.id,
      customerId: r.property.customerId,
      customerName: r.property.customer.name,
    }));

    // Duplicate account numbers do occur in the legacy data (the office's own
    // DUPLICADOS report existed for a reason), so every candidate is surfaced
    // for the reviewer to choose rather than one being picked arbitrarily.
    if (rows.length > 1) {
      return {
        propertyServiceId: null,
        customerId: null,
        note: `${rows.length} servicios comparten la referencia ${ref}`,
        confident: false,
        candidates,
      };
    }

    return {
      propertyServiceId: candidates[0].propertyServiceId,
      customerId: candidates[0].customerId,
      note: `coincidencia exacta por ${field === "accountNumber" ? "número de cuenta" : "medidor"} ${ref}`,
      confident: true,
      candidates,
    };
  }

  private async byCadastralKey(
    kind: ServiceKind,
    key: string,
    /** True when the clave is the identifier the statement was issued against. */
    primary: boolean,
  ): Promise<MatchResult | null> {
    const props = await this.prisma.property.findMany({
      where: { cadastralKey: key },
      select: {
        customerId: true,
        customer: { select: { name: true } },
        services: { where: { kind }, select: { id: true } },
      },
    });
    if (props.length === 0) return null;

    const candidates = props.flatMap((p) =>
      (p.services.length ? p.services.map((s) => s.id) : [null]).map((sid) => ({
        propertyServiceId: sid as string,
        customerId: p.customerId,
        customerName: p.customer.name,
      })),
    );

    if (candidates.length > 1) {
      return {
        propertyServiceId: null,
        customerId: null,
        note: `${candidates.length} propiedades comparten la clave catastral ${key}`,
        confident: false,
        candidates,
      };
    }

    // When the clave is the *secondary* key — a utility bill that also happens
    // to print it — the page is left for review, because the clave was not the
    // number the statement was issued against and confirming is what teaches
    // the matcher the account number for next month. When it is the primary key
    // (Rosarito and Ensenada predial, which print nothing else), a unique hit
    // is a real match and there is no second number to learn.
    return {
      propertyServiceId: candidates[0].propertyServiceId ?? null,
      customerId: candidates[0].customerId,
      note: primary
        ? `coincidencia exacta por clave catastral ${key}`
        : `identificado por clave catastral ${key}; confirme para registrar también el número de cuenta`,
      // A clave with no service row of the right kind behind it still needs a
      // human: there is nothing to attach the posting to.
      confident: primary && candidates[0].propertyServiceId != null,
      candidates,
    };
  }

  private unmatched(note: string): MatchResult {
    return {
      propertyServiceId: null,
      customerId: null,
      note,
      confident: false,
      candidates: [],
    };
  }
}