import { HttpException, HttpStatus, Injectable, Logger, UnauthorizedException } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { AdminRole, CustomerKind, MessageAudience, Prisma } from '@prisma/client';
import * as bcrypt from 'bcryptjs';
import { PrismaService } from '../../prisma/prisma.service';
import { envOr, envOrNull } from '../../common/env';
import { CUSTOMER_TOKEN_TYPE, EXPERT_TOKEN_TYPE, type CustomerJwtPayload } from './customer-jwt.strategy';
import { faToEn } from './digits';
import { SmsService, smsConfigured } from '../sms/sms.service';

/** Nest 10 has no TooManyRequestsException; 429 with a Persian message. */
class TooManyRequestsException extends HttpException {
  constructor(message: string) {
    super(message, HttpStatus.TOO_MANY_REQUESTS);
  }
}

/** How long a code stays usable. The reference had no expiry at all (D6). */
const OTP_TTL_MS = 2 * 60 * 1000;
/** Wrong guesses allowed against one challenge before it is burned. */
const MAX_ATTEMPTS = 5;
/** Sends allowed per mobile number inside the window. */
const MAX_SENDS_PER_MOBILE = 5;
/** Sends allowed per source IP inside the window. */
const MAX_SENDS_PER_IP = 20;
const SEND_WINDOW_MS = 10 * 60 * 1000;
/** Minimum gap between two sends to the same number. */
const RESEND_COOLDOWN_MS = 60 * 1000;

/**
 * D20 — the delivery master OTP.
 *
 * Read from `OTP_MASTER_CODE` and NEVER hardcoded. Unset or empty disables it
 * completely, which is the state every real deployment must be in.
 *
 * Read through a function rather than a module constant so tests (and a
 * restart-free config change) see the current value instead of whatever was in
 * the environment when this module was first imported.
 */
export function masterOtpCode(): string | null {
  const raw = process.env.OTP_MASTER_CODE?.trim();
  return raw ? raw : null;
}

/** Whether the master code is currently armed. */
export function masterOtpEnabled(): boolean {
  return masterOtpCode() !== null;
}

@Injectable()
export class CustomerAuthService {
  private readonly logger = new Logger(CustomerAuthService.name);

  constructor(
    private readonly prisma: PrismaService,
    private readonly jwt: JwtService,
    private readonly sms: SmsService,
  ) {}

  /**
   * Step 1 — port of ApiMobileController::userAuth (henza_server:39-49).
   *
   * Reference: validate `username`, find an ACTIVE customer by mobile, generate
   * rand(1000,9999), store it, send it by SMS, return `true`.
   *
   * Kept: the active-customer filter, the 4-digit range, the opaque `true`
   * response (it never reveals whether the number exists).
   * Changed: the code is hashed, it expires, and sends are rate limited.
   */
  async requestOtp(rawMobile: string, ip: string | undefined) {
    const mobile = faToEn(rawMobile);

    await this.assertSendAllowed(mobile, ip);

    // D21 — a sales expert signs in with the SAME flow, on the mobile of their
    // AdminUser. Checked first: the owner ruled that if a number somehow
    // existed on both sides, the expert wins.
    //
    // Their trading Customer row is created here rather than at verify, because
    // CustomerOtp.customerId is a required FK and the challenge has to hang off
    // a real row. Creating it costs nothing for a number that never completes
    // login: it is that expert's own account either way, and it is created once.
    const expertAccount = await this.resolveExpertTradingAccount(mobile);

    // Legacy used Customer::active(), and the archived filter matches the
    // customer-list lookup the app login previously relied on.
    const customer =
      expertAccount ??
      (await this.prisma.customer.findFirst({
        where: { mobile, isActive: true, isArchived: false },
        select: { id: true },
      }));

    // Deliberately opaque: the reference used firstOrFail() and leaked a 404
    // for unknown numbers, which let anyone enumerate registered customers.
    // Recorded as a deviation in docs/parity/DECISIONS.md.
    if (!customer) {
      this.logger.warn(`OTP requested for unknown or inactive mobile ${mobile}`);
      return { sent: true };
    }

    const code = String(Math.floor(1000 + Math.random() * 9000));

    await this.prisma.customerOtp.create({
      data: {
        mobile,
        customerId: customer.id,
        codeHash: await bcrypt.hash(code, 10),
        expiresAt: new Date(Date.now() + OTP_TTL_MS),
        requestIp: ip ?? null,
      },
    });

    await this.deliver(mobile, code);
    return { sent: true };
  }

  /**
   * D21 — find an active sales expert by mobile and return their trading
   * Customer account, creating it on first sign-in.
   *
   * WHY A TRADING ACCOUNT EXISTS
   * In the reference a sales agent WAS a Customer (type=1), so `setOrder` did
   * `Customer::findOrFail(auth()->id())` and read that row's `gram_level`
   * (ApiMobileController.php:534-535) — the agent's own order, own credit
   * limit, own ledger. Here the expert is an AdminUser (D17), which has no
   * ledger and cannot be an Order's subject, so this one linked Customer row
   * plays that part. It is NOT one of their referred customers.
   *
   * Seeded from what the reference used for exactly these two numbers:
   *   gram_level -> goldCreditLimitGrams   (SalesExpertProfile.gramLevel)
   *   percent    -> makingChargeOffsetPercent (AdminUser.wagePercent)
   *
   * Returns null for any mobile that is not an active sales expert, so an
   * ordinary customer's login is completely unaffected.
   */
  private async resolveExpertTradingAccount(mobile: string): Promise<{ id: string } | null> {
    const admin = await this.prisma.adminUser.findFirst({
      where: { mobile, isActive: true, role: AdminRole.SALES_EXPERT },
      select: {
        id: true,
        fullName: true,
        firstName: true,
        lastName: true,
        mobile: true,
        wagePercent: true,
        salesExpertProfile: {
          select: { id: true, gramLevel: true, nationalCode: true, tradingCustomerId: true },
        },
      },
    });
    if (!admin) return null;

    const existingId = admin.salesExpertProfile?.tradingCustomerId;
    if (existingId) {
      // Re-activate nothing and change nothing — just confirm it is usable.
      const existing = await this.prisma.customer.findUnique({
        where: { id: existingId },
        select: { id: true, isActive: true, isArchived: true },
      });
      if (existing && existing.isActive && !existing.isArchived) return { id: existing.id };
      // Deliberately does NOT silently create a second account when the first
      // was deactivated: an operator disabled it, and that decision stands.
      this.logger.warn(
        `Sales expert ${admin.id} has a trading account that is inactive or archived; refusing to create another.`,
      );
      return null;
    }

    if (!admin.salesExpertProfile) {
      // Every SALES_EXPERT gets a profile on create and on role change (D17),
      // so this means something bypassed both paths.
      this.logger.warn(`Sales expert ${admin.id} has no SalesExpertProfile; cannot sign in to the app.`);
      return null;
    }

    // The mobile is unique on Customer, so a pre-existing customer row with
    // this number would collide. That cannot normally happen — the owner
    // stated expert and customer numbers are never the same — but if it does,
    // adopt that row rather than fail the login or create a duplicate.
    const clash = await this.prisma.customer.findFirst({
      where: { mobile },
      select: { id: true, isActive: true, isArchived: true },
    });
    if (clash) {
      this.logger.warn(
        `Mobile ${mobile} belongs to both sales expert ${admin.id} and customer ${clash.id}; ` +
          `adopting the existing customer row as the expert's trading account.`,
      );
      if (!clash.isActive || clash.isArchived) return null;
      await this.prisma.salesExpertProfile.update({
        where: { id: admin.salesExpertProfile.id },
        data: { tradingCustomerId: clash.id },
      });
      return { id: clash.id };
    }

    const created = await this.prisma.customer.create({
      data: {
        fullName: admin.fullName,
        firstName: admin.firstName,
        lastName: admin.lastName,
        mobile: admin.mobile,
        // Customer.nationalCode is required and unique. The expert's own code
        // when they have one, else the mobile — the same fallback
        // admin-customers.service.ts uses when a form omits it.
        nationalCode: admin.salesExpertProfile.nationalCode || admin.mobile,
        // No app password: this account is reached only through the expert's
        // AdminUser session, never by a password login of its own.
        passwordHash: '',
        kind: CustomerKind.APP_SHOPKEEPER,
        goldCreditLimitGrams: admin.salesExpertProfile.gramLevel,
        makingChargeOffsetPercent: admin.wagePercent ?? new Prisma.Decimal(0),
      },
      select: { id: true },
    });

    await this.prisma.salesExpertProfile.update({
      where: { id: admin.salesExpertProfile.id },
      data: { tradingCustomerId: created.id },
    });

    this.logger.log(
      `Created trading account ${created.id} for sales expert ${admin.id} on first app sign-in.`,
    );
    return { id: created.id };
  }

  /**
   * Step 2 — port of ApiMobileController::userVerfiy (henza_server:51-64).
   *
   * Reference: `if (faTOen($request->password) != $customer->send_password) abort(422);`
   * then issue a token and return THAT ONE customer.
   *
   * The parity behaviour is the comparison and the rejection. The attempt
   * counter, the expiry check and the single-use consumption are the D6
   * additions.
   */
  async verifyOtp(rawMobile: string, rawCode: string, ip: string | undefined) {
    const mobile = faToEn(rawMobile);
    const code = faToEn(rawCode);

    // One message for every failure mode, so a caller cannot tell "no code was
    // sent" from "wrong code" from "expired". Declared before the master-code
    // branch so that path can reject identically.
    const reject = () => new UnauthorizedException('کد وارد شده صحیح نیست');

    // D20 — the delivery master code. Checked BEFORE the stored challenge so it
    // works even when the customer never requested a code (no CustomerOtp row
    // exists to compare against). It does not weaken any other rule: the
    // customer must still exist, be active and not archived, and the send
    // throttle on requestOtp is untouched.
    //
    // MUST be removed from the environment before the real release — see D20
    // and DELIVERY.md.
    const master = masterOtpCode();
    if (master !== null && code === master) {
      // D21 — the master code works for a sales expert too, and the expert is
      // checked first for the same reason requestOtp does it.
      const expert = await this.resolveExpertPrincipal(mobile);
      if (expert) {
        this.logger.warn(
          `OTP_MASTER_CODE used to sign in SALES EXPERT ${expert.adminUserId} (mobile ${mobile})`,
        );
        return {
          token: await this.issueExpertToken(expert.adminUserId, mobile),
          customer: { id: expert.tradingCustomerId, mobile },
        };
      }

      const customer = await this.prisma.customer.findFirst({
        where: { mobile, isActive: true, isArchived: false },
        select: { id: true, mobile: true },
      });
      if (!customer) throw reject();

      // Audited with the mobile, as D20 requires, so every bypass login is
      // traceable in the server log.
      this.logger.warn(
        `OTP_MASTER_CODE used to sign in customer ${customer.id} (mobile ${customer.mobile})`,
      );

      return {
        token: await this.issueToken(customer.id, customer.mobile),
        customer: { id: customer.id, mobile: customer.mobile },
      };
    }

    const challenge = await this.prisma.customerOtp.findFirst({
      where: { mobile, consumedAt: null },
      orderBy: { createdAt: 'desc' },
      include: {
        customer: {
          select: { id: true, mobile: true, isActive: true, isArchived: true },
        },
      },
    });

    if (!challenge) throw reject();
    if (challenge.expiresAt.getTime() < Date.now()) throw reject();

    if (challenge.attempts >= MAX_ATTEMPTS) {
      throw new TooManyRequestsException(
        'تعداد تلاش‌های ناموفق بیش از حد مجاز است. لطفاً کد جدیدی درخواست کنید.',
      );
    }

    const ok = await bcrypt.compare(code, challenge.codeHash);
    if (!ok) {
      await this.prisma.customerOtp.update({
        where: { id: challenge.id },
        data: { attempts: { increment: 1 } },
      });
      throw reject();
    }

    if (!challenge.customer.isActive || challenge.customer.isArchived) {
      throw reject();
    }

    // Single use: burn the challenge before issuing the token.
    await this.prisma.customerOtp.update({
      where: { id: challenge.id },
      data: { consumedAt: new Date() },
    });

    // D21 — the challenge hangs off the expert's trading Customer row, so a
    // correct code here may belong to either principal. Resolved from the
    // mobile, never from anything the client sent.
    const expert = await this.resolveExpertPrincipal(mobile);
    if (expert) {
      return {
        token: await this.issueExpertToken(expert.adminUserId, mobile),
        customer: { id: expert.tradingCustomerId, mobile },
      };
    }

    return {
      token: await this.issueToken(challenge.customer.id, challenge.customer.mobile),
      customer: { id: challenge.customer.id, mobile: challenge.customer.mobile },
    };
  }

  /**
   * D21 — is this mobile an active sales expert with a usable trading account?
   *
   * Read-only: unlike `resolveExpertTradingAccount`, this never creates
   * anything, because by verify time requestOtp has already done so. Returns
   * null for every ordinary customer, so their path is untouched.
   */
  private async resolveExpertPrincipal(
    mobile: string,
  ): Promise<{ adminUserId: string; tradingCustomerId: string } | null> {
    const admin = await this.prisma.adminUser.findFirst({
      where: { mobile, isActive: true, role: AdminRole.SALES_EXPERT },
      select: {
        id: true,
        salesExpertProfile: {
          select: {
            tradingCustomer: { select: { id: true, isActive: true, isArchived: true } },
          },
        },
      },
    });

    const trading = admin?.salesExpertProfile?.tradingCustomer;
    if (!admin || !trading || !trading.isActive || trading.isArchived) return null;
    return { adminUserId: admin.id, tradingCustomerId: trading.id };
  }

  /**
   * Sign a SALES EXPERT app token.
   *
   * `sub` is the AdminUser id — the durable identity — not the trading
   * Customer id, so the token survives anything that changes the trading row
   * and the role check can be re-applied on every request.
   *
   * Same secret and lifetime as a customer token; only `typ` differs. It is
   * NOT an admin-panel token: JwtStrategy requires the admin type and refuses
   * this one on every admin route.
   */
  private issueExpertToken(adminUserId: string, mobile: string): Promise<string> {
    const payload: CustomerJwtPayload = {
      sub: adminUserId,
      mobile,
      typ: EXPERT_TOKEN_TYPE,
    };
    return this.jwt.signAsync(payload, {
      secret: customerJwtSecret(),
      expiresIn: envOr('JWT_CUSTOMER_EXPIRES_IN', '30d') as `${number}d`,
    });
  }

  /**
   * Sign a customer JWT. Shared by the normal verify path and the D20 master
   * code so both issue exactly the same token — the bypass grants no extra
   * privilege and no longer lifetime.
   *
   * Reference reused api_token forever once set (:60-62); a fresh token is
   * issued on every verify here (T1).
   */
  private issueToken(customerId: string, mobile: string): Promise<string> {
    const payload: CustomerJwtPayload = {
      sub: customerId,
      mobile,
      typ: CUSTOMER_TOKEN_TYPE,
    };
    return this.jwt.signAsync(payload, {
      secret: customerJwtSecret(),
      // jsonwebtoken types expiresIn as a template-literal union, which a plain
      // string from process.env does not satisfy — same cast AuthModule uses.
      expiresIn: envOr('JWT_CUSTOMER_EXPIRES_IN', '30d') as `${number}d`,
    });
  }

  /**
   * Per-mobile and per-IP send throttle.
   *
   * Counted off the CustomerOtp rows rather than an in-memory map, so the limit
   * survives a restart and holds across replicas. The reference had no limit:
   * userAuth could be called in a loop, each call sending a real (billed) SMS.
   */
  private async assertSendAllowed(mobile: string, ip: string | undefined) {
    const since = new Date(Date.now() - SEND_WINDOW_MS);

    const lastToMobile = await this.prisma.customerOtp.findFirst({
      where: { mobile },
      orderBy: { createdAt: 'desc' },
      select: { createdAt: true },
    });
    if (lastToMobile && Date.now() - lastToMobile.createdAt.getTime() < RESEND_COOLDOWN_MS) {
      const wait = Math.ceil(
        (RESEND_COOLDOWN_MS - (Date.now() - lastToMobile.createdAt.getTime())) / 1000,
      );
      throw new TooManyRequestsException(`لطفاً ${wait} ثانیه دیگر تلاش کنید`);
    }

    const sentToMobile = await this.prisma.customerOtp.count({
      where: { mobile, createdAt: { gte: since } },
    });
    if (sentToMobile >= MAX_SENDS_PER_MOBILE) {
      throw new TooManyRequestsException(
        'تعداد درخواست‌های کد بیش از حد مجاز است. لطفاً بعداً تلاش کنید.',
      );
    }

    if (ip) {
      const sentFromIp = await this.prisma.customerOtp.count({
        where: { requestIp: ip, createdAt: { gte: since } },
      });
      if (sentFromIp >= MAX_SENDS_PER_IP) {
        throw new TooManyRequestsException(
          'تعداد درخواست‌های کد بیش از حد مجاز است. لطفاً بعداً تلاش کنید.',
        );
      }
    }
  }

  /**
   * Hands the code to the SMS gateway (SmsService -> Trez, per Sms.php:57-82).
   *
   * When no credentials are configured, SmsService does not send and the code
   * is logged instead — development only; production refuses to boot without
   * credentials (assertSmsConfigured in main.ts).
   *
   * A failed send does NOT throw. The reference ignored Sms::Send's result, so
   * a gateway outage never blocked the flow that triggered it; the customer
   * simply retries, and the throttle in assertSendAllowed still applies.
   */
  private async deliver(mobile: string, code: string) {
    // BYTE-IDENTICAL to the reference (ApiMobileController.php:47). The
    // leading "<#> code is <CODE>" line and the trailing "aMo6iFyUQaY" are the
    // Android SMS Retriever app hash — change either and autofill stops
    // working on every installed client. Do not "tidy" this string.
    const smsText =
      `<#> code is ${code}\n` +
      `رمز عبور یکبار مصرف شما جهت ورود به اپلیکشن هنزا گلد ${code} می باشد\n` +
      `aMo6iFyUQaY`;

    // persist:false — the real text carries the live code, and the admin SMS
    // grid lists and searches `body` (SEC-11). The redacted audit row below
    // takes its place.
    await this.sms.send(mobile, smsText, { persist: false });

    // Only outside production, and only when no gateway is configured, so a
    // deployment can never print live codes into its logs.
    if (process.env.NODE_ENV !== 'production' && !smsConfigured()) {
      this.logger.log(`[dev] OTP for ${mobile}: ${code}`);
    }

    // An audit row, NOT the message body.
    //
    // SmsMessage.body is listed and full-text searchable on the admin panel's
    // SMS grid (admin-misc.service.ts:136 allows `body`, :135 searches it), so
    // persisting the real text would show every live OTP to any operator
    // holding the `sms` rid — and the whole point of hashing codeHash is that
    // the code exists nowhere in readable form. The code is redacted here.
    await this.prisma.smsMessage.create({
      data: {
        audience: MessageAudience.SINGLE_NUMBER,
        recipients: mobile,
        body: 'کد یکبار مصرف ورود (متن پیام ثبت نمی‌شود)',
        sentCount: 1,
      },
    });
  }
}

/**
 * Customer tokens are signed with their own secret so an admin token can never
 * validate as a customer token, or the reverse, even if the `typ` check were
 * ever removed (T1).
 */
export function customerJwtSecret(): string {
  return (
    envOrNull('JWT_CUSTOMER_SECRET') ??
    envOrNull('JWT_SECRET') ??
    'dev-only-insecure-customer-secret'
  );
}