import { Injectable, Logger } from '@nestjs/common';
import { MessageAudience } from '@prisma/client';
import { PrismaService } from '../../prisma/prisma.service';

/**
 * SMS delivery — port of henza_server/app/Models/Sms.php.
 *
 * Reference behaviour (`Sms::Send`, `Sms.php:57-82`):
 *   * POST, form-urlencoded, to the Trez panel, 20s timeout
 *   * fields: PhoneNumber (sender line), Username, Password, Mobile, Message
 *   * the message is trim()ed before sending
 *   * EVERY message is persisted, via `Sms::set()` (`:80`)
 *   * the response body is returned and the callers ignore it
 *
 * Two things differ, both deliberate:
 *   1. Credentials come from the environment. The reference hardcodes live
 *      production credentials in the source (SEC-12); they are not copied here.
 *   2. The OTP message body is NOT persisted in readable form — see
 *      CustomerAuthService.deliver() and SEC-11.
 *
 * Failure handling matches the reference: `Sms::Send` is called inline and its
 * result is discarded, so a failed send never aborted the order, the document
 * approval or the customer creation that triggered it. `send()` therefore
 * never throws — it logs and reports failure in its return value.
 */

/** Reference endpoint (`Sms.php:69`). Overridable for staging. */
const DEFAULT_TREZ_URL = 'https://smspanel.trez.ir/SendMessageWithCode.ashx';

/** `Http::timeout(20)` in the reference (`Sms.php:72`). */
const REQUEST_TIMEOUT_MS = 20_000;

export interface SmsSendResult {
  ok: boolean;
  /** Provider response body, when one was received. */
  response?: string;
  error?: string;
}

export interface SmsSendOptions {
  /**
   * Persist the message body. Default true, matching `Sms::set()`.
   * OTP delivery passes false and writes its own redacted row (SEC-11).
   */
  persist?: boolean;
  audience?: MessageAudience;
}

/** Reads the provider config. Exported so main.ts can validate it at boot. */
export function smsConfig() {
  return {
    provider: (process.env.SMS_PROVIDER ?? 'trez').toLowerCase(),
    url: process.env.SMS_TREZ_URL ?? DEFAULT_TREZ_URL,
    username: process.env.SMS_TREZ_USERNAME ?? '',
    password: process.env.SMS_TREZ_PASSWORD ?? '',
    senderLine: process.env.SMS_TREZ_SENDER_LINE ?? '',
  };
}

/**
 * True when a real gateway is configured. When false the service stays in
 * development mode: nothing is sent, and OTP codes are logged locally.
 */
export function smsConfigured(): boolean {
  const c = smsConfig();
  if (c.provider === 'none') return false;
  return Boolean(c.username && c.password && c.senderLine);
}

/**
 * Called from main.ts before the app listens. In production a missing key is
 * fatal: without it no customer can log in, and a silent no-op gives no clue
 * why. Outside production it is only a warning, so local development works
 * with no credentials at all.
 */
export function assertSmsConfigured(logger: Logger = new Logger('SmsConfig')): void {
  const c = smsConfig();

  if (c.provider === 'none') {
    const message = 'SMS_PROVIDER=none — no SMS will be sent.';
    if (process.env.NODE_ENV === 'production') {
      throw new Error(
        `${message} Refusing to start in production: customers could not log in. ` +
          'Set SMS_PROVIDER=trez and the SMS_TREZ_* variables.',
      );
    }
    logger.warn(message);
    return;
  }

  if (c.provider !== 'trez') {
    throw new Error(
      `Unknown SMS_PROVIDER "${c.provider}". Supported values: "trez", "none".`,
    );
  }

  const missing = (
    [
      ['SMS_TREZ_USERNAME', c.username],
      ['SMS_TREZ_PASSWORD', c.password],
      ['SMS_TREZ_SENDER_LINE', c.senderLine],
    ] as const
  )
    .filter(([, v]) => !v)
    .map(([name]) => name);

  if (missing.length === 0) return;

  const message = `SMS provider "trez" is selected but these are not set: ${missing.join(', ')}.`;
  if (process.env.NODE_ENV === 'production') {
    throw new Error(
      `${message} Refusing to start in production: no customer could receive a login code. ` +
        'Set them, or set SMS_PROVIDER=none to acknowledge that SMS is disabled.',
    );
  }
  logger.warn(`${message} Running in development mode — messages are logged, not sent.`);
}

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

  constructor(private readonly prisma: PrismaService) {}

  /**
   * Sends one message. Never throws — a failed SMS must not roll back the
   * business operation that triggered it, exactly as in the reference.
   */
  async send(mobile: string, body: string, options: SmsSendOptions = {}): Promise<SmsSendResult> {
    const { persist = true, audience = MessageAudience.SINGLE_NUMBER } = options;
    // The reference trims before sending (`Sms.php:77`).
    const text = body.trim();

    let result: SmsSendResult;

    if (!smsConfigured()) {
      this.logger.warn(`[dev] SMS not configured; not sending to ${mobile}`);
      result = { ok: false, error: 'sms-not-configured' };
    } else {
      result = await this.deliverViaTrez(mobile, text);
    }

    if (persist) {
      // `Sms::set()` records every message, delivered or not.
      await this.record(mobile, text, audience);
    }

    return result;
  }

  /** POST to the Trez panel, shaped exactly as the reference's form post. */
  private async deliverViaTrez(mobile: string, text: string): Promise<SmsSendResult> {
    const c = smsConfig();
    const controller = new AbortController();
    const timer = setTimeout(() => controller.abort(), REQUEST_TIMEOUT_MS);

    try {
      const response = await fetch(c.url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
        body: new URLSearchParams({
          PhoneNumber: c.senderLine,
          Username: c.username,
          Password: c.password,
          Mobile: mobile,
          Message: text,
        }).toString(),
        signal: controller.signal,
      });

      const responseBody = await response.text();

      if (!response.ok) {
        // Logged, not thrown — see the class comment.
        this.logger.error(`SMS to ${mobile} failed: HTTP ${response.status} ${responseBody}`);
        return { ok: false, response: responseBody, error: `http-${response.status}` };
      }

      return { ok: true, response: responseBody };
    } catch (e) {
      const error = e instanceof Error ? e.message : String(e);
      this.logger.error(`SMS to ${mobile} failed: ${error}`);
      return { ok: false, error };
    } finally {
      clearTimeout(timer);
    }
  }

  /** The `messages` row the reference writes for every send (`Sms.php:120-129`). */
  private async record(mobile: string, body: string, audience: MessageAudience) {
    try {
      await this.prisma.smsMessage.create({
        data: { audience, recipients: mobile, body, sentCount: 1 },
      });
    } catch (e) {
      // Never let the audit write break the caller either.
      this.logger.error(`Could not record the SMS to ${mobile}: ${String(e)}`);
    }
  }
}