// src/integrations/paloalto/client.js
//
// Palo Alto Prisma SD-WAN (formerly CloudGenix) HTTP client. Wraps
// axios with dual-mode auth so the same client works against the
// unified SASE OAuth 2.0 surface (`api.sase.paloaltonetworks.com`)
// and the legacy CloudGenix session-token surface
// (`api.cloudgenix.com`) without any caller-visible differences.
//
// Auth mode selection lives in `PRISMA_AUTH_MODE`:
//   - `sase`   (default, recommended for production) — service-app
//     OAuth 2.0 client_credentials grant. Bearer token echoed on
//     every request. Access tokens are short-lived (~15 min); we
//     refresh 5 min ahead of expiry and forcibly refresh on the
//     first 401 with a one-shot retry.
//   - `legacy` — CloudGenix session-token flow. Interactive-user
//     credential (email + password), captured as `x-auth-token`
//     for every subsequent call. Kept for admins who only have
//     legacy creds provisioned; new deployments should prefer
//     `sase`.
//
// The single `paloAltoAxios` export is what business modules
// import — same pattern as `scAxios` / `merakiAxios`. Mutex around
// token refresh (same reason as Webex — a race would double-spend
// the refresh and leave one caller with a stale token).
//
// Only READ operations are used by /voicediag today (POSTs to the
// `/monitor/v2.0/api/monitor/*` metric endpoints). No PUT/DELETE
// surface is invoked from this client, so a config mishap during
// token refresh cannot mutate SD-WAN state.

import axios from 'axios';
import { Mutex } from 'async-mutex';
import { logger } from '../../utils/logger.js';

const AUTH_MODE_SASE = 'sase';
const AUTH_MODE_LEGACY = 'legacy';

const DEFAULT_SASE_BASE_URL = 'https://api.sase.paloaltonetworks.com';
const DEFAULT_SASE_AUTH_URL = 'https://auth.apps.paloaltonetworks.com/oauth2/access_token';
const DEFAULT_LEGACY_BASE_URL = 'https://api.cloudgenix.com';

// Refresh window: 5 minutes before actual token expiry. Prisma
// SASE tokens are 900s by default; a request landing at 895s could
// otherwise trip a 401 that we then re-authenticate through — not
// wrong, just wasteful.
const REFRESH_MARGIN_MS = 5 * 60 * 1000;

const mutex = new Mutex();
let cachedToken = null;
let tokenExpiresAt = 0;
// SASE unified SD-WAN calls require a one-shot GET /sdwan/v2.1/api/profile
// immediately after every new token is acquired — otherwise subsequent
// SD-WAN calls come back with 403 (or 503 "target url lookup failed"
// depending on which edge processes the miss). See pan.dev "Unified
// SASE SD-WAN APIs" page. This flag tracks whether the priming call
// has run since the last token acquisition; it's cleared on refresh.
let saseSessionPrimed = false;

// ──────────────────────────────────────────────
// Auth mode + base URL resolution
// ──────────────────────────────────────────────

function resolveAuthMode() {
  const raw = String(process.env.PRISMA_AUTH_MODE || AUTH_MODE_SASE).toLowerCase().trim();
  if (raw !== AUTH_MODE_SASE && raw !== AUTH_MODE_LEGACY) {
    throw new Error(
      `PRISMA_AUTH_MODE must be "${AUTH_MODE_SASE}" or "${AUTH_MODE_LEGACY}" (got "${raw}")`,
    );
  }
  return raw;
}

function resolveBaseUrl() {
  const mode = resolveAuthMode();
  if (mode === AUTH_MODE_SASE) {
    return process.env.PRISMA_SASE_BASE_URL || DEFAULT_SASE_BASE_URL;
  }
  return process.env.PRISMA_LEGACY_BASE_URL || DEFAULT_LEGACY_BASE_URL;
}

// ──────────────────────────────────────────────
// Axios instance — baseURL resolved at import time
// ──────────────────────────────────────────────

export const paloAltoAxios = axios.create({
  // baseURL resolved lazily on the first request so tests can set
  // PRISMA_SASE_BASE_URL / PRISMA_LEGACY_BASE_URL after import.
  timeout: 20000,
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json',
  },
});

// Request interceptor: (a) apply resolved baseURL on the fly if the
// caller passed a relative URL; (b) inject the correct auth header
// for the current auth mode; (c) prime the SASE unified SD-WAN
// session on first use of a new token.
paloAltoAxios.interceptors.request.use(async (cfg) => {
  const mode = resolveAuthMode();

  if (cfg.url && !/^https?:\/\//i.test(cfg.url)) {
    cfg.baseURL = resolveBaseUrl();
  }

  const token = await getPrismaToken();

  if (mode === AUTH_MODE_SASE) {
    if (!cfg.headers.Authorization) {
      cfg.headers.Authorization = `Bearer ${token}`;
    }
    // Prime the unified SD-WAN session — but skip when the current
    // request IS the profile call itself (avoids infinite recursion)
    // or when it's the auth POST (which uses raw axios, not this
    // instance, but belt-and-braces).
    if (!saseSessionPrimed && !cfg._skipSasePrime && !/\/sdwan\/v2\.1\/api\/profile$/.test(cfg.url || '')) {
      try {
        await primeSaseSession(token);
      } catch (err) {
        // Priming failed — log and continue. Downstream call will
        // 403 loudly which is a better signal than swallowing here.
        logger('paloalto:client', `SASE session prime failed: ${err.message}`, 'warn');
      }
    }
  } else {
    if (!cfg.headers['x-auth-token']) {
      cfg.headers['x-auth-token'] = token;
    }
  }

  logger('paloalto:request', `${cfg.method?.toUpperCase()} ${cfg.baseURL || ''}${cfg.url}`, 'debug');
  return cfg;
});

// Maximum attempts on a 429 (rate limit). One retry with backoff has
// been empirically enough in the observed Prisma tenant — the second
// attempt lands after the burst window resets. Bumping past 2 would
// stack requests behind an already-throttled endpoint and make things
// worse. `Retry-After` (seconds) is honored when present; otherwise
// exponential backoff kicks in.
const MAX_429_RETRIES = 2;
const BASE_429_BACKOFF_MS = 1500;

paloAltoAxios.interceptors.response.use(
  (response) => response,
  async (error) => {
    const status = error.response?.status;

    if (status === 401 && !error.config?._retry) {
      logger('paloalto:client', '401 → forcing token refresh + one-shot retry', 'warn');
      try {
        await getPrismaToken(true);
      } catch (refreshErr) {
        logger('paloalto:client', `Token refresh failed on 401: ${refreshErr.message}`, 'error');
        return Promise.reject(error);
      }

      const originalRequest = error.config;
      originalRequest._retry = true;
      const mode = resolveAuthMode();
      if (mode === AUTH_MODE_SASE) {
        originalRequest.headers.Authorization = `Bearer ${cachedToken}`;
      } else {
        originalRequest.headers['x-auth-token'] = cachedToken;
      }
      return paloAltoAxios(originalRequest);
    }

    // 429 — Prisma throttles bursts of parallel metric calls. Honor
    // the `Retry-After` header when present; otherwise exponential
    // backoff (1.5s / 3s / 6s). Only retry idempotent verbs (GET,
    // POST-with-body-that's-a-query — Prisma metric endpoints are
    // read-only despite being POSTs). Capped at MAX_429_RETRIES.
    if (status === 429) {
      const cfg = error.config || {};
      cfg._429retries = (cfg._429retries || 0) + 1;
      if (cfg._429retries <= MAX_429_RETRIES) {
        const retryAfterHdr = error.response?.headers?.['retry-after'];
        const retryAfterMs = retryAfterHdr
          ? Math.max(0, Number(retryAfterHdr) * 1000) || null
          : null;
        const waitMs = retryAfterMs != null
          ? retryAfterMs
          : BASE_429_BACKOFF_MS * Math.pow(2, cfg._429retries - 1);
        logger(
          'paloalto:client',
          `429 on ${cfg.method?.toUpperCase() || 'REQ'} ${cfg.url || ''} — retry ${cfg._429retries}/${MAX_429_RETRIES} in ${waitMs}ms` +
          (retryAfterMs != null ? ' (Retry-After honored)' : ''),
          'warn',
        );
        await new Promise((resolve) => setTimeout(resolve, waitMs));
        return paloAltoAxios(cfg);
      }
      logger(
        'paloalto:client',
        `429 on ${cfg.method?.toUpperCase() || 'REQ'} ${cfg.url || ''} — retries exhausted (${MAX_429_RETRIES})`,
        'warn',
      );
    }

    const body = error.response?.data;
    const msg = status
      ? `${status} — ${typeof body === 'string' ? body : JSON.stringify(body)}`
      : error.message;
    logger('paloalto:error', msg, status === 429 ? 'warn' : 'error');
    return Promise.reject(error);
  },
);

// ──────────────────────────────────────────────
// Token acquisition (dispatches on auth mode)
// ──────────────────────────────────────────────

/**
 * Return a valid Prisma auth token, refreshing if needed. Concurrent
 * callers coalesce onto a single refresh through the shared mutex.
 * Any refresh clears `saseSessionPrimed` so the interceptor knows to
 * re-run the mandatory GET /sdwan/v2.1/api/profile priming call on
 * the next SD-WAN request.
 */
export async function getPrismaToken(forceRefresh = false) {
  const release = await mutex.acquire();
  try {
    const now = Date.now();
    if (!forceRefresh && cachedToken && now < tokenExpiresAt) {
      return cachedToken;
    }

    const mode = resolveAuthMode();
    if (mode === AUTH_MODE_SASE) {
      await refreshSaseToken();
    } else {
      await refreshLegacyToken();
    }
    saseSessionPrimed = false;
    return cachedToken;
  } finally {
    release();
  }
}

/**
 * Mandatory session-init for the SASE unified SD-WAN surface. Per
 * pan.dev's "Unified SASE SD-WAN APIs" page, this exact GET call
 * MUST run immediately after obtaining a new access token — without
 * it, every subsequent SD-WAN call is rejected (usually 403, but
 * SASE Edge can also respond with 503 "target url lookup failed
 * for proxy: null in environment prod-global" if the priming state
 * is missing at the routing layer).
 *
 * We bypass the axios instance for this call (raw axios) to avoid
 * the request interceptor's own priming check firing recursively.
 * `_skipSasePrime` also protects the instance path if a caller ever
 * hits the profile URL directly.
 */
async function primeSaseSession(token) {
  const baseUrl = process.env.PRISMA_SASE_BASE_URL || DEFAULT_SASE_BASE_URL;
  logger('paloalto:client', 'Priming SASE SD-WAN session (GET /sdwan/v2.1/api/profile)', 'debug');
  await axios.get(`${baseUrl}/sdwan/v2.1/api/profile`, {
    headers: {
      'Authorization': `Bearer ${token}`,
      'Accept': 'application/json',
    },
    timeout: 10000,
  });
  saseSessionPrimed = true;
  logger('paloalto:client', 'SASE SD-WAN session primed');
}

async function refreshSaseToken() {
  const clientId     = process.env.PRISMA_CLIENT_ID;
  const clientSecret = process.env.PRISMA_CLIENT_SECRET;
  const tsgId        = process.env.PRISMA_TSG_ID;
  const authUrl      = process.env.PRISMA_AUTH_URL || DEFAULT_SASE_AUTH_URL;

  if (!clientId || !clientSecret || !tsgId) {
    throw new Error(
      'PRISMA_AUTH_MODE=sase requires PRISMA_CLIENT_ID, PRISMA_CLIENT_SECRET, and PRISMA_TSG_ID.',
    );
  }

  logger('paloalto:client', 'Fetching new SASE OAuth token', 'debug');

  const basicAuth = Buffer.from(`${clientId}:${clientSecret}`).toString('base64');
  const body = new URLSearchParams({
    grant_type: 'client_credentials',
    // SASE requires the TSG (Tenant Service Group) scope so the
    // token is bound to the right tenant.
    scope: `tsg_id:${tsgId}`,
  }).toString();

  const res = await axios.post(authUrl, body, {
    headers: {
      'Authorization': `Basic ${basicAuth}`,
      'Content-Type': 'application/x-www-form-urlencoded',
    },
    timeout: 10000,
  });

  const { access_token, expires_in } = res.data || {};
  if (!access_token) {
    throw new Error(`SASE token response missing access_token: ${JSON.stringify(res.data)}`);
  }

  cachedToken = access_token;
  tokenExpiresAt = Date.now() + ((Number(expires_in) || 900) * 1000) - REFRESH_MARGIN_MS;
  logger(
    'paloalto:client',
    `SASE token acquired (expires in ~${Math.round((Number(expires_in) || 900) / 60)} min)`,
  );
}

async function refreshLegacyToken() {
  const email    = process.env.PRISMA_EMAIL;
  const password = process.env.PRISMA_PASSWORD;
  const baseUrl  = process.env.PRISMA_LEGACY_BASE_URL || DEFAULT_LEGACY_BASE_URL;

  if (!email || !password) {
    throw new Error('PRISMA_AUTH_MODE=legacy requires PRISMA_EMAIL and PRISMA_PASSWORD.');
  }

  logger('paloalto:client', 'Fetching new legacy CloudGenix session token', 'debug');

  const res = await axios.post(
    `${baseUrl}/v2.0/api/login`,
    { email, password },
    {
      headers: { 'Content-Type': 'application/json' },
      timeout: 10000,
    },
  );

  const token =
    res.data?.x_auth_token ||
    res.data?.token ||
    res.headers?.['x-auth-token'];

  if (!token) {
    throw new Error(`Legacy login response missing token: ${JSON.stringify(res.data)}`);
  }

  cachedToken = token;
  // Legacy tokens don't declare expiry in the response body; treat
  // as 8h with the same refresh margin. If a mid-day 401 happens
  // the response interceptor still catches it and forces refresh.
  tokenExpiresAt = Date.now() + (8 * 60 * 60 * 1000) - REFRESH_MARGIN_MS;
  logger('paloalto:client', 'Legacy session token acquired (~8h validity)');
}

/**
 * Test-only helper — clears the in-memory token cache so a fresh
 * auth attempt happens on the next request. Not for production use
 * (the mutex-guarded refresh path already handles all real cases).
 */
export function _resetPrismaAuthCache() {
  cachedToken = null;
  tokenExpiresAt = 0;
  saseSessionPrimed = false;
}

export default paloAltoAxios;