/**
 * Workflow Service
 * Handles workflow fetching with lazy loading and caching
 * Workflows are only loaded when first requested (not at startup)
 *
 * Un cache par application (D26) : le paramètre `application` des outils
 * sélectionne l'application AD interrogée (défaut : celle du profil actif).
 */

const apiService = require('./api-service').getInstance();
const profileManager = require('../config/profile-manager');
const { createSingleFlight } = require('./single-flight');

// Cache state — un cache de workflows par application (D26)
let workflowCaches = {};      // application -> workflows[]
let cacheTimestamps = {};     // application -> timestamp
let applicationsCache = null; // liste allégée de POST /Application/GetAll
let applicationsTimestamp = null;
const CACHE_TTL = parseInt(process.env.WORKFLOW_CACHE_TTL) || 3600000; // 1 hour in milliseconds

// Déduplication des chargements concurrents, par clé de cache (D27). Deux
// clés distinctes ici : une par application, plus la liste d'applications.
const singleFlight = createSingleFlight('Workflow');

// Clear cache when profile changes — workflows are per-tenant, so the previous
// profile's cache is meaningless after a switch.
profileManager.onSwitch(() => clearCache());

/**
 * Application effective : celle demandée, sinon celle du profil actif.
 */
function resolveApplication(application) {
  return (application && application.trim()) || profileManager.getCurrent().application;
}

/**
 * Check if cache is still valid for an application
 */
function isCacheValid(application) {
  if (!workflowCaches[application] || !cacheTimestamps[application]) {
    return false;
  }

  const age = Date.now() - cacheTimestamps[application];
  return age < CACHE_TTL;
}

/**
 * Fetch all workflows of an application from API with pagination.
 * Uses high page size (5000) to minimize API calls.
 * Lazy : seule l'application effectivement demandée est chargée (D26) — ne
 * jamais précharger les 9 applications.
 * @param {string} [application] - Application AD (défaut : profil actif)
 */
async function fetchAllWorkflows(application) {
  const app = resolveApplication(application);

  // Check cache validity
  if (isCacheValid(app)) {
    console.error(`[Workflow] Using cached data for "${app}"`);
    return workflowCaches[app];
  }

  // Un seul chargement par application, même sous rafale concurrente (D27).
  return singleFlight.run(`workflows::${app}`, () => loadWorkflows(app));
}

/**
 * Chargement réel des workflows d'une application (pagination complète).
 * Appelé au plus une fois par application tant qu'il est en vol (D27).
 */
async function loadWorkflows(app) {
  console.error(`[Workflow] Cache expired or empty for "${app}", fetching from API...`);

  try {
    let allWorkflows = [];
    let offset = 0;
    const pageSize = parseInt(process.env.WORKFLOW_PAGE_SIZE) || 5000;
    const tenant = profileManager.getCurrent().tenant;

    while (true) {
      const body = [app, tenant, pageSize, offset];

      console.error(`[Workflow] Fetching page: application=${app}, offset=${offset}, pageSize=${pageSize}`);

      // Use AD API (useAdApi=true)
      const response = await apiService.post('/Workflow/GetByApplication', body, true);

      // Extract entities array from response
      const workflows = response?.entities || [];

      // Check if response is valid
      if (!workflows || workflows.length === 0) {
        console.error('[Workflow] No more workflows to fetch');
        break;
      }

      allWorkflows = allWorkflows.concat(workflows);
      console.error(`[Workflow] Fetched ${workflows.length} workflows (total: ${allWorkflows.length})`);

      // If we got less than page size, we've reached the last page
      if (workflows.length < pageSize) {
        console.error('[Workflow] Last page reached');
        break;
      }

      offset += pageSize;
    }

    // Update cache
    workflowCaches[app] = allWorkflows;
    cacheTimestamps[app] = Date.now();

    console.error(`[Workflow] Successfully cached ${allWorkflows.length} workflows for "${app}"`);
    return allWorkflows;
  } catch (error) {
    console.error(`[Workflow] Error fetching workflows for "${app}":`, error.message);
    throw new Error(`Failed to fetch workflows for application "${app}": ${error.message}`);
  }
}

/**
 * Liste les applications déclarées (POST /Application/GetAll, payload null).
 * La réponse est une enveloppe { entities: [...] } (D4) dont chaque élément
 * porte un blob `data` volumineux — on ne conserve que les champs légers.
 * Cache TTL commun, vidé au switch de profil.
 * @returns {Promise<Array<{name: string, id: string, version: number}>>}
 */
async function fetchApplications() {
  const cached = getCachedApplications();
  if (cached) return cached;

  // Même déduplication que les workflows, sur sa propre clé (D27).
  return singleFlight.run('applications', loadApplications);
}

/**
 * Chargement réel de la liste d'applications (D27).
 */
async function loadApplications() {
  console.error('[Workflow] Fetching application list (Application/GetAll)...');
  const response = await apiService.post('/Application/GetAll', null, true);
  const entities = response?.entities || [];

  applicationsCache = entities.map(a => ({
    name: a.name || a.Name,
    id: a.id || a.Id,
    version: a.version ?? a.Version,
  })).filter(a => a.name);
  applicationsTimestamp = Date.now();

  console.error(`[Workflow] Cached ${applicationsCache.length} application(s)`);
  return applicationsCache;
}

/**
 * Liste des applications déjà en cache, ou null si le cache est vide/expiré.
 * Ne déclenche AUCUN appel réseau — c'est ce qui permet d'enrichir une réponse
 * de recherche sans jamais précharger une application non demandée (D26).
 * @returns {Array<{name: string, id: string, version: number}>|null}
 */
function getCachedApplications() {
  if (applicationsCache && applicationsTimestamp &&
      Date.now() - applicationsTimestamp < CACHE_TTL) {
    return applicationsCache;
  }
  return null;
}

/**
 * Hint de découvrabilité (L5.4). Une recherche n'interroge qu'UNE application
 * sur les neuf déclarées, et rien dans la réponse ne le disait : une session
 * cherchant des workflows `CST_*` sans `application: "CustomApp"` a conclu à
 * tort qu'il n'y en avait aucun (25/08/2026).
 *
 * Les autres applications sont nommées depuis la liste allégée **déjà en
 * cache** ; sans elle, le hint reste générique et renvoie vers
 * `list_workflow_categories` — jamais de fetch pour construire un hint.
 *
 * @param {string} application - application effectivement interrogée
 * @param {string} sujet - ce qui a été cherché ('workflow', 'élément Command'…)
 */
function buildOtherApplicationsHint(application, sujet) {
  const cached = getCachedApplications();
  const others = (cached || []).map(a => a.name).filter(n => n !== application);

  const liste = others.length
    ? `Autres applications déclarées sur ce tenant : ${others.join(', ')}.`
    : `Appelez list_workflow_categories pour lister les autres applications déclarées.`;

  const custom = application.toLowerCase() === 'customapp'
    ? ''
    : ` Le spécifique client (préfixe CST_) vit dans "CustomApp" : relancez avec application: "CustomApp".`;

  return `Aucun ${sujet} trouvé dans l'application "${application}" — c'est la SEULE interrogée, ` +
    `les autres ne le sont jamais implicitement.${custom} ${liste}`;
}

/**
 * Search workflows by query string.
 * Real AD keys (lowercase, cf. D5): id, name, version, applicationName,
 * commonInfo — no description/code/category field exists.
 * @param {string} query - Search query (matches workflow name)
 * @param {string|null} category - Optional applicationName filter (the only
 *                                 grouping the AD API provides)
 * @param {number} limit - Maximum results to return
 * @param {string} [application] - Application AD interrogée (défaut : profil)
 */
async function searchWorkflows(query, category = null, limit = 50, application) {
  const workflows = await fetchAllWorkflows(application);

  let results = workflows;

  // Filter by query if provided
  if (query) {
    const lowerQuery = query.toLowerCase();
    results = results.filter(w => {
      const name = (w.name || w.Name || '').toLowerCase();
      return name.includes(lowerQuery);
    });
  }

  // Filter by applicationName if provided
  if (category) {
    const lowerCategory = category.toLowerCase();
    results = results.filter(w => {
      const applicationName = (w.applicationName || w.ApplicationName || '').toLowerCase();
      return applicationName.includes(lowerCategory);
    });
  }

  // Limit results
  return results.slice(0, limit);
}

/**
 * Get workflow details by ID
 * @param {string|number} workflowId - Workflow ID
 * @param {string} [application] - Application AD interrogée (défaut : profil)
 */
async function getWorkflowDetails(workflowId, application) {
  // Garde d'entrée : sans elle, un workflow_id absent matchait le premier
  // workflow du cache (undefined === undefined sur les clés mortes ci-dessous).
  if (workflowId == null || workflowId === '') {
    throw new Error('workflow_id est requis (id ou nom exact du workflow). Utilisez search_workflows pour le trouver.');
  }

  const app = resolveApplication(application);
  const workflows = await fetchAllWorkflows(app);

  // Clés réelles de l'API AD (minuscules, D5) : id, name. Les variantes
  // Id/Code/Name n'existent pas sur ces objets — les comparer faisait matcher
  // undefined === undefined dès que workflow_id manquait.
  const workflow = workflows.find(w =>
    w.id === workflowId ||
    w.name === workflowId
  );

  if (!workflow) {
    throw new Error(
      `Workflow not found: ${workflowId} (application "${app}"). ` +
      `Utilisez search_workflows pour trouver l'id ou le nom exact — ` +
      `pensez au paramètre application (ex: "CustomApp" pour le spécifique client).`
    );
  }

  return workflow;
}

/**
 * Get workflow statistics for one application
 * @param {string} [application] - Application AD interrogée (défaut : profil)
 */
async function getWorkflowStats(application) {
  const app = resolveApplication(application);
  const workflows = await fetchAllWorkflows(app);

  return {
    application: app,
    total: workflows.length,
    cacheAge: cacheTimestamps[app] ? Math.floor((Date.now() - cacheTimestamps[app]) / 1000) : null
  };
}

/**
 * Clear workflow caches (force refresh on next request) — toutes applications.
 */
function clearCache() {
  workflowCaches = {};
  cacheTimestamps = {};
  applicationsCache = null;
  applicationsTimestamp = null;
  console.error('[Workflow] Cache cleared');
}

/**
 * Get cache status, per application (D26)
 * @returns {Object} application -> { cached, count, timestamp, age, valid }
 */
function getCacheStatus() {
  const status = {};
  Object.keys(workflowCaches).forEach(app => {
    status[app] = {
      cached: true,
      count: workflowCaches[app].length,
      timestamp: cacheTimestamps[app],
      age: cacheTimestamps[app] ? Math.floor((Date.now() - cacheTimestamps[app]) / 1000) : null,
      valid: isCacheValid(app)
    };
  });
  return status;
}

module.exports = {
  fetchAllWorkflows,
  fetchApplications,
  getCachedApplications,
  buildOtherApplicationsHint,
  resolveApplication,
  searchWorkflows,
  getWorkflowDetails,
  getWorkflowStats,
  clearCache,
  getCacheStatus
};