/**
 * src/services/JobQueue.ts
 *
 * Job routing layer for titan_builder_queue.
 *
 * Changes from v2:
 *   - handleWebView: يقرأ buildType + manifestUrl من Firestore
 *     ويمررهم لـ triggerWebViewBuild
 *   - لو buildType = pwa_twa أو twa_native يسجل ذلك في اللوج
 */

import admin from 'firebase-admin';
import { logger } from '../utils/logger';
import {
  FirebaseManager,
  QUEUE_COLLECTION,
  type QueueDoc,
  type TranspilerJob,
} from '../managers/FirebaseManager';
import { LLMOrchestrator } from './llmOrchestrator';
import { GitHubActionsService } from './githubActions';
import { hfStorage } from './hfStorage';

// ─── Job Queue Service ────────────────────────────────────────────────────────

export class JobQueue {
  private readonly firebase: FirebaseManager;
  private readonly orchestrator: LLMOrchestrator;
  private readonly github: GitHubActionsService;
  private readonly inFlight = new Set<string>();
  private stopFn: (() => void) | null = null;

  constructor() {
    this.firebase     = FirebaseManager.getInstance();
    this.orchestrator = new LLMOrchestrator();
    this.github       = new GitHubActionsService();
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Lifecycle
  // ═══════════════════════════════════════════════════════════════════════════

  start(): () => void {
    const db    = (this.firebase as unknown as { db: admin.firestore.Firestore }).db
                  ?? admin.firestore();
    const query = db
      .collection(QUEUE_COLLECTION)
      .where('status', '==', 'pending')
      .orderBy('createdAt', 'asc');

    const unsubscribe = query.onSnapshot(
      async (snapshot) => {
        for (const change of snapshot.docChanges()) {
          if (change.type !== 'added' && change.type !== 'modified') continue;

          const doc  = change.doc;
          const data = doc.data() as Omit<QueueDoc, 'id'>;
          if (data.status !== 'pending') continue;

          const job: QueueDoc = { id: doc.id, ...data };
          if (this.inFlight.has(job.id)) continue;

          const claimed = await this.claimJob(doc.ref);
          if (!claimed) continue;

          this.inFlight.add(job.id);
          logger.info(`JobQueue: claimed job ${job.id} (type="${job.type}")`);

          this.dispatch(job)
            .catch(err =>
              logger.error(`JobQueue: unhandled error for job ${job.id}`, err)
            )
            .finally(() => this.inFlight.delete(job.id));
        }
      },
      (err) => {
        logger.error('JobQueue: Firestore listener error', err);
      }
    );

    this.stopFn = unsubscribe;
    logger.info(`JobQueue: ✅ listening on "${QUEUE_COLLECTION}"`);
    return unsubscribe;
  }

  stop(): void {
    this.stopFn?.();
    this.stopFn = null;
    logger.info('JobQueue: listener stopped');
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Distributed Claim
  // ═══════════════════════════════════════════════════════════════════════════

  private async claimJob(
    docRef: admin.firestore.DocumentReference
  ): Promise<boolean> {
    try {
      await admin.firestore().runTransaction(async (tx) => {
        const snap = await tx.get(docRef);
        if (!snap.exists) throw new Error('Job disappeared');
        const status = (snap.data() as Omit<QueueDoc, 'id'>).status;
        if (status !== 'pending') throw new Error(`Already claimed: ${status}`);
        tx.update(docRef, {
          status:    'processing',
          updatedAt: admin.firestore.Timestamp.now(),
        });
      });
      return true;
    } catch {
      return false;
    }
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Dispatch
  // ═══════════════════════════════════════════════════════════════════════════

  private async dispatch(job: QueueDoc): Promise<void> {
    try {
      switch (job.type) {
        case 'transpile': await this.handleTranspile(job); break;
        case 'build':     await this.handleBuild(job);     break;
        case 'webview':   await this.handleWebView(job);   break;
        default: {
          const unknown = (job as QueueDoc).type;
          logger.warn(`JobQueue: unknown type "${unknown}" for job ${job.id}`);
          await this.firebase.updateQueueDoc(job.id, {
            status:       'failed',
            errorMessage: `Unknown job type: "${unknown}"`,
          });
        }
      }
    } catch (err) {
      const msg = err instanceof Error ? err.message : String(err);
      logger.error(`JobQueue: top-level dispatch error for job ${job.id} — ${msg}`);
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: msg,
      }).catch(() => undefined);
    }
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Handler: 'transpile'
  // ═══════════════════════════════════════════════════════════════════════════

  private async handleTranspile(job: QueueDoc): Promise<void> {
    logger.info(`JobQueue[transpile]: starting job ${job.id}`);

    if (!job.zipUrl) {
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: 'transpile job is missing required field: zipUrl',
      });
      return;
    }

    const transpilerJob: TranspilerJob = {
      id:        job.id,
      zipUrl:    job.zipUrl,
      appName:   job.appName,
      status:    'processing',
      createdAt: job.createdAt ?? admin.firestore.Timestamp.now(),
    };

    await this.firebase.createTranspilerJobDoc(transpilerJob);
    await this.orchestrator.processJob(transpilerJob);

    const result = await this.firebase.getJob(job.id);

    if (result?.status === 'completed' && result.outputUrl) {
      await this.firebase.updateQueueDoc(job.id, {
        status:       'completed',
        resultZipUrl: result.outputUrl,
      });
      logger.info(`JobQueue[transpile]: ✅ completed — job ${job.id}`);
    } else {
      const reason = result?.errorMessage ?? 'Pipeline ended without an output URL';
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: reason,
      });
      logger.warn(`JobQueue[transpile]: ❌ failed — job ${job.id}: ${reason}`);
    }
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Handler: 'build'
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * The ZIP arrives as a base64 string in job.zipBase64.
   * No Firebase Storage needed.
   */
  private async handleBuild(job: QueueDoc): Promise<void> {
    logger.info(`JobQueue[build]: starting job ${job.id}`);

    if (!job.zipBase64) {
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: 'build job is missing required field: zipBase64',
      });
      return;
    }

    try {
      const buffer = Buffer.from(job.zipBase64, 'base64');
      await this.github.triggerBuild(buffer, job.id);
      await this.firebase.updateQueueDoc(job.id, { status: 'building' });
      logger.info(`JobQueue[build]: ✅ GitHub build triggered — job ${job.id}`);
    } catch (err) {
      const msg = err instanceof Error ? err.message : String(err);
      logger.error(`JobQueue[build]: ❌ failed — job ${job.id}: ${msg}`);
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: msg,
      });
    }
  }

  // ═══════════════════════════════════════════════════════════════════════════
  //  Handler: 'webview'
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Handles webview / pwa_twa / twa_native jobs.
   *
   * Changes v3:
   *   - يقرأ buildType + manifestUrl من الـ Firestore doc
   *   - يسجل في اللوج لو كان TWA build
   *   - يمرر buildType + manifestUrl لـ triggerWebViewBuild
   */
  private async handleWebView(job: QueueDoc): Promise<void> {
    logger.info(`JobQueue[webview]: starting job ${job.id}`);

    if (!job.url || !job.appName) {
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: 'webview job is missing required fields: url, appName',
      });
      return;
    }

    // ── قراءة buildType + manifestUrl ─────────────────────────────────────────
    const buildType   = job.buildType   ?? 'webview';
    const manifestUrl = job.manifestUrl ?? '';

    // ── تسجيل خاص للـ TWA builds ─────────────────────────────────────────────
    if (buildType === 'pwa_twa' || buildType === 'twa_native') {
      logger.info(
        `JobQueue[webview]: 🔷 TWA build detected — ` +
        `buildType="${buildType}", manifestUrl="${manifestUrl}", job=${job.id}`
      );
    }

    try {
      // ── رفع الأيقونة على HF Dataset لو موجودة ──────────────────────────────
      let finalIconUrl = job.iconUrl || '';

      if (job.iconBase64 && job.iconMime) {
        logger.info(`JobQueue[webview]: uploading icon for job ${job.id}`);
        const ext      = job.iconMime.split('/')[1] || 'png';
        const filename = `icons/${job.id}/icon.${ext}`;
        const buf      = Buffer.from(job.iconBase64, 'base64');
        finalIconUrl   = await hfStorage.uploadBuffer(buf, filename, job.iconMime);
        logger.info(`JobQueue[webview]: icon uploaded → ${finalIconUrl}`);
      } else if (job.iconUrl && job.iconUrl.startsWith('http')) {
        try {
          finalIconUrl = await hfStorage.uploadIconFromUrl(job.iconUrl, job.id);
        } catch {
          logger.warn(`JobQueue[webview]: icon re-upload failed, using original URL`);
          finalIconUrl = job.iconUrl;
        }
      }

      // ── Trigger GitHub Actions ────────────────────────────────────────────
      await this.github.triggerWebViewBuild({
        url:                  job.url,
        appName:              job.appName,
        iconUrl:              finalIconUrl,
        trackingId:           job.id,
        enableCamera:         job.enableCamera         ?? true,
        enableStorage:        job.enableStorage        ?? true,
        enableLocation:       job.enableLocation       ?? false,
        enableNotifications:  job.enableNotifications  ?? false,
        buildType,    // ← جديد: يُمرَّر من Firestore
        manifestUrl,  // ← جديد: يُمرَّر من Firestore
      });

      await this.firebase.updateQueueDoc(job.id, { status: 'building' });
      logger.info(
        `JobQueue[webview]: ✅ GitHub ${buildType} build triggered — job ${job.id}`
      );

    } catch (err) {
      const msg = err instanceof Error ? err.message : String(err);
      logger.error(`JobQueue[webview]: ❌ failed — job ${job.id}: ${msg}`);
      await this.firebase.updateQueueDoc(job.id, {
        status:       'failed',
        errorMessage: msg,
      });
    }
  }
}