office_translator/frontend/src/app/dashboard/translate/useTranslationSubmit.ts

'use client';

import { useState, useEffect, useCallback, useRef } from 'react';
import type { 
  UseTranslationSubmitReturn, 
  TranslationConfig, 
  TranslationStatus,
  TranslationSubmitResponse,
  TranslationStatusResponse 
} from './types';

const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000';
const POLLING_INTERVAL_MS = 2000;
const MAX_POLLING_FAILURES = 3;

export function useTranslationSubmit(): UseTranslationSubmitReturn {
  const [jobId, setJobId] = useState<string | null>(null);
  const [status, setStatus] = useState<TranslationStatus>('idle');
  const [progress, setProgress] = useState(0);
  const [currentStep, setCurrentStep] = useState('');
  const [error, setError] = useState<string | null>(null);
  const [estimatedRemaining, setEstimatedRemaining] = useState<number | null>(null);
  const [fileName, setFileName] = useState<string | null>(null);
  const [isSubmitting, setIsSubmitting] = useState(false);
  const [pollingFailures, setPollingFailures] = useState(0);
  const [isPolling, setIsPolling] = useState(false);
  
  const pollingIntervalRef = useRef<NodeJS.Timeout | null>(null);
  const isPollingRef = useRef(false);
  // Use a ref for failure count to avoid stale closure in the interval callback.
  // If we relied on state, the setInterval callback would always read the initial
  // value of pollingFailures (0) and never reach MAX_POLLING_FAILURES.
  const pollingFailuresRef = useRef(0);

  const stopPolling = useCallback(() => {
    if (pollingIntervalRef.current) {
      clearInterval(pollingIntervalRef.current);
      pollingIntervalRef.current = null;
    }
    isPollingRef.current = false;
    setIsPolling(false);
  }, []);

  const pollProgress = useCallback(async (id: string) => {
    if (isPollingRef.current) return;
    
    isPollingRef.current = true;
    
    try {
      const token = localStorage.getItem('token');
      const headers: Record<string, string> = {};
      if (token) {
        headers['Authorization'] = `Bearer ${token}`;
      }

      const response = await fetch(`${API_BASE}/api/v1/translations/${id}`, { headers });
      
      if (!response.ok) {
        if (response.status === 404) {
          stopPolling();
          setStatus('failed');
          setError('Translation job not found');
          return;
        }
        throw new Error(`HTTP error! status: ${response.status}`);
      }

      const data: TranslationStatusResponse = await response.json();
      const job = data.data;

      setStatus(job.status as TranslationStatus);
      setProgress(job.progress_percent || 0);
      setCurrentStep(job.current_step || '');
      setEstimatedRemaining(data.meta.estimated_remaining_seconds ?? null);
      pollingFailuresRef.current = 0;
      setPollingFailures(0);
      
      if (job.file_name) {
        setFileName(job.file_name);
      }

      if (job.status === 'completed' || job.status === 'failed') {
        stopPolling();
        if (job.status === 'failed') {
          setError(job.error_message || 'Translation failed');
        }
      }
    } catch (err) {
      console.error('Polling error:', err);
      pollingFailuresRef.current += 1;
      setPollingFailures(pollingFailuresRef.current);
      
      if (pollingFailuresRef.current >= MAX_POLLING_FAILURES) {
        stopPolling();
        setStatus('failed');
        setError('Lost connection to translation service. Please check your internet connection and try again.');
      }
    } finally {
      isPollingRef.current = false;
    }
  }, [stopPolling]);

  const startPolling = useCallback((id: string) => {
    stopPolling();
    pollingFailuresRef.current = 0;
    setIsPolling(true);
    setPollingFailures(0);
    
    pollProgress(id);
    
    pollingIntervalRef.current = setInterval(() => {
      pollProgress(id);
    }, POLLING_INTERVAL_MS);
  }, [pollProgress, stopPolling]);

  const submitTranslation = useCallback(async (file: File, config: TranslationConfig) => {
    setIsSubmitting(true);
    setError(null);
    setProgress(0);
    setCurrentStep('Uploading file...');
    setEstimatedRemaining(null);
    setStatus('processing'); // IMPORTANT: Set to 'processing' IMMEDIATELY so progress bar shows
    setFileName(file.name);
    setJobId(null);

    try {
      const formData = new FormData();
      formData.append('file', file);
      formData.append('source_lang', config.sourceLang);
      formData.append('target_lang', config.targetLang);
      formData.append('mode', config.mode);
      // Provider is configured server-side by admin — only send the provider name.
      if (config.mode === 'llm' && config.provider) {
        formData.append('provider', config.provider);
      }

      const token = localStorage.getItem('token');
      const headers: Record<string, string> = {};
      if (token) {
        headers['Authorization'] = `Bearer ${token}`;
      }

      const response = await fetch(`${API_BASE}/api/v1/translate`, {
        method: 'POST',
        headers,
        body: formData,
      });

      if (!response.ok) {
        let errorMessage = `Translation failed: ${response.status}`;
        try {
          const errorData = await response.json();
          errorMessage = errorData.message || errorData.error || errorMessage;
        } catch {
          // Response not JSON, use default message
        }
        throw new Error(errorMessage);
      }

      const data: TranslationSubmitResponse = await response.json();
      
      setJobId(data.data.id);
      setFileName(data.data.file_name || file.name);
      setProgress(data.data.progress_percent || 5); // Start with at least 5%
      setCurrentStep(data.data.current_step || 'Translating...');
      
      startPolling(data.data.id);
    } catch (err) {
      setStatus('failed');
      setError(err instanceof Error ? err.message : 'Translation failed');
      setIsSubmitting(false);
    }
    // NOTE: Don't set isSubmitting(false) here - let polling handle the transition
  }, [startPolling]);

  const reset = useCallback(() => {
    stopPolling();
    setJobId(null);
    setStatus('idle');
    setProgress(0);
    setCurrentStep('');
    setError(null);
    setEstimatedRemaining(null);
    setFileName(null);
    setIsSubmitting(false);
    setPollingFailures(0);
  }, [stopPolling]);

  useEffect(() => {
    return () => {
      stopPolling();
    };
  }, [stopPolling]);

  return {
    submitTranslation,
    jobId,
    status,
    progress,
    currentStep,
    error,
    estimatedRemaining,
    fileName,
    reset,
    isSubmitting,
    isPolling,
    pollingFailures,
  };
}