document.addEventListener('DOMContentLoaded', function() {
    const form = document.getElementById('translationForm');
    const progressArea = document.getElementById('progressArea');
    const progressBar = document.querySelector('.progress-bar');
    const progressText = document.getElementById('progressText');
    const resultArea = document.getElementById('resultArea');
    const mediaPlayer = document.getElementById('mediaPlayer');
    const downloadBtn = document.getElementById('downloadBtn');
    const submitBtn = document.getElementById('submitBtn');

    // Retry configuration
    const MAX_RETRIES = 3;
    const RETRY_DELAY = 5000; // 5 seconds

    async function delay(ms) {
        return new Promise(resolve => setTimeout(resolve, ms));
    }

    async function submitWithRetry(formData, retryCount = 0) {
        try {
            const response = await fetch('/api/translate', {
                method: 'POST',
                body: formData
            });

            if (response.status === 429) { // Rate limit error
                if (retryCount < MAX_RETRIES) {
                    const waitTime = (retryCount + 1) * RETRY_DELAY;
                    updateProgress(50, `Rate limit reached. Retrying in ${waitTime/1000} seconds... (Attempt ${retryCount + 1}/${MAX_RETRIES})`);
                    await delay(waitTime);
                    return submitWithRetry(formData, retryCount + 1);
                } else {
                    throw new Error('Rate limit exceeded. Please try again later.');
                }
            }

            if (!response.ok) {
                const error = await response.text();
                throw new Error(error);
            }

            return response;

        } catch (error) {
            if (error.message.includes('Rate limit exceeded')) {
                throw error;
            }
            throw new Error(`Request failed: ${error.message}`);
        }
    }

    form.addEventListener('submit', async function(e) {
        e.preventDefault();
        
        // Show progress and disable submit button
        progressArea.classList.remove('d-none');
        submitBtn.disabled = true;
        progressBar.style.width = '0%';
        resultArea.classList.add('d-none');
        downloadBtn.classList.add('d-none');
        
        // Remove any previous error styling
        progressBar.classList.remove('bg-danger');
        
        const updateProgress = (percent, message) => {
            progressBar.style.width = `${percent}%`;
            progressText.textContent = message;
        };
        
        try {
            const formData = new FormData(this);
            const file = formData.get('file');
            
            // Validate file size (max 500MB)
            if (file.size > 500 * 1024 * 1024) {
                throw new Error('File size exceeds 500MB limit');
            }
            
            updateProgress(10, 'Uploading file...');
            
            try {
                const response = await submitWithRetry(formData);
                const blob = await response.blob();
                const url = URL.createObjectURL(blob);
                
                // Update UI based on file type
                const outputType = formData.get('output_type');
                const mediaElement = document.createElement(outputType === 'video' ? 'video' : 'audio');
                mediaElement.src = url;
                mediaElement.controls = true;
                mediaElement.classList.add('w-100');
                
                // Clear previous media player content
                mediaPlayer.innerHTML = '';
                mediaPlayer.appendChild(mediaElement);
                
                // Setup download button
                downloadBtn.href = url;
                downloadBtn.download = `translated_media.${outputType === 'video' ? 'mp4' : 'mp3'}`;
                
                // Show results
                const thumbnailHTML = `
                    <div class="alert alert-success">
                        <div class="d-flex align-items-center">
                            <img src="${url}" alt="Video thumbnail" style="width: 210px; height: 120px; object-fit: cover; margin: 0 auto; border-radius: 9px; margin: 10px auto;">
                            <div>
                                <strong>Video úspěšně staženo!</strong>
                                <br>
                                <small class="text-muted">Připraveno ke zpracování</small>
                            </div>
                        </div>
                    </div>`;
                resultArea.innerHTML = thumbnailHTML;
                resultArea.classList.remove('d-none');
                downloadBtn.classList.remove('d-none');
                updateProgress(100, 'Translation complete!');
                
            } catch (error) {
                throw error;
            }
            
        } catch (error) {
            console.error('Error:', error);
            progressBar.classList.add('bg-danger');
            updateProgress(100, `Error: ${error.message}`);
        } finally {
            submitBtn.disabled = false;
        }
    });
});