add parallel chunk translation for massive speed improvement on large pages

src/translation.js

@@ -488,14 +488,39 @@ export async function translateHTML(htmlContent, targetLanguage, sourceUrl = nul
 		console.log('Converted relative URLs using base URL:', sourceUrl);
 	}
 
-	// Limit content length to avoid overwhelming the AI
-	const maxLength = 50000; // Much higher limit for complete page translation
-	const contentToTranslate =
-		processedContent.length > maxLength
-			? `${processedContent.substring(0, maxLength)}...`
-			: processedContent;
-
-	// Translation content is already handled above (chunked or single request)
+	// Use actual token limits instead of character limits
+	const maxTokens = getSelectedModelMaxTokens();
+	const reserveTokens = 1000; // Reserve tokens for prompt overhead
+	const availableTokens = Math.max(maxTokens - reserveTokens, 2000); // Ensure minimum
+	
+	// Check if content needs chunking based on token count
+	const contentTokens = await countTokens(processedContent, getSelectedModel());
+	
+	let translatedContent;
+	if (contentTokens <= availableTokens) {
+		// Content fits in one request
+		console.log(`Content fits in single request: ${contentTokens} tokens`);
+		translatedContent = await translateText(processedContent, targetLanguage);
+	} else {
+		// Content needs chunking - translate all chunks in parallel
+		console.log(`Content requires chunking: ${contentTokens} tokens > ${availableTokens} limit`);
+		
+		const chunks = await splitHTMLIntoChunks(processedContent, availableTokens, getSelectedModel());
+		console.log(`Split into ${chunks.length} chunks for parallel translation`);
+		
+		// Translate all chunks in parallel for much faster processing
+		const translationPromises = chunks.map((chunk, index) => {
+			console.log(`Queued chunk ${index + 1}/${chunks.length} for translation`);
+			return translateText(chunk, targetLanguage);
+		});
+		
+		// Wait for all translations to complete
+		const translatedChunks = await Promise.all(translationPromises);
+		console.log(`All ${chunks.length} chunks translated successfully in parallel`);
+		
+		// Reassemble the chunks in order
+		translatedContent = translatedChunks.join('');
+	}
 	
 	// Parse the content to add base tag for URL resolution
 	const parser = new DOMParser();