# Translation Issues Fixed

## Problems Addressed

### 1. Translation Not Working (Files Remained Untranslated)
**Problem**: Files were being processed but returned in the original language with 0 paragraphs translated.

**Root Causes**:
- Silent fallback behavior in `translate_text()` method
- No validation of translation results
- Missing error handling for API failures

**Fixes Applied**:
- **Enhanced `translate_text()` method**: 
  - Added API key validation before making requests
  - Improved translation prompts for better results with Google Gemini 2.5 Pro
  - Removed silent fallback to original text - now raises exceptions on failure
  - Added validation to ensure translation actually occurred
  - Increased token limits for better translation quality

- **Improved error handling**:
  - Added comprehensive exception handling in translation workflows
  - Better validation of translated content
  - Detailed logging to track translation progress

- **Enhanced validation**:
  - Check for empty or unchanged translation results
  - Verify API responses before processing
  - Ensure at least some content gets translated

### 2. Format Preservation Issue
**Problem**: User wanted files to maintain original filename and format (PDF→Word→translate→PDF workflow)

**Current Behavior**: Created separate "translated_" prefixed files
**Desired Behavior**: Receive PDF, convert to Word, translate, convert back to PDF with same filename

**Fixes Applied**:
- **Modified `translate_document()` method**:
  - Output file now uses original filename (no "translated_" prefix)
  - For PDF input: PDF→DOCX→translate→PDF with original filename
  - For DOCX input: DOCX→translate→DOCX with original filename

- **Updated file handling in `main.py`**:
  - Both original and translated files now use same filename
  - Better file copying and naming logic
  - Improved response structure

## Technical Improvements

### 1. Robust Translation Logic
```python
# Before: Silent fallback
if translation_failed:
    return original_text  # Silent failure

# After: Proper error handling  
if not translated or translated == text:
    raise Exception("Translation failed: received empty or unchanged text")
```

### 2. Enhanced Error Reporting
- Added detailed logging throughout the translation pipeline
- Better API error messages
- Validation at each step of the process

### 3. Format Preservation Workflow
```
PDF Input → LibreOffice Convert to DOCX → Translate DOCX → Convert back to PDF (same filename)
DOCX Input → Translate DOCX → Save as same filename
```

## Testing

### API Key Testing
Created `test_api.py` script to verify:
- OPENROUTER_API_KEY is set correctly
- API connection is working
- Basic translation functionality

### Usage
Run the test script to verify setup:
```bash
python test_api.py
```

## Expected Results

After these fixes:
1. **Translation will work**: Files will be actually translated, not returned unchanged
2. **Format preserved**: PDF files will be returned as PDF with same filename
3. **Better error messages**: Clear feedback when translation fails
4. **Robust operation**: Proper error handling instead of silent failures

## Key Files Modified

1. **`translator.py`**:
   - Enhanced `translate_text()` method with validation
   - Improved `translate_document()` for format preservation
   - Better error handling in `translate_docx()` and `translate_pdf_direct()`

2. **`app/main.py`**:
   - Updated translation endpoint with better validation
   - Fixed file naming to preserve original names
   - Enhanced error reporting

3. **`test_api.py`** (new):
   - API key and connection testing
   - Basic translation functionality verification

## Usage Instructions

1. **Set API Key**: Ensure `OPENROUTER_API_KEY` environment variable is set
2. **Test Setup**: Run `python test_api.py` to verify configuration
3. **Upload Files**: PDF or DOCX files will now be properly translated
4. **Download Results**: Translated files maintain original format and filename

The system now provides reliable translation with proper format preservation as requested.