malabar/step4_translate.py

#!/usr/bin/env python3
"""
Step 4: Translate transcripts to Chinese.

Input: Speaker files in "_speakers/" folder
Output: JSON files with bilingual content in "_translated/" folder

Features:
- Caches translations in "_translate_cache/" to avoid re-translating
- Reuses cached translations when available

Output format:
[
  {
    "timestamp": "[00:00]",
    "speaker": "Malabar",
    "english": "To the moon and back.",
    "chinese": "到月球再回来。"
  },
  ...
]

Usage:
    uv run step4_translate.py

Environment Variables:
    OPENAI_API_KEY - Required
    OPENAI_BASE_URL - Optional (for Kimi/GLM APIs)
    LLM_MODEL - Optional (e.g., "glm-4.5-air")
"""

import os
import re
import sys
import json
import hashlib
from pathlib import Path
from typing import List, Dict, Tuple, Optional
from openai import OpenAI

# ============== Configuration ==============

INPUT_DIR = Path("_speakers")
OUTPUT_DIR = Path("_translated")
CACHE_DIR = Path("_translate_cache")
BATCH_SIZE = 5  # Translate 5 lines at a time for efficiency

# Default configurations for different providers
DEFAULT_CONFIGS = {
    "openai": {
        "base_url": None,
        "model": "gpt-4o-mini"
    },
    "moonshot": {
        "base_url": "https://api.moonshot.cn/v1",
        "model": "kimi-latest"
    },
    "bigmodel": {  # Zhipu AI (GLM)
        "base_url": "https://open.bigmodel.cn/api/paas/v4",
        "model": "glm-4.5-air"
    }
}


def ensure_dirs():
    """Ensure output directories exist."""
    OUTPUT_DIR.mkdir(exist_ok=True)
    CACHE_DIR.mkdir(exist_ok=True)


def get_llm_config() -> Tuple[str, str]:
    """Get LLM configuration from environment."""
    api_key = os.getenv("OPENAI_API_KEY")
    if not api_key:
        raise ValueError("OPENAI_API_KEY environment variable is required")
    
    base_url = os.getenv("OPENAI_BASE_URL")
    model = os.getenv("LLM_MODEL")
    
    if base_url:
        if model:
            return base_url, model
        if "bigmodel" in base_url:
            return base_url, DEFAULT_CONFIGS["bigmodel"]["model"]
        elif "moonshot" in base_url or "kimi" in base_url:
            return base_url, DEFAULT_CONFIGS["moonshot"]["model"]
        else:
            return base_url, DEFAULT_CONFIGS["openai"]["model"]
    else:
        return None, model or DEFAULT_CONFIGS["openai"]["model"]


def get_cache_key(english: str) -> str:
    """Generate a cache key for an English sentence."""
    # Use MD5 hash for consistent cache keys
    return hashlib.md5(english.strip().encode('utf-8')).hexdigest()[:16]


def get_cached_translation(english: str) -> Optional[str]:
    """Check if a translation exists in cache."""
    cache_key = get_cache_key(english)
    cache_file = CACHE_DIR / f"{cache_key}.json"
    
    if cache_file.exists():
        try:
            with open(cache_file, 'r', encoding='utf-8') as f:
                data = json.load(f)
                if data.get("english") == english.strip():
                    return data.get("chinese")
        except Exception:
            pass
    return None


def save_translation_cache(english: str, chinese: str):
    """Save a translation to the cache."""
    if not chinese or chinese == "[Translation failed]":
        return
    
    cache_key = get_cache_key(english)
    cache_file = CACHE_DIR / f"{cache_key}.json"
    
    try:
        with open(cache_file, 'w', encoding='utf-8') as f:
            json.dump({
                "english": english.strip(),
                "chinese": chinese.strip()
            }, f, ensure_ascii=False)
    except Exception as e:
        print(f"    Warning: Failed to save cache: {e}")


def parse_line(line: str) -> Optional[Dict[str, str]]:
    """Parse a line from the speaker file."""
    pattern = r'^(\[\d{2}:\d{2}\])\(([^)]+)\) (.+)$'
    match = re.match(pattern, line.strip())
    if match:
        return {
            "timestamp": match.group(1),
            "speaker": match.group(2),
            "english": match.group(3)
        }
    return None


def translate_batch(lines: List[Dict[str, str]], client: OpenAI, model: str) -> List[str]:
    """Translate a batch of lines to Chinese."""
    # Build the prompt with numbered lines
    lines_text = "\n".join([f"{i+1}. {line['english']}" for i, line in enumerate(lines)])
    
    prompt = f"""Translate these lines from "Little Malabar" to natural Chinese.
Maintain the meaning and keep it child-friendly.

Lines to translate:
{lines_text}

Reply with ONLY the Chinese translations, one per line, numbered the same way:
1. [translation]
2. [translation]
..."""
    
    try:
        response = client.chat.completions.create(
            model=model,
            messages=[
                {"role": "user", "content": prompt}
            ],
            temperature=0.3,
            max_tokens=1000,
            extra_body={"thinking": {"type": "disabled"}}  # Disable thinking
        )
        
        message = response.choices[0].message
        result = message.content.strip() if message.content else ""
        
        # Parse the numbered responses
        translations = []
        result_lines = result.strip().split('\n')
        
        for i in range(len(lines)):
            expected_num = i + 1
            translation = ""
            
            # Find line starting with "N. "
            for line in result_lines:
                line = line.strip()
                match = re.match(rf'^{expected_num}\.\s*(.+)$', line)
                if match:
                    translation = match.group(1).strip()
                    break
            
            if not translation:
                # Fallback: try to extract any text
                for line in result_lines:
                    if line.strip() and not line.strip()[0].isdigit():
                        translation = line.strip()
                        break
            
            translations.append(translation or "[Translation failed]")
        
        return translations
        
    except Exception as e:
        print(f"    Batch translation error: {e}")
        return ["[Translation failed]"] * len(lines)


def translate_file(input_path: Path, client: OpenAI, model: str) -> Path:
    """Translate a single speaker file to Chinese."""
    print(f"\n{'='*50}")
    print(f"Translating: {input_path.name}")
    print(f"{'='*50}")
    
    # Read the file
    with open(input_path, 'r', encoding='utf-8') as f:
        lines = f.readlines()
    
    print(f"  Total lines: {len(lines)}")
    
    # Parse all lines first
    parsed_lines = []
    for i, line in enumerate(lines, 1):
        line = line.strip()
        if not line:
            continue
        
        line_data = parse_line(line)
        if line_data:
            parsed_lines.append(line_data)
        else:
            print(f"  Warning: Could not parse line {i}: {line[:50]}...")
    
    print(f"  Parsed {len(parsed_lines)} valid lines")
    
    # Check cache for each line
    cached_count = 0
    skipped_count = 0
    to_translate = []
    
    for line_data in parsed_lines:
        english = line_data["english"]
        speaker = line_data["speaker"]
        
        # Skip translation for opening song (speaker is "Song")
        if speaker == "Song":
            line_data["chinese"] = english  # Keep English for song lyrics
            skipped_count += 1
            continue
        
        # Skip dummy "THE END" line (added by step 2 for timing purposes)
        if english.strip() == "THE END":
            line_data["chinese"] = english  # Keep as-is
            skipped_count += 1
            continue
        
        cached = get_cached_translation(english)
        if cached:
            line_data["chinese"] = cached
            cached_count += 1
        else:
            to_translate.append(line_data)
    
    print(f"  Cached translations: {cached_count}")
    print(f"  Skipped (Song): {skipped_count}")
    print(f"  To translate: {len(to_translate)}")
    
    # Translate in batches
    total_batches = (len(to_translate) + BATCH_SIZE - 1) // BATCH_SIZE
    translated_count = 0
    
    for batch_idx in range(total_batches):
        start = batch_idx * BATCH_SIZE
        end = min(start + BATCH_SIZE, len(to_translate))
        batch = to_translate[start:end]
        
        print(f"    Translating batch {batch_idx + 1}/{total_batches} (lines {start+1}-{end})...")
        
        translations = translate_batch(batch, client, model)
        
        for i, line_data in enumerate(batch):
            translation = translations[i] if i < len(translations) else "[Translation failed]"
            line_data["chinese"] = translation
            translated_count += 1
            
            # Save to cache
            if translation and translation != "[Translation failed]":
                save_translation_cache(line_data["english"], translation)
    
    # Combine results (cached + translated + skipped)
    result = parsed_lines
    
    print(f"  Translation complete: {cached_count} from cache, {translated_count} new, {skipped_count} skipped (Song)")
    
    # Save JSON output
    output_filename = input_path.stem.replace("_speakers", "") + "_translated.json"
    output_path = OUTPUT_DIR / output_filename
    
    with open(output_path, 'w', encoding='utf-8') as f:
        json.dump(result, f, ensure_ascii=False, indent=2)
    
    print(f"  Saved to: {output_path}")
    
    return output_path


def get_input_files() -> list[Path]:
    """Discover all text files in _speakers/ folder."""
    if not INPUT_DIR.exists():
        return []
    files = [f for f in INPUT_DIR.iterdir() if f.is_file() and f.suffix == '.txt']
    return sorted(files)


def main():
    ensure_dirs()
    
    # Get LLM config
    base_url, model = get_llm_config()
    client = OpenAI(api_key=os.getenv("OPENAI_API_KEY"), base_url=base_url)
    
    # Count existing cache entries
    cache_count = len(list(CACHE_DIR.glob("*.json")))
    
    print(f"Using model: {model}")
    print(f"Endpoint: {base_url or 'OpenAI default'}")
    print(f"Batch size: {BATCH_SIZE} lines per request")
    print(f"Cache entries: {cache_count}")
    
    # Discover input files
    input_files = get_input_files()
    
    if not input_files:
        print(f"No .txt files found in {INPUT_DIR}/")
        sys.exit(1)
    
    print(f"Found {len(input_files)} file(s) to translate")
    print("")
    
    # Process all files
    success_count = 0
    fail_count = 0
    
    for input_path in input_files:
        try:
            output_path = translate_file(input_path, client, model)
            if output_path:
                success_count += 1
        except Exception as e:
            print(f"\n❌ Failed to translate {input_path.name}: {e}")
            import traceback
            traceback.print_exc()
            fail_count += 1
    
    # Summary
    final_cache_count = len(list(CACHE_DIR.glob("*.json")))
    print("\n" + "="*50)
    print(f"Step 4 Complete: {success_count} succeeded, {fail_count} failed")
    print(f"Total cache entries: {final_cache_count}")
    print(f"Output saved to: {OUTPUT_DIR}/")
    print("="*50)
    
    if fail_count > 0:
        sys.exit(1)


if __name__ == "__main__":
    main()