Make SubFox production-ready with parallel translation and UI controls

app/services/translator.py

@@ -0,0 +1,88 @@
+import os
+import re
+from openai import OpenAI
+
+BLOCK_MARKER = "<<<BLOCK_{index}>>>"
+BATCH_SIZE = 50
+
+
+def _build_batch_prompt(blocks):
+    parts = []
+    for block in blocks:
+        parts.append(BLOCK_MARKER.format(index=block["index"]))
+        parts.append(block["text"])
+        parts.append("")
+
+    joined = "\n".join(parts)
+
+    return f"""
+You are translating subtitle text from English to Danish.
+
+Rules:
+- Translate naturally into short, readable Danish suitable for subtitles.
+- Keep each block marker exactly unchanged.
+- Do not add explanations.
+- Do not remove markers.
+- Return only the translated blocks.
+
+Text to translate:
+
+{joined}
+""".strip()
+
+
+def _parse_translated_response(translated_text):
+    pattern = r"<<<BLOCK_(\d+)>>>\n?(.*?)(?=(?:\n<<<BLOCK_\d+>>>|\Z))"
+    matches = re.findall(pattern, translated_text, re.DOTALL)
+
+    result = {}
+    for block_id, text in matches:
+        result[int(block_id)] = text.strip()
+
+    return result
+
+
+def _chunked(seq, size):
+    for i in range(0, len(seq), size):
+        yield seq[i:i + size]
+
+
+def translate_blocks(blocks):
+    api_key = os.getenv("OPENAI_API_KEY", "").strip()
+
+    if not api_key:
+        print("DEBUG: no OPENAI_API_KEY found, using fallback translator", flush=True)
+        for block in blocks:
+            block["translated_text"] = "[DA] " + block["text"]
+        return blocks
+
+    client = OpenAI(api_key=api_key)
+    model = os.getenv("OPENAI_MODEL", "gpt-4.1-mini")
+
+    translated_map = {}
+
+    for batch_num, batch in enumerate(_chunked(blocks, BATCH_SIZE), start=1):
+        print(f"DEBUG: translating batch {batch_num} with {len(batch)} blocks", flush=True)
+
+        prompt = _build_batch_prompt(batch)
+
+        response = client.responses.create(
+            model=model,
+            input=prompt,
+        )
+
+        translated_output = response.output_text
+        parsed = _parse_translated_response(translated_output)
+
+        print(
+            f"DEBUG: batch {batch_num} parsed translations = {len(parsed)}",
+            flush=True
+        )
+
+        for block in batch:
+            translated_map[block["index"]] = parsed.get(block["index"], block["text"])
+
+    for block in blocks:
+        block["translated_text"] = translated_map.get(block["index"], block["text"])
+
+    return blocks