add the code

code_engine.py

@@ -0,0 +1,67 @@
+from schemas import CodeXRequest, CodeXResponse, CodeTaskType
+from code_router import detect_task_type
+from prompt_builder import build_prompt
+from model_client import model_client
+from response_formatter import build_response, build_error_response
+from config import settings
+
+
+def should_use_retrieval(task_type: CodeTaskType, request: CodeXRequest) -> bool:
+    if not request.use_retrieval:
+        return False
+
+    if task_type == CodeTaskType.FIX and settings.ENABLE_RETRIEVAL_FOR_FIX:
+        return True
+
+    if task_type == CodeTaskType.GENERATE and settings.ENABLE_RETRIEVAL_FOR_GENERATE:
+        return True
+
+    if task_type == CodeTaskType.EXPLAIN and settings.ENABLE_RETRIEVAL_FOR_EXPLAIN:
+        return True
+
+    return False
+
+
+def get_retrieved_evidence(task_type: CodeTaskType, request: CodeXRequest):
+    return []
+
+
+def process_codex_request(request: CodeXRequest) -> CodeXResponse:
+    try:
+        task_type = detect_task_type(
+            message=request.message,
+            code=request.code,
+            error_message=request.error_message,
+            mode_hint=request.mode,
+        )
+
+        evidence_list = []
+        if should_use_retrieval(task_type, request):
+            evidence_list = get_retrieved_evidence(task_type, request)
+
+        prompt = build_prompt(
+            task_type=task_type,
+            message=request.message,
+            code=request.code,
+            error_message=request.error_message,
+            language=request.language,
+            framework=request.framework,
+            previous_context=request.previous_context,
+            evidence_list=evidence_list,
+        )
+
+        model_output, model_used, used_fallback = model_client.generate(prompt)
+
+        return build_response(
+            task_type=task_type,
+            model_output=model_output,
+            model_used=model_used,
+            used_fallback=used_fallback,
+        )
+
+    except Exception as e:
+        fallback_task = request.mode if request.mode else CodeTaskType.UNKNOWN
+        return build_error_response(
+            task_type=fallback_task,
+            error_message=str(e),
+        )