add the code

code_retriever.py

@@ -0,0 +1,70 @@
+from typing import List
+
+from github_search import search_github
+from stack_search import search_stackoverflow
+from schemas import CodeTaskType, CodeXRequest, RetrievedEvidence
+from config import settings
+
+
+def normalize_text(text: str) -> str:
+    return (text or "").strip().lower()
+
+
+def deduplicate_evidence(evidence_list: List[RetrievedEvidence]) -> List[RetrievedEvidence]:
+    seen = set()
+    unique_items: List[RetrievedEvidence] = []
+
+    for item in evidence_list:
+        key = (
+            normalize_text(item.title),
+            normalize_text(item.url or ""),
+            item.source_type.value,
+        )
+
+        if key in seen:
+            continue
+
+        seen.add(key)
+        unique_items.append(item)
+
+    return unique_items
+
+
+def sort_evidence(evidence_list: List[RetrievedEvidence]) -> List[RetrievedEvidence]:
+    return sorted(
+        evidence_list,
+        key=lambda item: (item.score is not None, item.score if item.score is not None else -1),
+        reverse=True,
+    )
+
+
+def retrieve_code_evidence(task_type: CodeTaskType, request: CodeXRequest) -> List[RetrievedEvidence]:
+    if task_type != CodeTaskType.FIX:
+        return []
+
+    collected: List[RetrievedEvidence] = []
+
+    if settings.ENABLE_STACK_SEARCH:
+        stack_results = search_stackoverflow(
+            message=request.message,
+            error_message=request.error_message,
+            language=request.language,
+            framework=request.framework,
+            max_results=settings.MAX_STACK_RESULTS,
+        )
+        collected.extend(stack_results)
+
+    if settings.ENABLE_GITHUB_SEARCH:
+        github_results = search_github(
+            message=request.message,
+            error_message=request.error_message,
+            language=request.language,
+            framework=request.framework,
+            max_results=settings.MAX_GITHUB_RESULTS,
+        )
+        collected.extend(github_results)
+
+    unique_items = deduplicate_evidence(collected)
+    ranked_items = sort_evidence(unique_items)
+
+    return ranked_items[: settings.MAX_RETRIEVED_ITEMS]