Create Relay Bot MVP

app/memory/context_builder.py

@@ -0,0 +1,30 @@
+import tiktoken
+
+from app.database.models import Message, Summary
+
+
+class ContextBuilder:
+    def __init__(self, token_limit: int):
+        self.token_limit = token_limit
+        try:
+            self.encoder = tiktoken.get_encoding("cl100k_base")
+        except Exception:
+            self.encoder = None
+
+    def count_tokens(self, text: str) -> int:
+        return len(self.encoder.encode(text)) if self.encoder else max(1, len(text) // 4)
+
+    def build(self, summary: Summary | None, messages: list[Message]) -> str:
+        sections = [f"Current memory summary:\n{summary.text}" if summary else ""]
+        recent: list[str] = []
+        budget = self.token_limit - self.count_tokens(sections[0])
+        for item in reversed(messages):
+            line = f"[{item.sent_at.isoformat()}] {item.user_name}: {item.text}"
+            cost = self.count_tokens(line)
+            if cost > budget:
+                break
+            recent.append(line)
+            budget -= cost
+        if recent:
+            sections.append("Recent messages:\n" + "\n".join(reversed(recent)))
+        return "\n\n".join(part for part in sections if part)