# backend/memory/working_memory.py
# In-memory store for current session only — cleared on session end
import time

class WorkingMemory:
    def __init__(self): 
        self.messages: list[dict] = []
        
    def add(self, role: str, content: str):
        self.messages.append({"role": role, "content": content, "ts": time.time()})
        
    def get_context_window(self, max_tokens=4000) -> list[dict]:
        # trim from oldest until under max_tokens
        # Crude approximation: 1 token ~= 4 chars
        current_tokens = 0
        window = []
        for msg in reversed(self.messages):
            msg_tokens = len(msg["content"]) // 4
            if current_tokens + msg_tokens > max_tokens:
                break
            window.insert(0, msg)
            current_tokens += msg_tokens
        return window
        
    def clear(self): 
        self.messages.clear()