import time
import uuid
from collections import defaultdict


class SessionDB:

    def __init__(self):
        # session_id → full timeline
        self.sessions = {}

        # session_id → event log
        self.events = defaultdict(list)

        # session_id → snapshots (state checkpoints)
        self.snapshots = defaultdict(list)

    # -----------------------------
    # CREATE SESSION
    # -----------------------------
    def create_session(self, project):
        sid = str(uuid.uuid4())

        self.sessions[sid] = {
            "project": project,
            "created_at": time.time(),
            "status": "active"
        }

        return sid

    # -----------------------------
    # EVENT LOGGING (IMMUTABLE)
    # -----------------------------
    def log_event(self, session_id, event_type, payload):

        event = {
            "ts": time.time(),
            "type": event_type,
            "data": payload
        }

        self.events[session_id].append(event)

        return event

    # -----------------------------
    # SNAPSHOT (STATE CHECKPOINT)
    # -----------------------------
    def snapshot(self, session_id, state):

        snap = {
            "ts": time.time(),
            "state": state
        }

        self.snapshots[session_id].append(snap)

        return snap

    # -----------------------------
    # GET FULL TIMELINE
    # -----------------------------
    def get_session(self, session_id):

        return {
            "session": self.sessions.get(session_id),
            "events": self.events.get(session_id, []),
            "snapshots": self.snapshots.get(session_id, [])
        }

    # -----------------------------
    # REPLAY ENGINE INPUT
    # -----------------------------
    def get_replay_stream(self, session_id):

        return sorted(
            self.events[session_id],
            key=lambda e: e["ts"]
        )