from __future__ import annotations

import json
import uuid
from datetime import datetime, timezone
from pathlib import Path
from typing import Any


def utc_now() -> str:
    return datetime.now(timezone.utc).isoformat()


def new_session_id() -> str:
    return uuid.uuid4().hex[:12]


class SessionStore:
    def __init__(self, root: str | Path):
        self.root = Path(root)
        self.root.mkdir(parents=True, exist_ok=True)

    def _path(self, session_id: str) -> Path:
        safe = "".join(ch for ch in session_id if ch.isalnum() or ch in "-_")
        if not safe:
            raise ValueError("session_id invalide")
        return self.root / f"{safe}.jsonl"

    def append(self, session_id: str, event: dict[str, Any]) -> dict[str, Any]:
        enriched = {"created_at": utc_now(), "session_id": session_id, **event}
        path = self._path(session_id)
        with path.open("a", encoding="utf-8") as handle:
            handle.write(json.dumps(enriched, ensure_ascii=False) + "\n")
        return enriched

    def read(self, session_id: str) -> list[dict[str, Any]]:
        path = self._path(session_id)
        if not path.exists():
            return []
        events: list[dict[str, Any]] = []
        with path.open("r", encoding="utf-8") as handle:
            for line in handle:
                line = line.strip()
                if line:
                    events.append(json.loads(line))
        return events

    def list_sessions(self) -> list[dict[str, Any]]:
        sessions: list[dict[str, Any]] = []
        for path in sorted(self.root.glob("*.jsonl"), key=lambda p: p.stat().st_mtime, reverse=True):
            events = self.read(path.stem)
            sessions.append(
                {
                    "session_id": path.stem,
                    "events": len(events),
                    "updated_at": datetime.fromtimestamp(path.stat().st_mtime, timezone.utc).isoformat(),
                    "preview": next((e.get("content", "") for e in reversed(events) if e.get("content")), ""),
                }
            )
        return sessions