import sqlite3
import threading
from datetime import datetime, timezone


class SyncState:
    def __init__(self, db_path="./sync.db"):
        self.db_path = db_path
        self._lock = threading.Lock()
        self._conn = sqlite3.connect(db_path, timeout=30)
        self._conn.execute("PRAGMA journal_mode=WAL")
        self._conn.execute("""
            CREATE TABLE IF NOT EXISTS events (
                uid TEXT PRIMARY KEY,
                content_hash TEXT NOT NULL,
                synced_at TIMESTAMP NOT NULL
            )
        """)
        self._conn.execute("""
            CREATE TABLE IF NOT EXISTS ics_cache (
                id INTEGER PRIMARY KEY CHECK(id=1),
                ics_hash TEXT,
                etag TEXT,
                fetched_at TIMESTAMP
            )
        """)
        self._conn.commit()

    def get_event_uids(self) -> set[str]:
        with self._lock:
            cur = self._conn.execute("SELECT uid FROM events")
            return {row[0] for row in cur.fetchall()}

    def get_event_hash(self, uid: str) -> str | None:
        with self._lock:
            cur = self._conn.execute("SELECT content_hash FROM events WHERE uid = ?", (uid,))
            row = cur.fetchone()
            return row[0] if row else None

    def upsert_event(self, uid: str, content_hash: str) -> None:
        with self._lock:
            self._conn.execute("""
                INSERT OR REPLACE INTO events (uid, content_hash, synced_at)
                VALUES (?, ?, ?)
            """, (uid, content_hash, datetime.now(timezone.utc).isoformat()))
            self._conn.commit()

    def delete_event(self, uid: str) -> None:
        with self._lock:
            self._conn.execute("DELETE FROM events WHERE uid = ?", (uid,))
            self._conn.commit()

    def clear_events(self) -> int:
        with self._lock:
            cur = self._conn.execute("SELECT COUNT(*) FROM events")
            count = cur.fetchone()[0]
            self._conn.execute("DELETE FROM events")
            self._conn.commit()
            return count

    def get_ics_cache(self) -> tuple[str | None, str | None, str | None]:
        with self._lock:
            cur = self._conn.execute("SELECT ics_hash, etag, fetched_at FROM ics_cache WHERE id = 1")
            row = cur.fetchone()
            if row:
                return (row[0], row[1], row[2])
            return (None, None, None)

    def set_ics_cache(self, ics_hash: str, etag: str | None) -> None:
        with self._lock:
            self._conn.execute("""
                INSERT INTO ics_cache (id, ics_hash, etag, fetched_at)
                VALUES (1, ?, ?, ?)
                ON CONFLICT(id) DO UPDATE SET ics_hash = ?, etag = ?, fetched_at = ?
            """, (ics_hash, etag, datetime.now(timezone.utc).isoformat(),
                   ics_hash, etag, datetime.now(timezone.utc).isoformat()))
            self._conn.commit()

    def clear_ics_cache(self) -> None:
        with self._lock:
            self._conn.execute("DELETE FROM ics_cache")
            self._conn.commit()

    def snapshot(self) -> dict:
        with self._lock:
            cur = self._conn.execute("SELECT uid, content_hash FROM events")
            rows = cur.fetchall()
            return {
                "uids": [r[0] for r in rows],
                "hashes": {r[0]: r[1] for r in rows}
            }

    def restore_snapshot(self, data: dict) -> None:
        with self._lock:
            self._conn.execute("DELETE FROM events")
            for uid, content_hash in data.get("hashes", {}).items():
                self._conn.execute("""
                    INSERT INTO events (uid, content_hash, synced_at)
                    VALUES (?, ?, ?)
                """, (uid, content_hash, datetime.now(timezone.utc).isoformat()))
            self._conn.commit()

    def close(self) -> None:
        with self._lock:
            self._conn.close()