"""Session persistence — SQLite + FTS5 for conversation history."""

import sqlite3
import threading
import time


def log(msg):
    print(f"[sessions] {msg}", flush=True)


def set_logger(fn):
    global log
    log = fn


_write_lock = threading.Lock()


def init_db(db_path):
    """Create/open the session database. Returns a connection."""
    conn = sqlite3.connect(db_path, check_same_thread=False)
    conn.execute("PRAGMA journal_mode=WAL")
    conn.execute("""
        CREATE TABLE IF NOT EXISTS messages (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            ts REAL NOT NULL,
            nick TEXT NOT NULL,
            channel TEXT NOT NULL,
            text TEXT NOT NULL,
            full_text TEXT
        )
    """)
    conn.execute("""
        CREATE INDEX IF NOT EXISTS idx_messages_channel_ts
        ON messages(channel, ts)
    """)
    # FTS5 virtual table for full-text search
    conn.execute("""
        CREATE VIRTUAL TABLE IF NOT EXISTS messages_fts
        USING fts5(text, content=messages, content_rowid=id)
    """)
    conn.commit()
    _prune(conn)
    log(f"Session DB ready: {db_path}")
    return conn


def save_message(conn, nick, channel, text, full_text=None):
    """Persist a message to the session database."""
    with _write_lock:
        cur = conn.execute(
            "INSERT INTO messages (ts, nick, channel, text, full_text) VALUES (?, ?, ?, ?, ?)",
            (time.time(), nick, channel, text, full_text),
        )
        conn.execute(
            "INSERT INTO messages_fts(rowid, text) VALUES (?, ?)",
            (cur.lastrowid, text),
        )
        conn.commit()


def load_recent(conn, limit=20):
    """Load the last N messages for boot recovery.
    Returns list of {"nick", "text", "channel"} dicts in chronological order."""
    rows = conn.execute(
        "SELECT nick, text, channel FROM messages ORDER BY id DESC LIMIT ?",
        (limit,),
    ).fetchall()
    return [{"nick": r[0], "text": r[1], "channel": r[2]} for r in reversed(rows)]


def _prune(conn, keep=1000):
    """Delete old messages beyond the last `keep`. Runs once at init."""
    count = conn.execute("SELECT COUNT(*) FROM messages").fetchone()[0]
    if count <= keep:
        return
    deleted = count - keep
    conn.execute("""
        DELETE FROM messages WHERE id NOT IN (
            SELECT id FROM messages ORDER BY id DESC LIMIT ?
        )
    """, (keep,))
    # Rebuild FTS index after bulk delete
    conn.execute("INSERT INTO messages_fts(messages_fts) VALUES('rebuild')")
    conn.commit()
    log(f"Pruned {deleted} old messages (kept {keep})")