import os
import sqlite3
import time
from contextlib import closing

SCHEMA = """
CREATE TABLE IF NOT EXISTS samples (
    ts REAL NOT NULL,
    metric TEXT NOT NULL,
    value REAL
);
CREATE INDEX IF NOT EXISTS samples_metric_ts ON samples(metric, ts);
CREATE TABLE IF NOT EXISTS events (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    ts REAL NOT NULL,
    kind TEXT NOT NULL,
    message TEXT NOT NULL
);
CREATE INDEX IF NOT EXISTS events_ts ON events(ts);
CREATE TABLE IF NOT EXISTS kv (
    key TEXT PRIMARY KEY,
    value TEXT
);
"""


def _like_prefix(prefix):
    escaped = prefix.replace("\\", "\\\\").replace("%", "\\%").replace("_", "\\_")
    return escaped + "%"


class Storage:
    def __init__(self, path):
        directory = os.path.dirname(path)
        if directory:
            os.makedirs(directory, exist_ok=True)
        self.path = path
        with closing(self._connect()) as conn:
            conn.executescript(SCHEMA)

    def _connect(self):
        conn = sqlite3.connect(self.path, timeout=10)
        conn.execute("PRAGMA journal_mode=WAL")
        return conn

    def add_samples(self, pairs, ts=None):
        ts = ts or time.time()
        with closing(self._connect()) as conn, conn:
            conn.executemany(
                "INSERT INTO samples (ts, metric, value) VALUES (?, ?, ?)",
                [(ts, metric, value) for metric, value in pairs],
            )

    def add_sample(self, metric, value, ts=None):
        self.add_samples([(metric, value)], ts)

    def add_event(self, kind, message, ts=None):
        with closing(self._connect()) as conn, conn:
            conn.execute(
                "INSERT INTO events (ts, kind, message) VALUES (?, ?, ?)",
                (ts or time.time(), kind, message),
            )

    def events(self, limit=200):
        with closing(self._connect()) as conn:
            rows = conn.execute(
                "SELECT ts, kind, message FROM events ORDER BY ts DESC, id DESC LIMIT ?",
                (limit,),
            ).fetchall()
        return [{"ts": ts, "kind": kind, "message": message} for ts, kind, message in rows]

    def samples_by_prefix(self, prefix, since, bucket):
        bucket = max(1, int(bucket))
        with closing(self._connect()) as conn:
            rows = conn.execute(
                """
                SELECT metric, CAST(ts / ? AS INTEGER) * ? AS bucket, AVG(value)
                FROM samples
                WHERE metric LIKE ? ESCAPE '\\' AND ts >= ?
                GROUP BY metric, bucket
                ORDER BY metric, bucket
                """,
                (bucket, bucket, _like_prefix(prefix), since),
            ).fetchall()
        series = {}
        for metric, ts, value in rows:
            series.setdefault(metric, []).append([ts, value])
        return series

    def get(self, key):
        with closing(self._connect()) as conn:
            row = conn.execute("SELECT value FROM kv WHERE key = ?", (key,)).fetchone()
        return row[0] if row else None

    def set(self, key, value):
        with closing(self._connect()) as conn, conn:
            conn.execute(
                "INSERT INTO kv (key, value) VALUES (?, ?) "
                "ON CONFLICT(key) DO UPDATE SET value = excluded.value",
                (key, value),
            )

    def prune_samples(self, days):
        cutoff = time.time() - days * 86400
        with closing(self._connect()) as conn, conn:
            conn.execute("DELETE FROM samples WHERE ts < ?", (cutoff,))