"""
Pluggable data layer for Garmin Health Lab.

Supports both SQLite (stdlib, local dev) and MariaDB (PyMySQL, NAS production)
through a single unified API:

    init_db()                 -> create tables if missing
    execute(sql, params)      -> INSERT/UPDATE/DELETE, returns {id, changes}
    query_one(sql, params)    -> one row as dict or None
    query_all(sql, params)    -> list of row dicts

Both backends accept `?` placeholders; the SQL is translated to `%s` for
MariaDB automatically. Upserts must use backend-specific SQL (see services).
"""
import os
import sqlite3
import threading
import queue
import datetime

from config import (
    DB_TYPE,
    SQLITE_PATH,
    MARIADB_SOCKET,
    MARIADB_HOST,
    MARIADB_PORT,
    MARIADB_USER,
    MARIADB_PASSWORD,
    MARIADB_DATABASE,
)

SCHEMA = """
CREATE TABLE IF NOT EXISTS users (
  id VARCHAR(64) PRIMARY KEY,
  email VARCHAR(255) NOT NULL UNIQUE,
  garmin_email VARCHAR(255) NOT NULL,
  garmin_password_hash TEXT NOT NULL,
  jwt_token TEXT,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS health_data (
  id VARCHAR(64) PRIMARY KEY,
  user_id VARCHAR(64) NOT NULL,
  date DATE NOT NULL,
  steps INT,
  heart_rate INT,
  heart_rate_variability DOUBLE,
  blood_pressure_systolic INT,
  blood_pressure_diastolic INT,
  sleep_duration INT,
  sleep_quality DOUBLE,
  stress INT,
  calories_burned DOUBLE,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  UNIQUE(user_id, date),
  FOREIGN KEY (user_id) REFERENCES users(id)
);

CREATE TABLE IF NOT EXISTS activities (
  id VARCHAR(64) PRIMARY KEY,
  user_id VARCHAR(64) NOT NULL,
  activity_type VARCHAR(255) NOT NULL,
  start_time DATETIME NOT NULL,
  end_time DATETIME NOT NULL,
  duration INT,
  distance DOUBLE,
  calories DOUBLE,
  heart_rate_average INT,
  heart_rate_max INT,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (user_id) REFERENCES users(id)
);

CREATE TABLE IF NOT EXISTS sync_status (
  user_id VARCHAR(64) PRIMARY KEY,
  last_sync_time DATETIME,
  status VARCHAR(32) DEFAULT 'idle',
  last_error TEXT,
  records_synced INT DEFAULT 0,
  updated_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (user_id) REFERENCES users(id)
);

-- One cached LLM answer per user. Generating one takes minutes against a
-- large reasoning model, which is far too slow to sit in a page load, so the
-- result is stored and reused until the underlying data changes.
-- `fingerprint` identifies the health data the advice was derived from.
CREATE TABLE IF NOT EXISTS ai_recommendations (
  user_id VARCHAR(64) PRIMARY KEY,
  fingerprint VARCHAR(64) NOT NULL,
  model VARCHAR(64),
  upstream VARCHAR(64),
  days INT,
  payload TEXT NOT NULL,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (user_id) REFERENCES users(id)
);
"""

# --- MariaDB pool (lazy) ----------------------------------------------------
_mariadb_pool = None
_pool_lock = threading.Lock()


def _new_mariadb_conn():
    import pymysql
    from pymysql.cursors import DictCursor

    kwargs = dict(
        user=MARIADB_USER,
        password=MARIADB_PASSWORD,
        database=MARIADB_DATABASE,
        charset="utf8mb4",
        autocommit=True,
        cursorclass=DictCursor,
        connect_timeout=10,
    )
    if MARIADB_SOCKET:
        kwargs["unix_socket"] = MARIADB_SOCKET
    else:
        kwargs["host"] = MARIADB_HOST
        kwargs["port"] = MARIADB_PORT
    return pymysql.connect(**kwargs)


def _mariadb_acquire():
    global _mariadb_pool
    if _mariadb_pool is None:
        with _pool_lock:
            if _mariadb_pool is None:
                _mariadb_pool = queue.Queue(maxsize=10)
                for _ in range(10):
                    _mariadb_pool.put(_new_mariadb_conn())
    try:
        return _mariadb_pool.get(block=False)
    except queue.Empty:
        return _new_mariadb_conn()


def _mariadb_release(conn):
    try:
        conn.ping(reconnect=False)
        _mariadb_pool.put(conn)
    except Exception:
        try:
            conn.close()
        except Exception:
            pass


# --- SQLite connection ------------------------------------------------------
def _sqlite_connect():
    data_dir = os.path.dirname(SQLITE_PATH)
    if data_dir and not os.path.exists(data_dir):
        os.makedirs(data_dir, exist_ok=True)
    conn = sqlite3.connect(SQLITE_PATH, isolation_level=None)
    conn.row_factory = sqlite3.Row
    conn.execute("PRAGMA foreign_keys = ON")
    return conn


def _connect():
    if DB_TYPE == "mariadb":
        return _mariadb_acquire()
    return _sqlite_connect()


def _disconnect(conn):
    if DB_TYPE == "mariadb":
        _mariadb_release(conn)
    else:
        conn.close()


def _adapt_sql(sql):
    # pymysql uses %s placeholders; sqlite3 uses ?. Business code writes ?.
    return sql.replace("?", "%s") if DB_TYPE == "mariadb" else sql


def _serialize(value):
    if value is None:
        return None
    if isinstance(value, (datetime.datetime, datetime.date)):
        return value.isoformat()
    return value


def _row_to_dict(row):
    if row is None:
        return None
    if isinstance(row, dict):
        return {k: _serialize(v) for k, v in row.items()}
    return {k: _serialize(row[k]) for k in row.keys()}


# --- Public API -------------------------------------------------------------
def init_db():
    conn = _connect()
    try:
        cur = conn.cursor()
        for stmt in SCHEMA.split(";"):
            stmt = stmt.strip()
            if not stmt:
                continue
            cur.execute(_adapt_sql(stmt))
    finally:
        _disconnect(conn)


def execute(sql, params=None):
    params = params or []
    conn = _connect()
    try:
        cur = conn.cursor()
        cur.execute(_adapt_sql(sql), params)
        return {"id": cur.lastrowid, "changes": cur.rowcount}
    finally:
        _disconnect(conn)


def query_one(sql, params=None):
    params = params or []
    conn = _connect()
    try:
        cur = conn.cursor()
        cur.execute(_adapt_sql(sql), params)
        return _row_to_dict(cur.fetchone())
    finally:
        _disconnect(conn)


def query_all(sql, params=None):
    params = params or []
    conn = _connect()
    try:
        cur = conn.cursor()
        cur.execute(_adapt_sql(sql), params)
        return [_row_to_dict(r) for r in cur.fetchall()]
    finally:
        _disconnect(conn)