"""
Flask-приложение для доступа к PostgreSQL (managed k8s, internal-only).

Структура соответствует требованиям платформы Nubes:
  repo/
  └── site/
      ├── app.py
      ├── static/
      └── templates/

Подключение к БД — через переменные окружения:
  DB_HOST, DB_PORT, DB_NAME, DB_USER, DB_PASS, DB_SSLMODE
Если БД недоступна — приложение стартует и показывает ошибку на странице,
а не падает (важно для k8s health-проб и диагностики).

Запуск в dev:
  python site/app.py
"""

import os

from flask import Flask, abort, redirect, render_template, request, url_for

import psycopg2
import psycopg2.extras


app = Flask(__name__, template_folder="templates", static_folder="static")


def db_config():
    """Возвращает параметры подключения к PostgreSQL из окружения."""
    return {
        "host": os.getenv("DB_HOST", "postgresqlk8s-master.60bdf3e3-5087-41ff-b760-fe6ea544a80e.svc.cluster.local"),
        "port": int(os.getenv("DB_PORT", "5432")),
        "dbname": os.getenv("DB_NAME", "postgres"),
        "user": os.getenv("DB_USER", "super"),
        "password": os.getenv("DB_PASS", ""),
        "sslmode": os.getenv("DB_SSLMODE", "disable"),
        "connect_timeout": int(os.getenv("DB_CONNECT_TIMEOUT", "5")),
    }


def connect():
    """Открывает соединение с PostgreSQL."""
    try:
        return psycopg2.connect(**db_config())
    except psycopg2.Error as exc:
        raise ConnectionError(f"Нет соединения с PostgreSQL: {exc}") from exc


@app.route("/healthz")
def healthz():
    """Liveness-проба для k8s."""
    try:
        with connect() as conn:
            with conn.cursor() as cur:
                cur.execute("SELECT 1")
                cur.fetchone()
        return {"status": "ok", "db": "connected"}, 200
    except Exception:
        return {"status": "degraded", "db": "unreachable"}, 503


@app.route("/")
def index():
    """Главная: состояние подключения + список таблиц."""
    cfg = db_config()
    show_password = os.getenv("SHOW_DB_PASSWORD", "").lower() in ("1", "true", "yes")

    tables = None
    error = None

    try:
        with connect() as conn:
            with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
                cur.execute(
                    """
                    SELECT schemaname, tablename
                    FROM pg_tables
                    WHERE schemaname NOT IN ('pg_catalog', 'information_schema')
                    ORDER BY schemaname, tablename
                    """
                )
                tables = cur.fetchall()
    except ConnectionError as exc:
        error = str(exc)
    except psycopg2.Error as exc:
        error = f"Ошибка базы данных: {exc}"

    if show_password:
        cfg["password"] = "***"

    return render_template(
        "index.html",
        cfg=cfg,
        tables=tables,
        error=error,
        env=os.getenv("APP_ENV", "production"),
    )


@app.route("/table")
def table():
    """Просмотр содержимого таблицы с пагинацией."""
    schema = request.args.get("schema", "public")
    name = request.args.get("name", "")
    page = max(request.args.get("page", 1, type=int), 1)
    per_page = min(max(request.args.get("per_page", 50, type=int), 1), 500)

    if not name:
        return redirect(url_for("index"))

    full_name = f'"{schema}"."{name}"'
    rows = None
    columns = None
    count = None
    error = None

    try:
        with connect() as conn:
            with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
                # Проверяем, что таблица существует
                cur.execute(
                    """
                    SELECT to_regclass(%s) AS reg
                    """,
                    (full_name,),
                )
                if cur.fetchone()["reg"] is None:
                    abort(404, f"Таблица {full_name} не найдена")

                cur.execute(f'SELECT COUNT(*) AS n FROM {full_name}')
                count = cur.fetchone()["n"]

                offset = (page - 1) * per_page
                cur.execute(
                    f'SELECT * FROM {full_name} ORDER BY 1 LIMIT %s OFFSET %s',
                    (per_page, offset),
                )
                rows = cur.fetchall()
                if rows:
                    columns = list(rows[0].keys())
    except ConnectionError as exc:
        error = str(exc)
    except psycopg2.Error as exc:
        error = f"Ошибка базы данных: {exc}"

    return render_template(
        "table.html",
        schema=schema,
        name=name,
        columns=columns,
        rows=rows,
        count=count,
        page=page,
        per_page=per_page,
        error=error,
    )


@app.route("/query", methods=["GET", "POST"])
def query():
    """Простейшая консоль SQL (read-only SELECT)."""
    sql = request.form.get("sql", "") if request.method == "POST" else request.args.get("sql", "")
    columns = None
    rows = None
    error = None
    elapsed = None

    if sql:
        sql_clean = sql.strip().rstrip(";")
        if not sql_clean.lower().lstrip().startswith("select"):
            error = "Разрешены только SELECT-запросы (read-only режим)"
        else:
            import time
            start = time.time()
            try:
                with connect() as conn:
                    with conn.cursor(cursor_factory=psycopg2.extras.RealDictCursor) as cur:
                        cur.execute(sql_clean)
                        if cur.description:
                            max_rows = int(os.getenv("QUERY_MAX_ROWS", "200"))
                            rows = cur.fetchmany(max_rows)
                            columns = list(rows[0].keys()) if rows else [d.name for d in cur.description]
            except ConnectionError as exc:
                error = str(exc)
            except psycopg2.Error as exc:
                error = f"Ошибка базы данных: {exc}"
            elapsed = round(time.time() - start, 3)

    return render_template(
        "query.html",
        sql=sql,
        columns=columns,
        rows=rows,
        error=error,
        elapsed=elapsed,
        QUERY_MAX_ROWS=int(os.getenv("QUERY_MAX_ROWS", "200")),
    )


@app.errorhandler(404)
def not_found(exc):
    return render_template("error.html", code=404, message=exc.description or "Страница не найдена"), 404


if __name__ == "__main__":
    app.run(debug=os.getenv("FLASK_DEBUG", "true").lower() in ("1", "true", "yes"),
            host="0.0.0.0",
            port=int(os.getenv("PORT", "5000")))