from __future__ import annotations

from contextlib import asynccontextmanager
from typing import AsyncGenerator, Optional
import aiosqlite

from backend import config


@asynccontextmanager
async def _get_conn() -> AsyncGenerator[aiosqlite.Connection, None]:
    conn = await aiosqlite.connect(config.DB_PATH)
    await conn.execute("PRAGMA journal_mode=WAL")
    await conn.execute("PRAGMA busy_timeout=5000")
    await conn.execute("PRAGMA synchronous=NORMAL")
    conn.row_factory = aiosqlite.Row
    try:
        yield conn
    finally:
        await conn.close()


async def init_db() -> None:
    async with _get_conn() as conn:
        await conn.executescript("""
            CREATE TABLE IF NOT EXISTS users (
                id            INTEGER PRIMARY KEY AUTOINCREMENT,
                uuid          TEXT UNIQUE NOT NULL,
                name          TEXT NOT NULL,
                is_blocked    INTEGER NOT NULL DEFAULT 0,
                password_hash TEXT DEFAULT NULL,
                api_key_hash  TEXT DEFAULT NULL,
                created_at    TEXT DEFAULT (datetime('now'))
            );

            CREATE TABLE IF NOT EXISTS signals (
                id                INTEGER PRIMARY KEY AUTOINCREMENT,
                user_uuid         TEXT NOT NULL REFERENCES users(uuid),
                timestamp         INTEGER NOT NULL,
                lat               REAL DEFAULT NULL,
                lon               REAL DEFAULT NULL,
                accuracy          REAL DEFAULT NULL,
                created_at        TEXT DEFAULT (datetime('now')),
                telegram_batch_id INTEGER DEFAULT NULL
            );

            CREATE TABLE IF NOT EXISTS telegram_batches (
                id            INTEGER PRIMARY KEY AUTOINCREMENT,
                message_text  TEXT DEFAULT NULL,
                sent_at       TEXT DEFAULT NULL,
                signals_count INTEGER DEFAULT 0,
                status        TEXT DEFAULT 'pending'
            );

            CREATE UNIQUE INDEX IF NOT EXISTS idx_users_uuid
                ON users(uuid);
            CREATE INDEX IF NOT EXISTS idx_signals_user_uuid
                ON signals(user_uuid);
            CREATE INDEX IF NOT EXISTS idx_signals_created_at
                ON signals(created_at);
            CREATE INDEX IF NOT EXISTS idx_batches_status
                ON telegram_batches(status);
        """)
        # Migrations for existing databases (silently ignore if columns already exist)
        for stmt in [
            "ALTER TABLE users ADD COLUMN is_blocked INTEGER NOT NULL DEFAULT 0",
            "ALTER TABLE users ADD COLUMN password_hash TEXT DEFAULT NULL",
            "ALTER TABLE users ADD COLUMN api_key_hash TEXT DEFAULT NULL",
        ]:
            try:
                await conn.execute(stmt)
                await conn.commit()
            except Exception:
                pass  # Column already exists
        await conn.commit()


async def register_user(uuid: str, name: str, api_key_hash: Optional[str] = None) -> dict:
    async with _get_conn() as conn:
        if api_key_hash is not None:
            await conn.execute(
                """
                INSERT INTO users (uuid, name, api_key_hash) VALUES (?, ?, ?)
                ON CONFLICT(uuid) DO UPDATE SET api_key_hash = excluded.api_key_hash
                """,
                (uuid, name, api_key_hash),
            )
        else:
            await conn.execute(
                "INSERT OR IGNORE INTO users (uuid, name) VALUES (?, ?)",
                (uuid, name),
            )
        await conn.commit()
        async with conn.execute(
            "SELECT id, uuid FROM users WHERE uuid = ?", (uuid,)
        ) as cur:
            row = await cur.fetchone()
    return {"user_id": row["id"], "uuid": row["uuid"]}


async def get_api_key_hash_by_uuid(uuid: str) -> Optional[str]:
    async with _get_conn() as conn:
        async with conn.execute(
            "SELECT api_key_hash FROM users WHERE uuid = ?", (uuid,)
        ) as cur:
            row = await cur.fetchone()
    return row["api_key_hash"] if row else None


async def save_signal(
    user_uuid: str,
    timestamp: int,
    lat: Optional[float],
    lon: Optional[float],
    accuracy: Optional[float],
) -> int:
    async with _get_conn() as conn:
        async with conn.execute(
            """
            INSERT INTO signals (user_uuid, timestamp, lat, lon, accuracy)
            VALUES (?, ?, ?, ?, ?)
            """,
            (user_uuid, timestamp, lat, lon, accuracy),
        ) as cur:
            signal_id = cur.lastrowid
        await conn.commit()
    return signal_id


async def get_user_name(uuid: str) -> Optional[str]:
    async with _get_conn() as conn:
        async with conn.execute(
            "SELECT name FROM users WHERE uuid = ?", (uuid,)
        ) as cur:
            row = await cur.fetchone()
    return row["name"] if row else None


async def is_user_blocked(uuid: str) -> bool:
    async with _get_conn() as conn:
        async with conn.execute(
            "SELECT is_blocked FROM users WHERE uuid = ?", (uuid,)
        ) as cur:
            row = await cur.fetchone()
    return bool(row["is_blocked"]) if row else False


async def admin_list_users() -> list[dict]:
    async with _get_conn() as conn:
        async with conn.execute(
            "SELECT id, uuid, name, is_blocked, created_at FROM users ORDER BY id"
        ) as cur:
            rows = await cur.fetchall()
    return [
        {
            "id": row["id"],
            "uuid": row["uuid"],
            "name": row["name"],
            "is_blocked": bool(row["is_blocked"]),
            "created_at": row["created_at"],
        }
        for row in rows
    ]


async def admin_get_user_by_id(user_id: int) -> Optional[dict]:
    async with _get_conn() as conn:
        async with conn.execute(
            "SELECT id, uuid, name, is_blocked, created_at FROM users WHERE id = ?",
            (user_id,),
        ) as cur:
            row = await cur.fetchone()
    if row is None:
        return None
    return {
        "id": row["id"],
        "uuid": row["uuid"],
        "name": row["name"],
        "is_blocked": bool(row["is_blocked"]),
        "created_at": row["created_at"],
    }


async def admin_create_user(
    uuid: str, name: str, password_hash: Optional[str] = None
) -> Optional[dict]:
    """Returns None if UUID already exists."""
    async with _get_conn() as conn:
        try:
            async with conn.execute(
                "INSERT INTO users (uuid, name, password_hash) VALUES (?, ?, ?)",
                (uuid, name, password_hash),
            ) as cur:
                new_id = cur.lastrowid
        except Exception:
            return None  # UNIQUE constraint violation — UUID already exists
        await conn.commit()
        async with conn.execute(
            "SELECT id, uuid, name, is_blocked, created_at FROM users WHERE id = ?",
            (new_id,),
        ) as cur:
            row = await cur.fetchone()
    return {
        "id": row["id"],
        "uuid": row["uuid"],
        "name": row["name"],
        "is_blocked": bool(row["is_blocked"]),
        "created_at": row["created_at"],
    }


async def admin_set_password(user_id: int, password_hash: str) -> bool:
    async with _get_conn() as conn:
        async with conn.execute(
            "UPDATE users SET password_hash = ? WHERE id = ?",
            (password_hash, user_id),
        ) as cur:
            changed = cur.rowcount > 0
        await conn.commit()
    return changed


async def admin_set_blocked(user_id: int, is_blocked: bool) -> bool:
    async with _get_conn() as conn:
        async with conn.execute(
            "UPDATE users SET is_blocked = ? WHERE id = ?",
            (1 if is_blocked else 0, user_id),
        ) as cur:
            changed = cur.rowcount > 0
        await conn.commit()
    return changed


async def admin_delete_user(user_id: int) -> bool:
    async with _get_conn() as conn:
        # Delete signals first (no FK cascade in SQLite by default)
        async with conn.execute(
            "DELETE FROM signals WHERE user_uuid = (SELECT uuid FROM users WHERE id = ?)",
            (user_id,),
        ):
            pass
        async with conn.execute(
            "DELETE FROM users WHERE id = ?",
            (user_id,),
        ) as cur:
            changed = cur.rowcount > 0
        await conn.commit()
    return changed


async def save_telegram_batch(
    message_text: str,
    signals_count: int,
    signal_ids: list[int],
) -> int:
    async with _get_conn() as conn:
        async with conn.execute(
            """
            INSERT INTO telegram_batches (message_text, sent_at, signals_count, status)
            VALUES (?, datetime('now'), ?, 'sent')
            """,
            (message_text, signals_count),
        ) as cur:
            batch_id = cur.lastrowid
        if signal_ids:
            placeholders = ",".join("?" * len(signal_ids))
            await conn.execute(
                f"UPDATE signals SET telegram_batch_id = ? WHERE id IN ({placeholders})",
                [batch_id, *signal_ids],
            )
        await conn.commit()
    return batch_id