from __future__ import annotations

from pathlib import Path

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.config import settings
from app.models import Protocol, VpnClient, VpnServer
from app.services.crypto import (
    generate_keypair,
    generate_preshared_key,
    next_client_ip,
    render_client_config,
    render_server_config,
    server_address,
)


async def ensure_default_servers(session: AsyncSession) -> None:
    existing = (await session.execute(select(VpnServer))).scalars().all()
    by_protocol = {s.protocol: s for s in existing}

    if Protocol.WIREGUARD.value not in by_protocol:
        keys = generate_keypair()
        private = settings.server_private_key or keys.private_key
        public = settings.server_public_key or keys.public_key
        if settings.server_private_key and settings.server_public_key:
            private, public = settings.server_private_key, settings.server_public_key
        elif settings.server_private_key:
            private = settings.server_private_key
            # derive not available without raw parse; keep generated public if only private set
        session.add(
            VpnServer(
                name="WireGuard",
                protocol=Protocol.WIREGUARD.value,
                public_host=settings.public_host,
                public_port=settings.public_port,
                interface_name=settings.wg_interface,
                subnet=settings.wg_subnet,
                dns=settings.wg_dns,
                server_private_key=private,
                server_public_key=public,
            )
        )

    if Protocol.AWG2.value not in by_protocol:
        keys = generate_keypair()
        private = settings.awg_server_private_key or keys.private_key
        public = settings.awg_server_public_key or keys.public_key
        session.add(
            VpnServer(
                name="AmneziaWG 2.0",
                protocol=Protocol.AWG2.value,
                public_host=settings.public_host,
                public_port=settings.awg_public_port,
                interface_name=settings.awg_interface,
                subnet=settings.awg_subnet,
                dns=settings.wg_dns,
                server_private_key=private,
                server_public_key=public,
                jc=4,
                jmin=40,
                jmax=70,
                s1=0,
                s2=0,
                h1=1,
                h2=2,
                h3=3,
                h4=4,
            )
        )

    await session.commit()


async def create_client(
    session: AsyncSession,
    *,
    server_id: int,
    name: str,
    notes: str | None = None,
    allowed_ips: str = "0.0.0.0/0, ::/0",
) -> VpnClient:
    server = await session.get(VpnServer, server_id)
    if not server:
        raise ValueError("Server not found")

    used = (
        await session.execute(select(VpnClient.address).where(VpnClient.server_id == server_id))
    ).scalars().all()
    address = next_client_ip(server.subnet, list(used))
    keys = generate_keypair()
    client = VpnClient(
        server_id=server_id,
        name=name.strip(),
        private_key=keys.private_key,
        public_key=keys.public_key,
        preshared_key=generate_preshared_key(),
        address=address,
        allowed_ips=allowed_ips,
        notes=notes,
        is_enabled=True,
    )
    session.add(client)
    await session.commit()
    await session.refresh(client)
    await sync_server_config(session, server_id)
    return client


async def set_client_enabled(session: AsyncSession, client_id: int, enabled: bool) -> VpnClient:
    client = await session.get(VpnClient, client_id)
    if not client:
        raise ValueError("Client not found")
    client.is_enabled = enabled
    await session.commit()
    await session.refresh(client)
    await sync_server_config(session, client.server_id)
    return client


async def delete_client(session: AsyncSession, client_id: int) -> None:
    client = await session.get(VpnClient, client_id)
    if not client:
        raise ValueError("Client not found")
    server_id = client.server_id
    await session.delete(client)
    await session.commit()
    await sync_server_config(session, server_id)


async def get_client_config(session: AsyncSession, client_id: int) -> str:
    result = await session.execute(
        select(VpnClient).options(selectinload(VpnClient.server)).where(VpnClient.id == client_id)
    )
    client = result.scalar_one_or_none()
    if not client:
        raise ValueError("Client not found")
    server = client.server
    return render_client_config(
        protocol=server.protocol,
        client_private_key=client.private_key,
        client_address=client.address,
        dns=server.dns,
        server_public_key=server.server_public_key,
        preshared_key=client.preshared_key,
        endpoint_host=server.public_host,
        endpoint_port=server.public_port,
        allowed_ips=client.allowed_ips,
        jc=server.jc,
        jmin=server.jmin,
        jmax=server.jmax,
        s1=server.s1,
        s2=server.s2,
        h1=server.h1,
        h2=server.h2,
        h3=server.h3,
        h4=server.h4,
    )


async def sync_server_config(session: AsyncSession, server_id: int) -> Path:
    result = await session.execute(
        select(VpnServer).options(selectinload(VpnServer.clients)).where(VpnServer.id == server_id)
    )
    server = result.scalar_one()
    peers = [
        {
            "name": c.name,
            "public_key": c.public_key,
            "preshared_key": c.preshared_key,
            "address": c.address if c.address.endswith("/32") else f"{c.address.split('/')[0]}/32",
        }
        for c in server.clients
        if c.is_enabled
    ]
    content = render_server_config(
        protocol=server.protocol,
        interface_name=server.interface_name,
        private_key=server.server_private_key,
        address=server_address(server.subnet),
        listen_port=server.public_port,
        peers=peers,
        jc=server.jc,
        jmin=server.jmin,
        jmax=server.jmax,
        s1=server.s1,
        s2=server.s2,
        h1=server.h1,
        h2=server.h2,
        h3=server.h3,
        h4=server.h4,
    )

    base = Path(settings.wg_config_dir if server.protocol == Protocol.WIREGUARD.value else settings.awg_config_dir)
    base.mkdir(parents=True, exist_ok=True)
    path = base / f"{server.interface_name}.conf"
    path.write_text(content, encoding="utf-8")
    return path