"""Scale Flamenco worker containers via the Docker socket.

Uses the Docker Python SDK (docker>=6.1.0) to list, start, and stop containers.
Requires /var/run/docker.sock to be mounted into the backend container.
"""
import os
import logging

log = logging.getLogger(__name__)

COMPOSE_PROJECT = os.getenv("COMPOSE_PROJECT_NAME", "schaefflerautomat")
SERVICE_NAME = "flamenco-worker"


def _get_client():
    import docker
    return docker.from_env()


def get_worker_containers(client=None):
    """Return all flamenco-worker containers (running + stopped) sorted by name."""
    if client is None:
        client = _get_client()
    return sorted(
        client.containers.list(
            all=True,
            filters={
                "label": [
                    f"com.docker.compose.project={COMPOSE_PROJECT}",
                    f"com.docker.compose.service={SERVICE_NAME}",
                ]
            },
        ),
        key=lambda c: c.name,
    )


def get_running_worker_count(client=None) -> int:
    """Return how many flamenco-worker containers are currently running."""
    try:
        if client is None:
            client = _get_client()
        containers = get_worker_containers(client)
        return sum(1 for c in containers if c.status == "running")
    except Exception as exc:
        log.warning("docker_scaler: could not read worker count: %s", exc)
        return -1


def scale_workers(target: int) -> dict:
    """Scale flamenco-worker containers to *target* count.

    Returns a dict with keys:
      previous  – containers running before
      current   – containers running after
      delta     – change (negative = stopped, positive = started)
      message   – human-readable summary
    """
    import docker
    from docker.types import Mount

    client = _get_client()

    all_workers = get_worker_containers(client)
    running = [c for c in all_workers if c.status == "running"]
    previous = len(running)

    if target == previous:
        return {"previous": previous, "current": previous, "delta": 0,
                "message": f"Already at {previous} worker(s) — no change"}

    # ── Scale down ────────────────────────────────────────────────────────────
    if target < previous:
        # Stop highest-numbered containers first to minimise disruption
        to_stop = sorted(running, key=lambda c: c.name, reverse=True)[: previous - target]
        for c in to_stop:
            log.info("docker_scaler: stopping %s", c.name)
            c.stop(timeout=20)
            c.remove()
        return {
            "previous": previous,
            "current": target,
            "delta": target - previous,
            "message": f"Stopped {len(to_stop)} worker(s): {[c.name for c in to_stop]}",
        }

    # ── Scale up ──────────────────────────────────────────────────────────────
    template = running[0] if running else (all_workers[0] if all_workers else None)
    if template is None:
        raise RuntimeError(
            "No existing flamenco-worker container found to clone configuration from. "
            "Ensure at least one worker container exists (even if stopped)."
        )

    attrs = template.attrs
    image = attrs["Config"]["Image"]
    env = attrs["Config"].get("Env") or []

    # Reconstruct mounts from the template container
    mounts = []
    for m in (attrs.get("Mounts") or []):
        mount_type = m.get("Type", "bind")
        source = m.get("Name", "") if mount_type == "volume" else m.get("Source", "")
        mounts.append(
            Mount(
                target=m["Destination"],
                source=source,
                type=mount_type,
                read_only=not m.get("RW", True),
            )
        )

    # Reconstruct GPU device requests (nvidia)
    device_requests = None
    raw_dr = (attrs.get("HostConfig") or {}).get("DeviceRequests") or []
    if raw_dr:
        device_requests = []
        for dr in raw_dr:
            device_requests.append(
                docker.types.DeviceRequest(
                    driver=dr.get("Driver", ""),
                    count=dr.get("Count", -1),
                    device_ids=dr.get("DeviceIDs") or [],
                    capabilities=dr.get("Capabilities") or [],
                    options=dr.get("Options") or {},
                )
            )

    # Network(s) the template is connected to
    network_names = list(
        (attrs.get("NetworkSettings") or {}).get("Networks", {}).keys()
    )

    restart_policy_name = (
        (attrs.get("HostConfig") or {})
        .get("RestartPolicy", {})
        .get("Name", "unless-stopped")
    ) or "unless-stopped"

    started = []
    for i in range(previous + 1, target + 1):
        new_name = f"{COMPOSE_PROJECT}-{SERVICE_NAME}-{i}"
        labels = {
            "com.docker.compose.project": COMPOSE_PROJECT,
            "com.docker.compose.service": SERVICE_NAME,
            "com.docker.compose.container-number": str(i),
        }

        log.info("docker_scaler: creating %s from image %s", new_name, image)
        container = client.containers.create(
            image=image,
            name=new_name,
            environment=env,
            labels=labels,
            mounts=mounts,
            restart_policy={"Name": restart_policy_name},
            device_requests=device_requests,
        )

        for net_name in network_names:
            try:
                net = client.networks.get(net_name)
                net.connect(container)
                log.info("docker_scaler: connected %s to network %s", new_name, net_name)
            except Exception as exc:
                log.warning("docker_scaler: could not connect to network %s: %s", net_name, exc)

        container.start()
        started.append(new_name)
        log.info("docker_scaler: started %s", new_name)

    return {
        "previous": previous,
        "current": target,
        "delta": target - previous,
        "message": f"Started {len(started)} new worker(s): {started}",
    }