"""
Storage router — unified entry point for workspace preparation,
btrfs CAS, tmpfs acceleration, and qcow2 freeze.

Used by:
    - BuildRunner (to prepare per-build workspace)
    - /api/storage/* endpoints (status, config, freeze)
"""

import time
from pathlib import Path
from typing import Any, Dict, Optional

from backend.storage.config import load_storage_config, save_storage_config
from backend.storage.tmpfs import get_tmpfs_workspace
from backend.storage.btrfs_cas import (
    cas_path, cas_store, cas_exists, cas_retrieve, is_btrfs, reflink_snapshot,
)
from backend.storage.qcow2_freeze import (
    freeze_to_qcow2, qcow2_info, list_snapshots,
)


def prepare_workspace(project_name: str) -> Dict[str, Any]:
    """Prepare a workspace for a build. Always returns a tmpfs path,
    optionally also a btrfs CAS path."""
    cfg = load_storage_config()

    workspace = {
        "tmpfs": None,
        "cas": None,
        "freeze": None,
        "config": cfg,
    }

    # Always: tmpfs workspace
    try:
        workspace["tmpfs"] = get_tmpfs_workspace(cfg, project_name)
    except Exception:
        workspace["tmpfs"] = None

    # Optional: btrfs CAS path
    if cfg.get("btrfs"):
        try:
            workspace["cas"] = cas_path(cfg, project_name)
        except Exception:
            workspace["cas"] = None

    return workspace


def maybe_freeze_workspace(workdir, project_name) -> Optional[str]:
    """If qcow2_freeze is enabled, snapshot the workdir into a qcow2 image.
    Returns the path to the .qcow2 file, or None if freezing is disabled
    or failed."""
    cfg = load_storage_config()

    if not cfg.get("qcow2_freeze"):
        return None

    output_dir = Path(cfg.get("qcow2_path", "/var/lib/fester/snapshots"))
    output = output_dir / f"{project_name}-{int(time.time())}.qcow2"

    return freeze_to_qcow2(workdir, str(output))


def storage_status() -> Dict[str, Any]:
    """Return a snapshot of the current storage configuration + capabilities."""
    cfg = load_storage_config()

    # Check which capabilities are actually available
    import shutil as _sh
    have_qemu_img = _sh.which("qemu-img") is not None
    have_qemu_nbd = _sh.which("qemu-nbd") is not None
    have_rsync = _sh.which("rsync") is not None

    # Check if tmpfs path is on tmpfs
    tmpfs_path = Path(cfg.get("tmpfs_path", "/dev/shm/fester-build"))
    on_tmpfs = False
    if tmpfs_path.exists():
        try:
            import subprocess
            out = subprocess.check_output(
                ["stat", "-f", "-c", "%T", str(tmpfs_path)],
                stderr=subprocess.DEVNULL,
            ).decode().strip()
            on_tmpfs = out == "tmpfs"
        except Exception:
            pass

    # Check if btrfs path is on btrfs
    btrfs_path = Path(cfg.get("btrfs_path", "/var/lib/fester/cas"))
    on_btrfs = is_btrfs(btrfs_path) if btrfs_path.exists() else False

    return {
        "config": cfg,
        "capabilities": {
            "tmpfs": {
                "enabled": cfg.get("tmpfs", False),
                "path": str(tmpfs_path),
                "on_tmpfs": on_tmpfs,
            },
            "btrfs_cas": {
                "enabled": cfg.get("btrfs", False),
                "path": str(btrfs_path),
                "on_btrfs": on_btrfs,
            },
            "qcow2_freeze": {
                "enabled": cfg.get("qcow2_freeze", False),
                "path": cfg.get("qcow2_path", "/var/lib/fester/snapshots"),
                "qemu_img_available": have_qemu_img,
                "qemu_nbd_available": have_qemu_nbd,
                "rsync_available": have_rsync,
            },
        },
    }


def update_storage_config(updates: Dict[str, Any]) -> Dict[str, Any]:
    """Merge updates into the storage config and persist."""
    cfg = load_storage_config()
    cfg.update(updates)
    saved = save_storage_config(cfg)
    return {"saved": saved, "config": cfg}