"""System tools — disk usage."""

from __future__ import annotations

from datetime import datetime, timezone

from ..config import validate_host
from ..schemas import DiskResult, FileSystemInfo
from .ssh import run_command, SSHError


def _now() -> str:
    return datetime.now(timezone.utc).isoformat()


def _parse_df(output: str) -> list[FileSystemInfo]:
    """Parse `df -h` output into structured filesystem info."""
    filesystems = []
    for line in output.strip().splitlines()[1:]:  # skip header
        parts = line.split()
        if len(parts) < 6:
            continue
        # df -h columns: Filesystem Size Used Avail Use% Mounted
        mount = parts[-1]
        # Skip pseudo-filesystems
        if mount.startswith(("/dev", "/sys", "/proc", "/run", "/snap")):
            continue
        if parts[0] in ("tmpfs", "devtmpfs", "overlay", "shm", "none"):
            continue

        try:
            used_pct = int(parts[4].rstrip("%"))
        except ValueError:
            continue

        filesystems.append(FileSystemInfo(
            mount=mount,
            total=parts[1],
            used=parts[2],
            avail=parts[3],
            used_pct=used_pct,
        ))
    return filesystems


async def disk_usage(host: str) -> DiskResult:
    """Get disk usage for a host with structured filesystem info."""
    try:
        cfg = validate_host("disk_usage", host)
    except ValueError as e:
        return DiskResult(
            ok=False, checked_at=_now(), host=host,
            error_type="parse_error", error=str(e),
        )

    try:
        stdout, _ = await run_command(cfg, "df -h", use_sudo=cfg.needs_sudo)
    except SSHError as e:
        return DiskResult(
            ok=False, checked_at=_now(), host=host,
            error_type=e.error_type, error=str(e),
        )

    filesystems = _parse_df(stdout)

    warnings = []
    WARN_THRESHOLD = 85
    for fs in filesystems:
        if fs.used_pct >= WARN_THRESHOLD:
            warnings.append(f"{fs.mount} 사용률 {fs.used_pct}% — 임계값 {WARN_THRESHOLD}% 초과")

    return DiskResult(
        ok=True,
        checked_at=_now(),
        host=host,
        filesystems=filesystems,
        warnings=warnings,
        raw=stdout.strip(),
    )