"""On-disk presence + deletion for Hugging Face model caches on the Sparks.

The HF cache layout for a repo `org/name` is:

    ~/.cache/huggingface/hub/models--org--name/

We use `du -sb` to measure size (bytes) and `rm -rf` to free it. All operations
are gated by the server endpoints, which refuse to delete a currently-loaded
model or one tied to an in-flight swap/download.
"""
from __future__ import annotations
import asyncio
import re
from dataclasses import dataclass
from typing import Optional

from .config import Settings
from .shellsafe import quote_arg
from .ssh import ssh_run


# HF cache dirnames are `models--<org>--<name>` where <org> and <name> only contain
# Hugging Face's allowed identifier chars: letters, digits, dot, dash, underscore.
# Validate against this whitelist so we can safely embed the dirname into a shell
# command without quoting (we need $HOME outside the quotes to expand).
_SAFE_DIRNAME = re.compile(r"^[A-Za-z0-9._\-]+$")


def repo_to_cache_dirname(repo: str) -> str:
    """Convert 'org/name' to 'models--org--name' (the HF hub cache directory)."""
    if "/" not in repo:
        raise ValueError(f"repo must be in 'org/name' form: {repo!r}")
    dn = "models--" + repo.replace("/", "--")
    if not _SAFE_DIRNAME.fullmatch(dn):
        raise ValueError(f"unsafe cache dirname (rejected by whitelist): {dn!r}")
    return dn


@dataclass
class HostDiskResult:
    host: str
    on_disk: bool
    size_bytes: int = 0
    error: Optional[str] = None


@dataclass
class DiskStatus:
    repo: str
    on_disk: bool                     # True if present on AT LEAST one host
    total_bytes: int                  # sum across hosts
    per_host: list[HostDiskResult]


async def probe_host(host: str, user: str, repo: str, settings: Settings) -> HostDiskResult:
    """Return whether the model's cache dir exists on this host and its size."""
    if not host or not user:
        return HostDiskResult(host=host or "?", on_disk=False, error="host not configured")
    dn = repo_to_cache_dirname(repo)  # whitelisted; safe to embed
    # $HOME must expand server-side, so we build the path with double quotes
    # (which DO allow variable expansion) rather than shlex.quote single quotes.
    cmd = (
        f'P="$HOME/.cache/huggingface/hub/{dn}"; '
        f'if [ -d "$P" ]; then du -sb "$P" 2>/dev/null | cut -f1; '
        f'else echo MISSING; fi'
    )
    rc, out, err = await ssh_run(host, user, cmd, settings, timeout=20.0)
    if rc != 0:
        return HostDiskResult(host=host, on_disk=False, error=(err or out).strip() or f"rc={rc}")
    raw = out.strip()
    if raw == "MISSING" or raw == "":
        return HostDiskResult(host=host, on_disk=False)
    try:
        size = int(raw.splitlines()[-1])
    except ValueError:
        return HostDiskResult(host=host, on_disk=False, error=f"unparsable du output: {raw!r}")
    return HostDiskResult(host=host, on_disk=True, size_bytes=size)


async def probe_local_host(host: str, user: str, path: str, settings: Settings) -> HostDiskResult:
    """Return whether a local model directory exists on this host and its size.

    For locally fine-tuned models (a Spark directory, not an HF cache entry). The
    path is whitelisted at the API boundary (shellsafe.validate_local_path); we
    shlex-quote it here in depth.
    """
    if not host or not user:
        return HostDiskResult(host=host or "?", on_disk=False, error="host not configured")
    qp = quote_arg(path)
    cmd = f"if [ -d {qp} ]; then du -sb {qp} 2>/dev/null | cut -f1; else echo MISSING; fi"
    rc, out, err = await ssh_run(host, user, cmd, settings, timeout=20.0)
    if rc != 0:
        return HostDiskResult(host=host, on_disk=False, error=(err or out).strip() or f"rc={rc}")
    raw = out.strip()
    if raw == "MISSING" or raw == "":
        return HostDiskResult(host=host, on_disk=False)
    try:
        size = int(raw.splitlines()[-1])
    except ValueError:
        return HostDiskResult(host=host, on_disk=False, error=f"unparsable du output: {raw!r}")
    return HostDiskResult(host=host, on_disk=True, size_bytes=size)


async def probe_disk(
    repo: str, mode: str, settings: Settings, *, local_path: str | None = None
) -> DiskStatus:
    """Probe one model across the relevant Sparks based on its mode (solo|cluster).

    A local model (local_path set) is probed by directory; otherwise by HF cache.
    """
    hosts: list[tuple[str, str]] = [(settings.spark1_host, settings.spark1_user)]
    if mode == "cluster" and settings.spark2_host:
        hosts.append((settings.spark2_host, settings.spark2_user))

    if local_path:
        results = await asyncio.gather(
            *(probe_local_host(h, u, local_path, settings) for h, u in hosts)
        )
        key = local_path
    else:
        results = await asyncio.gather(*(probe_host(h, u, repo, settings) for h, u in hosts))
        key = repo
    on_disk = any(r.on_disk for r in results)
    total = sum(r.size_bytes for r in results)
    return DiskStatus(repo=key, on_disk=on_disk, total_bytes=total, per_host=list(results))


async def delete_host(host: str, user: str, repo: str, settings: Settings) -> HostDiskResult:
    """Probe + rm -rf on one host. Returns bytes freed (0 if the dir wasn't there)."""
    if not host or not user:
        return HostDiskResult(host=host or "?", on_disk=False, error="host not configured")
    dn = repo_to_cache_dirname(repo)  # whitelisted; safe to embed
    # Compute size first, then remove. If absent, still return success (idempotent).
    # $HOME is in double-quoted context so it expands; the dirname is whitelisted.
    cmd = (
        f'set -e; '
        f'P="$HOME/.cache/huggingface/hub/{dn}"; '
        f'if [ -d "$P" ]; then '
        f'  SIZE=$(du -sb "$P" 2>/dev/null | cut -f1); '
        f'  rm -rf -- "$P"; '
        f'  echo "FREED $SIZE"; '
        f'else '
        f'  echo "FREED 0"; '
        f'fi'
    )
    rc, out, err = await ssh_run(host, user, cmd, settings, timeout=120.0)
    if rc != 0:
        return HostDiskResult(host=host, on_disk=False, error=(err or out).strip() or f"rc={rc}")
    # Parse the "FREED N" line
    freed = 0
    for line in out.splitlines():
        parts = line.strip().split()
        if len(parts) == 2 and parts[0] == "FREED":
            try:
                freed = int(parts[1])
            except ValueError:
                pass
            break
    return HostDiskResult(host=host, on_disk=False, size_bytes=freed)


async def delete_from_disk(repo: str, mode: str, settings: Settings) -> DiskStatus:
    """rm -rf the model's cache dir on the relevant Sparks. Idempotent."""
    hosts: list[tuple[str, str]] = [(settings.spark1_host, settings.spark1_user)]
    if mode == "cluster" and settings.spark2_host:
        hosts.append((settings.spark2_host, settings.spark2_user))

    results = await asyncio.gather(*(delete_host(h, u, repo, settings) for h, u in hosts))
    total_freed = sum(r.size_bytes for r in results)
    # After deletion, on_disk should be False on all hosts.
    return DiskStatus(repo=repo, on_disk=False, total_bytes=total_freed, per_host=list(results))