# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0

"""llama.cpp prebuilt freshness check.

Reads UNSLOTH_PREBUILT_INFO.json (written by install_llama_prebuilt.py)
and compares the installed release tag against the latest on GitHub.
Surfaced via main.py:lifespan() and /api/inference/status. Fails open
on any missing data so we never show a misleading banner.
"""

from __future__ import annotations

import json
import os
import re
import time
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional

import structlog

logger = structlog.get_logger(__name__)

# 3 days matches Unsloth's typical llama.cpp release cadence.
STALENESS_THRESHOLD_DAYS = 3

# 24h TTL keeps the GitHub call off the hot path and within rate limits.
_RELEASE_CACHE_TTL_SECONDS = 24 * 60 * 60

_INSTALL_MARKER_NAME = "UNSLOTH_PREBUILT_INFO.json"

_marker_cache: dict[str, Optional[dict]] = {}
_release_memo: dict[str, tuple[float, Optional[str]]] = {}
# Newest-release asset sizes (name -> bytes), memoized like the tag (24h TTL).
_assets_memo: dict[str, tuple[float, dict[str, int]]] = {}


def _cache_dir() -> Path:
    """Lazy import so tests can stub storage_roots."""
    try:
        from utils.paths.storage_roots import cache_root
        return cache_root() / "llama_cpp_freshness"
    except Exception:
        return Path.home() / ".unsloth" / "studio" / "cache" / "llama_cpp_freshness"


def read_install_marker(binary_path: Optional[str]) -> Optional[dict]:
    """Walk up from binary_path to find UNSLOTH_PREBUILT_INFO.json.
    None = no marker (source build / custom path) or invalid JSON."""
    if not binary_path:
        return None
    cached = _marker_cache.get(binary_path)
    if cached is not None or binary_path in _marker_cache:
        return cached
    p = Path(binary_path)
    marker: Optional[dict] = None
    # Cover all _find_llama_server_binary layouts (binary is 1-4 dirs deep):
    for parent in p.parents[:5]:
        candidate = parent / _INSTALL_MARKER_NAME
        if candidate.is_file():
            try:
                marker = json.loads(candidate.read_text(encoding = "utf-8"))
            except (OSError, json.JSONDecodeError) as exc:
                logger.debug(
                    "failed to parse install marker",
                    path = str(candidate),
                    error = str(exc),
                )
                marker = None
            break
    _marker_cache[binary_path] = marker
    return marker


def _cache_path_for(repo: str) -> Path:
    safe = repo.replace("/", "__")
    return _cache_dir() / f"{safe}.json"


def _load_disk_cache(repo: str) -> Optional[tuple[float, Optional[str]]]:
    path = _cache_path_for(repo)
    try:
        payload = json.loads(path.read_text(encoding = "utf-8"))
    except (OSError, json.JSONDecodeError):
        return None
    ts = payload.get("fetched_at")
    tag = payload.get("latest_tag")
    if not isinstance(ts, (int, float)):
        return None
    return float(ts), tag if isinstance(tag, str) else None


def _save_disk_cache(repo: str, latest_tag: Optional[str]) -> None:
    path = _cache_path_for(repo)
    try:
        path.parent.mkdir(parents = True, exist_ok = True)
        tmp = path.with_suffix(".tmp")
        tmp.write_text(
            json.dumps({"fetched_at": time.time(), "latest_tag": latest_tag}),
            encoding = "utf-8",
        )
        tmp.replace(path)
    except OSError as exc:
        logger.debug("freshness cache write failed", repo = repo, error = str(exc))


def _fetch_latest_release_tag(repo: str, timeout: float = 5.0) -> Optional[str]:
    """Newest published release tag for `repo`, by publish time.

    Resolves "latest" the way install_llama_prebuilt.py does (newest
    non-draft/non-prerelease by ``published_at``), NOT via GitHub's
    ``/releases/latest`` pointer. That pointer sorts by commit date and can lag
    behind the build the installer actually installs, so detection and apply
    disagreed -- the cause of the downgrade/sticky banner. None on any failure
    (offline, rate-limited, etc)."""
    import urllib.error
    import urllib.request

    url = f"https://api.github.com/repos/{repo}/releases?per_page=30"
    headers = {
        "Accept": "application/vnd.github+json",
        "User-Agent": "unsloth-studio-freshness-check",
    }
    token = os.environ.get("GITHUB_TOKEN") or os.environ.get("GH_TOKEN")
    if token:
        headers["Authorization"] = f"Bearer {token}"
    req = urllib.request.Request(url, headers = headers)
    try:
        with urllib.request.urlopen(req, timeout = timeout) as resp:
            data = json.loads(resp.read().decode("utf-8"))
    except (
        urllib.error.URLError,
        urllib.error.HTTPError,
        OSError,
        json.JSONDecodeError,
    ) as exc:
        logger.debug("freshness fetch failed", repo = repo, error = str(exc))
        return None
    if not isinstance(data, list):
        return None
    published = [
        r
        for r in data
        if isinstance(r, dict)
        and not r.get("draft")
        and not r.get("prerelease")
        and isinstance(r.get("tag_name"), str)
        and r.get("tag_name")
    ]
    if not published:
        return None
    newest = max(published, key = lambda r: r.get("published_at") or "")
    return newest["tag_name"]


def latest_published_release(repo: str, *, force_refresh: bool = False) -> Optional[str]:
    """Latest release tag for `repo`. Memo + disk-cached (24h TTL).
    None when offline and never previously cached."""
    if not repo:
        return None
    now = time.time()
    if not force_refresh:
        memo = _release_memo.get(repo)
        if memo and now - memo[0] < _RELEASE_CACHE_TTL_SECONDS:
            return memo[1]
        disk = _load_disk_cache(repo)
        if disk and now - disk[0] < _RELEASE_CACHE_TTL_SECONDS:
            _release_memo[repo] = disk
            return disk[1]
    latest = _fetch_latest_release_tag(repo)
    if latest is None:
        # Keep last-good disk value rather than poisoning with None.
        disk = _load_disk_cache(repo)
        if disk:
            _release_memo[repo] = disk
            return disk[1]
        return None
    _release_memo[repo] = (now, latest)
    _save_disk_cache(repo, latest)
    return latest


def _fetch_latest_release_assets(repo: str, timeout: float = 5.0) -> Optional[dict[str, int]]:
    """Asset name -> size (bytes) for the newest published release of `repo`,
    selected exactly like _fetch_latest_release_tag. None on any failure."""
    import urllib.error
    import urllib.request

    url = f"https://api.github.com/repos/{repo}/releases?per_page=30"
    headers = {
        "Accept": "application/vnd.github+json",
        "User-Agent": "unsloth-studio-freshness-check",
    }
    token = os.environ.get("GITHUB_TOKEN") or os.environ.get("GH_TOKEN")
    if token:
        headers["Authorization"] = f"Bearer {token}"
    req = urllib.request.Request(url, headers = headers)
    try:
        with urllib.request.urlopen(req, timeout = timeout) as resp:
            data = json.loads(resp.read().decode("utf-8"))
    except (
        urllib.error.URLError,
        urllib.error.HTTPError,
        OSError,
        json.JSONDecodeError,
    ) as exc:
        logger.debug("freshness asset fetch failed", repo = repo, error = str(exc))
        return None
    if not isinstance(data, list):
        return None
    published = [
        r
        for r in data
        if isinstance(r, dict)
        and not r.get("draft")
        and not r.get("prerelease")
        and isinstance(r.get("tag_name"), str)
        and r.get("tag_name")
    ]
    if not published:
        return None
    newest = max(published, key = lambda r: r.get("published_at") or "")
    assets: dict[str, int] = {}
    for a in newest.get("assets") or []:
        name, size = a.get("name"), a.get("size")
        if isinstance(name, str) and isinstance(size, int):
            assets[name] = size
    return assets


def latest_release_assets(repo: str, *, force_refresh: bool = False) -> Optional[dict[str, int]]:
    """Newest-release asset sizes for `repo`, memoized (24h TTL). None when
    offline and never fetched. In-memory only -- a restart simply re-fetches."""
    if not repo:
        return None
    now = time.time()
    if not force_refresh:
        memo = _assets_memo.get(repo)
        if memo and now - memo[0] < _RELEASE_CACHE_TTL_SECONDS:
            return memo[1]
    assets = _fetch_latest_release_assets(repo)
    if assets is None:
        memo = _assets_memo.get(repo)
        return memo[1] if memo else None
    _assets_memo[repo] = (now, assets)
    return assets


def update_download_size_bytes(
    marker: Optional[dict],
    latest_tag: Optional[str],
    repo: Optional[str],
    *,
    force_refresh: bool = False,
) -> Optional[int]:
    """Download size of the latest-release asset matching this host's installed
    bundle (same platform/arch/runtime suffix as the installed asset). None when
    there is no marker asset, the latest assets can't be read, or no match."""
    if not marker or not latest_tag or not repo:
        return None
    installed_asset = marker.get("asset")
    if not isinstance(installed_asset, str):
        return None
    # Tag-independent platform suffix: accept the fork's "app-*" bundles and the
    # upstream ggml-org "ubuntu-*"/"win-*" prebuilts ("windows" before "win").
    m = re.search(r"-((?:linux|ubuntu|windows|win|macos|darwin)-.*)$", installed_asset)
    if not m:
        return None
    suffix = m.group(1)
    # Upstream ubuntu/win assets live in the marker's binary_repo, not the fork
    # publish repo; try the publish repo first, then it.
    repos = [repo]
    binary_repo = marker.get("binary_repo")
    if isinstance(binary_repo, str) and binary_repo and binary_repo != repo:
        repos.append(binary_repo)
    want = f"app-{latest_tag}-{suffix}"
    for r in repos:
        assets = latest_release_assets(r, force_refresh = force_refresh)
        if not assets:
            continue
        if want in assets:
            return assets[want]
        # Tag formatting can vary (mix suffixes); fall back to the platform suffix.
        for name, size in assets.items():
            if name.endswith(suffix):
                return size
    return None


def _parse_installed_at(value: object) -> Optional[datetime]:
    if not isinstance(value, str) or not value:
        return None
    s = value.replace("Z", "+00:00") if value.endswith("Z") else value
    try:
        dt = datetime.fromisoformat(s)
    except ValueError:
        return None
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo = timezone.utc)
    return dt


def parse_base_build(tag: object) -> Optional[int]:
    """Numeric base build from a release tag. Handles both a plain ``bNNNN`` and
    a mix-build tag like ``b9596-mix-<sha>`` (anchored at the start, so the mix
    suffix doesn't defeat it). None for anything not starting with ``bNNNN``."""
    if not isinstance(tag, str):
        return None
    m = re.match(r"b(\d+)", tag.strip())
    return int(m.group(1)) if m else None


def is_behind(installed: Optional[str], latest: Optional[str]) -> bool:
    """Whether `installed` is genuinely behind `latest`, comparing the FULL
    release identity (so a mix build can legitimately be the latest) with a
    base-build guard so a lagging GitHub /releases/latest can never read as an
    update or a downgrade.

    - identical tags -> not behind (clears the sticky banner post-update)
    - higher base build on `latest` -> behind; lower -> NOT behind (downgrade guard)
    - same base build: a different/new mix -> behind, but a bare ``bNNNN`` never
      supersedes a mix build (extra PRs) at that base -> not behind
    - non-bNNNN tags -> behind (plain inequality, since they already differ)
    """
    if not installed or not latest:
        return False
    installed, latest = installed.strip(), latest.strip()
    if installed == latest:
        return False
    ib, lb = parse_base_build(installed), parse_base_build(latest)
    if ib is None or lb is None:
        return True
    if lb != ib:
        return lb > ib
    # Same base build, different tags: offer a mix (latest carries a suffix), but
    # never offer a bare base over a mix install at the same base.
    return latest != f"b{lb}"


def check_prebuilt_freshness(
    binary_path: Optional[str],
    *,
    threshold_days: int = STALENESS_THRESHOLD_DAYS,
    now: Optional[datetime] = None,
) -> dict:
    """Returns {has_marker, stale, behind, installed_tag, latest_tag,
    installed_at_utc, age_days, published_repo, threshold_days}.
    behind = installed genuinely older than latest (see is_behind).
    stale = behind AND age >= threshold.
    Fails open on missing data (behind/stale stay False)."""
    out: dict = {
        "has_marker": False,
        "stale": False,
        "behind": False,
        "installed_tag": None,
        "latest_tag": None,
        "installed_at_utc": None,
        "age_days": None,
        "published_repo": None,
        "threshold_days": int(threshold_days),
    }
    marker = read_install_marker(binary_path)
    if not marker:
        return out
    out["has_marker"] = True
    # Display prefers the normalized base ("tag"); comparison below prefers the
    # full "release_tag" -- deliberately opposite fallbacks.
    out["installed_tag"] = marker.get("tag") or marker.get("release_tag")
    out["installed_at_utc"] = marker.get("installed_at_utc")
    out["published_repo"] = marker.get("published_repo")

    # The marker records both a normalized base tag ("tag", e.g. b9596) and the
    # full release tag ("release_tag", e.g. b9596-mix-<sha>). Compare against the
    # FULL identity, since GitHub /releases/latest returns the full tag_name --
    # comparing the normalized base against the full latest is what produced the
    # permanent "downgrade" banner on every mix release.
    installed_full = marker.get("release_tag") or marker.get("tag")
    repo = out["published_repo"]
    if not repo or not installed_full:
        return out
    latest = latest_published_release(repo)
    out["latest_tag"] = latest
    out["behind"] = is_behind(installed_full, latest)
    if not out["behind"]:
        return out

    installed_at = _parse_installed_at(out["installed_at_utc"])
    if installed_at is None:
        return out
    now = now or datetime.now(tz = timezone.utc)
    age_seconds = (now - installed_at).total_seconds()
    out["age_days"] = max(0, int(age_seconds // 86400))
    if age_seconds >= threshold_days * 86400:
        out["stale"] = True
    return out


def format_stale_warning(info: dict) -> str:
    """Human-readable one-liner for stale prebuilt info."""
    age = info.get("age_days")
    installed = info.get("installed_tag") or "unknown"
    latest = info.get("latest_tag") or "unknown"
    age_str = f"{age} day{'s' if age != 1 else ''}" if age is not None else "some time"
    return (
        f"llama.cpp prebuilt is {age_str} behind: installed "
        f"{installed}, latest {latest}. Run `unsloth studio update` "
        f"to refresh."
    )


def reset_caches(*, drop_disk: bool = False) -> None:
    """Drop the in-memory freshness caches. The no-arg form is test-only.

    With ``drop_disk = True`` also delete the on-disk 24h release cache. Used by
    the post-install/update path: in-memory clearing alone leaves the stale
    same-base value on disk, so if the post-install GitHub refresh can't reach
    the network, ``latest_published_release`` would replay that stale disk value
    (see its last-good fallback) and the banner could linger. Dropping the disk
    cache makes latest read as None in that offline case, so the banner fails
    open (off) instead of pointing at the just-replaced build."""
    _marker_cache.clear()
    _release_memo.clear()
    _assets_memo.clear()
    if drop_disk:
        import shutil

        # _cache_dir() is a dedicated freshness-only subdir; it is re-created on
        # the next _save_disk_cache. ignore_errors so a missing/locked dir is a
        # no-op rather than breaking an otherwise successful install.
        shutil.rmtree(_cache_dir(), ignore_errors = True)