"""URI parsing + dataset fetching for the Harbor Visualiser.

Accepts the same URI shapes as `repo2rlenv pull`:
  owner/name                              → HF Hub (default)
  owner/name@<rev>                        → HF Hub, revision pinned
  hf://owner/name[@rev]                   → HF Hub, explicit prefix
  gh://owner/repo[@ref]                   → GitHub, optional branch/tag/sha
  https://github.com/owner/repo[.git]     → GitHub, full URL

All datasets land in a local cache dir; subsequent loads in the same Space
process are free.
"""

from __future__ import annotations

import logging
import os
import shutil
import subprocess
import tempfile
from dataclasses import dataclass
from pathlib import Path

logger = logging.getLogger(__name__)


# Where downloads are cached during a single Space-process lifetime.
# In Spaces, /tmp survives across requests for the same instance.
CACHE_ROOT = Path(os.environ.get("HARBOR_VIEWER_CACHE", "/tmp/.harbor-viewer-cache"))


@dataclass(slots=True, frozen=True)
class DatasetSource:
    """A parsed dataset URI ready for fetch.

    `kind` is one of "hf" | "gh" | "local". `ident` is the canonical id
    (`owner/name` for HF/GH, absolute path for local). `revision` is the
    optional @-suffix (tag / branch / commit / Hub revision).
    """

    kind: str
    ident: str
    revision: str | None

    @property
    def display(self) -> str:
        rev = f"@{self.revision}" if self.revision else ""
        if self.kind == "hf":
            return f"hf://{self.ident}{rev}"
        if self.kind == "gh":
            return f"gh://{self.ident}{rev}"
        if self.kind == "harbor":
            return f"harbor://{self.ident}{rev}"
        return str(self.ident)

    @property
    def cache_key(self) -> str:
        rev = (self.revision or "head").replace("/", "_")
        return f"{self.kind}__{self.ident.replace('/', '__')}__{rev}"


# ---------------------------------------------------------------------------
# URI parsing
# ---------------------------------------------------------------------------


def _split_revision(s: str) -> tuple[str, str | None]:
    """Split `name@rev` into (name, rev). Returns (name, None) if no `@`."""
    if "@" in s:
        name, _, rev = s.rpartition("@")
        return name, (rev or None)
    return s, None


def parse_dataset_uri(uri: str) -> DatasetSource:
    """Classify a URI string into a DatasetSource. Raises ValueError on malformed input."""
    s = (uri or "").strip()
    if not s:
        raise ValueError("empty dataset URI")

    # Absolute / relative path → local
    if s.startswith("/") or s.startswith("./") or s.startswith("../"):
        path = Path(s).expanduser().resolve()
        if not path.is_dir():
            raise ValueError(f"local dataset directory not found: {path}")
        return DatasetSource(kind="local", ident=str(path), revision=None)

    # GitHub full URL
    for prefix in ("https://github.com/", "http://github.com/", "git@github.com:"):
        if s.startswith(prefix):
            tail = s.removeprefix(prefix).removesuffix(".git")
            base, rev = _split_revision(tail)
            parts = [p for p in base.split("/") if p]
            if len(parts) < 2:
                raise ValueError(f"GitHub URL needs owner/repo, got {uri!r}")
            return DatasetSource(kind="gh", ident=f"{parts[0]}/{parts[1]}", revision=rev)

    if s.startswith("gh://"):
        base, rev = _split_revision(s.removeprefix("gh://"))
        parts = [p for p in base.split("/") if p]
        if len(parts) != 2 or not all(parts):
            raise ValueError(f"gh:// expects owner/repo, got {uri!r}")
        return DatasetSource(kind="gh", ident=f"{parts[0]}/{parts[1]}", revision=rev)

    if s.startswith("harbor://"):
        base, rev = _split_revision(s.removeprefix("harbor://"))
        parts = [p for p in base.split("/") if p]
        # Harbor accepts both bare-name and org/name
        if len(parts) == 2 and base.count("/") == 1:
            return DatasetSource(kind="harbor", ident=f"{parts[0]}/{parts[1]}", revision=rev)
        if len(parts) == 1 and "/" not in base:
            return DatasetSource(kind="harbor", ident=parts[0], revision=rev)
        raise ValueError(
            f"harbor:// expects 'name' or 'org/name' (optionally @tag), got {uri!r}"
        )

    if s.startswith("hf://"):
        s = s.removeprefix("hf://")
        # fall through to HF parsing

    base, rev = _split_revision(s)
    parts = [p for p in base.split("/") if p]
    if len(parts) == 2 and base.count("/") == 1:
        return DatasetSource(kind="hf", ident=f"{parts[0]}/{parts[1]}", revision=rev)
    raise ValueError(
        f"unrecognized dataset URI {uri!r}. "
        f"Accepted: owner/name, hf://owner/name[@rev], gh://owner/repo[@ref], "
        f"https://github.com/owner/repo, or an absolute local path."
    )


# ---------------------------------------------------------------------------
# Fetching
# ---------------------------------------------------------------------------


def _fetch_hf(source: DatasetSource, force: bool) -> Path:
    """Snapshot-download an HF Hub dataset into the cache."""
    from huggingface_hub import snapshot_download

    target = CACHE_ROOT / source.cache_key
    # Pinned revisions (tag/commit) are immutable → caching is always safe.
    # Unpinned ("head") datasets MUST re-sync every load so we never show stale
    # data — snapshot_download is etag-aware, so re-syncing only pulls files
    # that actually changed (cheap). This is the fix for "doesn't show latest".
    pinned = source.revision is not None
    if not force and pinned and target.exists() and any(target.iterdir()):
        logger.info("hf cache hit (pinned %s): %s", source.revision, target)
        return target

    target.mkdir(parents=True, exist_ok=True)
    # Public datasets work without a token; private ones rely on $HF_TOKEN
    # being set in the Space's secrets.
    token = os.environ.get("HF_TOKEN") or None
    logger.info("hf %s: %s@%s", "fetch" if pinned else "re-sync",
                source.ident, source.revision or "head")
    snapshot_download(
        repo_id=source.ident,
        repo_type="dataset",
        revision=source.revision,
        local_dir=str(target),
        token=token,
    )
    return target


def fetch_hf_task(source: DatasetSource, task_id: str, *, force: bool = False) -> Path:
    """Download ONLY one task's files from an HF dataset (not the whole repo).

    Snapshot-downloading a 2k-task dataset just to open one task is the slowness
    the user hit; even `snapshot_download(allow_patterns=...)` still walks the
    entire repo tree first. Instead we list just this task's subtree (one shallow
    API call) and `hf_hub_download` each file. A handful of small files, no
    full-repo walk. Files accumulate under one per-dataset cache dir so
    revisiting is free. Returns a root that `load_task(root, task_id)` resolves
    for either flat or nested layout.
    """
    from huggingface_hub import HfApi, hf_hub_download

    target = CACHE_ROOT / f"{source.cache_key}__bytask"
    target.mkdir(parents=True, exist_ok=True)
    token = os.environ.get("HF_TOKEN") or None
    api = HfApi(token=token)
    logger.info("hf per-task fetch: %s :: %s", source.ident, task_id)

    # Resolve the task's directory in the repo: nested (`tasks/<id>`) first, then flat.
    # `list_repo_tree` is a generator, so the 404 for a non-existent prefix only
    # fires while iterating — force it inside the try (via list()) so we fall
    # through to the other layout instead of bubbling the error up.
    files: list[str] = []
    for prefix in (f"tasks/{task_id}", task_id):
        try:
            entries = list(api.list_repo_tree(
                source.ident, prefix, repo_type="dataset",
                revision=source.revision, recursive=True,
            ))
        except Exception:  # noqa: BLE001 — path doesn't exist in this layout
            continue
        files = [e.path for e in entries if getattr(e, "size", None) is not None]
        if files:
            break
    if not files:
        raise FileNotFoundError(f"task {task_id!r} not found in {source.ident}")

    for f in files:
        hf_hub_download(
            repo_id=source.ident, repo_type="dataset", revision=source.revision,
            filename=f, local_dir=str(target), token=token,
        )
    return target


def _fetch_harbor(source: DatasetSource, force: bool) -> Path:
    """Shell out to `harbor datasets download` to fetch a Harbor-registry dataset.

    Harbor handles its own registry resolution, auth, and tag pinning via
    `<org>/<name>@<tag>`. We just orchestrate + flatten the result into a
    standard dataset layout.
    """
    target = CACHE_ROOT / source.cache_key
    if not force and target.exists() and any(target.iterdir()):
        logger.info("harbor cache hit: %s", target)
        return target

    if not shutil.which("harbor"):
        raise RuntimeError(
            "`harbor` CLI not on PATH. "
            "It's listed in `requirements.txt` — on a Hugging Face Space it "
            "installs automatically. Locally: `pip install harbor`."
        )

    if target.exists():
        shutil.rmtree(target)
    target.mkdir(parents=True, exist_ok=True)

    selector = source.ident + (f"@{source.revision}" if source.revision else "")
    with tempfile.TemporaryDirectory(prefix="harbor-viewer-harbor-") as tmp:
        args = ["harbor", "datasets", "download", selector, "-o", tmp]
        logger.info("running: %s", " ".join(args))
        proc = subprocess.run(args, capture_output=True, text=True, timeout=600, check=False)
        if proc.returncode != 0:
            shutil.rmtree(target, ignore_errors=True)
            raise RuntimeError(
                f"harbor download failed (exit {proc.returncode}): "
                f"{proc.stderr.strip()[:400] or proc.stdout.strip()[:400]}"
            )
        # If the downloaded tree has exactly one subdirectory and no task.toml at the
        # top, recurse one level — that's harbor's typical layout (`<tmp>/<name>/...`).
        downloaded = Path(tmp)
        children = [c for c in downloaded.iterdir() if c.is_dir()]
        if len(children) == 1 and not (downloaded / "task.toml").exists():
            downloaded = children[0]
        # Move everything under the cache target
        for child in downloaded.iterdir():
            shutil.move(str(child), str(target / child.name))

    return target


def _fetch_github(source: DatasetSource, force: bool) -> Path:
    """git clone --depth 1 a GitHub repo into the cache."""
    target = CACHE_ROOT / source.cache_key
    if not force and target.exists() and any(target.iterdir()):
        logger.info("gh cache hit: %s", target)
        return target

    if target.exists():
        shutil.rmtree(target)
    target.parent.mkdir(parents=True, exist_ok=True)

    if not shutil.which("git"):
        raise RuntimeError(
            "`git` not found on PATH. Install git (or rely on the HF Space sandbox which ships it)."
        )

    with tempfile.TemporaryDirectory(prefix="harbor-viewer-clone-") as tmp:
        tmp_clone = Path(tmp) / "clone"
        args = ["git", "clone", "--depth", "1"]
        if source.revision:
            args += ["--branch", source.revision]
        args += [f"https://github.com/{source.ident}.git", str(tmp_clone)]
        logger.info("running: git clone --depth 1 [...] %s", source.ident)
        proc = subprocess.run(args, capture_output=True, text=True, timeout=300, check=False)
        if proc.returncode != 0:
            raise RuntimeError(
                f"git clone failed (exit {proc.returncode}): {proc.stderr.strip()[:400]}"
            )
        shutil.move(str(tmp_clone), str(target))
    return target


def fetch_dataset(source: DatasetSource, *, force: bool = False) -> Path:
    """Materialize a dataset into the local cache. Returns the on-disk root."""
    if source.kind == "hf":
        return _fetch_hf(source, force=force)
    if source.kind == "gh":
        return _fetch_github(source, force=force)
    if source.kind == "harbor":
        return _fetch_harbor(source, force=force)
    if source.kind == "local":
        return Path(source.ident)
    raise ValueError(f"unknown source kind: {source.kind!r}")