"""Download hosted Warbler packs selectively from a Hugging Face dataset repo."""

import fnmatch
import json
import logging
import math
import os
from pathlib import Path
from typing import Dict, List, Optional

from huggingface_hub import HfApi, hf_hub_download, snapshot_download

logger = logging.getLogger(__name__)


class RemotePackLoader:
    """Download only the pack files needed for hosted-safe startup."""

    def __init__(
        self,
        repo_id: str,
        cache_dir: Optional[str] = None,
        include_packs: Optional[List[str]] = None,
        exclude_packs: Optional[List[str]] = None,
        max_documents_per_pack: Optional[int] = None,
        token: Optional[str] = None,
    ):
        self.repo_id = repo_id
        self.cache_dir = cache_dir or os.getenv("HF_PACK_CACHE", ".hf_pack_cache")
        self.include_packs = include_packs or []
        self.exclude_packs = exclude_packs or []
        self.max_documents_per_pack = max_documents_per_pack
        self.local_dir: Optional[Path] = None
        self.api = HfApi(token=token)

    @classmethod
    def from_environment(cls, repo_id: str):
        """Create a remote loader configured with the same hosted-safe defaults as PackLoader."""
        include_packs = cls._split_csv_env("WARBLER_INCLUDE_PACKS")
        exclude_packs = cls._split_csv_env("WARBLER_EXCLUDE_PACKS")
        max_documents_per_pack = cls._parse_int_env("WARBLER_MAX_DOCUMENTS_PER_PACK")

        if cls._is_hosted_environment():
            if not exclude_packs:
                exclude_packs = ["warbler-pack-hf-tinystories"]
            if max_documents_per_pack is None:
                max_documents_per_pack = 5000

        return cls(
            repo_id=repo_id,
            include_packs=include_packs,
            exclude_packs=exclude_packs,
            max_documents_per_pack=max_documents_per_pack,
            token=os.getenv("HF_TOKEN"),
        )

    @staticmethod
    def _is_hosted_environment() -> bool:
        hosted_flag = os.getenv("WARBLER_HOSTED_MODE", "").lower()
        return hosted_flag in {"1", "true", "yes", "on"} or bool(
            os.getenv("SPACE_ID") or os.getenv("HF_SPACE_ID")
        )

    @staticmethod
    def _split_csv_env(name: str) -> List[str]:
        raw_value = os.getenv(name, "")
        return [part.strip() for part in raw_value.split(",") if part.strip()]

    @staticmethod
    def _parse_int_env(name: str) -> Optional[int]:
        raw_value = os.getenv(name)
        if raw_value in (None, ""):
            return None
        try:
            return int(raw_value)
        except ValueError:
            logger.warning("Ignoring invalid integer for %s: %s", name, raw_value)
            return None

    def _should_load_pack(self, pack_name: str) -> bool:
        if self.include_packs:
            included = any(fnmatch.fnmatch(pack_name, pattern) for pattern in self.include_packs)
            if not included:
                return False

        if self.exclude_packs:
            excluded = any(fnmatch.fnmatch(pack_name, pattern) for pattern in self.exclude_packs)
            if excluded:
                return False

        return True

    def _list_repo_files(self) -> List[str]:
        return self.api.list_repo_files(repo_id=self.repo_id, repo_type="dataset")

    def _load_pack_metadata(self, pack_name: str) -> Dict[str, object]:
        metadata_path = f"packs/{pack_name}/package.json"
        try:
            downloaded_path = hf_hub_download(
                repo_id=self.repo_id,
                repo_type="dataset",
                filename=metadata_path,
                cache_dir=self.cache_dir,
                token=os.getenv("HF_TOKEN"),
            )
        except Exception:
            return {}

        try:
            return json.loads(Path(downloaded_path).read_text(encoding="utf-8"))
        except (OSError, json.JSONDecodeError):
            logger.warning("Failed to parse remote metadata for %s", pack_name)
            return {}

    def build_allow_patterns(self) -> List[str]:
        """Build a minimal file set for the selected remote packs."""
        repo_files = self._list_repo_files()
        pack_files: Dict[str, List[str]] = {}

        for repo_file in repo_files:
            parts = Path(repo_file).parts
            if len(parts) < 3 or parts[0] != "packs":
                continue
            pack_name = parts[1]
            if not self._should_load_pack(pack_name):
                continue
            pack_files.setdefault(pack_name, []).append(repo_file)

        allow_patterns: List[str] = []
        for pack_name in sorted(pack_files):
            files = sorted(pack_files[pack_name])
            metadata = self._load_pack_metadata(pack_name)
            package_json = f"packs/{pack_name}/package.json"
            if package_json in files:
                allow_patterns.append(package_json)

            templates_path = f"packs/{pack_name}/pack/templates.json"
            if templates_path in files:
                allow_patterns.append(templates_path)

            jsonl_files = [path for path in files if path.endswith(".jsonl")]
            if metadata.get("chunked"):
                docs_per_chunk = metadata.get("docs_per_chunk")
                chunk_limit = None
                if self.max_documents_per_pack and isinstance(docs_per_chunk, int) and docs_per_chunk > 0:
                    chunk_limit = max(1, math.ceil(self.max_documents_per_pack / docs_per_chunk))
                elif self.max_documents_per_pack:
                    chunk_limit = 1

                selected_jsonl = jsonl_files[:chunk_limit] if chunk_limit is not None else jsonl_files
            else:
                preferred_jsonl = f"packs/{pack_name}/{pack_name}.jsonl"
                selected_jsonl = [preferred_jsonl] if preferred_jsonl in jsonl_files else jsonl_files[:1]

            allow_patterns.extend(selected_jsonl)

        return allow_patterns

    def fetch_packs(self) -> Path:
        """Download only the selected pack files from the remote dataset repo."""
        allow_patterns = self.build_allow_patterns()
        if not allow_patterns:
            raise RuntimeError(f"No remote pack files selected for repo {self.repo_id}")

        self.local_dir = Path(
            snapshot_download(
                repo_id=self.repo_id,
                repo_type="dataset",
                cache_dir=self.cache_dir,
                allow_patterns=allow_patterns,
                local_files_only=False,
                token=os.getenv("HF_TOKEN"),
            )
        )
        return self.local_dir / "packs"

    def get_local_packs_dir(self) -> Path:
        if self.local_dir is None:
            raise RuntimeError("fetch_packs() must be called first")
        return self.local_dir / "packs"