"""Thread-safe expense ledger with HuggingFace Hub CSV persistence."""

import os
import logging
import threading
import pandas as pd
from pathlib import Path

logger = logging.getLogger(__name__)

COLUMNS = ["Date", "Description", "Category", "Amount"]
CSV_NAME = "ledger.csv"
CACHE_PATH = Path("/tmp/finance_ledger.csv")


class Ledger:
    def __init__(self):
        self._lock = threading.RLock()
        self.token = os.getenv("HF_TOKEN")
        self.repo = os.getenv("HF_LEDGER_REPO")
        self.enabled = bool(self.token and self.repo)
        self.df = self._load()

    # ── persistence ──────────────────────────────────────────────────────────

    def _load(self) -> pd.DataFrame:
        if self.enabled:
            try:
                self._ensure_repo()
                from huggingface_hub import hf_hub_download
                path = hf_hub_download(
                    self.repo, CSV_NAME, repo_type="dataset",
                    token=self.token, local_dir="/tmp",
                )
                return self._read_csv(path)
            except Exception as e:
                logger.warning(f"HF load failed ({e}), falling back to local cache")

        if CACHE_PATH.exists():
            try:
                return self._read_csv(CACHE_PATH)
            except Exception as e:
                logger.warning(f"Local cache load failed: {e}")

        return pd.DataFrame(columns=COLUMNS)

    def _read_csv(self, path) -> pd.DataFrame:
        df = pd.read_csv(path)
        df["Date"] = pd.to_datetime(df["Date"])
        df["Amount"] = pd.to_numeric(df["Amount"])
        return df.sort_values("Date", ascending=False).reset_index(drop=True)

    def _ensure_repo(self):
        from huggingface_hub import repo_exists, create_repo
        if not repo_exists(self.repo, repo_type="dataset", token=self.token):
            create_repo(self.repo, repo_type="dataset", private=True,
                        token=self.token, exist_ok=True)

    def _persist(self):
        df_copy = self.df.copy()
        if not df_copy.empty:
            df_copy["Date"] = df_copy["Date"].dt.strftime("%Y-%m-%d")
        df_copy.to_csv(CACHE_PATH, index=False)

        if not self.enabled:
            return
        try:
            from huggingface_hub import upload_file
            upload_file(
                path_or_fileobj=str(CACHE_PATH),
                path_in_repo=CSV_NAME,
                repo_id=self.repo,
                repo_type="dataset",
                token=self.token,
                commit_message="ledger update",
            )
        except Exception as e:
            logger.error(f"HF upload failed: {e}")

    # ── mutations ─────────────────────────────────────────────────────────────

    def add(self, date: str, description: str, category: str, amount: float) -> bool:
        with self._lock:
            try:
                row = pd.DataFrame({
                    "Date": [pd.to_datetime(date)],
                    "Description": [description],
                    "Category": [category],
                    "Amount": [float(amount)],
                })
                self.df = pd.concat([self.df, row], ignore_index=True)
                self.df = self.df.sort_values("Date", ascending=False).reset_index(drop=True)
                self._persist()
                return True
            except Exception as e:
                logger.error(f"add failed: {e}")
                return False

    def delete_last(self) -> bool:
        with self._lock:
            if self.df.empty:
                return False
            self.df = self.df.iloc[1:].reset_index(drop=True)
            self._persist()
            return True

    # ── queries ───────────────────────────────────────────────────────────────

    def total(self) -> float:
        return float(self.df["Amount"].sum()) if not self.df.empty else 0.0

    def by_category(self) -> dict[str, float]:
        if self.df.empty:
            return {}
        return self.df.groupby("Category")["Amount"].sum().to_dict()

    def recent(self, n: int = 50) -> pd.DataFrame:
        df = self.df.head(n).copy()
        if not df.empty:
            df["Date"] = df["Date"].dt.strftime("%Y-%m-%d")
        return df

    @property
    def status(self) -> str:
        return f"✅ HF Hub: `{self.repo}`" if self.enabled else "⚠️ Local cache only"


# ── singleton ─────────────────────────────────────────────────────────────────

_instance: Ledger | None = None


def get_ledger() -> Ledger:
    global _instance
    if _instance is None:
        _instance = Ledger()
    return _instance