"""Lightweight usage event logger for HF Space demos.

Appends JSONL events to a local folder, which huggingface_hub's CommitScheduler
periodically pushes to a private HF Dataset repo. Auto-enables on HF Spaces;
disabled locally unless USAGE_ANALYTICS=1.
"""

from __future__ import annotations

import io
import json
import os
import sys
import uuid
from datetime import datetime, timezone
from pathlib import Path
from typing import TYPE_CHECKING

from log_utils import setup_logger

if TYPE_CHECKING:
    from huggingface_hub import CommitInfo

logger = setup_logger("UsageTracker")


def _make_cleanup_scheduler(active_log_file: Path, **kwargs: object) -> object:
    """Build a CommitScheduler that deletes pushed files (except the active one).

    Prevents stale files from being re-uploaded under a different ``path_in_repo``
    if the demo name changes between process restarts.
    """
    from huggingface_hub import CommitScheduler

    class _Cleanup(CommitScheduler):
        def __init__(self, active_file: Path, **kw: object) -> None:
            self._active_file = active_file.resolve()
            super().__init__(**kw)

        def push_to_hub(self) -> CommitInfo | None:
            result = super().push_to_hub()
            if result is None:
                return None
            with self.lock:
                for path in sorted(self.folder_path.glob("**/*")):
                    if path.is_file() and path.resolve() != self._active_file:
                        path.unlink(missing_ok=True)
                        self.last_uploaded.pop(path, None)
            return result

    return _Cleanup(active_file=active_log_file, **kwargs)


class UsageTracker:
    """Append-only usage event logger backed by a private HF Dataset repo.

    Events are written as JSONL to a local folder. A background thread
    (CommitScheduler) batches and pushes them to the dataset repo every
    ``push_interval_minutes``. Thread-safe, never raises from ``log()``.

    Args:
        repo_id: Target HF dataset repo
            (e.g. ``"LatticeSemi/STAGING-Demo-Analytics-v1.0"``).
        push_interval_minutes: How often CommitScheduler pushes to HF Hub.
        enabled: Explicit on/off. ``None`` = auto-detect (on when ``SPACE_ID``
            env var is set, off otherwise). The ``USAGE_ANALYTICS`` env var
            always takes precedence over both this parameter and ``SPACE_ID``.
    """

    def __init__(
        self,
        repo_id: str,
        push_interval_minutes: int = 10,
        enabled: bool | None = None,
    ) -> None:
        self._enabled = False
        self._log_file: Path | None = None
        self._fh: io.TextIOWrapper | None = None
        self._scheduler: object | None = None

        should_enable = self._resolve_enabled(enabled)
        if not should_enable:
            logger.info("Usage analytics: disabled")
            return

        demo_name = self._resolve_demo_name()

        try:
            log_dir = Path("usage_logs")
            log_dir.mkdir(exist_ok=True)
            self._log_file = log_dir / f"events_{uuid.uuid4().hex[:12]}.jsonl"

            token = (
                os.environ.get("ANALYTICS_TOKEN")
                or os.environ.get("HF_TOKEN")
                or os.environ.get("MODEL_ACCESS_TOKEN")
            )

            self._fh = self._log_file.open("a")
            self._scheduler = _make_cleanup_scheduler(
                active_log_file=self._log_file,
                repo_id=repo_id,
                repo_type="dataset",
                folder_path=log_dir,
                path_in_repo=demo_name,
                every=push_interval_minutes,
                token=token,
            )
            self._enabled = True
            logger.info(
                f"Usage analytics: enabled -> {repo_id}/{demo_name} "
                f"(push every {push_interval_minutes}m)"
            )
        except Exception as exc:
            logger.warning(f"Usage analytics: init failed, continuing without ({exc})")

    @property
    def enabled(self) -> bool:
        return self._enabled

    def log(self, session_hash: str, event: str, **details: str | int | float | bool) -> None:
        """Append a usage event. Thread-safe, never raises.

        Args:
            session_hash: Gradio session hash (truncated to 8 chars for privacy).
            event: Event name (e.g. ``"session_start"``, ``"video_process"``).
            **details: Arbitrary key-value pairs stored alongside the event.
        """
        if not self._enabled or self._fh is None or self._scheduler is None:
            return
        try:
            entry = {
                "ts": datetime.now(timezone.utc).isoformat(),
                "session": session_hash[:8] if session_hash else "unknown",
                "event": event,
                **details,
            }
            with self._scheduler.lock:
                self._fh.write(json.dumps(entry, separators=(",", ":")) + "\n")
                self._fh.flush()
        except Exception:
            pass

    def shutdown(self) -> None:
        """Flush and close the log file handle."""
        if self._fh is not None:
            try:
                self._fh.flush()
                self._fh.close()
            except Exception:
                pass
            self._fh = None

    @staticmethod
    def _resolve_demo_name() -> str:
        """Derive demo name from the HF Space name, or ``"debug-<folder>"`` locally.

        The folder suffix keeps eve_hmi / eve_gmod / future demos from
        sharing the same ``debug/`` path_in_repo when they're run locally.
        """
        space_id = os.environ.get("SPACE_ID", "")
        if "/" in space_id:
            return space_id.split("/", 1)[1]
        if space_id:
            return space_id
        try:
            folder = Path(sys.argv[0]).resolve().parent.name
            if folder:
                return f"debug-{folder}"
        except Exception:
            pass
        return "debug"

    @staticmethod
    def _resolve_enabled(explicit: bool | None) -> bool:
        """Determine whether analytics should be enabled.

        Priority: USAGE_ANALYTICS env var > explicit param > SPACE_ID auto-detect.
        """
        env = os.environ.get("USAGE_ANALYTICS", "").strip().lower()
        if env in ("0", "false", "off"):
            return False
        if env in ("1", "true", "on"):
            return True
        if explicit is not None:
            return explicit
        return bool(os.environ.get("SPACE_ID"))