"""TensorBoard scalar ingestion with optional dependency isolation."""

from __future__ import annotations

from pathlib import Path

from .storage import TuningStorage


class TensorboardUnavailable(RuntimeError):
    pass


def ingest_scalars(storage: TuningStorage, trial_id: str, log_dir: Path) -> int:
    """Reload all scalar events and idempotently upsert them into SQLite."""
    try:
        from tensorboard.backend.event_processing.event_accumulator import EventAccumulator
    except ImportError as error:
        raise TensorboardUnavailable(
            "缺少 tensorboard，请安装 training_server/requirements.txt"
        ) from error
    if not log_dir.is_dir():
        return 0
    accumulator = EventAccumulator(str(log_dir), size_guidance={"scalars": 0})
    try:
        accumulator.Reload()
    except (OSError, ValueError):
        return 0
    points: list[tuple[str, int, float, float]] = []
    for tag in accumulator.Tags().get("scalars", []):
        for event in accumulator.Scalars(tag):
            points.append((tag, int(event.step), float(event.wall_time), float(event.value)))
    if points:
        storage.insert_metrics(trial_id, points)
    return len(points)