from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime
from pathlib import Path
from typing import Optional


@dataclass(frozen=True)
class RecordingItem:
  camera: str
  filename: str
  timestamp: str
  url: str


def _parse_filename(filename: str) -> Optional[datetime]:
  if not filename.endswith(".fmp4"):
    return None
  stem = filename[:-5]
  try:
    return datetime.strptime(stem, "%Y-%m-%d_%H-%M-%S-%f")
  except ValueError:
    return None


def list_recordings(
  recordings_dir: str,
  camera: str,
  date: Optional[str],
  limit: int,
  offset: int,
) -> list[RecordingItem]:
  base = Path(recordings_dir)
  cam_dir = base / camera
  if not cam_dir.exists() or not cam_dir.is_dir():
    return []

  items: list[tuple[datetime, str]] = []
  for p in cam_dir.iterdir():
    if not p.is_file():
      continue
    dt = _parse_filename(p.name)
    if dt is None:
      continue
    if date is not None and dt.strftime("%Y-%m-%d") != date:
      continue
    items.append((dt, p.name))

  items.sort(key=lambda x: x[0], reverse=True)
  sliced = items[offset : offset + limit]

  out: list[RecordingItem] = []
  for dt, name in sliced:
    out.append(
      RecordingItem(
        camera=camera,
        filename=name,
        timestamp=dt.isoformat(),
        url=f"/videos/{camera}/{name}",
      )
    )
  return out