"""Session data loading — reads frame/transcript indexes, returns plain data."""

import json
import logging
from pathlib import Path

log = logging.getLogger(__name__)


def load_frame_index(frames_dir: Path) -> list[dict]:
    """Read frames/index.json and return list of {id, path, timestamp}.

    Returns only entries where the image file exists on disk.
    Paths are resolved relative to *frames_dir* if needed.
    """
    index_path = frames_dir / "index.json"
    if not index_path.exists():
        return []
    try:
        index = json.loads(index_path.read_text())
    except (json.JSONDecodeError, IOError):
        return []
    result = []
    for entry in index:
        fpath = Path(entry["path"])
        if not fpath.exists():
            fpath = frames_dir / fpath.name
        if not fpath.exists():
            continue
        result.append({
            "id": entry["id"],
            "path": fpath,
            "timestamp": entry.get("timestamp", 0),
        })
    return result