from __future__ import annotations
import re
from pathlib import Path

_LINE_RE = re.compile(
    r'\[ep_(\d+)\]'
    r'.*avg_reward=([+-]?\d+\.?\d*)'
    r'.*avg_steps=(\d+\.?\d*)'
    r'.*epsilon=(\d+\.?\d*)'
    r'.*avg_loss=(\d+\.?\d*)'
)


def parse_checkpoints(log_path: Path) -> list[dict]:
    """Parse checkpoint lines from a training log. Returns a list of dicts
    with keys: episode, avg_reward, avg_steps, epsilon, avg_loss."""
    results = []
    if not log_path.exists():
        return results
    for line in log_path.read_text().splitlines():
        m = _LINE_RE.search(line)
        if m:
            results.append({
                'episode':    int(m.group(1)),
                'avg_reward': float(m.group(2)),
                'avg_steps':  float(m.group(3)),
                'epsilon':    float(m.group(4)),
                'avg_loss':   float(m.group(5)),
            })
    return results