"""tutor/curriculum_loader.py — loads curriculum JSON and samples items."""
from __future__ import annotations
import json, random
from pathlib import Path
from typing import List, Dict, Any


def load(path) -> List[Dict[str, Any]]:
    path = Path(path)
    if not path.exists():
        raise FileNotFoundError(f"Curriculum not found: {path}")
    with open(path, "r", encoding="utf-8") as f:
        data = json.load(f)
    return data if isinstance(data, list) else data.get("items", [])


def sample_diagnostic_probes(
    items: List[Dict[str, Any]],
    n_per_skill: int = 1,
    diff_min: float = 1,
    diff_max: float = 10,
) -> List[Dict[str, Any]]:
    by_skill: Dict[str, List[Dict]] = {}
    for item in items:
        if diff_min <= item.get("difficulty", 5) <= diff_max:
            by_skill.setdefault(item.get("skill", "unknown"), []).append(item)
    probes = []
    for skill_items in by_skill.values():
        probes.extend(random.sample(skill_items, min(n_per_skill, len(skill_items))))
    random.shuffle(probes)
    return probes


def filter_by_skill(items, skill, diff_min=1, diff_max=10):
    return [i for i in items
            if i.get("skill") == skill and diff_min <= i.get("difficulty", 5) <= diff_max]