"""Unified benchmark task sets (#20) — the shared, frozen tasks every system runs.

Fairness rule (standard §9.1 / baseline-comparison §3): swarm and every baseline run the SAME
task_set_id under the SAME model gateway. A task set groups tasks of one scenario; each task
references a fixture (objective + HELD-OUT acceptance tests + offline reference solution).

Layout:  benchmark/tasksets/<task_set_id>/taskset.json

`taskset.json`:
    {
      "task_set_id": "coding-set-1",
      "scenario": "coding",            # coding | refactoring | architecture | devops | bugfix
      "tasks": [ { "id": "add_function", "fixture": "add_function" } ]
    }

Coverage is honest: only scenarios with real fixtures are loadable. The other four scenarios
(refactoring/architecture/devops/bugfix) are declared TODO in this package's README until their
fixtures + held-out tests exist — we do not ship empty task sets that would silently pass.
"""
from __future__ import annotations

import json
from dataclasses import dataclass, field
from pathlib import Path
from typing import List

from ..fixtures import Fixture, load_fixture

_TASKSET_ROOT = Path(__file__).resolve().parent
SCENARIOS = {"coding", "refactoring", "architecture", "devops", "bugfix"}


@dataclass
class TaskSetItem:
    id: str
    fixture_id: str

    @property
    def fixture(self) -> Fixture:
        return load_fixture(self.fixture_id)


@dataclass
class TaskSet:
    task_set_id: str
    scenario: str
    tasks: List[TaskSetItem] = field(default_factory=list)


def available_tasksets() -> List[str]:
    return sorted(
        p.name for p in _TASKSET_ROOT.iterdir()
        if p.is_dir() and (p / "taskset.json").exists()
    )


def load_taskset(task_set_id: str) -> TaskSet:
    meta_path = _TASKSET_ROOT / task_set_id / "taskset.json"
    if not meta_path.exists():
        raise FileNotFoundError(f"unknown task set: {task_set_id}")
    meta = json.loads(meta_path.read_text(encoding="utf-8"))
    scenario = meta.get("scenario", "")
    if scenario not in SCENARIOS:
        raise ValueError(f"task set {task_set_id} has unknown scenario '{scenario}'")
    tasks = [TaskSetItem(id=t["id"], fixture_id=t["fixture"]) for t in meta.get("tasks", [])]
    if not tasks:
        raise ValueError(f"task set {task_set_id} has no tasks (refusing to ship an empty set)")
    return TaskSet(task_set_id=meta["task_set_id"], scenario=scenario, tasks=tasks)