"""纯非 AR 题库端到端 byte-identical 黄金测试（Task 10）。

Phase 1 验收铁律：引入 QuestionUnit 后，纯 single 题库过 pools 抽样 → batching 分批
→ checkpoint 折叠/恢复 → momentum 采样，端到端结果与"引入 QuestionUnit 前"的逐题
旧算法逐字节一致。golden 用固定 seed 的确定性对照（忠实重实现旧逐题逻辑），非空断言。

momentum 设计偏差：momentum 采样在逐题粒度进行、不折叠 unit，故仅保证纯非 AR 的抽样
序列 byte-identical；Phase 1 不保证混格 momentum byte-identical（见 runner
_sample_momentum_candidates docstring）。本测试保守证明纯非 AR momentum 不漂。
"""

from __future__ import annotations

import math
import random

from app.harness.batching import build_batches
from app.harness.pools import build_pools
from app.harness.question_units import build_units
from app.harness.runner import _batch_from_ids, _batch_unit_ids, _sample_momentum_candidates
from core.types import GeneratedQuestion

# ---------------------------------------------------------------------------
# 辅助构造
# ---------------------------------------------------------------------------


def _single(qid: str, task_type: str = "RETRIEVAL", video_id: str = "v1") -> GeneratedQuestion:
    """构造最小 single 题目。"""
    return GeneratedQuestion(
        question_id=qid,
        video_id=video_id,
        task_type=task_type,
        question=f"q_{qid}",
        options=("A. a", "B. b", "C. c", "D. d"),
        answer="A",
        source_nodes=("n1",),
        difficulty="medium",
        question_role="single",
    )


def _pair(
    pair_id: str, task_type: str = "AR", video_id: str = "v1"
) -> tuple[GeneratedQuestion, GeneratedQuestion]:
    """构造一个孪生对（original + mirror）。"""
    common = {
        "video_id": video_id,
        "task_type": task_type,
        "question": "?",
        "options": ("A. a", "B. b", "C. c", "D. d"),
        "answer": "A",
        "source_nodes": ("n1",),
        "difficulty": "medium",
        "pair_id": pair_id,
        "flip_axis": "before_after",
    }
    original = GeneratedQuestion(
        question_id=f"{pair_id}_o", question_role="pair_original", **common
    )
    mirror = GeneratedQuestion(question_id=f"{pair_id}_m", question_role="pair_mirror", **common)
    return original, mirror


# ---------------------------------------------------------------------------
# 引入 QuestionUnit 前的旧逐题 build_batches 忠实副本（单一 rng，无 unit 折叠）
# ---------------------------------------------------------------------------


def _reference_select_mixed(
    items: list[GeneratedQuestion],
    correctness: dict[str, bool],
    correct_ratio: float,
    rng: random.Random,
) -> dict[str, list[GeneratedQuestion]]:
    """旧版 _select_mixed_by_task_type 的忠实副本（逐题、单一 rng）。"""
    errors_by_type: dict[str, list[GeneratedQuestion]] = {}
    correct_by_type: dict[str, list[GeneratedQuestion]] = {}
    for q in items:
        qid = q.question_id
        if correctness.get(qid) is False:
            errors_by_type.setdefault(q.task_type, []).append(q)
        elif correctness.get(qid, False):
            correct_by_type.setdefault(q.task_type, []).append(q)
    if correct_ratio <= 0:
        return errors_by_type
    grouped: dict[str, list[GeneratedQuestion]] = {}
    for task_type in sorted(errors_by_type):
        errs = errors_by_type[task_type]
        n_correct = round(len(errs) * correct_ratio / (1 - correct_ratio))
        available = correct_by_type.get(task_type, [])
        sampled = (
            list(available) if len(available) <= n_correct else rng.sample(available, n_correct)
        )
        grouped[task_type] = errs + sampled
    return grouped


def _reference_build_batches(
    items: list[GeneratedQuestion],
    correctness: dict[str, bool],
    batch_size: int,
    min_class_per_batch: int,
    seed: int,
    correct_ratio: float = 0.0,
) -> list[list[GeneratedQuestion]]:
    """引入 QuestionUnit 前的旧版 build_batches 忠实副本（逐题、单一 rng）。"""
    rng = random.Random(seed)
    grouped = _reference_select_mixed(items, correctness, correct_ratio, rng)
    total = sum(len(g) for g in grouped.values())
    if total == 0:
        return []
    nb = max(1, math.ceil(total / batch_size))
    batches: list[list[GeneratedQuestion]] = [[] for _ in range(nb)]
    small = {t: g for t, g in grouped.items() if len(g) <= min_class_per_batch}
    large = {t: g for t, g in grouped.items() if len(g) > min_class_per_batch}
    for t in sorted(small, key=lambda t: (-len(small[t]), t)):
        group = small[t]
        placed = False
        for b in batches:
            if len(b) + len(group) <= batch_size:
                b.extend(group)
                placed = True
                break
        if not placed:
            batches.append(list(group))
    nb_live = len(batches)
    pointer = 0
    for task_type in sorted(large):
        group = list(large[task_type])
        rng.shuffle(group)
        for q in group:
            for offset in range(nb_live):
                idx = (pointer + offset) % nb_live
                if len(batches[idx]) < batch_size:
                    batches[idx].append(q)
                    pointer = (idx + 1) % nb_live
                    break
    return [b for b in batches if b]


def _ids(batches: list[list[GeneratedQuestion]]) -> list[list[str]]:
    """提取 batch 的 question_id 序列，便于逐字节对比。"""
    return [[q.question_id for q in b] for b in batches]


# ---------------------------------------------------------------------------
# (1) 纯非 AR 走 size=1 unit：unit_id == question_id
# ---------------------------------------------------------------------------


class TestPureSingleAreSizeOneUnits:
    """纯 single 输入折叠出的每个 unit 都是 size=1、unit_id 等于 question_id。"""

    def test_all_units_size_one(self) -> None:
        items = [_single(f"s{i}", task_type=f"t{i % 3}") for i in range(15)]
        units = build_units(items)
        assert len(units) == len(items)
        assert all(u.kind == "single" and u.size == 1 for u in units)
        assert [u.unit_id for u in units] == [q.question_id for q in items]


# ---------------------------------------------------------------------------
# (2) batching 逐字节一致（黄金对照）
# ---------------------------------------------------------------------------


class TestBatchingByteIdentical:
    """纯 single build_batches 与旧逐题算法逐字节一致。"""

    def _assert(self, items, correctness, batch_size, min_cls, seed, ratio) -> None:
        got, _ = build_batches(items, correctness, batch_size, min_cls, seed, ratio)
        ref = _reference_build_batches(items, correctness, batch_size, min_cls, seed, ratio)
        assert _ids(got) == _ids(ref)

    def test_pure_errors(self) -> None:
        items = [_single(f"q{i}", task_type=f"t{i % 3}") for i in range(20)]
        correctness = {f"q{i}": False for i in range(20)}
        self._assert(items, correctness, 5, 2, 42, 0.0)

    def test_mixed_ratio(self) -> None:
        items = [_single(f"q{i}", task_type=f"t{i % 4}") for i in range(40)]
        correctness = {f"q{i}": (i % 3 == 0) for i in range(40)}
        self._assert(items, correctness, 8, 3, 7, 0.5)


# ---------------------------------------------------------------------------
# (3) 端到端：pools 抽样 → batching → checkpoint 折叠/恢复 逐字节一致
# ---------------------------------------------------------------------------


class TestEndToEndByteIdentical:
    """pools → batching → checkpoint unit_id round-trip 全链纯非 AR 逐字节稳定。"""

    def _make_pool_questions(self) -> tuple[list[GeneratedQuestion], dict[str, bool]]:
        items = [_single(f"s{i}", task_type=f"t{i % 3}") for i in range(60)]
        correctness = {f"s{i}": (i % 2 == 0) for i in range(60)}
        return items, correctness

    def test_pools_deterministic_and_pure_single(self) -> None:
        items, correctness = self._make_pool_questions()
        cfg = {
            "diag_cfg": {
                "size": 18,
                "correct_ratio": 0.5,
                "task_types": None,
                "seed": 5,
                "min_per_class": None,
            },
            "val_cfg": {
                "size": 12,
                "correct_ratio": 0.5,
                "task_types": None,
                "seed": 5,
                "min_per_class": None,
            },
            "test_cfg": {"size": 10, "seed": 5},
            "baseline_run_id": "baseline",
        }
        p1 = build_pools(items, correctness, **cfg)
        p2 = build_pools(items, correctness, **cfg)
        # 确定性：同 seed 同输入池划分逐字节一致
        assert [q.question_id for q in p1.diagnosis] == [q.question_id for q in p2.diagnosis]
        # 诊断池纯 single：折叠出的 unit 与逐题一一对应
        units = build_units(p1.diagnosis)
        assert [u.unit_id for u in units] == [q.question_id for q in p1.diagnosis]

    def test_batching_then_checkpoint_roundtrip(self) -> None:
        items, correctness = self._make_pool_questions()
        p = build_pools(
            items,
            correctness,
            diag_cfg={
                "size": 18,
                "correct_ratio": 0.5,
                "task_types": None,
                "seed": 5,
                "min_per_class": None,
            },
            val_cfg={
                "size": 12,
                "correct_ratio": 0.5,
                "task_types": None,
                "seed": 5,
                "min_per_class": None,
            },
            test_cfg={"size": 10, "seed": 5},
            baseline_run_id="baseline",
        )
        batches, _ = build_batches(p.diagnosis, p.correctness, 6, 2, seed=3, correct_ratio=0.5)

        # checkpoint 折叠为 unit_id（纯 single 即 question_id）后恢复
        epoch_batches = [_batch_unit_ids(b) for b in batches]
        assert epoch_batches == _ids(batches)  # 纯非 AR：unit_id 序列 == question_id 序列
        rebuilt = [_batch_from_ids(p, ids) for ids in epoch_batches]
        # 恢复的 batch 与原 batch 逐字节一致（inference 消费的题序不变）
        assert _ids(rebuilt) == _ids(batches)


# ---------------------------------------------------------------------------
# (4) momentum 纯非 AR byte-identical（混格偏差已在 runner docstring 记录）
# ---------------------------------------------------------------------------


class TestMomentumPureNonARByteIdentical:
    """momentum 采样纯非 AR 与旧逐题 random.Random(epoch).sample 逐字节一致。"""

    def test_matches_legacy_rng(self) -> None:
        pool = [_single(f"s{i}", task_type="RETRIEVAL") for i in range(30)]
        allowed = {"RETRIEVAL"}
        epoch = 11
        samples = 8
        got = _sample_momentum_candidates(pool, allowed, samples, epoch)

        candidates = [q for q in pool if q.task_type in allowed]
        ref = random.Random(epoch).sample(candidates, samples)
        assert [q.question_id for q in got] == [q.question_id for q in ref]

    def test_ar_pairs_of_other_type_do_not_shift(self) -> None:
        """向池中加入其它题型的 AR pair，不改变非 AR momentum 的抽样序列。"""
        singles = [_single(f"s{i}", task_type="RETRIEVAL") for i in range(30)]
        allowed = {"RETRIEVAL"}
        epoch = 11
        samples = 8
        base = _sample_momentum_candidates(singles, allowed, samples, epoch)

        mixed = list(singles)
        for k in range(4):
            po, pm = _pair(f"p{k}", task_type="AR")
            mixed.extend([po, pm])
        after = _sample_momentum_candidates(mixed, allowed, samples, epoch)
        assert [q.question_id for q in base] == [q.question_id for q in after]

    def test_fewer_candidates_than_samples_returns_all(self) -> None:
        pool = [_single(f"s{i}", task_type="RETRIEVAL") for i in range(3)]
        got = _sample_momentum_candidates(pool, {"RETRIEVAL"}, 10, epoch=1)
        assert {q.question_id for q in got} == {"s0", "s1", "s2"}