"""
合成数据集指纹与清单辅助工具。

用于识别“样本数量足够但生成规则已变化”的情况，避免静默复用过期数据。
"""

from __future__ import annotations

import hashlib
import inspect
import json
from pathlib import Path
from typing import Callable

MANIFEST_NAME = ".dataset_meta.json"


def _stable_json(data: dict) -> str:
    return json.dumps(data, ensure_ascii=True, sort_keys=True, separators=(",", ":"))


def _sha256_text(text: str) -> str:
    return hashlib.sha256(text.encode("utf-8")).hexdigest()


def _source_hash(obj) -> str:
    try:
        source = inspect.getsource(obj)
    except (OSError, TypeError):
        source = repr(obj)
    return _sha256_text(source)


def dataset_manifest_path(dataset_dir: str | Path) -> Path:
    return Path(dataset_dir) / MANIFEST_NAME


def dataset_spec_hash(spec: dict) -> str:
    return _sha256_text(_stable_json(spec))


def build_dataset_spec(
    generator_cls,
    *,
    config_key: str,
    config_snapshot: dict,
) -> dict:
    """构造可稳定哈希的数据集规格说明。"""
    return {
        "config_key": config_key,
        "generator": f"{generator_cls.__module__}.{generator_cls.__name__}",
        "generator_source_hash": _source_hash(generator_cls),
        "config_snapshot": config_snapshot,
    }


def load_dataset_manifest(dataset_dir: str | Path) -> dict | None:
    path = dataset_manifest_path(dataset_dir)
    if not path.exists():
        return None
    with path.open("r", encoding="utf-8") as f:
        return json.load(f)


def write_dataset_manifest(
    dataset_dir: str | Path,
    *,
    spec: dict,
    sample_count: int,
    adopted_existing: bool,
) -> dict:
    path = dataset_manifest_path(dataset_dir)
    manifest = {
        "version": 1,
        "spec": spec,
        "spec_hash": dataset_spec_hash(spec),
        "sample_count": sample_count,
        "adopted_existing": adopted_existing,
    }
    path.parent.mkdir(parents=True, exist_ok=True)
    with path.open("w", encoding="utf-8") as f:
        json.dump(manifest, f, ensure_ascii=True, indent=2, sort_keys=True)
        f.write("\n")
    return manifest


def labels_cover_tokens(files: list[Path], required_tokens: tuple[str, ...]) -> bool:
    """检查文件名标签中是否至少覆盖每个目标 token 一次。"""
    remaining = set(required_tokens)
    if not remaining:
        return True

    for path in files:
        label = path.stem.rsplit("_", 1)[0]
        matched = {token for token in remaining if token in label}
        if matched:
            remaining -= matched
            if not remaining:
                return True
    return not remaining


def _count_matches(count: int, *, exact_count: int | None, min_count: int | None) -> bool:
    if exact_count is not None and count != exact_count:
        return False
    if min_count is not None and count < min_count:
        return False
    return True


def _dataset_valid(
    files: list[Path],
    *,
    exact_count: int | None,
    min_count: int | None,
    validator: Callable[[list[Path]], bool] | None,
) -> bool:
    counts_ok = _count_matches(len(files), exact_count=exact_count, min_count=min_count)
    if not counts_ok:
        return False
    if validator is None:
        return True
    return validator(files)


def clear_generated_dataset(dataset_dir: str | Path) -> None:
    dataset_dir = Path(dataset_dir)
    for path in dataset_dir.glob("*.png"):
        path.unlink()
    manifest = dataset_manifest_path(dataset_dir)
    if manifest.exists():
        manifest.unlink()


def ensure_synthetic_dataset(
    dataset_dir: str | Path,
    *,
    generator_cls,
    spec: dict,
    gen_count: int,
    exact_count: int | None = None,
    min_count: int | None = None,
    validator: Callable[[list[Path]], bool] | None = None,
    adopt_if_missing: bool = False,
) -> dict:
    """
    确保合成数据与当前生成规则一致。

    返回:
        {
            "manifest": dict,
            "sample_count": int,
            "refreshed": bool,
            "adopted": bool,
        }
    """
    dataset_dir = Path(dataset_dir)
    dataset_dir.mkdir(parents=True, exist_ok=True)

    files = sorted(dataset_dir.glob("*.png"))
    sample_count = len(files)
    counts_ok = _count_matches(sample_count, exact_count=exact_count, min_count=min_count)
    validator_ok = _dataset_valid(
        files,
        exact_count=exact_count,
        min_count=min_count,
        validator=validator,
    )
    manifest = load_dataset_manifest(dataset_dir)
    spec_hash = dataset_spec_hash(spec)

    manifest_ok = (
        manifest is not None
        and manifest.get("spec_hash") == spec_hash
        and manifest.get("sample_count") == sample_count
    )

    if manifest_ok and counts_ok and validator_ok:
        return {
            "manifest": manifest,
            "sample_count": sample_count,
            "refreshed": False,
            "adopted": False,
        }

    if manifest is None and adopt_if_missing and counts_ok and validator_ok:
        manifest = write_dataset_manifest(
            dataset_dir,
            spec=spec,
            sample_count=sample_count,
            adopted_existing=True,
        )
        return {
            "manifest": manifest,
            "sample_count": sample_count,
            "refreshed": False,
            "adopted": True,
        }

    clear_generated_dataset(dataset_dir)
    gen = generator_cls()
    gen.generate_dataset(gen_count, str(dataset_dir))

    files = sorted(dataset_dir.glob("*.png"))
    sample_count = len(files)
    if not _dataset_valid(
        files,
        exact_count=exact_count,
        min_count=min_count,
        validator=validator,
    ):
        raise RuntimeError(
            f"生成后的数据集不符合要求: {dataset_dir} (count={sample_count})"
        )
    manifest = write_dataset_manifest(
        dataset_dir,
        spec=spec,
        sample_count=sample_count,
        adopted_existing=False,
    )
    return {
        "manifest": manifest,
        "sample_count": sample_count,
        "refreshed": True,
        "adopted": False,
    }