"""I/O helpers and standard output layout for LSV benchmarks."""

from __future__ import annotations

import json
import shutil
from dataclasses import dataclass
from pathlib import Path
from typing import Any, Iterable


BENCHMARK_ROOT = Path(__file__).resolve().parents[1]
DATA_DIR = BENCHMARK_ROOT / "data"


@dataclass(frozen=True)
class OutputLayout:
    root: Path

    @property
    def run_config_path(self) -> Path:
        return self.root / "run_config.json"

    def task_dir(self, task_name: str) -> Path:
        return self.root / task_name

    def predictions_path(self, task_name: str) -> Path:
        return self.task_dir(task_name) / "predictions.jsonl"

    def legacy_predictions_path(self, task_name: str) -> Path:
        return self.task_dir(task_name) / "per_video_results.jsonl"

    def shard_path(self, task_name: str, shard_index: int) -> Path:
        return self.task_dir(task_name) / f"predictions_shard_{shard_index:02d}.jsonl"


def read_json(path: Path) -> dict[str, Any]:
    return json.loads(path.read_text(encoding="utf-8"))


def write_json(path: Path, value: Any) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    path.write_text(json.dumps(value, indent=2, sort_keys=True, ensure_ascii=False) + "\n", encoding="utf-8")


def read_jsonl(path: Path) -> list[dict[str, Any]]:
    rows: list[dict[str, Any]] = []
    if not path.exists():
        return rows
    with path.open("r", encoding="utf-8") as fh:
        for line in fh:
            line = line.strip()
            if not line:
                continue
            try:
                rows.append(json.loads(line))
            except json.JSONDecodeError:
                continue
    return rows


def write_jsonl(path: Path, rows: Iterable[dict[str, Any]]) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    with path.open("w", encoding="utf-8") as fh:
        for row in rows:
            fh.write(json.dumps(row, ensure_ascii=False, sort_keys=True) + "\n")


def append_jsonl(path: Path, row: dict[str, Any]) -> None:
    path.parent.mkdir(parents=True, exist_ok=True)
    with path.open("a", encoding="utf-8") as fh:
        fh.write(json.dumps(row, ensure_ascii=False) + "\n")


def load_json_manifest(path: Path) -> dict[str, Any]:
    return read_json(path)


def manifest_examples(path: Path) -> list[dict[str, Any]]:
    payload = load_json_manifest(path)
    rows = payload.get("examples")
    if not isinstance(rows, list):
        raise ValueError(f"Manifest has no examples list: {path}")
    return [dict(row) for row in rows if isinstance(row, dict)]


def read_parquet(path: Path) -> list[dict[str, Any]]:
    import pyarrow.parquet as pq

    return pq.read_table(path).to_pylist()


def select_shard(rows: list[dict[str, Any]], num_shards: int, shard_index: int) -> list[dict[str, Any]]:
    if num_shards < 1:
        raise ValueError("num_shards must be >= 1")
    if not (0 <= shard_index < num_shards):
        raise ValueError("shard_index must satisfy 0 <= shard_index < num_shards")
    if num_shards == 1:
        return rows
    return [row for idx, row in enumerate(rows) if idx % num_shards == shard_index]


def candidate_prediction_files(task_dir: Path) -> list[Path]:
    paths = sorted(task_dir.glob("predictions_shard_*.jsonl"))
    if paths:
        return paths
    paths = sorted(task_dir.glob("per_video_results_shard_*.jsonl"))
    if paths:
        return paths
    for name in ("predictions.jsonl", "per_video_results.jsonl"):
        path = task_dir / name
        if path.exists():
            return [path]
    return []


def load_prediction_rows(task_dir: Path, *, sort_key: str = "eval_id") -> list[dict[str, Any]]:
    rows: list[dict[str, Any]] = []
    for path in candidate_prediction_files(task_dir):
        rows.extend(read_jsonl(path))
    return sorted(rows, key=lambda row: str(row.get(sort_key) or row.get("video_id") or row.get("eval_id") or ""))


def merge_shards(task_dir: Path, *, sort_key: str = "eval_id") -> list[dict[str, Any]]:
    rows = load_prediction_rows(task_dir, sort_key=sort_key)
    if rows:
        write_jsonl(task_dir / "predictions.jsonl", rows)
    return rows


def copy_legacy_predictions(task_dir: Path) -> None:
    predictions = task_dir / "predictions.jsonl"
    legacy = task_dir / "per_video_results.jsonl"
    if predictions.exists() and not legacy.exists():
        shutil.copyfile(predictions, legacy)