from __future__ import annotations

import csv
import json
from dataclasses import dataclass
from pathlib import Path
from typing import Iterable, List

REQUIRED_FIELDS = ["file_id", "file_name", "data_type", "data_format", "size", "md5"]


@dataclass(frozen=True)
class ManifestRecord:
    file_id: str
    file_name: str
    data_type: str
    data_format: str
    size: int
    md5: str


def _validate_record(rec: ManifestRecord) -> None:
    if not rec.file_id or not rec.file_name:
        raise ValueError("file_id and file_name are required")
    if rec.size < 0:
        raise ValueError("size must be non-negative")


def write_manifest(records: Iterable[ManifestRecord], path: Path, fmt: str = "tsv") -> None:
    path = Path(path)
    if fmt not in {"tsv", "json"}:
        raise ValueError("fmt must be 'tsv' or 'json'")
    records = list(records)
    for rec in records:
        _validate_record(rec)

    if fmt == "json":
        data = [rec.__dict__ for rec in records]
        path.write_text(json.dumps(data, indent=2))
        return

    with path.open("w", newline="") as f:
        writer = csv.DictWriter(f, fieldnames=REQUIRED_FIELDS, delimiter="\t")
        writer.writeheader()
        for rec in records:
            writer.writerow(rec.__dict__)


def load_manifest(path: Path) -> List[ManifestRecord]:
    path = Path(path)
    if path.suffix.lower() == ".json":
        data = json.loads(path.read_text())
        return [ManifestRecord(**row) for row in data]

    with path.open("r", newline="") as f:
        reader = csv.DictReader(f, delimiter="\t")
        records: List[ManifestRecord] = []
        for row in reader:
            row["size"] = int(row["size"])
            records.append(ManifestRecord(**row))
        return records