import json
import uuid
from dataclasses import asdict, dataclass
from pathlib import Path

from app.services.exporter import ExportResult, write_export


@dataclass(slots=True)
class ResultMetadata:
    result_id: str
    file_path: str
    download_name: str
    mimetype: str


def persist_result(
    output_dir: Path,
    records: list[dict[str, str]],
    union_keys: list[str],
    mode: str,
    output_format: str,
    preview_record_limit: int,
) -> tuple[ResultMetadata, ExportResult]:
    """Persist generated output and sidecar metadata in a temporary directory."""
    result_id = uuid.uuid4().hex
    extension = "txt" if output_format == "text" else "csv"
    mimetype = "text/plain; charset=utf-8" if extension == "txt" else "text/csv; charset=utf-8"

    file_path = output_dir / f"{result_id}.{extension}"
    metadata_path = output_dir / f"{result_id}.json"

    export_result = write_export(
        file_path=file_path,
        records=records,
        union_keys=union_keys,
        mode=mode,
        output_format=output_format,
        preview_record_limit=preview_record_limit,
    )
    metadata = ResultMetadata(
        result_id=result_id,
        file_path=str(file_path),
        download_name=f"waf-report.{extension}",
        mimetype=mimetype,
    )
    metadata_path.write_text(json.dumps(asdict(metadata)), encoding="utf-8")
    return metadata, export_result


def load_result_metadata(output_dir: Path, result_id: str) -> dict[str, str] | None:
    """Load sidecar metadata for a generated file."""
    metadata_path = output_dir / f"{result_id}.json"
    if not metadata_path.exists():
        return None

    return json.loads(metadata_path.read_text(encoding="utf-8"))