"""Preview service for manually selected knowledge-base chunking."""
from __future__ import annotations

from pathlib import Path

from rag.chunk_config import resolve_chunk_config
from rag.chunking import SUPPORTED_STRATEGIES, chunk_document
from rag.cleaning import clean_document_text
from rag.document_parser import parse_document


def preview_document(
    path: str | Path,
    *,
    strategy: str,
    chunk_size: int | None = None,
    chunk_overlap: int | None = None,
) -> dict:
    """Parse and preview a document without writing anything to Milvus."""
    if strategy not in SUPPORTED_STRATEGIES:
        raise ValueError(f"Unsupported chunk strategy: {strategy}")
    config = resolve_chunk_config(chunk_size=chunk_size, chunk_overlap=chunk_overlap)
    cleaned = clean_document_text(parse_document(path))
    result = chunk_document(cleaned.text, strategy, config=config)
    return {
        "strategy": result.requested_strategy,
        "actual_strategy": result.actual_strategy,
        "degraded": result.degraded,
        "warning": result.warning,
        "cleaning_changed": cleaned.changed,
        "cleaning_warnings": cleaned.warnings,
        "chunk_size": config.size,
        "chunk_overlap": config.overlap,
        "chunks": [
            {"text": chunk.text, "section_title": chunk.section_title}
            for chunk in result.chunks
        ],
    }