"""Document ingestion helpers for Memory Gateway."""
from __future__ import annotations

import re
from datetime import datetime, timezone
from pathlib import Path


def slugify(value: str, fallback: str = "document") -> str:
    slug = re.sub(r"[^a-zA-Z0-9\u4e00-\u9fff_-]+", "-", value.lower()).strip("-")
    slug = re.sub(r"-+", "-", slug)[:100].strip("-")
    return slug or fallback


def convert_file_to_markdown(file_path: str | Path) -> str:
    """Convert a local document to Markdown using Microsoft MarkItDown."""
    try:
        from markitdown import MarkItDown
    except ModuleNotFoundError as exc:
        raise RuntimeError("markitdown is not installed. Install with: pip install 'markitdown[all]'") from exc

    file_path = Path(file_path)
    converter = MarkItDown(enable_plugins=False)
    if hasattr(converter, "convert_local"):
        result = converter.convert_local(str(file_path))
    else:
        result = converter.convert(str(file_path))
    markdown = getattr(result, "text_content", "") or ""
    if not markdown.strip():
        raise RuntimeError("Document conversion produced empty Markdown")
    return markdown


def build_markdown_note(
    *,
    title: str,
    markdown: str,
    source_filename: str,
    tags: list[str],
    knowledge_type: str,
    summary: str | None = None,
) -> str:
    tag_text = ", ".join(tags)
    frontmatter = [
        "---",
        f"title: {title}",
        f"knowledge_type: {knowledge_type}",
        f"source_filename: {source_filename}",
        f"created_at: {datetime.now(timezone.utc).isoformat()}",
        f"tags: [{tag_text}]" if tag_text else "tags: []",
    ]
    if summary:
        escaped = summary.replace('"', '\\"')
        frontmatter.append(f'summary: "{escaped}"')
    frontmatter.extend(["---", "", f"# {title}", "", markdown.strip(), ""])
    return "\n".join(frontmatter)


def save_markdown_to_obsidian(
    *,
    vault_path: str | Path,
    relative_dir: str,
    title: str,
    markdown: str,
    source_filename: str,
    tags: list[str],
    knowledge_type: str,
    summary: str | None = None,
) -> Path:
    vault = Path(vault_path)
    target_dir = vault / relative_dir.strip("/")
    target_dir.mkdir(parents=True, exist_ok=True)
    digest = slugify(source_filename.rsplit(".", 1)[0] or title)
    note_name = f"{slugify(title, digest)}.md"
    target = target_dir / note_name
    target.write_text(
        build_markdown_note(
            title=title,
            markdown=markdown,
            source_filename=source_filename,
            tags=tags,
            knowledge_type=knowledge_type,
            summary=summary,
        ),
        encoding="utf-8",
    )
    return target