"""
Extension → extractor dispatch.

Maps a file extension to an extractor "family" module under doocus/extractors/.
Families are imported lazily so an app that only handles text files doesn't need
the office/pdf/image dependencies installed. Unknown extensions (and families
whose optional deps are missing) are reported as "unhandled" — never fatal.
"""
import importlib
import logging
from pathlib import Path
from typing import Dict, Optional

from .extractors.base import ExtractionResult

logger = logging.getLogger(__name__)

# extension (no dot, lowercase) → family module name under doocus.extractors
EXT_FAMILY: Dict[str, str] = {
    "md": "text", "markdown": "text", "txt": "text",
    "yaml": "text", "yml": "text", "json": "text",
    "csv": "tabular",
    "docx": "office", "pptx": "office", "xlsx": "office",
    "pdf": "pdf",
    "html": "web", "htm": "web",
    "jpg": "image", "jpeg": "image", "png": "image",
    "mp4": "media",
}


def ext_of(source: Path) -> str:
    return source.suffix.lower().lstrip(".")


def family_for(source: Path) -> Optional[str]:
    return EXT_FAMILY.get(ext_of(source))


def extract(source: Path, options: dict) -> ExtractionResult:
    """Dispatch to the right family extractor.

    Returns an ExtractionResult in all cases — unhandled types and import/extract
    failures come back as an empty result carrying a warning, so a batch keeps
    going.
    """
    family = family_for(source)
    if family is None:
        return ExtractionResult(
            extractor="unhandled",
            warnings=[f"no extractor for extension '.{ext_of(source)}'"],
        )
    try:
        module = importlib.import_module(f".extractors.{family}", package=__package__)
    except ImportError as e:
        return ExtractionResult(
            extractor=f"{family}/unavailable",
            warnings=[f"extractor '{family}' unavailable (missing dependency): {e}"],
        )
    try:
        return module.extract(source, options)
    except Exception as e:  # isolate: one bad file must not abort the batch
        logger.warning("extractor '%s' failed on %s: %s", family, source.name, e)
        return ExtractionResult(
            extractor=f"{family}/error",
            warnings=[f"extraction failed: {e}"],
        )