"""Pluggable parser registry for answer-sheet extraction.

Auto mode: picks the best parser based on file type and data_type.
Manual mode: caller specifies parser name from `list_parsers()`.

Adding a new parser:
1. Create a module that exposes a subclass of `AnswerSheetParser`.
2. Import and register it below in `_REGISTRY`.
"""

from __future__ import annotations

from .base import AnswerSheetParser, ParserResult, get_extension
from .csv_strict import StrictCsvParser
from .llm_vision import LLMVisionParser
from .native_pdf_tables import NativePdfParser

AUTO = "auto"

_REGISTRY: dict[str, AnswerSheetParser] = {
    NativePdfParser.name: NativePdfParser(),
    StrictCsvParser.name: StrictCsvParser(),
    LLMVisionParser.name: LLMVisionParser(),
}


def list_parsers() -> list[dict[str, str]]:
    """Return parser metadata for UI dropdowns."""
    out: list[dict[str, str]] = [
        {
            "id": AUTO,
            "name": "Auto (recommended)",
            "description": "System picks the best parser for each file.",
        }
    ]
    for p in _REGISTRY.values():
        out.append({"id": p.name, "name": p.display_name, "description": p.description})
    return out


def get_parser(name: str) -> AnswerSheetParser:
    if name not in _REGISTRY:
        raise ValueError(f"Unknown parser: {name}")
    return _REGISTRY[name]


def pick_auto(file_bytes: bytes, filename: str, data_type: str) -> AnswerSheetParser:
    """Auto-mode selector.

    - Questions always use LLM vision (text rarely fits a clean grid).
    - .csv answer-side uploads → StrictCsvParser.
    - Native PDF tables for student/teacher answers when there's a text layer.
    - Otherwise fall back to LLM vision.
    """
    if data_type == "questions":
        return _REGISTRY[LLMVisionParser.name]

    # The "answers" combined zone runs the parser twice (once per subtype);
    # treat it the same as student_answers for routing purposes.
    routing_data_type = "student_answers" if data_type == "answers" else data_type

    if get_extension(filename) == ".csv":
        return _REGISTRY[StrictCsvParser.name]

    native = _REGISTRY[NativePdfParser.name]
    if native.can_handle(file_bytes, filename, routing_data_type):
        return native
    return _REGISTRY[LLMVisionParser.name]


__all__ = [
    "AUTO",
    "AnswerSheetParser",
    "ParserResult",
    "get_parser",
    "list_parsers",
    "pick_auto",
]