from __future__ import annotations

from dataclasses import dataclass
import re
from typing import Iterable, Mapping, Optional

from publication_meta import clean, parse_meta


class MarkerError(ValueError):
    pass


@dataclass(frozen=True)
class PageMarker:
    block_id: str
    raw: str
    meta: dict[str, str]


def find_marker(blocks: Iterable[Mapping[str, object]]) -> Optional[PageMarker]:
    valid: list[PageMarker] = []
    near_misses: list[str] = []

    for block in blocks:
        block_id = str(block.get("id", "unknown"))
        raw_value = block.get("text", "")
        raw = raw_value if isinstance(raw_value, str) else ""
        normalized = clean(raw)
        if re.search(r"anwarpy", normalized, re.IGNORECASE) is None:
            continue
        if not normalized.startswith("anwarpy:"):
            near_misses.append(block_id)
            continue
        try:
            meta = parse_meta(normalized)
        except ValueError:
            near_misses.append(block_id)
            continue
        valid.append(PageMarker(block_id=block_id, raw=raw, meta=meta))

    if len(valid) > 1:
        ids = ", ".join(marker.block_id for marker in valid)
        raise MarkerError(f"multiple anwarpy markers found in blocks: {ids}")
    if valid and near_misses:
        ids = ", ".join(near_misses)
        raise MarkerError(f"ambiguous anwarpy markers; near-miss blocks: {ids}")
    if near_misses:
        ids = ", ".join(near_misses)
        raise MarkerError(f"near-miss anwarpy marker in blocks: {ids}")
    return valid[0] if valid else None