import re
from dataclasses import dataclass

from app.services.vehicle_identity import normalize_license_plate, validate_vin


@dataclass
class OcrCandidate:
    type: str
    value: str
    confidence: float


@dataclass
class OcrResult:
    recognized_text: str
    candidates: list[OcrCandidate]


class OCRProvider:
    async def recognize(self, content: bytes, filename: str | None = None) -> OcrResult:
        raise NotImplementedError


class StubOCRProvider(OCRProvider):
    async def recognize(self, content: bytes, filename: str | None = None) -> OcrResult:
        text = " ".join(
            [
                filename or "",
                content.decode("utf-8", errors="ignore"),
            ]
        )
        compact = re.sub(r"\s+", " ", text).strip()
        candidates: list[OcrCandidate] = []
        for raw in re.findall(r"\b[A-HJ-NPR-Z0-9]{17}\b", compact.upper()):
            try:
                candidates.append(OcrCandidate(type="vin", value=validate_vin(raw) or raw, confidence=0.84))
            except ValueError:
                continue
        for raw in re.findall(r"\b[0-9A-ZА-Я가-힣][0-9A-ZА-Я가-힣\-\s]{4,10}\b", compact.upper()):
            normalized = normalize_license_plate(raw)
            if normalized and 5 <= len(normalized) <= 10 and not any(item.value == normalized for item in candidates):
                candidates.append(OcrCandidate(type="license_plate", value=normalized, confidence=0.62))
        return OcrResult(recognized_text=compact, candidates=candidates[:8])


def get_ocr_provider() -> OCRProvider:
    return StubOCRProvider()