"""Fuel receipt specialization with validation and cross-checking."""
import logging
from dataclasses import dataclass
from typing import Optional

from app.extractors.receipt_extractor import (
    ExtractedField,
    ReceiptExtractionResult,
    receipt_extractor,
)

logger = logging.getLogger(__name__)


@dataclass
class FuelReceiptValidation:
    """Validation result for fuel receipt extraction."""

    is_valid: bool
    issues: list[str]
    confidence_score: float


class FuelReceiptExtractor:
    """Specialized fuel receipt extractor with cross-validation.

    Provides additional validation and confidence scoring specific
    to fuel receipts by cross-checking extracted values.
    """

    # Expected fields for a complete fuel receipt
    REQUIRED_FIELDS = ["totalAmount"]
    OPTIONAL_FIELDS = [
        "merchantName",
        "transactionDate",
        "fuelQuantity",
        "pricePerUnit",
        "fuelGrade",
    ]

    def extract(
        self,
        image_bytes: bytes,
        content_type: Optional[str] = None,
    ) -> ReceiptExtractionResult:
        """
        Extract fuel receipt data with validation.

        Args:
            image_bytes: Raw image bytes
            content_type: MIME type

        Returns:
            ReceiptExtractionResult with fuel-specific extraction
        """
        # Use base receipt extractor with fuel hint
        result = receipt_extractor.extract(
            image_bytes=image_bytes,
            content_type=content_type,
            receipt_type="fuel",
        )

        if not result.success:
            return result

        # Validate and cross-check fuel fields
        validation = self._validate_fuel_receipt(result.extracted_fields)

        if validation.issues:
            logger.warning(
                f"Fuel receipt validation issues: {validation.issues}"
            )

        # Update overall confidence based on validation
        result.extracted_fields = self._adjust_confidences(
            result.extracted_fields, validation
        )

        return result

    def _validate_fuel_receipt(
        self, fields: dict[str, ExtractedField]
    ) -> FuelReceiptValidation:
        """
        Validate extracted fuel receipt fields.

        Cross-checks:
        - total = quantity * price per unit (within tolerance)
        - quantity is reasonable for a single fill-up
        - price per unit is within market range

        Args:
            fields: Extracted fields

        Returns:
            FuelReceiptValidation with issues and confidence
        """
        issues = []
        confidence_score = 1.0

        # Check required fields
        for field_name in self.REQUIRED_FIELDS:
            if field_name not in fields:
                issues.append(f"Missing required field: {field_name}")
                confidence_score *= 0.5

        # Cross-validate total = quantity * price
        if all(
            f in fields for f in ["totalAmount", "fuelQuantity", "pricePerUnit"]
        ):
            total = fields["totalAmount"].value
            quantity = fields["fuelQuantity"].value
            price = fields["pricePerUnit"].value

            calculated_total = quantity * price
            tolerance = 0.10  # Allow 10% tolerance for rounding

            if abs(total - calculated_total) > total * tolerance:
                issues.append(
                    f"Total ({total}) doesn't match quantity ({quantity}) * "
                    f"price ({price}) = {calculated_total:.2f}"
                )
                confidence_score *= 0.7

        # Validate quantity is reasonable
        if "fuelQuantity" in fields:
            quantity = fields["fuelQuantity"].value
            if quantity < 0.5:
                issues.append(f"Fuel quantity too small: {quantity}")
                confidence_score *= 0.6
            elif quantity > 40:  # 40 gallons is very large tank
                issues.append(f"Fuel quantity unusually large: {quantity}")
                confidence_score *= 0.8

        # Validate price is reasonable (current US market range)
        if "pricePerUnit" in fields:
            price = fields["pricePerUnit"].value
            if price < 1.50:
                issues.append(f"Price per unit too low: ${price}")
                confidence_score *= 0.7
            elif price > 7.00:
                issues.append(f"Price per unit unusually high: ${price}")
                confidence_score *= 0.8

        # Validate fuel grade
        if "fuelGrade" in fields:
            grade = fields["fuelGrade"].value
            valid_grades = ["87", "89", "91", "93", "DIESEL", "E85"]
            if grade not in valid_grades:
                issues.append(f"Unknown fuel grade: {grade}")
                confidence_score *= 0.9

        is_valid = len(issues) == 0
        return FuelReceiptValidation(
            is_valid=is_valid,
            issues=issues,
            confidence_score=confidence_score,
        )

    def _adjust_confidences(
        self,
        fields: dict[str, ExtractedField],
        validation: FuelReceiptValidation,
    ) -> dict[str, ExtractedField]:
        """
        Adjust field confidences based on validation.

        Args:
            fields: Extracted fields
            validation: Validation result

        Returns:
            Fields with adjusted confidences
        """
        if validation.is_valid:
            # Boost confidences when cross-validation passes
            boost = 1.1
        else:
            # Reduce confidences when there are issues
            boost = validation.confidence_score

        adjusted = {}
        for name, field in fields.items():
            adjusted[name] = ExtractedField(
                value=field.value,
                confidence=min(1.0, field.confidence * boost),
            )

        return adjusted


# Singleton instance
fuel_receipt_extractor = FuelReceiptExtractor()