"""Fuel-specific pattern matching for receipt extraction."""
import re
from dataclasses import dataclass
from typing import Optional


@dataclass
class FuelQuantityMatch:
    """Result of fuel quantity pattern matching."""

    value: float  # Gallons or liters
    unit: str  # "GAL" or "L"
    raw_match: str
    confidence: float
    pattern_name: str


@dataclass
class FuelPriceMatch:
    """Result of fuel price per unit pattern matching."""

    value: float
    unit: str  # "GAL" or "L"
    raw_match: str
    confidence: float
    pattern_name: str


@dataclass
class FuelGradeMatch:
    """Result of fuel grade pattern matching."""

    value: str  # e.g., "87", "89", "93", "DIESEL"
    display_name: str  # e.g., "Regular 87", "Premium 93"
    raw_match: str
    confidence: float


class FuelPatternMatcher:
    """Extract fuel-specific data from receipt text."""

    # Gallons patterns
    GALLONS_PATTERNS = [
        # XX.XXX GAL or XX.XXX GALLONS
        (
            r"(\d{1,3}\.\d{1,3})\s*(?:GAL(?:LON)?S?)",
            "gallons_suffix",
            0.95,
        ),
        # GALLONS: XX.XXX or GAL: XX.XXX
        (
            r"(?:GAL(?:LON)?S?)[:\s]+(\d{1,3}\.\d{1,3})",
            "gallons_prefix",
            0.93,
        ),
        # VOLUME XX.XXX
        (
            r"VOLUME[:\s]+(\d{1,3}\.\d{1,3})",
            "volume",
            0.85,
        ),
        # QTY XX.XXX (near fuel context)
        (
            r"QTY[:\s]+(\d{1,3}\.\d{1,3})",
            "qty",
            0.70,
        ),
    ]

    # Liters patterns (for international receipts)
    LITERS_PATTERNS = [
        # XX.XX L or XX.XX LITERS
        (
            r"(\d{1,3}\.\d{1,3})\s*(?:L(?:ITERS?)?)",
            "liters_suffix",
            0.95,
        ),
        # LITERS: XX.XX
        (
            r"(?:L(?:ITERS?)?)[:\s]+(\d{1,3}\.\d{1,3})",
            "liters_prefix",
            0.93,
        ),
    ]

    # Price per gallon patterns
    PRICE_PER_UNIT_PATTERNS = [
        # $X.XXX/GAL or $X.XX/GAL
        (
            r"\$?\s*(\d{1,2}\.\d{2,3})\s*/\s*GAL",
            "price_per_gal",
            0.98,
        ),
        # PRICE/GAL $X.XXX
        (
            r"PRICE\s*/\s*GAL[:\s]*\$?\s*(\d{1,2}\.\d{2,3})",
            "labeled_price_gal",
            0.96,
        ),
        # UNIT PRICE $X.XXX
        (
            r"UNIT\s*PRICE[:\s]*\$?\s*(\d{1,2}\.\d{2,3})",
            "unit_price",
            0.90,
        ),
        # @ $X.XXX (per unit implied)
        (
            r"@\s*\$?\s*(\d{1,2}\.\d{2,3})",
            "at_price",
            0.85,
        ),
        # PPG $X.XXX (price per gallon)
        (
            r"PPG[:\s]*\$?\s*(\d{1,2}\.\d{2,3})",
            "ppg",
            0.92,
        ),
    ]

    # Fuel grade patterns
    GRADE_PATTERNS = [
        # REGULAR 87, REG 87
        (r"(?:REGULAR|REG)\s*(\d{2})", "regular", 0.95),
        # UNLEADED 87
        (r"UNLEADED\s*(\d{2})", "unleaded", 0.93),
        # PLUS 89, MID 89, MIDGRADE 89
        (r"(?:PLUS|MID(?:GRADE)?)\s*(\d{2})", "plus", 0.95),
        # PREMIUM 91/93, PREM 91/93, SUPER 91/93
        (r"(?:PREMIUM|PREM|SUPER)\s*(\d{2})", "premium", 0.95),
        # Just the octane number near fuel context (87, 89, 91, 93)
        (r"(?<!\d)\s*(87|89|91|93)\s*(?:OCT(?:ANE)?)?", "octane_only", 0.75),
        # DIESEL (no octane)
        (r"DIESEL(?:\s*#?\d)?", "diesel", 0.98),
        # E85 (ethanol blend)
        (r"E\s*85", "e85", 0.95),
    ]

    # Common gas station names
    STATION_NAMES = [
        "SHELL", "CHEVRON", "EXXON", "MOBIL", "BP", "SUNOCO", "76",
        "CIRCLE K", "SPEEDWAY", "WAWA", "SHEETZ", "CASEY", "PILOT",
        "FLYING J", "LOVES", "TA", "PETRO", "MARATHON", "CITGO",
        "VALERO", "MURPHY", "COSTCO", "SAMS CLUB", "SAM'S CLUB",
        "KROGER", "QT", "QUIKTRIP", "RACETRAC", "KUM & GO",
        "KWIK TRIP", "HOLIDAY", "SINCLAIR", "CONOCO", "PHILLIPS 66",
        "ARCO", "AMPM", "AM/PM", "7-ELEVEN", "7 ELEVEN", "GETTY",
        "GULF", "HESS", "TEXACO", "TURKEY HILL", "CUMBERLAND FARMS",
    ]

    def extract_gallons(self, text: str) -> Optional[FuelQuantityMatch]:
        """
        Extract fuel quantity in gallons.

        Args:
            text: Receipt text to search

        Returns:
            FuelQuantityMatch or None
        """
        text_upper = text.upper()

        for pattern, name, confidence in self.GALLONS_PATTERNS:
            match = re.search(pattern, text_upper)
            if match:
                quantity = float(match.group(1))
                if self._is_reasonable_quantity(quantity):
                    return FuelQuantityMatch(
                        value=quantity,
                        unit="GAL",
                        raw_match=match.group(0),
                        confidence=confidence,
                        pattern_name=name,
                    )

        return None

    def extract_liters(self, text: str) -> Optional[FuelQuantityMatch]:
        """
        Extract fuel quantity in liters.

        Args:
            text: Receipt text to search

        Returns:
            FuelQuantityMatch or None
        """
        text_upper = text.upper()

        for pattern, name, confidence in self.LITERS_PATTERNS:
            match = re.search(pattern, text_upper)
            if match:
                quantity = float(match.group(1))
                if self._is_reasonable_quantity(quantity, is_liters=True):
                    return FuelQuantityMatch(
                        value=quantity,
                        unit="L",
                        raw_match=match.group(0),
                        confidence=confidence,
                        pattern_name=name,
                    )

        return None

    def extract_quantity(self, text: str) -> Optional[FuelQuantityMatch]:
        """
        Extract fuel quantity (gallons or liters).

        Prefers gallons for US receipts.

        Args:
            text: Receipt text to search

        Returns:
            FuelQuantityMatch or None
        """
        # Try gallons first (more common in US)
        gallons = self.extract_gallons(text)
        if gallons:
            return gallons

        # Fall back to liters
        return self.extract_liters(text)

    def extract_price_per_unit(self, text: str) -> Optional[FuelPriceMatch]:
        """
        Extract price per gallon/liter.

        Args:
            text: Receipt text to search

        Returns:
            FuelPriceMatch or None
        """
        text_upper = text.upper()

        for pattern, name, confidence in self.PRICE_PER_UNIT_PATTERNS:
            match = re.search(pattern, text_upper)
            if match:
                price = float(match.group(1))
                if self._is_reasonable_price(price):
                    return FuelPriceMatch(
                        value=price,
                        unit="GAL",  # Default to gallons for US
                        raw_match=match.group(0),
                        confidence=confidence,
                        pattern_name=name,
                    )

        return None

    def extract_grade(self, text: str) -> Optional[FuelGradeMatch]:
        """
        Extract fuel grade (octane rating or diesel).

        Args:
            text: Receipt text to search

        Returns:
            FuelGradeMatch or None
        """
        text_upper = text.upper()

        for pattern, name, confidence in self.GRADE_PATTERNS:
            match = re.search(pattern, text_upper)
            if match:
                if name == "diesel":
                    return FuelGradeMatch(
                        value="DIESEL",
                        display_name="Diesel",
                        raw_match=match.group(0),
                        confidence=confidence,
                    )
                elif name == "e85":
                    return FuelGradeMatch(
                        value="E85",
                        display_name="E85 Ethanol",
                        raw_match=match.group(0),
                        confidence=confidence,
                    )
                else:
                    octane = match.group(1)
                    display = self._get_grade_display_name(octane, name)
                    return FuelGradeMatch(
                        value=octane,
                        display_name=display,
                        raw_match=match.group(0),
                        confidence=confidence,
                    )

        return None

    def extract_merchant_name(self, text: str) -> Optional[tuple[str, float]]:
        """
        Extract gas station/merchant name.

        Args:
            text: Receipt text to search

        Returns:
            Tuple of (merchant_name, confidence) or None
        """
        text_upper = text.upper()

        # Check for known station names
        for station in self.STATION_NAMES:
            if station in text_upper:
                # Try to get the full line for context
                for line in text.split("\n"):
                    if station in line.upper():
                        # Clean up the line
                        cleaned = line.strip()
                        if len(cleaned) <= 50:  # Reasonable length
                            return (cleaned, 0.90)
                        return (station.title(), 0.85)

        # Fall back to first non-empty line (often the merchant)
        lines = [l.strip() for l in text.split("\n") if l.strip()]
        if lines:
            first_line = lines[0]
            # Skip if it looks like a date or number
            if not re.match(r"^\d+[/\-.]", first_line):
                return (first_line[:50], 0.50)  # Low confidence

        return None

    def _is_reasonable_quantity(
        self, quantity: float, is_liters: bool = False
    ) -> bool:
        """Check if fuel quantity is reasonable."""
        if is_liters:
            # Typical fill: 20-100 liters
            return 0.5 <= quantity <= 150.0
        else:
            # Typical fill: 5-30 gallons
            return 0.1 <= quantity <= 50.0

    def _is_reasonable_price(self, price: float) -> bool:
        """Check if price per unit is reasonable."""
        # US gas prices: $1.50 - $8.00 per gallon (allowing for fluctuation)
        return 1.00 <= price <= 10.00

    def _get_grade_display_name(self, octane: str, pattern_name: str) -> str:
        """Get display name for fuel grade."""
        grade_names = {
            "87": "Regular 87",
            "89": "Plus 89",
            "91": "Premium 91",
            "93": "Premium 93",
        }

        if octane in grade_names:
            return grade_names[octane]

        # Use pattern hint
        if pattern_name == "premium":
            return f"Premium {octane}"
        elif pattern_name == "plus":
            return f"Plus {octane}"
        else:
            return f"Unleaded {octane}"


# Singleton instance
fuel_matcher = FuelPatternMatcher()