"""PII detection and de-identification utilities."""

import hashlib
import re
from typing import Any


class PIIDetector:
    """PII detection and de-identification utilities"""

    # Regex patterns for common PII
    PII_PATTERNS = {
        "uk_ni_number": r"\b[A-CEGHJ-PR-TW-Z]{2}\d{6}[A-D]\b",
        "uk_utr": r"\b\d{10}\b",
        "uk_postcode": r"\b[A-Z]{1,2}\d[A-Z0-9]?\s*\d[A-Z]{2}\b",
        "uk_sort_code": r"\b\d{2}-\d{2}-\d{2}\b",
        "uk_account_number": r"\b\d{8}\b",
        "email": r"\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b",
        "phone": r"\b(?:\+44|0)\d{10,11}\b",
        "iban": r"\bGB\d{2}[A-Z]{4}\d{14}\b",
        "amount": r"£\d{1,3}(?:,\d{3})*(?:\.\d{2})?",
        "date": r"\b\d{1,2}[/-]\d{1,2}[/-]\d{2,4}\b",
    }

    def __init__(self) -> None:
        self.compiled_patterns = {
            name: re.compile(pattern, re.IGNORECASE)
            for name, pattern in self.PII_PATTERNS.items()
        }

    def detect_pii(self, text: str) -> list[dict[str, Any]]:
        """Detect PII in text and return matches with positions"""
        matches = []

        for pii_type, pattern in self.compiled_patterns.items():
            for match in pattern.finditer(text):
                matches.append(
                    {
                        "type": pii_type,
                        "value": match.group(),
                        "start": match.start(),
                        "end": match.end(),
                        "placeholder": self._generate_placeholder(
                            pii_type, match.group()
                        ),
                    }
                )

        return sorted(matches, key=lambda x: x["start"])

    def de_identify_text(self, text: str) -> tuple[str, dict[str, str]]:
        """De-identify text by replacing PII with placeholders"""
        pii_matches = self.detect_pii(text)
        pii_mapping = {}

        # Replace PII from end to start to maintain positions
        de_identified = text
        for match in reversed(pii_matches):
            placeholder = match["placeholder"]
            pii_mapping[placeholder] = match["value"]
            de_identified = (
                de_identified[: match["start"]]
                + placeholder
                + de_identified[match["end"] :]
            )

        return de_identified, pii_mapping

    def _generate_placeholder(self, pii_type: str, value: str) -> str:
        """Generate consistent placeholder for PII value"""
        # Create hash of the value for consistent placeholders
        value_hash = hashlib.md5(value.encode()).hexdigest()[:8]
        return f"[{pii_type.upper()}_{value_hash}]"

    def has_pii(self, text: str) -> bool:
        """Check if text contains any PII"""
        return len(self.detect_pii(text)) > 0