"""Token service for secure form pre-filling.

Generates signed tokens for cross-system communication between
Customer Portal and WordPress kurs-booking plugin.

Sprint 6.6: Extended to include all custom_fields for dynamic sync.
"""

import base64
import hashlib
import hmac
import json
import time
from typing import Any

from flask import current_app


class TokenService:
    """Generate and validate signed tokens for cross-system communication."""

    @staticmethod
    def generate_prefill_token(customer: Any) -> str:
        """
        Generate signed token for WordPress form pre-fill.

        The token contains all customer data (core fields + custom_fields)
        signed with the shared WP_API_SECRET. WordPress validates the
        signature and uses the data to pre-fill the booking form.

        Sprint 6.6: Now includes all custom_fields for complete sync.

        Args:
            customer: Customer model instance with id, name, email, phone, custom_fields

        Returns:
            Base64-URL-safe encoded signed token string

        Raises:
            ValueError: If WP_API_SECRET is not configured
        """
        secret = current_app.config.get("WP_API_SECRET", "")
        expiry = current_app.config.get("PREFILL_TOKEN_EXPIRY", 300)

        if not secret:
            raise ValueError("WP_API_SECRET not configured")

        # Sprint 12: Use display properties - all data from custom_fields
        addr = customer.display_address
        payload = {
            "customer_id": customer.id,
            "name": customer.display_name,
            "email": customer.email or "",
            "phone": customer.display_phone,
            "address_street": addr.get("street", ""),
            "address_city": addr.get("city", ""),
            "address_zip": addr.get("zip", ""),
            "exp": int(time.time()) + expiry,
        }

        # Add all custom_fields to payload for full data access
        custom_fields = customer.get_custom_fields()
        if custom_fields:
            payload["custom_fields"] = custom_fields

        # JSON encode with minimal whitespace.
        payload_json = json.dumps(payload, separators=(",", ":"), ensure_ascii=False)

        # Create HMAC-SHA256 signature.
        signature = hmac.new(
            secret.encode("utf-8"),
            payload_json.encode("utf-8"),
            hashlib.sha256,
        ).hexdigest()

        # Combine payload and signature.
        token_data = f"{payload_json}.{signature}"

        # Base64 URL-safe encode.
        return base64.urlsafe_b64encode(token_data.encode("utf-8")).decode("utf-8")

    @staticmethod
    def validate_prefill_token(token: str) -> dict | None:
        """
        Validate a prefill token and extract customer data.

        This method is primarily for testing purposes. The actual validation
        happens in WordPress (class-frontend.php).

        Args:
            token: Base64-URL-safe encoded signed token

        Returns:
            Dictionary with customer data if valid, None otherwise
        """
        secret = current_app.config.get("WP_API_SECRET", "")

        if not secret:
            return None

        try:
            # Decode base64.
            decoded = base64.urlsafe_b64decode(token.encode("utf-8")).decode("utf-8")

            # Split payload and signature.
            parts = decoded.split(".", 1)
            if len(parts) != 2:
                return None

            payload_json, signature = parts

            # Verify signature.
            expected_sig = hmac.new(
                secret.encode("utf-8"),
                payload_json.encode("utf-8"),
                hashlib.sha256,
            ).hexdigest()

            if not hmac.compare_digest(expected_sig, signature):
                return None

            # Parse payload.
            payload = json.loads(payload_json)

            # Check expiration.
            if payload.get("exp", 0) < time.time():
                return None

            # Sprint 6.6: Return all fields including custom_fields
            result = {
                "customer_id": payload.get("customer_id"),
                "name": payload.get("name", ""),
                "email": payload.get("email", ""),
                "phone": payload.get("phone", ""),
                "address_street": payload.get("address_street", ""),
                "address_city": payload.get("address_city", ""),
                "address_zip": payload.get("address_zip", ""),
            }

            # Include custom_fields if present
            if "custom_fields" in payload:
                result["custom_fields"] = payload["custom_fields"]

            return result

        except (ValueError, json.JSONDecodeError, UnicodeDecodeError):
            return None