"""User settings validation and defaults."""

import json
import logging
import re

from config import MAX_COMMUNITY_NAME_LENGTH
from security import is_safe_filterset

logger = logging.getLogger(__name__)


class SettingsService:
    """Parse and sanitize user settings JSON shared by page and API routes."""

    EXPERIENCE_DEFAULTS = {
        "infinite_scroll": False,
        "auto_refresh": False,
        "push_notifications": False,
        "dark_patterns_opt_in": False,
        "time_filter_enabled": False,
        "time_filter_days": 7,
    }

    EXPERIENCE_BOOL_FIELDS = {
        "infinite_scroll",
        "auto_refresh",
        "push_notifications",
        "dark_patterns_opt_in",
        "time_filter_enabled",
    }

    @classmethod
    def parse(cls, settings_str):
        """Return settings JSON as a dict, or an empty dict if invalid."""
        if not settings_str:
            return {}
        try:
            settings = json.loads(settings_str)
        except json.JSONDecodeError as e:
            logger.warning(f"Invalid user settings JSON: {e}")
            return {}
        if not isinstance(settings, dict):
            logger.warning("User settings must be a JSON object")
            return {}
        return settings

    @classmethod
    def validate(cls, settings_str):
        """Validate and sanitize persisted user settings JSON."""
        settings = cls.parse(settings_str)
        validated = {}

        filter_set = settings.get("filter_set")
        if isinstance(filter_set, str) and is_safe_filterset(filter_set):
            validated["filter_set"] = filter_set

        communities = settings.get("communities")
        if isinstance(communities, list):
            safe_communities = []
            for community in communities:
                if (
                    isinstance(community, str)
                    and len(community) <= MAX_COMMUNITY_NAME_LENGTH
                    and re.match(r"^[a-zA-Z0-9_-]+$", community)
                ):
                    safe_communities.append(community)
            validated["communities"] = safe_communities

        experience = settings.get("experience")
        if isinstance(experience, dict):
            safe_experience = {}
            for field in cls.EXPERIENCE_BOOL_FIELDS:
                if field in experience and isinstance(experience[field], bool):
                    safe_experience[field] = experience[field]

            time_filter_days = experience.get("time_filter_days")
            if isinstance(time_filter_days, int) and time_filter_days > 0:
                safe_experience["time_filter_days"] = time_filter_days

            validated["experience"] = safe_experience

        return validated

    @classmethod
    def experience_settings(cls, settings_str):
        """Return experience settings with defaults filled in."""
        settings = cls.parse(settings_str)
        experience = settings.get("experience", {})
        if not isinstance(experience, dict):
            experience = {}
        return {**cls.EXPERIENCE_DEFAULTS, **experience}