import { readFile } from 'node:fs/promises';

export type FeatureGeometry = {
  type: 'Polygon' | 'MultiPolygon';
  coordinates: unknown;
};

export type GeoJsonFeature = {
  type: 'Feature';
  properties?: Record<string, unknown> | null;
  geometry?: FeatureGeometry | null;
};

export type GeoJsonFeatureCollection = {
  type: 'FeatureCollection';
  features: GeoJsonFeature[];
};

export type PostalDatasetConfig = {
  countryCode: 'US' | 'CA';
  label: string;
  filePath: string;
  postalCodeKeys: string[];
  displayNameKeys: string[];
};

export async function readFeatureCollection(filePath: string) {
  const raw = await readFile(filePath, 'utf8');
  const parsed = JSON.parse(raw) as GeoJsonFeatureCollection;

  if (parsed.type !== 'FeatureCollection' || !Array.isArray(parsed.features)) {
    throw new Error(`Dataset at ${filePath} is not a valid GeoJSON FeatureCollection.`);
  }

  return parsed;
}

export function normalizePostalCode(countryCode: 'US' | 'CA', rawPostalCode: string) {
  const trimmed = rawPostalCode.trim();

  if (countryCode === 'US') {
    const digits = trimmed.replace(/\D/g, '').slice(0, 5);
    return digits.length === 5 ? digits : null;
  }

  const compact = trimmed.replace(/\s+/g, '').toUpperCase();
  return compact.length >= 3 ? compact.slice(0, 3) : null;
}

export function getStringProperty(properties: Record<string, unknown> | null | undefined, keys: string[]) {
  if (!properties) {
    return null;
  }

  for (const key of keys) {
    const value = properties[key];

    if (typeof value === 'string' && value.trim().length > 0) {
      return value.trim();
    }

    if (typeof value === 'number' && Number.isFinite(value)) {
      return String(value);
    }
  }

  return null;
}

export function getFeatureGeometry(feature: GeoJsonFeature, filePath: string, index: number) {
  if (!feature.geometry || (feature.geometry.type !== 'Polygon' && feature.geometry.type !== 'MultiPolygon')) {
    throw new Error(`Feature ${index} in ${filePath} is missing a Polygon or MultiPolygon geometry.`);
  }

  return feature.geometry;
}