@loaders.gl/mvt/src/lib/get-schemas-from-tilejson.ts

Loader for Mapbox Vector Tiles

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

import type {Schema, Field, DataType, SchemaMetadata, FieldMetadata} from '@loaders.gl/schema';
import type {TileJSONLayer, TileJSONField} from './parse-tilejson';

// LAYERS

export function getSchemaFromTileJSONLayer(layer: TileJSONLayer): Schema {
  const fields: Field[] = [];
  if (layer.fields) {
    for (const field of layer.fields) {
      fields.push({
        name: field.name,
        type: getDataTypeFromTileJSONField(field),
        metadata: getMetadataFromTileJSONField(field)
      });
    }
  }
  return {
    metadata: getMetadataFromTileJSONLayer(layer),
    fields
  };
}

function getMetadataFromTileJSONLayer(layer: TileJSONLayer): SchemaMetadata {
  const metadata: Record<string, string> = {};
  for (const [key, value] of Object.entries(layer)) {
    if (key !== 'fields' && value) {
      metadata[key] = JSON.stringify(value);
    }
  }
  return metadata;
}

// FIELDS

function getDataTypeFromTileJSONField(field: TileJSONField): DataType {
  switch (field.type.toLowerCase()) {
    case 'float32':
      return 'float32';
    case 'number':
    case 'float64':
      return 'float64';
    case 'string':
    case 'utf8':
      return 'utf8';
    case 'boolean':
      return 'bool';
    default:
      return 'null';
  }
}

function getMetadataFromTileJSONField(field: TileJSONField): FieldMetadata {
  const metadata: Record<string, string> = {};
  for (const [key, value] of Object.entries(field)) {
    if (key !== 'name' && value) {
      metadata[key] = JSON.stringify(value);
    }
  }
  return metadata;
}