mapshaper-info-recreated-via-gdal

index.js

import fs from 'fs'
import got from 'got'
import gdal from 'gdal-async'
import { pipeline } from 'stream/promises'

const url = 'https://github.com/deldersveld/topojson/raw/master/countries/germany/germany-regions.json'
const fileName = url.substring(url.lastIndexOf('/') + 1)

const downloadStream = got.stream(url)
const fileWriterStream = fs.createWriteStream(fileName)

// function getAllPropertyNames(obj) {
//   var props = [];

//   do {
//     Object.getOwnPropertyNames(obj).forEach(function (prop) {
//       if (props.indexOf(prop) === -1 ) {
//         props.push( prop );
//       }
//     });
//   } while (obj = Object.getPrototypeOf(obj));

//   return props;
// }

downloadStream.on("downloadProgress", ({ transferred, total, percent }) => {
  const percentage = Math.round(percent * 100)
  //console.error(`progress: ${transferred}/${total} (${percentage}%)`)
});

async function main() {
  try {
    await pipeline(downloadStream, fileWriterStream)
    // console.log(`File downloaded to ${fileName}`)
    const ds = gdal.open(fileName)
    console.log(`[info]\n==================================================`)
    for (const layer of ds.layers) {
      // console.log(layer.features)
      console.log(`Layer:    ${layer.name}`)
      console.log('--------------------------------------------------')
      console.log(`Type:     ${gdal.Geometry.getName(layer.geomType)}`)
      console.log(`Records:  ${layer.features.count()}`)
      const extent = layer.getExtent()
      const {minX, minY, maxX, maxY} = extent
      console.log(`Bounds:   ${minX},${minY},${maxX},${maxY}`)
      let crs = null
      if (ds.driver.description == 'TopoJSON') {
        crs = '+proj=longlat +datum=WGS84'
        let json_content = fs.readFileSync(fileName)
        json_content = JSON.parse(json_content)
        // Issue with Mapshaper: it reports polygon whereas there are polygon and multipolygon
        // (uncomment below to confirm)
        // console.log(json_content.objects[layer.name].geometries.map(el => el.type))
      } else if (layer.srs) {
        crs = layer.srs.toWKT()
      }
      console.log(
        `CRS:      ${crs}`
      )
      console.log(`Source:   ${fileName}`)

      // console.log('  Fields: ')
      var first = layer.features.first()
      // console.log(first)

      const content = first.defn.fields.map(f => [f.name, first.fields.get(f.name)])
      let max_length_attribute_name = Math.max(...content.filter(el => !!(el[0])).map(el => el[0].length))
      if (max_length_attribute_name < 7) {
        max_length_attribute_name = 7
      }
      let max_length_attribute_value = Math.max(...content.filter(el => !!(el[1])).map(el => `${el[1]}`.length))
      if (max_length_attribute_value < 13) {
        max_length_attribute_value = 13
      }
      if (content.length > 0) {
        console.log(`\nAttribute data`)
        console.log(`${'-'.repeat(max_length_attribute_name + 2)}+--------------------------------------`)
        console.log(` Field ${' '.repeat(max_length_attribute_name - 5)}| First value`)
        console.log(`${'-'.repeat(max_length_attribute_name + 2)}+--------------------------------------`)
      }
      // console.log(max_length_attribute_name)
      // console.log(max_length_attribute_value)
      console.log(content
        .filter(el => el[0] != 'id')
        .slice()
        .sort((a, b) => a[0].localeCompare(b[0]))
        .map(el => ` ${el[0]} ${' '.repeat(max_length_attribute_name - el[0].length)}| ${el[1]}`)
        .join('\n'))
      console.log(`${'-'.repeat(max_length_attribute_name + 2)}+--------------------------------------`)
    }
  } catch (error) {
    console.error(`Something went wrong. ${error.message}`);
  }
}

main().catch(error => {
  console.error(error)
  process.exit(1)
})

package.json

{
  "name": "mapshaper-info-recreated-via-gdal",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "type": "module",
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "gdal-async": "^3.5.1",
    "got": "^12.4.1"
  }
}