geo2topo

#!/usr/bin/env node

var fs = require("fs"),
    path = require("path"),
    readline = require("readline"),
    commander = require("commander"),
    topojson = require("../");

commander
    .version(require("../package.json").version)
    .usage("[options] <[name=]file>…")
    .description("Converts GeoJSON features to TopoJSON objects.")
    .option("-o, --out <file>", "output file name; defaults to “-” for stdout", "-")
    .option("-n, --newline-delimited", "accept newline-delimited JSON")
    .option("-q, --quantization <count>", "pre-quantization parameter; 0 disables quantization", 0)
    .parse(process.argv);

if (commander.args.length < 1) commander.args[0] = "-";

var nullType = {},
    nullObject = {type: nullType},
    objects = {},
    out = (commander.out === "-" ? process.stdout : fs.createWriteStream(commander.out)).on("error", handleEpipe);

Promise.all(commander.args.map(read)).then(write).catch(abort);

function read(specifier) {
  var i = specifier.indexOf("="),
      file = i >= 0 ? specifier.slice(i + 1) : specifier,
      name = i >= 0 ? specifier.slice(0, i) : path.basename(specifier, path.extname(specifier));
  if (name in objects) {
    console.error();
    console.error("  error: object “" + name + "” is not unique");
    console.error();
    process.exit(1);
  }
  objects[name] = undefined;
  return (commander.newlineDelimited ? readNewlineDelimitedObject : readObject)(file === "-"
      ? process.stdin : fs.createReadStream(file))
      .then(function(object) { objects[name] = object; });
}

function readNewlineDelimitedObject(stream) {
  return new Promise(function(resolve, reject) {
    var collection;
    readline.createInterface({
      input: stream,
      output: null
    }).on("line", function(line) {
      var object = JSON.parse(line);
      if (object == null) object = nullObject;
      switch (object.type) {
        case "Feature": {
          if (collection) {
            if (collection.type !== "FeatureCollection") {
              console.error();
              console.error("  error: expected geometry, not Feature");
              console.error();
              process.exit(1);
            }
            collection.features.push(object);
          } else {
            collection = {type: "FeatureCollection", features: [object]};
          }
          break;
        }
        case nullType:
        case "GeometryCollection":
        case "MultiLineString":
        case "LineString":
        case "Polygon":
        case "MultiPolygon":
        case "Point":
        case "MultiPoint": {
          if (collection) {
            if (collection.type !== "GeometryCollection") {
              console.error();
              console.error("  error: expected Feature, not " + object.type);
              console.error();
              process.exit(1);
            }
            collection.geometries.push(object);
          } else {
            collection = {type: "GeometryCollection", geometries: [object]};
          }
          break;
        }
        default: {
          console.error();
          console.error("  error: expected Feature or geometry, not " + object.type);
          console.error();
          process.exit(1);
          break;
        }
      }
    }).on("close", function() {
      resolve(collection || {type: "FeatureCollection", features: []});
    }).on("error", reject);
  });
}

function readObject(stream) {
  return new Promise(function(resolve, reject) {
    var data = [];
    stream
        .on("data", function(d) { data.push(d); })
        .on("end", function() { resolve(JSON.parse(Buffer.concat(data))); })
        .on("error", reject);
  });
}

function write() {
  out.write(JSON.stringify(topojson.topology(objects, +commander.quantization)));
  out[out === process.stdout ? "write" : "end"]("\n");
}

function handleEpipe(error) {
  if (error.code === "EPIPE" || error.errno === "EPIPE") {
    process.exit(0);
  }
}

function abort(error) {
  console.error(error.stack);
}