OSM move waterway tags to parent relations

waterway-tags-to-relations.js

/*
Overpass QL for the input file (waterway-rels.osm):

```
[out:xml][timeout:90];
{{geocodeArea:slovakia}}->.searchArea;
(
  relation["type"="waterway"](area.searchArea);
);
(._;>;);
out meta;
```
*/

const fs = require("fs");
const xml2js = require("xml2js");

let data;

xml2js.parseString(fs.readFileSync("waterway-rels.osm"), (err, result) => {
  data = result;
});

const wayMap = new Map();

for (const way of data.osm.way) {
  wayMap.set(way.$.id, way);
}

rel: for (const relation of data.osm.relation) {
  const tags = tagsToMap(relation);

  const members = ensureArray(relation.member);

  const ways = members
    .filter((member) => member.$.type === "way")
    .map((member) => wayMap.get(member.$.ref));

  let modifyRel = false;

  for (const way of ways) {
    let conflict = false;

    for (const tag of ensureArray(way.tag)) {
      const key = tag.$.k;
      const value = tag.$.v;

      if (
        key.startsWith("name:") ||
        key.endsWith("_name") ||
        key === "wikipedia" ||
        key === "wikidata" ||
        key === "ref" ||
        key === "destination"
      ) {
        if (!tags[key]) {
          tags[key] = value;

          modifyRel = true;
        } else if (tags[key] !== value) {
          console.error(
            `Conflict! "${key}"="${tags[key]}" vs "${value}" r${relation.$.id} w${way.$.id}`
          );

          conflict = true;
        }
      }
    }

    if (conflict) {
      continue rel;
    }
  }

  for (let i = 0; i < ways.length; i++) {
    const way = ways[i];

    const tagArray = ensureArray(way.tag);

    for (let j = tagArray.length - 1; j >= 0; j--) {
      const tag = tagArray[j];
      const key = tag.$.k;
      const value = tag.$.v;

      if (
        key.startsWith("name:") ||
        key.endsWith("_name") ||
        key === "wikipedia" ||
        key === "wikidata" ||
        key === "ref" ||
        key === "destination"
      ) {
        way.$.action = "modify";

        tagArray.splice(j, 1);
      }
    }
  }

  if (modifyRel) {
    relation.$.action = "modify";

    relation.tag = Object.entries(tags).map(([k, v]) => ({
      $: {
        k,
        v,
      },
    }));
  }
}

const builder = new xml2js.Builder();
console.log(builder.buildObject(data));

function tagsToMap(a) {
  const tags = {};

  for (const tag of ensureArray(a.tag)) {
    tags[tag.$.k] = tag.$.v;
  }

  return tags;
}

function ensureArray(a) {
  return !a ? [] : Array.isArray(a) ? a : [a];
}