decode.js

var fs = require("fs");

function decode(encoded) {
    var path = [];

    for (var i = 0, j = 0, n = [0, 0]; i < encoded.length; i++) {
        var k = encoded.charCodeAt(i) - 0x30;
        n[j] = (n[j] << 5) | k & 0x1f;
        if ((k & 0x20)) {
            n[j] = ((n[j] & 0x01) ? (~(n[j] >> 1)) : (n[j] >> 1)) * 1e-7;
            if (++j == 2) {
                var latLon = path.length > 0 ? path[path.length - 1] : [0, 0];
                path.push([latLon[0] + n[0], latLon[1] + n[1]]);
            }
            n[j = j % 2] = 0;
        }
    }

    return path.map(function (latLon) {
        return [latLon[1], latLon[0]];
    });
}

var paths = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    },
    bases = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    },
    caves = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    },
    nodes = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    },
    places = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    },
    shelters = {
        type: "FeatureCollection",
        crs: {
            type: "name",
            properties: {
                name: "urn:ogc:def:crs:OGC:1.3:CRS84"
            }
        },
        features: []
    };

fs.readdirSync("./dat").forEach(function (filename) {
    var json,
        file = fs.readFileSync("./dat/" + filename, { encoding: "utf-8" });

    json = JSON.parse(file);

    Object.keys(json.trails).forEach(function (id) {
        var trail = json.trails[id];

        paths.features.push({
            type: "Feature",
            geometry: {
                type: "LineString",
                coordinates: decode(trail.encoded)
            },
            properties: {
                name: trail.name,
                colors: trail.colors.map(function (hsl) {
                    return "hsl(" + hsl.split(",").join(", ") + ")";
                }),
                times: trail.times,
                distance: trail.distance
            }
        });
    });

    Object.keys(json.nodes).forEach(function (id) {
        var node = json.nodes[id],
            feature = {
                type: "Feature",
                geometry: {
                    type: "Point",
                    coordinates: [node.coord[1], node.coord[0]]
                },
                properties: {
                    name: node.name,
                    elevation: node.elevation
                }
            };

        switch(node.icon) {
        case "base,24,96":
            bases.features.push(feature);
            break;
        case "cave,24,72":
            caves.features.push(feature);
            break;
        case "node,10,24":
            nodes.features.push(feature);
            break;
        case "place,24,120":
            places.features.push(feature);
            break;
        case "shelter,24,48":
            shelters.features.push(feature);
            break;
        default:
            console.log("unknown type: " + node.icon);
        }
    });
});

fs.writeFileSync("paths.json", JSON.stringify(paths));
fs.writeFileSync("bases.json", JSON.stringify(bases));
fs.writeFileSync("caves.json", JSON.stringify(caves));
fs.writeFileSync("nodes.json", JSON.stringify(nodes));
fs.writeFileSync("places.json", JSON.stringify(places));
fs.writeFileSync("shelters.json", JSON.stringify(shelters));