{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "Line drawn between airports in the U.S. simulating a flight itinerary",
  "background": "white",
  "padding": 5,
  "width": 800,
  "height": 500,
  "data": [
    {
      "name": "source_0",
      "url": "data/us-10m.json",
      "format": {"type": "topojson", "feature": "states"}
    },
    {"name": "source_1", "url": "data/airports.csv", "format": {"type": "csv"}},
    {
      "name": "source_2",
      "values": [
        {"airport": "SEA", "order": 1},
        {"airport": "SFO", "order": 2},
        {"airport": "LAX", "order": 3},
        {"airport": "LAS", "order": 4},
        {"airport": "DFW", "order": 5},
        {"airport": "DEN", "order": 6},
        {"airport": "ORD", "order": 7},
        {"airport": "JFK", "order": 8}
      ]
    },
    {
      "name": "data_0",
      "source": "source_1",
      "transform": [
        {
          "type": "geojson",
          "fields": ["longitude", "latitude"],
          "signal": "layer_1_geojson_0"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"],
          "as": ["layer_1_x", "layer_1_y"]
        }
      ]
    },
    {
      "name": "data_1",
      "source": "source_2",
      "transform": [
        {
          "type": "lookup",
          "from": "source_1",
          "key": "iata",
          "fields": ["airport"],
          "values": ["latitude", "longitude"]
        },
        {
          "type": "geojson",
          "fields": ["longitude", "latitude"],
          "signal": "layer_2_geojson_0"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"],
          "as": ["layer_2_x", "layer_2_y"]
        }
      ]
    }
  ],
  "projections": [
    {
      "name": "projection",
      "size": {"signal": "[width, height]"},
      "fit": {
        "signal": "[data('source_0'), layer_1_geojson_0, layer_2_geojson_0]"
      },
      "type": "albersUsa"
    }
  ],
  "marks": [
    {
      "name": "layer_0_marks",
      "type": "shape",
      "style": ["geoshape"],
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "fill": {"value": "#eee"},
          "stroke": {"value": "white"},
          "ariaRoleDescription": {"value": "geoshape"}
        }
      },
      "transform": [{"type": "geoshape", "projection": "projection"}]
    },
    {
      "name": "layer_1_marks",
      "type": "symbol",
      "style": ["circle"],
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "gray"},
          "ariaRoleDescription": {"value": "circle"},
          "description": {
            "signal": "\"longitude: \" + (format(datum[\"longitude\"], \"\")) + \"; latitude: \" + (format(datum[\"latitude\"], \"\"))"
          },
          "x": {"field": "layer_1_x"},
          "y": {"field": "layer_1_y"},
          "size": {"value": 5},
          "shape": {"value": "circle"}
        }
      }
    },
    {
      "name": "layer_2_marks",
      "type": "line",
      "style": ["line"],
      "sort": {"field": ["datum[\"order\"]"], "order": ["ascending"]},
      "from": {"data": "data_1"},
      "encode": {
        "update": {
          "stroke": {"value": "#4c78a8"},
          "description": {
            "signal": "\"longitude: \" + (format(datum[\"longitude\"], \"\")) + \"; latitude: \" + (format(datum[\"latitude\"], \"\")) + \"; order: \" + (isValid(datum[\"order\"]) ? datum[\"order\"] : \"\"+datum[\"order\"])"
          },
          "x": {"field": "layer_2_x"},
          "y": {"field": "layer_2_y"}
        }
      }
    }
  ]
}