Add basic API docs to readme

README.md

@@ -14,6 +14,95 @@ npm install --save @carto/api-client
 
 WORK IN PROGRESS.
 
+### Fetching data
+
+```javascript
+import { vectorTableSource } from '@carto/api-client';
+
+const data = vectorTableSource({
+  accessToken: '••••',
+  connectionName: 'carto_dw',
+  tableName: 'carto-demo-data.demo_tables.retail_stores'
+});
+
+const { widgetSource } = await data;
+
+// → {name: string; value: number}[]
+const categories = await widgetSource.getCategories({
+  column: 'store_type',
+  operation: 'count',
+});
+
+// → {value: number}
+const formula = await widgetSource.getFormula({operation: 'count'});
+
+// → {totalCount: number; rows: Record<string, number | string>[]}
+const table = await widgetSource.getTable({
+  columns: ['a', 'b', 'c'],
+  sortBy: ['a'],
+  rowsPerPage: 20
+});
+
+...
+```
+
+### Column filter
+
+To filter the widget source by a non-geospatial column, pass a `filters`
+property to the source factory function.
+
+```javascript
+import { vectorTableSource } from '@carto/api-client';
+
+const data = vectorTableSource({
+  accessToken: '••••',
+  connectionName: 'carto_dw',
+  tableName: 'carto-demo-data.demo_tables.retail_stores',
+  filters: {
+    'store_type': {owner: 'widget-id', values: ['retail']}
+  }
+});
+```
+
+By default, filters affect all layers and widgets using a given data source. To
+exclude a particular widget from the filter, pass a `filterOwner` parameter
+matching the filters from which it should be excluded. In some cases, a widget's
+results should not be affected by a filter that the widget itself created.
+
+```javascript
+// → {name: string; value: number}[]
+const categories = await widgetSource.getCategories({
+  filterOwner: 'widget-id',
+  column: 'store_type',
+  operation: 'count',
+});
+```
+
+### Spatial filter
+
+To filter the widget source by a geospatial column, including the map viewport,
+pass a `spatialFilter` parameter (GeoJSON Polygon or MultiPolygon geometry) to any widget data fetching function.
+
+```javascript
+// → {name: string; value: number}[]
+const categories = await widgetSource.getCategories({
+  column: 'store_type',
+  operation: 'count',
+  spatialFilter: {
+    type: "Polygon"
+    coordinates: [
+      [
+        [-74.0562, 40.8331],
+        [-74.0562, 40.6933],
+        [-73.8734, 40.6933],
+        [-73.8734, 40.8331],
+        [-74.0562, 40.8331]
+      ]
+    ],
+  }
+});
+```
+
 ## Versioning
 
 Package versioning follows [Semantic Versioning 2.0.0](https://semver.org/).