Add data source renderer

app/src/tiles/renderers/datasourceRenderer.ts

@@ -0,0 +1,105 @@
+import path from 'path';
+
+import mapnik from "mapnik";
+
+import { TileParams, TileRenderer } from "../types";
+import { getBbox, TILE_SIZE } from "../util";
+import { promisify } from "util";
+
+interface DataConfig {
+    table: string;
+    geometry_field: string;
+}
+
+const TILE_BUFFER_SIZE = 64;
+const PROJ4_STRING = '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over';
+
+// connection details from environment variables
+const DATASOURCE_CONFIG = {
+    'host': process.env.PGHOST,
+    'dbname': process.env.PGDATABASE,
+    'user': process.env.PGUSER,
+    'password': process.env.PGPASSWORD,
+    'port': process.env.PGPORT,
+    'extent': '-20005048.4188,-9039211.13765,19907487.2779,17096598.5401',
+    'srid': 3857,
+    'type': 'postgis'
+};
+
+// register datasource adapters for mapnik database connection
+if (mapnik.register_default_input_plugins) {
+    mapnik.register_default_input_plugins();
+}
+// register fonts for text rendering
+mapnik.register_default_fonts();
+
+
+class DatasourceRenderer implements TileRenderer {
+    constructor(private getTableDefinitionFn: (tileset: string, dataParams: any) => DataConfig) {}
+
+    async getTile({tileset, z, x, y, scale}: TileParams, dataParams: any): Promise<mapnik.Image> {
+        const bbox = getBbox(z, x, y);
+
+        const tileSize = TILE_SIZE * scale;
+        let map = new mapnik.Map(tileSize, tileSize, PROJ4_STRING);
+        map.bufferSize = TILE_BUFFER_SIZE;
+        const layer = new mapnik.Layer('tile', PROJ4_STRING);
+
+        const dataSourceConfig = this.getTableDefinitionFn(tileset, dataParams);
+
+        const conf = Object.assign(dataSourceConfig, DATASOURCE_CONFIG);
+
+        const postgis = new mapnik.Datasource(conf);
+        layer.datasource = postgis;
+        layer.styles = [tileset];
+
+        const stylePath = path.join(__dirname, '..', 'map_styles', 'polygon.xml');
+
+        map = await promisify(map.load.bind(map))(stylePath, {strict: true});
+
+        map.add_layer(layer);
+        const im = new mapnik.Image(map.width, map.height);
+        map.extent = bbox;
+        const rendered = await promisify(map.render.bind(map))(im, {});
+
+        return await promisify(rendered.encode.bind(rendered))('png');
+    }
+}
+
+function promiseHandler(resolve, reject) {
+    return function(err, result) {
+        if(err) reject(err);
+        else resolve(result);
+    }
+}
+
+/**
+ * Utility function which promisifies a method of an object and binds it to the object
+ * This makes it easier to use callback-based object methods in a promise-based way
+ * @param obj Object containing the target method
+ * @param methodName Method name to promisify and return
+ */
+function promisifyMethod<T, F>(obj: T, methodName: keyof T);
+/**
+ * @param methodGetter accessor function to get the method from the object
+ */
+function promisifyMethod<T, S>(obj: T, methodGetter: (o: T) => S);
+function promisifyMethod<T, S>(obj: T, paramTwo: keyof T | ((o: T) => S)) {
+    let method;
+    if (typeof paramTwo === 'string') {
+        method = obj[paramTwo];
+    } else if (typeof paramTwo === 'function') {
+        method = paramTwo(obj);
+    }
+
+    if (typeof method === 'function') {
+        return promisify(method.bind(obj));
+    } else {
+        throw new Error(`Cannot promisify non-function property '${paramTwo}'`);
+    }
+}
+
+export {
+    DatasourceRenderer,
+    DataConfig
+};