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website/src/lib/scripts/example-statistics.ts

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+/**
+ * Computes the statistics of `assets/example.gpx` with the engine, and writes them to
+ * `assets/example-data.ts`, where the pages that show an example (the home page, the
+ * documentation) take them from. Run it when the example, or the way the engine computes the
+ * statistics, changes:
+ *
+ *     npm run generate:example
+ *
+ * The engine has to be built (`wasm-pack build wasm --target bundler --out-dir ../pkg`, in
+ * `gpx-rs`).
+ */
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath, pathToFileURL } from 'url';
+import prettier from 'prettier';
+
+const here = path.dirname(fileURLToPath(import.meta.url));
+const assets = path.resolve(here, '../assets');
+const packageDirectory = path.resolve(here, '../../../../gpx-rs/pkg');
+
+export const exampleGPX = path.join(assets, 'example.gpx');
+export const exampleData = path.join(assets, 'example-data.ts');
+
+/** Whether the engine is built. */
+export function engineIsBuilt() {
+    return fs.existsSync(path.join(packageDirectory, 'gpx_rs_bg.wasm'));
+}
+
+/** Loads the engine in Node: the package is made for bundlers, which import the wasm file. */
+async function loadEngine() {
+    const glue = await import(pathToFileURL(path.join(packageDirectory, 'gpx_rs_bg.js')).href);
+    const { instance } = await WebAssembly.instantiate(
+        fs.readFileSync(path.join(packageDirectory, 'gpx_rs_bg.wasm')),
+        { './gpx_rs_bg.js': glue }
+    );
+    glue.__wbg_set_wasm(instance.exports);
+    (instance.exports.__wbindgen_start as () => void)();
+    return glue as typeof import('gpx-rs');
+}
+
+type Values = Float64Array | BigInt64Array | undefined;
+
+/** The arrays that the engine has for the example, which are all the pages need. */
+export async function computeExampleData() {
+    const engine = await loadEngine();
+    engine.start();
+    const data = fs.readFileSync(exampleGPX);
+    engine.load_files(new Uint8Array(data), Uint32Array.from([data.length]), ['example']);
+
+    // numbers are enough for the times, which are milliseconds
+    const numbers = (values: Values) =>
+        values && Array.from(values as ArrayLike<number | bigint>, (value) => Number(value));
+    return {
+        global: engine.selection_statistics(),
+        totalDistance: numbers(engine.total_distance()),
+        movingDistance: numbers(engine.moving_distance()),
+        totalTime: numbers(engine.total_time()),
+        movingTime: numbers(engine.moving_time()),
+        elevationGain: numbers(engine.elevation_gain()),
+        elevationLoss: numbers(engine.elevation_loss()),
+        slope: numbers(engine.slope()),
+        slopeSegmentSlope: numbers(engine.slope_segment_slope()),
+        slopeSegmentDistance: numbers(engine.slope_segment_distance()),
+        lng: numbers(engine.lng()),
+        lat: numbers(engine.lat()),
+        ele: numbers(engine.ele()),
+        timestamps: numbers(engine.timestamps()),
+        speed: numbers(engine.speed()),
+        atemp: numbers(engine.atemp()),
+    };
+}
+
+async function generate() {
+    const data = await computeExampleData();
+    const source = `// Generated by src/lib/scripts/example-statistics.ts from example.gpx: do not edit.
+export const exampleData = ${JSON.stringify(data)};
+`;
+    const options = (await prettier.resolveConfig(exampleData)) ?? {};
+    fs.writeFileSync(
+        exampleData,
+        await prettier.format(source, { ...options, parser: 'typescript' })
+    );
+    console.log(`Wrote ${path.relative(process.cwd(), exampleData)}`);
+}
+
+if (process.argv[1] && pathToFileURL(process.argv[1]).href === import.meta.url) {
+    generate();
+}