website_next: snapshot

website_next/chart/loader.js

@@ -0,0 +1,55 @@
+import { brk } from "../utils/client.js";
+import { fetchTimeframe } from "./timeframes.js";
+
+/**
+ * @param {ChartResult} result
+ * @returns {ChartEntry[]}
+ */
+function createEntries(result) {
+  /** @type {ChartEntry[]} */
+  const entries = [];
+  /** @type {number | undefined} */
+  let lastValue;
+
+  for (const [date, value] of result.dateEntries()) {
+    if (typeof value === "number" && Number.isFinite(value)) lastValue = value;
+    if (lastValue !== undefined) entries.push({ date, value: lastValue });
+  }
+
+  return entries;
+}
+
+/**
+ * @param {Chart} chart
+ * @param {TimeframeValue} timeframe
+ */
+function loadSeries(chart, timeframe) {
+  return Promise.all(
+    chart.series.map(async (item) => ({
+      series: item,
+      color: item.color(),
+      entries: createEntries(await fetchTimeframe(item.metric(brk), timeframe)),
+    })),
+  );
+}
+
+/** @param {Chart} chart */
+export function createSeriesLoader(chart) {
+  /** @type {TimeframeValue | undefined} */
+  let cachedTimeframe;
+  /** @type {Promise<LoadedSeries[]> | undefined} */
+  let cachedPromise;
+
+  /** @param {TimeframeValue} timeframe */
+  return function loadTimeframe(timeframe) {
+    if (timeframe !== cachedTimeframe || !cachedPromise) {
+      cachedTimeframe = timeframe;
+      cachedPromise = loadSeries(chart, timeframe).catch((error) => {
+        if (timeframe === cachedTimeframe) cachedPromise = undefined;
+        throw error;
+      });
+    }
+
+    return cachedPromise;
+  };
+}