feat: highlight lines, refactorings

src/web/questions/components/HistoryChart.tsx

@@ -1,7 +1,7 @@
 import {
     addDays, differenceInDays, format, startOfDay, startOfToday, startOfTomorrow
 } from "date-fns";
-import React, { useState } from "react";
+import React, { useMemo, useState } from "react";
 import {
     VictoryAxis, VictoryChart, VictoryGroup, VictoryLabel, VictoryLine, VictoryScatter,
     VictoryTheme, VictoryTooltip, VictoryVoronoiContainer
@@ -15,7 +15,17 @@ interface Props {
 
 type DataSet = { x: Date; y: number; name: string }[];
 
-const colors = ["dodgerblue", "crimson", "seagreen", "darkviolet", "turquoise"];
+const MAX_LINES = 5;
+
+// number of colors should match MAX_LINES
+// colors are taken from tailwind, https://tailwindcss.com/docs/customizing-colors
+const colors = [
+  "#0284C7", // sky-600
+  "#DC2626", // red-600
+  "#15803D", // green-700
+  "#7E22CE", // purple-700
+  "#F59E0B", // amber-500
+];
 
 // can't be replaced with React component, VictoryChart requires VictoryGroup elements to be immediate children
 const getVictoryGroup = ({
@@ -29,12 +39,18 @@ const getVictoryGroup = ({
 }) => {
   return (
     <VictoryGroup color={colors[i] || "darkgray"} data={data} key={i}>
+      <VictoryLine
+        name={`line-${i}`}
+        style={{
+          data: {
+            strokeOpacity: highlight ? 1 : 0.5,
+          },
+        }}
+      />
       <VictoryScatter
         name={`scatter-${i}`}
         size={({ active }) => (active || highlight ? 3.75 : 3)}
       />
-
-      <VictoryLine name={`line-${i}`} />
     </VictoryGroup>
   );
 };
@@ -63,13 +79,11 @@ const Legend: React.FC<{
   );
 };
 
-export const HistoryChart: React.FC<Props> = ({ question }) => {
-  const [highlight, setHighlight] = useState<number | undefined>(undefined);
-
+const buildDataSets = (question: QuestionWithHistoryFragment) => {
   let dataSetsNames = question.options
     .sort((a, b) => (a.probability > b.probability ? -1 : 1))
-    .map((o) => o.name);
-  dataSetsNames = [...new Set(dataSetsNames)].slice(0, 5); // take the first 5
+    .map((o) => o.name)
+    .slice(0, MAX_LINES);
 
   const isBinary =
     (dataSetsNames[0] === "Yes" && dataSetsNames[1] === "No") ||
@@ -78,51 +92,45 @@ export const HistoryChart: React.FC<Props> = ({ question }) => {
     dataSetsNames = ["Yes"];
   }
 
-  let dataSets: DataSet[] = [];
-  let maxProbability = 0;
+  const nameToIndex = Object.fromEntries(
+    dataSetsNames.map((name, i) => [name, i])
+  );
+  let dataSets: DataSet[] = [...Array(dataSetsNames.length)].map((x) => []);
 
   const sortedHistory = question.history.sort((a, b) =>
     a.timestamp < b.timestamp ? -1 : 1
   );
 
-  for (const name of dataSetsNames) {
-    let newDataset: DataSet = [];
+  {
     let previousDate = -Infinity;
     for (const item of sortedHistory) {
-      const relevantItemsArray = item.options.filter((x) => x.name === name);
+      if (item.timestamp - previousDate < 12 * 60 * 60) {
+        continue;
+      }
       const date = new Date(item.timestamp * 1000);
-      if (
-        relevantItemsArray.length === 1 &&
-        item.timestamp - previousDate > 12 * 60 * 60
-      ) {
-        let relevantItem = relevantItemsArray[0];
+
+      for (const option of item.options) {
+        const idx = nameToIndex[option.name];
+        if (idx === undefined) {
+          continue;
+        }
         const result = {
           x: date,
-          y: relevantItem.probability,
-          name: relevantItem.name,
+          y: option.probability,
+          name: option.name,
         };
-        maxProbability =
-          relevantItem.probability > maxProbability
-            ? relevantItem.probability
-            : maxProbability;
-        newDataset.push(result);
-        previousDate = item.timestamp;
+        dataSets[idx].push(result);
       }
+      previousDate = item.timestamp;
     }
-    dataSets.push(newDataset);
   }
 
-  const domainMax =
-    maxProbability < 0.5 ? Math.round(10 * (maxProbability + 0.05)) / 10 : 1;
-  const goldenRatio = (1 + Math.sqrt(5)) / 2;
-  const width = 750;
-  const height = width / goldenRatio;
-  const padding = {
-    top: 20,
-    bottom: 60,
-    left: 60,
-    right: 20,
-  };
+  let maxProbability = 0;
+  for (const dataSet of dataSets) {
+    for (const item of dataSet) {
+      maxProbability = Math.max(maxProbability, item.y);
+    }
+  }
 
   const minDate = sortedHistory.length
     ? startOfDay(new Date(sortedHistory[0].timestamp * 1000))
@@ -136,6 +144,36 @@ export const HistoryChart: React.FC<Props> = ({ question }) => {
       )
     : startOfTomorrow();
 
+  const result = {
+    dataSets,
+    dataSetsNames,
+    maxProbability,
+    minDate,
+    maxDate,
+  };
+  return result;
+};
+
+export const HistoryChart: React.FC<Props> = ({ question }) => {
+  const [highlight, setHighlight] = useState<number | undefined>(undefined);
+
+  const { dataSets, dataSetsNames, maxProbability, minDate, maxDate } = useMemo(
+    () => buildDataSets(question),
+    [question]
+  );
+
+  const domainMax =
+    maxProbability < 0.5 ? Math.round(10 * (maxProbability + 0.05)) / 10 : 1;
+  const goldenRatio = (1 + Math.sqrt(5)) / 2;
+  const width = 750;
+  const height = width / goldenRatio;
+  const padding = {
+    top: 20,
+    bottom: 60,
+    left: 60,
+    right: 20,
+  };
+
   return (
     <div className="flex items-center flex-col sm:flex-row">
       <VictoryChart
@@ -190,7 +228,7 @@ export const HistoryChart: React.FC<Props> = ({ question }) => {
             }
             radius={50}
             voronoiBlacklist={
-              [...Array(5).keys()].map((i) => `line-${i}`)
+              [...Array(MAX_LINES).keys()].map((i) => `line-${i}`)
               // see: https://github.com/FormidableLabs/victory/issues/545
             }
           />
@@ -204,9 +242,6 @@ export const HistoryChart: React.FC<Props> = ({ question }) => {
           y: [0, domainMax],
         }}
       >
-        {dataSets.map((dataset, i) =>
-          getVictoryGroup({ data: dataset, i, highlight: i === highlight })
-        )}
         <VictoryAxis
           tickCount={Math.min(7, differenceInDays(maxDate, minDate) + 1)}
           style={{
@@ -234,6 +269,13 @@ export const HistoryChart: React.FC<Props> = ({ question }) => {
           // tickFormat specifies how ticks should be displayed
           tickFormat={(x) => `${x * 100}%`}
         />
+        {
+          dataSets
+            .map((dataSet, i) =>
+              getVictoryGroup({ data: dataSet, i, highlight: i === highlight })
+            )
+            .reverse() // affects svg render order, we want to render largest datasets on top of others
+        }
       </VictoryChart>
       <Legend
         items={dataSetsNames.map((name, i) => ({ name, color: colors[i] }))}