Refactor chart

app/src/components/Chart/effects/useCustomYDomain.tsx

@@ -0,0 +1,39 @@
+import { Props } from '../Chart'
+import { useMemo } from 'react'
+import { Point } from '../Model'
+
+export function useCustomYDomain(props: Props) {
+  return useMemo(() => {
+    const data = props.data
+    const calculatedDomain = domainForData(data)
+    const yDomain: [number, number] = props.range
+      ? [props.range[0] || calculatedDomain[0], props.range[1] || calculatedDomain[1]]
+      : calculatedDomain
+
+    return yDomain
+  }, [props.data])
+}
+
+function domainForData(data: Array<Point>): [number, number] {
+  if (!data[0]) {
+    const defaultDomain: [number, number] = [-1, 1]
+    return defaultDomain
+  }
+  let max = data[0].y
+  let min = data[0].y
+  data.forEach(d => {
+    if (max < d.y) {
+      max = d.y
+    }
+    if (min > d.y) {
+      min = d.y
+    }
+  })
+  if ((max === 1 || max === 0) && (min === 1 || min === 0)) {
+    return [0, 1]
+  }
+  if (min === max) {
+    return [min - 0.5 * min, min + 0.5 * min]
+  }
+  return [min, max]
+}