Moves out chart (data modelling) helpers to a separate file

components/helpers/chart.js

@@ -0,0 +1,67 @@
+import { scaleObservable, unitObservable } from '../../local-storage'
+import config from '../../config'
+
+export function normalizeToScale(temp, columnHeight) {
+  const scale = scaleObservable.value
+  const valueRelativeToScale = (scale.max - temp) / (scale.max - scale.min)
+  return getAbsoluteValue(valueRelativeToScale, columnHeight)
+}
+
+function getAbsoluteValue(relative, columnHeight) {
+  // we add some height to have some breathing room
+  const verticalPadding = columnHeight * config.temperatureScale.verticalPadding
+  const scaleHeight = columnHeight - 2 * verticalPadding
+  return scaleHeight * relative + verticalPadding
+}
+
+export function getTickPositions(columnHeight) {
+  const units = unitObservable.value
+  const scaleMin = scaleObservable.value.min
+  const scaleMax = scaleObservable.value.max
+  const numberOfTicks = (scaleMax - scaleMin) * (1 / units) + 1
+  const tickDistance = 1 / (numberOfTicks - 1)
+  const tickPositions = []
+  for (let i = 0; i < numberOfTicks; i++) {
+    const position = getAbsoluteValue(tickDistance * i, columnHeight)
+    tickPositions.push(position)
+  }
+  return tickPositions
+}
+
+export function getTickList(columnHeight) {
+
+  const units = unitObservable.value
+  const scaleMax = scaleObservable.value.max
+
+  return getTickPositions(columnHeight).map((tickPosition, i) => {
+
+    const tick = scaleMax - i * units
+    let isBold, label, shouldShowLabel
+
+    if (Number.isInteger(tick)) {
+      isBold = true
+      label = tick.toString() + '.0'
+    } else {
+      isBold = false
+      label = tick.toString()
+    }
+
+    // when temp range <= 3, units === 0.1 we show temp values with step 0.2
+    // when temp range > 3, units === 0.5 we show temp values with step 0.5
+
+    if (units === 0.1) {
+      // show label with step 0.2
+      shouldShowLabel = !(tick * 10 % 2)
+    } else {
+      // show label with step 0.5
+      shouldShowLabel = !(tick * 10 % 5)
+    }
+
+    return {
+      position: tickPosition,
+      label,
+      isBold,
+      shouldShowLabel,
+    }
+  })
+}