From 5f4611d65e40eae3ca6191a15f68d69ea5a1c4cb Mon Sep 17 00:00:00 2001
From: Kirill Rogovoy <kirill@rogovoy.me>
Date: Tue, 20 Jul 2021 21:24:52 +0300
Subject: WIP

---
 app_expo/components/switch/switch.tsx | 114 ++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 app_expo/components/switch/switch.tsx

(limited to 'app_expo/components/switch/switch.tsx')

diff --git a/app_expo/components/switch/switch.tsx b/app_expo/components/switch/switch.tsx
new file mode 100644
index 0000000..845d964
--- /dev/null
+++ b/app_expo/components/switch/switch.tsx
@@ -0,0 +1,114 @@
+import React from 'react'
+import { ViewStyle, Animated, Easing, TouchableWithoutFeedback } from 'react-native'
+import { color } from '../../theme'
+import { SwitchProps } from './switch.props'
+
+// dimensions
+const THUMB_SIZE = 30
+const WIDTH = 56
+const MARGIN = 2
+const OFF_POSITION = -0.5
+const ON_POSITION = WIDTH - THUMB_SIZE - MARGIN
+const BORDER_RADIUS = (THUMB_SIZE * 3) / 4
+
+// colors
+const ON_COLOR = color.primary
+const OFF_COLOR = color.palette.offWhite
+const BORDER_ON_COLOR = ON_COLOR
+const BORDER_OFF_COLOR = 'rgba(0, 0, 0, 0.1)'
+
+// animation
+const DURATION = 250
+
+// the track always has these props
+const TRACK = {
+  height: THUMB_SIZE + MARGIN,
+  width: WIDTH,
+  borderRadius: BORDER_RADIUS,
+  borderWidth: MARGIN / 2,
+  backgroundColor: color.background,
+}
+
+// the thumb always has these props
+const THUMB: ViewStyle = {
+  position: 'absolute',
+  width: THUMB_SIZE,
+  height: THUMB_SIZE,
+  borderColor: BORDER_OFF_COLOR,
+  borderRadius: THUMB_SIZE / 2,
+  borderWidth: MARGIN / 2,
+  backgroundColor: color.background,
+  shadowColor: BORDER_OFF_COLOR,
+  shadowOffset: { width: 1, height: 2 },
+  shadowOpacity: 1,
+  shadowRadius: 2,
+  elevation: 2,
+}
+
+const makeAnimatedValue = (switchOn) => new Animated.Value(switchOn ? 1 : 0)
+
+export function Switch(props: SwitchProps) {
+  const [timer] = React.useState<Animated.Value>(makeAnimatedValue(props.value))
+  const startAnimation = React.useMemo(
+    () => (newValue: boolean) => {
+      const toValue = newValue ? 1 : 0
+      const easing = Easing.out(Easing.circle)
+      Animated.timing(timer, {
+        toValue,
+        duration: DURATION,
+        easing,
+        useNativeDriver: true,
+      }).start()
+    },
+    [timer],
+  )
+
+  const [previousValue, setPreviousValue] = React.useState<boolean>(props.value)
+  React.useEffect(() => {
+    if (props.value !== previousValue) {
+      startAnimation(props.value)
+      setPreviousValue(props.value)
+    }
+  }, [props.value])
+
+  const handlePress = React.useMemo(
+    () => () => props.onToggle && props.onToggle(!props.value),
+    [props.onToggle, props.value],
+  )
+
+  if (!timer) {
+    return null
+  }
+
+  const translateX = timer.interpolate({
+    inputRange: [0, 1],
+    outputRange: [OFF_POSITION, ON_POSITION],
+  })
+
+  const style = props.style
+
+  const trackStyle = [
+    TRACK,
+    {
+      backgroundColor: props.value ? ON_COLOR : OFF_COLOR,
+      borderColor: props.value ? BORDER_ON_COLOR : BORDER_OFF_COLOR,
+    },
+    props.value ? props.trackOnStyle : props.trackOffStyle,
+  ]
+
+  const thumbStyle = [
+    THUMB,
+    {
+      transform: [{ translateX }],
+    },
+    props.value ? props.thumbOnStyle : props.thumbOffStyle,
+  ]
+
+  return (
+    <TouchableWithoutFeedback onPress={handlePress} style={style}>
+      <Animated.View style={trackStyle}>
+        <Animated.View style={thumbStyle} />
+      </Animated.View>
+    </TouchableWithoutFeedback>
+  )
+}
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