Add quality of service option to subscriptions

Fixes #323, #14, #334
Fixes #132

app/src/components/QosSelect.tsx

@@ -0,0 +1,48 @@
+import * as React from 'react'
+import { TextField, MenuItem, Tooltip } from '@material-ui/core'
+import { QoS } from '../../../backend/src/DataSource/MqttSource'
+
+export function QosSelect(props: { selected: QoS; onChange: (value: QoS) => void; label?: string }) {
+  const tooltipStyle = { textAlign: 'center' as 'center', width: '100%' }
+  const itemStyle = { padding: '0' }
+
+  const onChangeQos = React.useCallback(
+    (event: React.ChangeEvent<HTMLInputElement>) => {
+      const value = parseInt(event.target.value, 10)
+      if (value !== 0 && value !== 1 && value !== 2) {
+        return
+      }
+      props.onChange(value)
+    },
+    [props.onChange]
+  )
+
+  return (
+    <TextField
+      select={true}
+      label={props.label}
+      value={props.selected}
+      margin="normal"
+      style={{ margin: '8px 0 8px 8px' }}
+      onChange={onChangeQos}
+    >
+      <MenuItem key={0} value={0} style={itemStyle}>
+        <Tooltip title="At most once">
+          <div style={tooltipStyle}>0</div>
+        </Tooltip>
+      </MenuItem>
+      <MenuItem key={1} value={1} style={itemStyle}>
+        <Tooltip title="At least once">
+          <div style={tooltipStyle}>1</div>
+        </Tooltip>
+      </MenuItem>
+      <MenuItem key={2} value={2} style={itemStyle}>
+        <Tooltip title="Exactly once">
+          <div style={tooltipStyle}>2</div>
+        </Tooltip>
+      </MenuItem>
+    </TextField>
+  )
+}
+
+export default React.memo(QosSelect)