1 files changed, 130 insertions, 0 deletions
diff --git a/src/pages/Timer/TimerButton.tsx b/src/pages/Timer/TimerButton.tsx
new file mode 100644
index 0000000..0a3bf38
--- /dev/null
+++ b/src/pages/Timer/TimerButton.tsx
@@ -0,0 +1,130 @@
+import React, { useState, useEffect } from 'react';
+
+import { Paper, Typography } from '@material-ui/core';
+import { makeStyles } from '@material-ui/core/styles';
+
+const useStyles = makeStyles(theme => ({
+  root: {
+    textAlign: 'center',
+    padding: theme.spacing(5),
+    background: theme.palette.background.elevation3,
+    marginTop: theme.spacing(10),
+  },
+}));
+
+
+interface PropTypes {
+  registerResult: (result: string) => void;
+}
+
+type Mode = 'idle' | 'countdown' | 'running' | 'over';
+
+
+const TimerButton: React.FC<PropTypes> = ({ registerResult }) => {
+  const classes = useStyles();
+
+  const SPACE = 32;
+  const maxCountdown = 15000;
+  const [time, setTime] = useState<string>('00:00:00');
+  const [mode, setMode] = useState<Mode>('idle');
+
+  useEffect(()=> {
+    const timestamp = Date.now();
+
+    if (mode === 'countdown') {
+      const repeater = setInterval(() => {
+        const timeDelta = maxCountdown - (Date.now() - timestamp);
+        if (timeDelta <= 0) setMode('over');
+        setTime(convertTimeToString(timeDelta));
+      }, 10);
+      return (): void => clearInterval(repeater);
+    }
+
+    if (mode === 'running') {
+      const repeater = setInterval(() => {
+        setTime(convertTimeToString(Date.now() - timestamp));
+      }, 10);
+      return (): void => clearInterval(repeater);
+    }
+
+    if (mode === 'over') {
+      setTime('00:00:00');
+    }
+  }, [mode]);
+
+  const handleKeyPress = (event: KeyboardEvent): void => {
+    event.preventDefault();
+    if (event.keyCode === SPACE && mode === 'idle' ) setMode('countdown');
+  };
+
+  const handleKeyUp = (event: KeyboardEvent): void => {
+    if (event.keyCode === SPACE) {
+      if (mode === 'running') {
+        registerResult(time);
+        setMode('idle');
+      } else if (mode === 'over') {
+        setMode('idle');
+      } else {
+        setMode('running');
+      }
+    }
+  };
+
+  useEffect(() => {
+    window.addEventListener('keyup', handleKeyUp);
+    window.addEventListener('keypress', handleKeyPress);
+
+    return (): void => {
+      window.removeEventListener('keyup', handleKeyUp);
+      window.removeEventListener('keypress', handleKeyPress);
+    };
+  });
+
+  const composeHelperText = (): string => {
+    switch (mode) {
+      case 'running': return 'Go fast!';
+      case 'countdown': return 'Release SPACE to begin';
+      case 'over': return 'You are too late!';
+      default: return 'Hold SPACE to start countdown';
+    }
+  };
+
+  const helperColor = (): 'primary' | 'secondary' | 'textSecondary' => {
+    switch (mode) {
+      case 'running': return 'primary';
+      case 'over': return 'secondary';
+      default: return 'textSecondary';
+    }
+  };
+
+  return (
+    <Paper className={classes.root}>
+      <Typography variant="h1"> {time} </Typography>
+      <Typography variant="h5" color={helperColor()}>
+        {composeHelperText()}
+      </Typography>
+    </Paper>
+  );
+};
+
+const convertTimeToString = (timeDelta: number): string => {
+  let resultTime = '';
+
+  const minute = Math.floor(timeDelta / 60000);
+  if (minute < 10) resultTime += '0';
+  resultTime += minute + ':';
+
+  let second = Math.floor(timeDelta / 1000);
+  if (second > 59) second %= 60;
+  if (second < 10) resultTime += '0';
+  resultTime += second + ':';
+
+  const mill = Math.floor((timeDelta % 1000) / 10);
+  if (mill < 10) resultTime += '0';
+  resultTime += mill;
+
+  return resultTime;
+};
+
+
+export default TimerButton;