1 files changed, 119 insertions, 0 deletions
diff --git a/src/components/TimerPage/Timer/Timer.js b/src/components/TimerPage/Timer/Timer.js
new file mode 100644
index 0000000..92b153d
--- /dev/null
+++ b/src/components/TimerPage/Timer/Timer.js
@@ -0,0 +1,119 @@
+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.primary.main,
+    marginTop: theme.spacing(20),
+  },
+}));
+
+const Timer = ({ registerResult }) => {
+  const classes = useStyles();
+
+  const SPACE = 32;
+  const maxCountdown = 15000;
+  const [time, setTime] = useState('00:00:00');
+  const [mode, setMode] = useState('idle');
+  const [repeater, setRepeater] = useState(0);
+
+  useEffect(()=> {
+    clearInterval(repeater);
+    const timestamp = Date.now();
+
+    if (mode === 'countdown') setRepeater(setInterval(() => {
+      const timeDelta = maxCountdown - (Date.now() - timestamp);
+      if (timeDelta <= 0) setMode('over');
+      setTime(convertTimeToString(timeDelta));
+    }, 10));
+
+    if (mode === 'running') setRepeater(setInterval(() => {
+      setTime(convertTimeToString(Date.now() - timestamp));
+    }, 10));
+
+    if (mode === 'over') {
+      setTime('00:00:00');
+    }
+  }, [mode]);
+
+  const handleKeyPress = event => {
+    event.preventDefault();
+    if (event.keyCode === SPACE && mode === 'idle' ) setMode('countdown');
+  };
+
+  const handleKeyUp = event => {
+    clearInterval(repeater);
+    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 () => {
+      window.removeEventListener('keyup', handleKeyUp);
+      window.removeEventListener('keypress', handleKeyPress);
+    };
+  });
+
+  const composeHelperText = () => {
+    switch (mode) {
+      case 'running': return '_';
+      case 'countdown': return 'Release SPACE to begin';
+      case 'over': return 'You are too late!';
+      default: return 'Hold SPACE to start countdown';
+    }
+  };
+
+  const helperColor = () => {
+    switch (mode) {
+      case 'running': return 'primary';
+      case 'over': return 'secondary';
+      default: return 'textSecondary';
+    }
+  };
+
+  return (
+    <Paper elevation={3} className={classes.root}>
+      <Typography variant="h1"> {time} </Typography>
+      <Typography variant="h5" color={helperColor()}>
+        {composeHelperText()}
+      </Typography>
+    </Paper>
+  );
+};
+
+const convertTimeToString = timeDelta => {
+  let resultTime = '';
+
+  const minute = Math.floor(timeDelta / 60000);
+  if (minute < 10) resultTime += '0';
+  resultTime += minute + ':';
+
+  let second = Math.floor(timeDelta / 1000);
+  if (second < 10) resultTime += '0';
+  if (second > 59) second %= 60;
+  resultTime += second + ':';
+
+  const mill = Math.floor((timeDelta % 1000) / 10);
+  if (mill < 10) resultTime += '0';
+  resultTime += mill;
+
+  return resultTime;
+};
+
+
+export default Timer;