const { useState, useEffect } = React;
const { createGlobalStyle, css } = styled;

const GlobalStyle = createGlobalStyle`
  body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial,
    sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';
    font-size: 16px;
  }
`;

const StyledApp = styled.div`
  width: 100%;
  max-width: 320px;
  margin-top: 20px;
  margin-left: auto;
  margin-right: auto;

  @media (min-height: 700px) {
    margin-top: 50px;
  }

  @media (min-height: 800px) {
    margin-top: 100px;
  }
`;

const App = () => {
  // Calculator's states
  const [memory, setMemory] = useState(0);
  const [result, setResult] = useState(0);
  const [waitingForOperand, setWaitingForOperand] = useState(true);
  const [pendingOperator, setPendingOperator] = useState();
  const [display, setDisplay] = useState("0");

  const calculate = (rightOperand, pendingOperator) => {
    let newResult = result;

    switch (pendingOperator) {
      case "+":
        newResult += rightOperand;
        break;
      case "-":
        newResult -= rightOperand;
        break;
      case "×":
        newResult *= rightOperand;
        break;
      case "÷":
        if (rightOperand === 0) {
          return false;
        }

        newResult /= rightOperand;
        break;
      default:
    }

    setResult(newResult);
    setDisplay(newResult.toString().toString().slice(0, 12));

    return true;
  };

  // Pad buttons handlers
  const onDigitButtonClick = (digit) => {
    let newDisplay = display;

    if ((display === "0" && digit === 0) || display.length > 12) {
      return;
    }

    if (waitingForOperand) {
      newDisplay = "";
      setWaitingForOperand(false);
    }

    if (display !== "0") {
      newDisplay = newDisplay + digit.toString();
    } else {
      newDisplay = digit.toString();
    }

    setDisplay(newDisplay);
  };

  const onPointButtonClick = () => {
    let newDisplay = display;

    if (waitingForOperand) {
      newDisplay = "0";
    }

    if (newDisplay.indexOf(".") === -1) {
      newDisplay = newDisplay + ".";
    }

    setDisplay(newDisplay);
    setWaitingForOperand(false);
  };

  const onOperatorButtonClick = (operator) => {
    const operand = Number(display);

    if (typeof pendingOperator !== "undefined" && !waitingForOperand) {
      if (!calculate(operand, pendingOperator)) {
        return;
      }
    } else {
      setResult(operand);
    }

    setPendingOperator(operator);
    setWaitingForOperand(true);
  };

  const onChangeSignButtonClick = () => {
    const value = Number(display);

    if (value > 0) {
      setDisplay("-" + display);
    } else if (value < 0) {
      setDisplay(display.slice(1));
    }
  };

  const onEqualButtonClick = () => {
    const operand = Number(display);

    if (typeof pendingOperator !== "undefined" && !waitingForOperand) {
      if (!calculate(operand, pendingOperator)) {
        return;
      }

      setPendingOperator(undefined);
    } else {
      setDisplay(operand.toString());
    }

    setResult(operand);
    setWaitingForOperand(true);
  };

  const onAllClearButtonClick = () => {
    setMemory(0);
    setResult(0);
    setPendingOperator(undefined);
    setDisplay("0");
    setWaitingForOperand(true);
  };

  const onClearEntryButtonClick = () => {
    setDisplay("0");
    setWaitingForOperand(true);
  };

  const onMemoryRecallButtonClick = () => {
    setDisplay(memory.toString());
    setWaitingForOperand(true);
  };

  const onMemoryClearButtonClick = () => {
    setMemory(0);
    setWaitingForOperand(true);
  };

  const onMemoryPlusButtonClick = () => {
    setMemory(memory + Number(display));
    setWaitingForOperand(true);
  };

  const onMemoryMinusButtonClick = () => {
    setMemory(memory - Number(display));
    setWaitingForOperand(true);
  };

  return (
    <>
      <GlobalStyle />
      <StyledApp>
        <Display
          value={display}
          hasMemory={memory !== 0}
          expression={
            typeof pendingOperator !== "undefined"
              ? `${result}${pendingOperator}${waitingForOperand ? "" : display}`
              : ""
          }
        />
        <Pad
          onDigitButtonClick={onDigitButtonClick}
          onPointButtonClick={onPointButtonClick}
          onOperatorButtonClick={onOperatorButtonClick}
          onChangeSignButtonClick={onChangeSignButtonClick}
          onEqualButtonClick={onEqualButtonClick}
          onAllClearButtonClick={onAllClearButtonClick}
          onClearEntryButtonClick={onClearEntryButtonClick}
          onMemoryRecallButtonClick={onMemoryRecallButtonClick}
          onMemoryClearButtonClick={onMemoryClearButtonClick}
          onMemoryPlusButtonClick={onMemoryPlusButtonClick}
          onMemoryMinusButtonClick={onMemoryMinusButtonClick}
        />
      </StyledApp>
    </>
  );
};

const colorToCss = (color) => {
  switch (color) {
    case "red":
      return css`
        background-color: #c04444;
        color: #fff;

        &:hover,
        &:focus {
          background-color: #af3b3b;
        }
      `;
    case "green":
      return css`
        background-color: #018645;
        color: #fff;

        &:hover,
        &:focus {
          background-color: #016d38;
        }
      `;
    case "dark":
      return css`
        background-color: #272727;
        color: #c5830d;

        &:hover,
        &:focus {
          background-color: #1a1a1a;
        }
      `;
    default:
  }

  return css`
    background-color: #2e2e2e;
    color: #fff;

    &:hover,
    &:focus {
      background-color: #212121;
    }
  `;
};

const StyledButton = styled.button`
  font-family: inherit;
  font-size: inherit;
  border: 1px solid rgba(0, 0, 0, 0.05);
  border-radius: 0;
  padding-top: 1em;
  padding-bottom: 1em;
  transition: background-color 0.15s ease-in-out, opacity 0.15s ease-in-out;
  ${({ color }) => colorToCss(color)}
  ${({ isLarge }) =>
    isLarge &&
    css`
      grid-column-end: span 2;
    `}

  position: relative;
  overflow: hidden;
  transform: translate3d(0, 0, 0);

  &:focus {
    outline: 0;
  }

  :after {
    content: "";
    display: block;
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    pointer-events: none;
    background-image: radial-gradient(circle, #fff 10%, transparent 10.01%);
    background-repeat: no-repeat;
    background-position: 50%;
    transform: scale(10, 10);
    opacity: 0;
    transition: transform 0.3s, opacity 1s;
  }

  :active:after {
    transform: scale(0, 0);
    opacity: 0.2;
    transition: 0s;
  }
`;

const Button = ({ children, color, isLarge, onClick }) => {
  return (
    <StyledButton color={color} isLarge={isLarge} onClick={onClick}>
      {children}
    </StyledButton>
  );
};

const StyledIndicatorList = styled.div`
  font-size: 0.75em;
  line-height: 1;
  opacity: 0.4;
  text-align: right;
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.25em;
  min-height: 1em;
`;

const StyledExpression = styled.span`
  margin-left: auto;
`;

const StyleScreen = styled.div`
  font-size: 2.5em;
  min-height: 1.4em;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  overflow: hidden;
`;

const StyledDisplay = styled.div`
  background-color: #393939;
  color: #fff;
  padding: 1.5em 1em;
`;

const Display = ({ value, hasMemory, expression }) => {
  return (
    <StyledDisplay>
      <StyledIndicatorList>
        {hasMemory && <span>M</span>}

        <StyledExpression>{expression}</StyledExpression>
      </StyledIndicatorList>

      <StyleScreen>{value}</StyleScreen>
    </StyledDisplay>
  );
};

const StyledPad = styled.div`
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-auto-rows: 1fr;
`;

const Pad = ({
  onDigitButtonClick,
  onPointButtonClick,
  onOperatorButtonClick,
  onChangeSignButtonClick,
  onEqualButtonClick,
  onAllClearButtonClick,
  onClearEntryButtonClick,
  onMemoryRecallButtonClick,
  onMemoryClearButtonClick,
  onMemoryPlusButtonClick,
  onMemoryMinusButtonClick
}) => {
  const handleKeyDown = ({ keyCode, shiftKey }) => {
    console.log(keyCode);
    if (keyCode >= 48 && keyCode <= 57 && !shiftKey) {
      onDigitButtonClick(keyCode - 48);
    } else if (keyCode >= 96 && keyCode <= 105) {
      onDigitButtonClick(keyCode - 96);
    } else if (keyCode === 107 || (keyCode === 187 && shiftKey)) {
      onOperatorButtonClick("+");
    } else if (keyCode === 109 || keyCode === 189) {
      onOperatorButtonClick("-");
    } else if (keyCode === 106 || (keyCode === 56 && shiftKey)) {
      onOperatorButtonClick("×");
    } else if (keyCode === 111 || keyCode === 191) {
      onOperatorButtonClick("÷");
    } else if (keyCode === 13 || (keyCode === 187 && !shiftKey)) {
      onEqualButtonClick();
    } else if (keyCode === 46) {
      onClearEntryButtonClick();
    } else if (keyCode === 27) {
      onAllClearButtonClick();
    } else if (keyCode === 78) {
      onChangeSignButtonClick();
    } else if (keyCode === 80) {
      onMemoryPlusButtonClick();
    } else if (keyCode === 81) {
      onMemoryMinusButtonClick();
    } else if (keyCode === 82) {
      onMemoryRecallButtonClick();
    }
  };

  useEffect(() => {
    document.body.addEventListener("keydown", handleKeyDown);
    return () => document.body.removeEventListener("keydown", handleKeyDown);
  });

  return (
    <StyledPad>
      <Button onClick={onMemoryRecallButtonClick}>MR</Button>
      <Button onClick={onMemoryClearButtonClick}>MC</Button>
      <Button onClick={onMemoryPlusButtonClick}>M+</Button>
      <Button onClick={onMemoryMinusButtonClick}>M-</Button>
      <Button color="red" onClick={onAllClearButtonClick}>
        AC
      </Button>
      <Button onClick={onClearEntryButtonClick}>C</Button>
      <Button onClick={onChangeSignButtonClick}>-/+</Button>
      <Button color="dark" onClick={() => onOperatorButtonClick("÷")}>
        ÷
      </Button>
      <Button onClick={() => onDigitButtonClick(7)}>7</Button>
      <Button onClick={() => onDigitButtonClick(8)}>8</Button>
      <Button onClick={() => onDigitButtonClick(9)}>9</Button>
      <Button color="dark" onClick={() => onOperatorButtonClick("×")}>
        ×
      </Button>
      <Button onClick={() => onDigitButtonClick(4)}>4</Button>
      <Button onClick={() => onDigitButtonClick(5)}>5</Button>
      <Button onClick={() => onDigitButtonClick(6)}>6</Button>
      <Button color="dark" onClick={() => onOperatorButtonClick("-")}>
        -
      </Button>
      <Button onClick={() => onDigitButtonClick(1)}>1</Button>
      <Button onClick={() => onDigitButtonClick(2)}>2</Button>
      <Button onClick={() => onDigitButtonClick(3)}>3</Button>
      <Button color="dark" onClick={() => onOperatorButtonClick("+")}>
        +
      </Button>
      <Button onClick={() => onDigitButtonClick(0)}>0</Button>
      <Button onClick={onPointButtonClick}>.</Button>
      <Button color="green" isLarge={true} onClick={onEqualButtonClick}>
        =
      </Button>
    </StyledPad>
  );
};

ReactDOM.render(<App />, document.getElementById("root"));