mih-project/Frontend/lib/mih_packages/calculator/simple_calc.dart

import 'package:Mzansi_Innovation_Hub/main.dart';
import 'package:Mzansi_Innovation_Hub/mih_components/mih_inputs_and_buttons/mih_button.dart';
import 'package:flutter/material.dart';
import 'package:math_expressions/math_expressions.dart';

class SimpleCalc extends StatefulWidget {
  const SimpleCalc({super.key});

  @override
  State<SimpleCalc> createState() => _SimpleCalcState();
}

class _SimpleCalcState extends State<SimpleCalc> {
  var userInput = '';
  var answer = '0';

  // Array of button
  final List<String> buttons = [
    'C',
    '(',
    ')',
    'Del',
    '7',
    '8',
    '9',
    '/',
    '4',
    '5',
    '6',
    'x',
    '1',
    '2',
    '3',
    '-',
    '0',
    '.',
    '=',
    '+',
  ];

// function to calculate the input operation
  void equalPressed() {
    String finaluserinput = userInput;
    finaluserinput = userInput.replaceAll('x', '*');

    Parser p = Parser();
    Expression exp = p.parse(finaluserinput);
    ContextModel cm = ContextModel();
    double eval = exp.evaluate(EvaluationType.REAL, cm);
    answer = eval.toString();
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisSize: MainAxisSize.max,
      children: <Widget>[
        Text(
          "Simple Calculator",
          textAlign: TextAlign.center,
          style: TextStyle(
            fontSize: 25,
            fontWeight: FontWeight.bold,
            color: MzanziInnovationHub.of(context)!.theme.secondaryColor(),
          ),
        ),
        Divider(color: MzanziInnovationHub.of(context)!.theme.secondaryColor()),
        const SizedBox(height: 10),
        Container(
          //color: Colors.white,
          padding: const EdgeInsets.all(20),
          alignment: Alignment.centerRight,
          child: Text(
            userInput,
            style: TextStyle(
              fontSize: 18,
              color: MzanziInnovationHub.of(context)!.theme.secondaryColor(),
            ),
          ),
        ),
        Container(
          width: double.infinity,
          //color: Colors.white,
          padding: const EdgeInsets.all(15),
          alignment: Alignment.centerRight,
          child: Text(
            answer,
            style: TextStyle(
                fontSize: 30,
                color: MzanziInnovationHub.of(context)!.theme.secondaryColor(),
                fontWeight: FontWeight.bold),
          ),
        ),
        GridView.builder(
          physics: const NeverScrollableScrollPhysics(),
          shrinkWrap: true,
          // padding: EdgeInsets.only(
          //   left: width / 10,
          //   right: width / 10,
          //   bottom: height / 15,
          //   //top: 20,
          // ),
          // shrinkWrap: true,
          itemCount: buttons.length,
          gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
              crossAxisCount: 4),
          itemBuilder: (context, index) {
            // Clear Button
            if (index == 0) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      userInput = '';
                      answer = '0';
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.messageTextColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }

            // +/- button
            else if (index == 1) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      userInput += buttons[index];
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.messageTextColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
            // % Button
            else if (index == 2) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      userInput += buttons[index];
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.messageTextColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
            // Delete Button
            else if (index == 3) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      userInput = userInput.substring(0, userInput.length - 1);
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.errorColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
            // Equal_to Button
            else if (index == 18) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      equalPressed();
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.successColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
            //  +, -, / x buttons
            else if (index == 7 || index == 11 || index == 15 || index == 19) {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    if (answer == "0") {
                      setState(() {
                        userInput += buttons[index];
                      });
                    } else {
                      setState(() {
                        userInput = answer;
                        answer = "0";
                        userInput += buttons[index];
                      });
                    }
                    // setState(() {
                    //   userInput += buttons[index];
                    // });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.messageTextColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
            //  other buttons
            else {
              return Padding(
                padding: const EdgeInsets.all(4.0),
                child: MIHButton(
                  onTap: () {
                    setState(() {
                      userInput += buttons[index];
                    });
                  },
                  buttonText: buttons[index],
                  buttonColor:
                      MzanziInnovationHub.of(context)!.theme.secondaryColor(),
                  textColor:
                      MzanziInnovationHub.of(context)!.theme.primaryColor(),
                ),
              );
            }
          },
        ),
      ],
    );
  }
}