DDM 2021-11-24

package com.joythis.android.distanceindays;

import android.app.Activity;

import java.util.Calendar;

public class AmCalendar {
    Activity mActivity; //to bridge to Activity tools
    /*
    Calendar objects represent
    month as 0-based data
    days of week as 1-based data
     */
    private Calendar mCalendar;
    private int mYear; //2021
    private int mMonth; //11
    private int mDay; //10

    private int mAbsDayInYear;
    private int mDayOfWeek;

    public Calendar getmCalendar() {
        return mCalendar;
    }

    public int getmYear() {
        return mYear;
    }

    public int getmMonth() {
        return mMonth;
    }

    public int getmDay() {
        return mDay;
    }

    public int getmAbsDayInYear() {
        return mAbsDayInYear;
    }

    public int getmDayOfWeek() {
        return mDayOfWeek;
    }

    /*
        constructs an AmCalendar object
        corresponding to the current date
        default constructor - the constructor without
        arguments
         */
    public AmCalendar(Activity pA){
        this.mActivity = pA;
        this.mCalendar = Calendar.getInstance();
        this.mYear = this.mCalendar.get(Calendar.YEAR);
        this.mMonth =
            1+this.mCalendar.get(Calendar.MONTH);
        this.mDay = this.mCalendar.get(Calendar.DATE);
        this.mAbsDayInYear =
            this.mCalendar.get(Calendar.DAY_OF_YEAR);
        this.mDayOfWeek =
            this.mCalendar.get(Calendar.DAY_OF_WEEK);
    }//AmCalendar

    public AmCalendar(
        Activity pA,
        int pYear,
        int pMonth, //natural
        int pDay
    ){
        this.mActivity = pA;

        this.mCalendar = Calendar.getInstance();
        this.mCalendar.clear();
        this.mCalendar.set(
            Calendar.YEAR,
            pYear
        );
        //because Calendar's month are 0-based
        //after having received a "natural" month
        //we must discount it 1
        this.mCalendar.set(
            Calendar.MONTH,
            pMonth-1
        );
        this.mCalendar.set(
            Calendar.DATE,
            pDay
        );
        this.mYear = pYear;
        this.mMonth = pMonth;
        this.mDay = pDay;
        this.mAbsDayInYear = this.mCalendar.get(
            Calendar.DAY_OF_YEAR
        );
        //1 - Sunday, 2 - Monday ... 7 - Saturday
        this.mDayOfWeek = this.mCalendar.get(
            Calendar.DAY_OF_WEEK
        );

        this.mDayOfWeek = this.mDayOfWeek;
    }//AmCalendar

    public AmCalendar (Activity pA, String pStrYMD){
        this.mActivity = pA;
        String[] aParts = pStrYMD.split("-");
        boolean bCorrectNumberOfParts =
            aParts.length == 3;
        int y=0,m=0,d=0;
        this.mCalendar = Calendar.getInstance();

        if (bCorrectNumberOfParts){
            y = Integer.parseInt(aParts[0]);
            m = Integer.parseInt(aParts[1]);
            d = Integer.parseInt(aParts[2]);

            this.mCalendar.clear();
            this.mYear=y;
            this.mMonth=m;
            this.mDay=d;

            this.mCalendar.set(Calendar.YEAR, y);
            this.mCalendar.set(Calendar.MONTH, m-1);
            this.mCalendar.set(Calendar.DATE, d);
        }//if
        else {
            //if not possible to extract y,m,d from String
            this.mYear = this.mCalendar.get(Calendar.YEAR);
            this.mMonth = this.mCalendar.get(Calendar.MONTH) + 1;
            this.mDay = this.mCalendar.get(Calendar.DATE);
        }
        //disaster or not
        this.mAbsDayInYear=
            this.mCalendar.get(Calendar.DAY_OF_YEAR);
        this.mDayOfWeek=
            this.mCalendar.get(Calendar.DAY_OF_WEEK);
    }//AmCalendar

    /*
    computes the distance, in days,
    relatively to the device's current date
     */
    public long distanceInDays(){
        /*
        One needs to compute the difference
        between 2 moments
        moments represented as Calendar objects
        one of the 2 moments is the user's date
        the other moment is the system's date
        BOTH can be represented as Calendar objects
        All Calendar objects provide a method named
        getTimeInMillis
        which computes the time in milliseconds
        since the "Epoch" time (1970-1-1)
        So, the subtraction of these ints (long)
        gives the wanted number (in ms)
         */
        Calendar cNow = Calendar.getInstance();
        long lNow = cNow.getTimeInMillis();

        long lUser = this.mCalendar.getTimeInMillis();

        long lDiffMs = Math.abs(lNow-lUser);
        long lDiffDays = lDiffMs/1000/60/60/24;
        return lDiffDays;
    }//distanceInDays

    /*
    computes the distance, in days, relatively
    to a given date (as a Calendar object)
     */
    public long distanceInDays(Calendar pC){
        long lDiffMS =
            Math.abs(pC.getTimeInMillis()-this.mCalendar.getTimeInMillis());
        long lDays = lDiffMS/1000/60/60/24;
        return lDays;
    }//distanceInDays


    public long distanceInDays(int y, int m, int d){
        Calendar c = Calendar.getInstance();
        c.clear();
        c.set(Calendar.YEAR, y);
        c.set(Calendar.MONTH, m-1);
        c.set(Calendar.DATE, d);
        long lDiffMS =
            Math.abs(this.mCalendar.getTimeInMillis() - c.getTimeInMillis());
        long lDays = lDiffMS/1000/60/60/24;
        return lDays;
    }//distanceInDays

    public String toString(){
        String strRet = "";

        String strDayOfWeek = "";
        /* 0=>"sunday", ... 6=>"saturday"*/
        String[] dow = this.mActivity.getResources().
                getStringArray(R.array.aDaysOfWeek);
        /* 1=>"sunday" .. 7=>"saturday"*/
        strDayOfWeek = dow[this.mDayOfWeek-1];

        strRet = String.format(
            "%d-%d-%d #%d (%d = %s) => %d day(s) distant",
            this.mYear,
            this.mMonth,
            this.mDay,
            this.mAbsDayInYear,
            this.mDayOfWeek,
            strDayOfWeek,
            distanceInDays()
        );

        return strRet;
    }//toString

    public static boolean validYear(int pYear){
        return pYear>=1;
    }//validYear

    public static boolean validMonth(int pMonth){
        return pMonth>=1 && pMonth<=12;
    }//validMonth

    public static boolean validDay(
        int pY, int pM, int pD
    ){
        boolean bY = validYear(pY);
        boolean bM = validMonth(pM);
        if (bY && bM)
            return pD>=1 && pD<=daysInMonth(pY, pM);
        return false;
    }//validDay

    public final static int IMPOSSIBLE_MONTH = -1;
    public static int daysInMonth(int pY, int pM){
        switch(pM){
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                return 31;
            case 4:
            case 6:
            case 9:
            case 11:
                return 30;
            case 2:
                return leapYear(pY) ? 29:28;
            default:
                return IMPOSSIBLE_MONTH;
        }//switch
    }//daysInMonth

    public static boolean leapYear(int pY){
        boolean bM4 = pY%4==0;
        boolean bM100 = pY%100==0;
        boolean bM400 = pY%400==0;

        return bM400 || (bM4 && !bM100);
    }//leapYear
}//AmCalendar


*****************************************************

package com.joythis.android.distanceindays;

import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {
    AmUtil mUtil;
    TextView mTvResults;
    AmCalendar mCalendar;
    EditText mEtDate1, mEtDate2;
    Button mBtnComputeDistance, mBtnRequestDate1, mBtnRequestDate2;

    View.OnClickListener mClickHandler = new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            switch(v.getId()){
                case R.id.idBtnComputeDistance:
                    actionComputeDistance();
                    break;
                case R.id.idBtnRequestDate1:
                    actionRequestDate1();
                    break;
                case R.id.idBtnRequestDate2:
                    actionRequestDate2();
                    break;
            }//switch
        }//onClick
    };

    public final static int CALL_ME_ON_THIS_REQUEST_CODE_WHEN_POSSIBLE = 123;
    void actionRequestDate1(){
        Intent goInputDate = new Intent(
            this,
            InputDateActivity.class
        );
        goInputDate.putExtra("DATE", 1);
        //startActivity(goInputDate);

        startActivityForResult(
            goInputDate,
            CALL_ME_ON_THIS_REQUEST_CODE_WHEN_POSSIBLE
        );
    }//actionRequestDate1

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        boolean bConfirm, bCancel;
        bConfirm = resultCode == RESULT_OK;
        bCancel = resultCode == RESULT_CANCELED;
        if (bConfirm) {
            if(requestCode==CALL_ME_ON_THIS_REQUEST_CODE_WHEN_POSSIBLE){
                //unpacking of the result responded by called Activity
                int y, m, d;
                y = data.getIntExtra(
                    InputDateActivity.KEY_RESULT_YEAR,
                    //Calendar.getInstance().get(Calendar.YEAR)
                    -1
                );
                m = data.getIntExtra(
                    "RESULT_MONTH",
                    -1
                );
                d = data.getIntExtra(
                "RESULT_DAY",
                -1
                );

                int iDate = data.getIntExtra(
                    "RESULT_DATE",
                    -1
                );

                String strDate = data.getStringExtra(
                    "STR_DATE"
                );

                boolean bProblem = y==-1 || m==-1 || d==-1 || iDate==-1;
                if (bProblem){
                    mUtil.fb
                    ("Unacceptable date component received, nothing done");
                    return;
                }//bProblem

                String strDateRecv =
                    String.format("%d-%d-%d", y, m, d);
                switch(iDate){
                    case 1:
                        mEtDate1.setText(strDate);
                        //ALT
                        mEtDate1.setText(strDateRecv);
                        break;
                    case 2:
                        mEtDate2.setText(strDate);
                        //ALT
                        mEtDate2.setText(strDateRecv);
                        break;
                }


            }
        }

        if (bCancel){
            mUtil.fb("Date selection canceled");
        }
    }

    void actionRequestDate2(){
        Intent goInputDate = new Intent(
                this,
                InputDateActivity.class
        );
        goInputDate.putExtra("DATE", 2);
        //startActivity(goInputDate);

        startActivityForResult(
                goInputDate,
                CALL_ME_ON_THIS_REQUEST_CODE_WHEN_POSSIBLE
        );
    }

    void actionComputeDistance(){
        int y,m,d;
        try {
            AmCalendar calendarCorrespondingToD1 =
                new AmCalendar(this, mEtDate1.getText().toString());
            AmCalendar calendarCorrespondingToD2 =
                new AmCalendar(this, mEtDate2.getText().toString());

            long lDistanceInDays =
                calendarCorrespondingToD1.distanceInDays(
                    calendarCorrespondingToD2.getmCalendar()
                );

                String strD1 = calendarCorrespondingToD1.toString();
                String strD2 = calendarCorrespondingToD2.toString();

                //TODO show the result
            String strResult = String.format(
                "The distance in days between:\n"+
                "%s\n"+
                "%s\n"+
                "is %d day(s).",
                strD1,
                strD2,
                lDistanceInDays
            );

            //String strAll=strResult +"\n" + mTvResults.getText().toString();
            //mTvResults.setText(strAll);
            mTvResults.setText(strResult);
        }
        catch (Exception e){
            //TODO
            mUtil.fb("Empty field.");
        }

    }//actionComputeDistance

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.rl_distance_in_days_v2);

        init();
    }//onCreate

    void init(){
        mUtil = new AmUtil (this);
        mEtDate1 = findViewById(R.id.idEtDate1);
        mEtDate2 = findViewById(R.id.idEtDate2);
        mBtnRequestDate1 = findViewById(R.id.idBtnRequestDate1);
        mBtnRequestDate2 = findViewById(R.id.idBtnRequestDate2);

        mBtnComputeDistance = findViewById(R.id.idBtnComputeDistance);

        String[] aDaysOfWeek =
            getResources().getStringArray
                (R.array.aDaysOfWeek);

        mTvResults = findViewById(R.id.idTvResults);

        mBtnRequestDate1.setOnClickListener(mClickHandler);
        mBtnRequestDate2.setOnClickListener(mClickHandler);

        mBtnComputeDistance.setOnClickListener(
            mClickHandler
        );
        displayCurrentYMD();

    }//init

    void displayCurrentYMD(){
        Calendar c = Calendar.getInstance();
        int y = c.get(Calendar.YEAR);
        int m = c.get(Calendar.MONTH)+1;
        int d = c.get(Calendar.DATE);
        /*
        mEtYear.setText(String.valueOf(y));
        mEtMonth.setText(String.valueOf(m));
        mEtDay.setText(String.valueOf(d));

         */
    }//displayCurrentYMD

    void auxTests(){
        //testing
        for (int day=1; day<=31; day+=1){
            AmCalendar calendarAtDay = new AmCalendar
                    (MainActivity.this, 2021, 1, day);
            String strDay = calendarAtDay.toString();
            mTvResults.setText(
                    strDay+"\n"+
                            mTvResults.getText().toString()
            );
        }//for
    }//auxTests

    /*
    EX1: on init make sure the EditTexts for
    year, month and day, are initialized to the
    device's current year, month and day

    EX2: create and print an AmCalendar object,
    corresponding to the user date
     */
}//MainActivity