Controller to upload data in CSV format to Contact and Custom object (Cases__c) as child of Contact. This example uses mapping fields, to make this programme generate and easily adopted to another object just modify the mapping.

SSSCsvReader.cls

/**
 * Used to read a delimited file.
 * https://gist.github.com/ngaller/858086
 */
public class SSSCsvReader {
  private String delim = ',';
  // the input data
  private String[] buffer;
  
  public SSSCsvReader(String data){
        data = data.replaceAll('(\r\n|\r)','\n');
    this.buffer = data.split('\n'); 
  }
  
  public SSSCsvReader(String data, String delim){
    this.buffer = data.split('\n'); 
    this.delim = delim;
  }
  
  /**
   * Read and parse next available line.  Return null if end of stream.
   */
  public String[] readLine(){
    if(buffer.size() == 0)
      return null;
    String line = this.buffer.remove(0);
    String[] parts = new String[] {};
    while(line != ''){
      Integer next = 0;
      if(line.startsWith('"')){
        line = line.substring(1); // strip initial
        Integer quoteIndex = findQuote(line, 0);
        while(quoteIndex == -1){
          if(buffer.size() == 0){
            // EOT!
            quoteIndex = line.length();
          } else { 
            // grab the next line
            Integer skip = line.length();
            line += '\n' + this.buffer.remove(0);
            quoteIndex = findQuote(line, skip);
          }
        }
        // advance to comma
        next = quoteIndex + 1;
        parts.add(line.substring(0, quoteIndex).replace('""', '"'));
      } else {
        next = line.indexOf(this.delim, next);
        if(next == -1)
          next = line.length();
        // NB in Substring, "endindex" is the index of the character AFTER the last index to get
        parts.add(line.substring(0, next));
      }    
      if(next == line.length() - 1)
        // case of a terminating comma.
        parts.add('');
      line = next < line.length() ? line.substring(next+1) : '';
    }
    if(parts.size() == 0)
      // empty string - we still want to return something...
      parts.add('');
    return parts;
  }
  
  static private Pattern quotePattern = Pattern.compile('(?<!")"(?!")');
  /**
   * Find next quote in the line
   */
  private Integer findQuote(String line, Integer skip){
    Matcher m = quotePattern.matcher(line);
    m.region(skip, m.regionEnd());
    if(!m.find())
      return -1;
    return m.start();
  }
}

TestClass.cls

@isTest
public class UploadContactCaseTest {
    static String getSampleCsv(){
        String strTmp;
        strTmp = 'SN,Client Name,"Client ID Type","Client ID",Name of SSO,Date Last Known to SSO,Last Known Assistance Period at SSO,Enquiry ID,Date of Enquiry,Rate of Response,Mode of Enquiry,Enquiry Worker,Source of Referral,Outcome of Enquiry,Duration of Contact for Enquiry (mins),Intake ID,Date of Intake,Presenting Issue,Age,Gender,Ethnicity,Marital Status,Household Dwelling Type,Family Type,Education Level,Residential Status,Religion,Occupation,Employment Status,Gross Household Income,Disability/Special Needs,Assessed Risk of Recurrence at Intake Assessment,"Suicidal Risk at Intake Assessment","Risk of Harm to Others at Intake Assessment",Recommendation at Intake,Duration of Contact for Intake (mins),Outcome Plan ID,Case Manager,CSWP Classification at 1st Assessment,CSWP Classification at 1st Review,CSWP Classification at 2nd Review,CSWP Classification at 3rd Review,Agencies Family known to,Outcome Plan Status,CSWP Classification at Case Closure,Case Open Date ,Case Closure Date,Reason for Case Closure,No. of Sessions (Outcome Plan + Intervention),No. of Goals Achieved (Goals Met / Total No. of Goals),Milestones Met at Case Closure (No. of Milestones Met / Total No. of Milestones),Duration of Case (Days)';
        strTmp += '\n';
      strTmp += '1,Testing,Singapore Pink Identification Card,S000005J,SSO Bukit Merah,01/12/2020,July 2020 - December 2020,,,,,,,,,,,,60,M,Malay,Divorced,HDB 2 Room,,Pre-School,Singapore Citizen,Muslim,,Not Working (Temporarily Medically Unfit less than 3 months),0,,,,,,,OTPC30003009196,"Aasfafsd",2,2,4,,,Open,,16/10/2008,,,55,,,';
        strTmp += '\n';
      strTmp += '2,test2,Singapore Pink Identification Card,S000000G,SSO Bukit Merah,05/09/2020,May 2020 - October 2020,,,,,,,,,,,,46,M,Malay,Married,HDB 2 Room,,Polytechnic Diploma,Singapore Citizen,Muslim,"Plant and Machine Operators and Assemblers (Taxi, Bus drivers)",Working,0,,,,,,,OTPC30003009475,Asdfsdfsd,2,2,2,,,Open,,30/05/2013,,,20,,,';
      return strTmp;
    }
    
    @isTest static void myTest1() {
        Blob fileCsv = Blob.valueOf(getSampleCsv());
        List<Contact> lsContacts = new List<Contact>();
        ApexPages.StandardSetController pg1 = new ApexPages.StandardSetController(lsContacts);
        UploadContactCaseController cnt1 = new UploadContactCaseController(pg1);
        
        cnt1.fileCsv = fileCsv;
        cnt1.upload();
        cnt1.next();
        cnt1.back();
        
    }
}

UploadContactCase.vfp

<apex:page standardController="Contact"  tabStyle="Contact" extensions="UploadContactCaseController" recordSetVar="contacts" lightningStylesheets="true">
    <apex:form >
    <apex:pageBlock title="UPLOAD MEMBER">
        <apex:pageBlockButtons id="commandBlock">
            <apex:commandButton value="Upload" action="{!upload}" rendered="{!totalData = totalProceed}" status="status1" />
            <apex:commandButton value="Proceed Next" action="{!next}" rendered="{!totalData > totalProceed}" status="status1" />
            <apex:commandButton value="Back" action="{!back}" immediate="true" />
        </apex:pageBlockButtons>
        <apex:messages style="border: 1px solid red;padding:5px;" />        
        <apex:pageBlockSection columns="3">
            <apex:outputText ></apex:outputText>
            <apex:outputLabel >Please select a csv file <apex:inputFile value="{!fileCsv}" title="CSV File" /> </apex:outputLabel>
            <apex:actionStatus id="status1" startStyle="text-align:center;font-weight:bold;color: blue;" startText="Processing, please wait ... " stopText=""></apex:actionStatus>
        </apex:pageBlockSection>
    </apex:pageBlock>      
    <apex:pageBlock rendered="{!totalData > 0}"  id="resultBlock">
        <apex:pageBlockSection title="Result" columns="2">
            <apex:outputText value="{!totalData}" label="Total Data"></apex:outputText>
            <apex:outputText value="{!totalSuccess}" label="Total Success"></apex:outputText>
            <apex:outputText value="{!totalProceed}" label="Total Proceed"></apex:outputText>
            <apex:outputText value="{!totalFailed}" label="Total Failed"></apex:outputText>            
        </apex:pageBlockSection>
        <apex:pageBlockSection columns="1" title="Error">
            <apex:outputText value="{!strInfo}" label="" style="" escape="false" ></apex:outputText>
        </apex:pageBlockSection>
    </apex:pageBlock>
    </apex:form>
</apex:page>

UploadContactCaseController.cls

/* 
 *  Controller for VF page to upload CSV file for Contact and Case
*/
public class UploadContactCaseController {

    public List<Contact> contacts{get;set;}
    public Blob fileCsv {get;set;} 
    public String strInfo {get;set;}
    public String strWarning {get;set;}
    
    Map<String, Integer> mapContactField {get;set;}
    Map<String, Integer> mapCaseField {get;set;}
    Set<String> stDateField {get;set;}
    Set<String> stIntegerField {get;set;}
    Set<String> stDoubleField {get;set;}
    
    List<List<String>> dataAll {get;set; }    
    public Integer totalData {get;set;}
    public Integer totalProceed {get;set;}
    public Integer totalSuccess {get;set;}
    public Integer totalFailed {get;set;}
    public Integer intCurrent {get;set;}
    
    public Integer totalProceedCase {get;set;} // just for tracking
    Map<String, Integer> mapSNRow {get;set;} // map of SN with Row number
    
    public UploadContactCaseController(ApexPages.StandardSetController controller)
    {
        contacts = New List<Contact>(); 
        totalData = totalSuccess = totalFailed = totalProceed = 0;
        strInfo = '';
        strWarning = '';
        intCurrent = totalProceedCase = 0;
        
        initMapFields();
        dataAll = new List<List<String>>();
        mapSNRow = new Map<String, Integer>();
    }
    
    /* initiate mapping field with column in csv */
    private void initMapFields()
    {
        mapContactField = new Map<String, Integer>();
        mapCaseField = new Map<String, Integer>();
        
        stDateField = new Set<String>{'Date_of_Enquiry__c', 'Date_of_Intake__c', 'Date_Client_was_Last_Known_to_SSO__c', 'Case_Closure_Date__c', 'Case_Open_Date__c'};
        stDoubleField = new Set<String> {'Household_income__c'};
        stIntegerField = new Set<String> {'Age1__c', 'Sessions_Outcome_Plan_Intervention__c', 'No_of_Goals_Achieved__c', 'Milestones_Met_at_Case_Closure__c', 
                            'Duration_of_Case_Days__c', 'Duration_of_Contact_for_Intake_mins__c', 'Duration_of_Contact_for_Enquiry_mins__c'};
            
        mapContactField.put('LastName',1); // Client Name (Only for FSCs)
        mapContactField.put('ID_Type__c',2); // Client ID Type (Only for FSCs)
        mapContactField.put('ID_No__c',3); // Client ID (Only for FSCs)
        mapContactField.put('Enquiry_ID__c',7); // Enquiry ID
        mapContactField.put('Date_of_Enquiry__c',8); // Date of Enquiry
        mapContactField.put('Rate_of_Response__c',9); // Rate of Response
        mapContactField.put('Mode_of_Enquiry__c',10); // Mode of Enquiry
        mapContactField.put('Enquiry_Worker__c',11); // Enquiry Worker
        mapContactField.put('Source_of_Referral__c',12); // Source of Referral
        mapContactField.put('Outcome_of_Enquiry__c',13); // Outcome of Enquiry
        mapContactField.put('Duration_of_Contact_for_Enquiry_mins__c',14); // Duration of Contact for Enquiry (mins)
        mapContactField.put('Intake_ID__c',15); // Intake ID
        mapContactField.put('Date_of_Intake__c',16); // Date of Intake
        mapContactField.put('Presenting_Issue__c',17); // Presenting Issue
        mapContactField.put('Age1__c',18); // Age
        mapContactField.put('Gender__c',19); // Gender
        mapContactField.put('Ethnicity__c',20); // Ethnicity
        mapContactField.put('Marital_Status__c',21); // Marital Status
        mapContactField.put('Household_Dwelling_Type__c',22); // Household Dwelling Type
        mapContactField.put('Family_Type__c',23); // Family Type
        mapContactField.put('Highest_Education_Level__c',24); // Education Level
        mapContactField.put('Citizenship__c',25); // Residential Status
        mapContactField.put('Religion__c',26); // Religion
        mapContactField.put('Occupation_Volunteer__c',27); // Occupation
        mapContactField.put('Employment_Status__c',28); // Employment Status
        mapContactField.put('Household_income__c',29); // Gross Household Income
        mapContactField.put('Special_Needs_Disabilities__c',30); // Disability/Special Needs
        mapContactField.put('Recommendation_at_Intake__c',34); // Recommendation at Intake
        mapContactField.put('Duration_of_Contact_for_Intake_mins__c',35); // Duration of Contact for Intake (mins)
        mapContactField.put('Outcome_Plan_Status__c',43); // Outcome Plan Status
        
        if (mapContactField.containskey('')) mapContactField.remove('');
        
        // CASE
        mapCaseField.put('Name_of_SSO_if_know_to_SSO__c',4); // Name of SSO (If known to SSO)
        mapCaseField.put('Date_Client_was_Last_Known_to_SSO__c',5); // Date on which Client was Last Known to SSO
        mapCaseField.put('Last_Known_Assistance_Period_at_SSO__c',6); // Last Known Assistance Period at SSO
        mapCaseField.put('Assessed_Risk_of_Recurrence_at_Intake__c',31); // Assessed Risk of Recurrence at Intake Assessment(L/M/H/Unable to assess)
        mapCaseField.put('Suicidal_Risk_at_Intake_Assessment__c',32); // Suicidal Risk at Intake Assessment (L/M/H/Unable to assess)
        mapCaseField.put('Risk_of_Harm_to_Others_at_Intake_Assessm__c',33); // Risk of Harm to Others at Intake Assessment (L/M/H/Unable to assess)
        mapCaseField.put('Name',36); // Outcome Plan ID
        mapCaseField.put('Case_Manager_Name_of_Social_Worker__c',37); // Case Manager        
        mapCaseField.put('CSWP_Classification_1st_Assessment__c',38); // CSWP Classification at 1st Assessment
        mapCaseField.put('CSWP_Classification_1st_Assement_Date__c',39); // CSWP Classification at 1st Review
        mapCaseField.put('CSWP_Classification_2nd_Review_Date__c',40); // CSWP Classification at 2nd Review  
        mapCaseField.put('CSWP_Classification_3rd_Review_Date__c',41); // CSWP Classification at 3rd Review
        mapCaseField.put('Agencies_Family_known_to__c',42); // Agencies Family known to
        mapCaseField.put('Outcome_Plan_Status__c',43); // Outcome Plan Status
        mapCaseField.put('CSWP_Classification_at_Case_Closure__c',44); // CSWP Classification at Case Closure
        mapCaseField.put('Case_Open_Date__c',45); // Case Open Date 
        mapCaseField.put('Case_Closure_Date__c',46); // Case Closure Date
        mapCaseField.put('Reason_for_Case_Closure__c',47); // Reason for Case Closure
        mapCaseField.put('Sessions_Outcome_Plan_Intervention__c',48); // No. of Sessions (Outcome Plan + Intervention)
        mapCaseField.put('No_of_Goals_Achieved__c',49); // No. of Goals Achieved (Goals Met / Total No. of Goals)
        mapCaseField.put('Milestones_Met_at_Case_Closure__c',50); // Milestones Met at Case Closure (No. of Milestones Met / Total No. of Milestones)
        mapCaseField.put('Duration_of_Case_Days__c',51); // Duration of Case (Days)
        
        if (mapCaseField.containskey('')) mapCaseField.remove('');
    }
    
    /* generate string of field for Contact */
    private String getObjectFields(String strObj)
    {
        String str = 'Id';
        
        if (strObj == 'Contact') {
            for(String s: mapContactField.keySet()) {
                str += ', ' + s;
            }
        }
        else if (strObj == 'Cases__c') {
            for(String s: mapCaseField.keySet()) {
                str += ', ' + s;
            }
        }
        
        return str;
    }
    
    // handle csv upload, load to dataAll
    public PageReference upload()
    {
        // mapping
        Integer iTmp, iTmp2, iContact, iCase;
        String strTmp, strTmp2;
        
        // check csv
        if (fileCsv != null)
        {
            
            // extract csv
            SSSCsvReader objCsv = new SSSCsvReader(fileCsv.toString());
            List<String> dataLine = new List<String>();
            
            Set<String> lsClientID = new Set<String>(); // list of client ID
            Set<String> lsCaseID = new Set<String>(); // id of case
            
            dataLine = objCsv.readLine();
            if (dataLine != null) {
                dataLine = objCsv.readLine(); // ignore first row
            }
            while (dataLine != null)
            {
                dataAll.add(dataLine);
                
                // validation, check if duplicate row (based on unique column)
                iTmp = getCol('Contact', 'ID_No__c');
                if (dataLine.size() > iTmp && dataLine[iTmp] != null && dataLine[iTmp] != '') {
                    strTmp = dataLine[iTmp];
                    if (lsClientID.contains(strTmp)) {
                        // duplicate
                        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR,'Error: Duplicate Client ID ' + strTmp));
                        totalData = 0;
                        return null;
                    }
                    else {
                        lsClientID.add(strTmp);
                    }
                    
                }
                
                iTmp = getCol('Cases__c', 'Name');
                if (dataLine.size() > iTmp && dataLine[iTmp] != null && dataLine[iTmp] != '') {
                    strTmp = dataLine[iTmp];
                    if (lsCaseId.contains(strTmp))
                    {
                        // duplicate
                        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.ERROR,'Error: Duplicate Output Plan ID ' + strTmp));
                        return null;
                    }
                    else {
                        lsCaseID.add(dataLine[iTmp]);
                    }
                    
                }
                
                // get SN information
                if (dataLine[0] != null && dataLine[0] != '') {
                    mapSNRow.put(dataLine[0], totalData);
                }
                
                totalData++;                
                dataLine = objCsv.readLine();
            }
            
        }
        proceed();
        return null;
    }
    
    // procceed data in dataAll to DB
    public void proceed()
    {
        List<String> dataLine = new List<String>();
        
        List<String> lsClientID = new List<String>(); // list of client ID
        List<String> lsCaseID = new List<String>(); // id of case
        
        Integer maxProceed = 100; // max record per proceed
        Integer startP = 0;
        Integer endP = 0;
        Integer i, j, k, iTmp, iTmp2, iTmp3;
        String strTmp, strTmp2;
        Boolean bolNew;
        Id RTContactMember = Schema.SObjectType.Contact.getRecordTypeInfosByName().get('Member').getRecordTypeId();        
        Integer iCase, iContact;
        Integer intRow;
        String strErr;
        
        if (totalData > 0 && totalProceed < totalData)
        {
            startP = totalProceed; // index
            endP = totalData - 1;
            if ((endP - startP) > maxProceed) {
                endP = startP + maxProceed - 1;
            }
            
            system.debug('DEBUG: process from ' + startP + ' to ' + endP);
            
            for (i = startP; i <= endP; i++)
            {
                dataLine = dataAll[i];
                iTmp = getCol('Contact', 'ID_No__c');
                if (dataLine.size() > iTmp) lsClientID.add(dataLine[iTmp]);
                iTmp = getCol('Cases__c', 'Name');
                if (dataLine.size() > iTmp) lsCaseID.add(dataLine[iTmp]);
                
            } // for
            
            
            // get existing contact and case
            system.debug('DEBUG: client id ' + lsClientID);
            system.debug('DEBUG: case id ' + lsCaseID);
            Map<String, Contact> mapContacts = new Map<String, Contact>();
            Map<String, Cases__c> mapCases = new Map<String, Cases__c>();
            List<Contact> lsContactRecord = new List<Contact>();
            List<Cases__c> lsCaseRecord = new List<Cases__c>();
            Set<Id> stContactSuccess = new Set<Id>();
            Contact objCnt;
            Cases__c objCase;
            
            strTmp = 'SELECT ' + getObjectFields('Contact') + ', RecordTypeId FROM Contact WHERE ID_No__c IN :lsClientID ';
            system.debug('DEBUG Query ' + strTmp);
            for(SObject cnt : Database.query(strTmp))
            {
                objCnt = (Contact)cnt;
                mapContacts.put(objCnt.ID_No__c, objCnt);
            }
            strTmp = 'SELECT ' + getObjectFields('Cases__c') + ', Contact__c FROM Cases__c WHERE Name IN :lsCaseID  ';
            system.debug('DEBUG Query ' + strTmp);
            for(SObject css : Database.query(strTmp))
            {
                objCase = (Cases__c)css;
                mapCases.put(objCase.Name, objCase);
            }
            
            // create/update data for Contact
            Integer iData = 0;
            String strSN = '';
            Map<Integer, String> mapRowSN = new Map<Integer, String>(); // index -> SN
            iContact = getCol('Contact', 'ID_No__c');
            
              for (i = startP; i <= endP; i++)
              {
                dataLine = dataAll[i];
                totalProceed++;
                intCurrent++;
                if (dataLine.size() > 51) { // make sure correct data
                     
                    strSN = dataLine[0]; // get serial number
                    mapRowSN.put(iData, strSN);
                    intRow = 0;
                    if (mapSNRow.get(strSN) != null) {
                        intRow = mapSNROw.get(strSN);
                    }
                    strErr = ''; // for skipped error
                    
                  strTmp = dataLine[iContact]; 
                    bolNew = true;
                    objCnt = new Contact();
                    system.debug('DEBUG: ID No ' + strTmp);
                    if (strTmp != null && strTmp != '' && mapContacts.get(strTmp) != null) {
                        objCnt = mapContacts.get(strTmp);
                        bolNew = false;
                        
                        system.debug('DEBUG: NOT NEW ' + objCnt.Id);
                    }
                    objCnt.RecordTypeId = RTContactMember;
                    
                    // update fields
                    try {
                      for (String strF: mapContactField.keySet()) {
                        iTmp = getCol('Contact', strF);
                        if (dataLine[iTmp] != null && dataLine[iTmp] != '' )
                        {
                            system.debug('DEBUG: ' + strF + ' = ' + dataLine[iTmp]);
                            if (stIntegerField.contains(strF)) {
                                if (isValidNumber(dataLine[iTmp], true)) {
                                    objCnt.put(strF, Integer.valueOf(dataLine[iTmp]));
                                }
                                else {
                                    strErr += 'Invalid number ' + dataLine[iTmp] + ' ;';
                                }
                            }
                            else if (stDoubleField.contains(strF)) {
                                if (isValidNumber(dataLine[iTmp], false)) {
                                    objCnt.put(strF, Double.valueOf(dataLine[iTmp]));
                                }
                                else {
                                    strErr += 'Invalid number ' + dataLine[iTmp] + ' ;';
                                }
                            }
                            else if (stDateField.contains(strF)) {                                
                                objCnt.put(strF, Date.valueOf(convertDate(dataLine[iTmp])));
                            }
                            else {
                                objCnt.put(strF, dataLine[iTmp]);
                            }
                        }
                        else {
                            objCnt.put(strF, null);
                        }
                      }
                    }
                    catch (Exception e) {
                        //ApexPages.addMessages(e);
                        strWarning += 'Row ' + String.valueOf(i+2) + ': ' + e.getMessage() + ' <br/>\n';
                    }
                    
                    iData++;
                    if (strErr != '') {
                        strWarning += 'Row ' + String.valueOf(i+2) + ': ' + strErr + ' <br/>\n';
                    }
                    lsContactRecord.add(objCnt);
                }
              }
            
            
            Database.UpsertResult[] srList;
            Database.Error[] listErr;
            // save
            try {
               // srList  = Database.upsert(lsContactRecord, 'ID_No__c', false);
               srList = Database.upsert(lsContactRecord, false);
            }
            catch(DmlException e) {
                ApexPages.addMessages(e);  
                strWarning += 'ERR on Contact ' + e.getMessage() + '<br/>\n';
            }
            
            if (srList != null) {
                iTmp = 1;
                iTmp2 = 0;
                for(Database.UpsertResult sr: srList) {
                    iTmp++;
                    if (listErr != null) listErr.clear();
                    
                    if (sr.isSuccess()) {
                        stContactSuccess.add(sr.getId());
                        totalSuccess++;
                    }
                    else {
                        listErr = sr.getErrors();
                        
                        // check row number
                        strTmp = strTmp2 = '';
                        if (mapRowSN.get(iTmp2) != null) {
                            strTmp = mapRowSN.get(iTmp2); // SN
                            if (mapSNRow.get(strTmp) != null) {
                                strTmp2 = String.valueOf(mapSNRow.get(strTmp) + 2); // actual row (+2 because index start with 0, but data start at row 2)
                            }
                            
                        }
                        
                        for(j = 0; j < listErr.size();j++) {
                            // strInfo += 'Row ' + String.valueOf(iTmp) + ': ' + listErr[j].getMessage() + '<br/>\n';
                            strInfo += 'Row ' + strTmp2 + ' [' + strTmp + ']: ' + listErr[j].getMessage() + '<br/>\n';
                        }
                        
                        totalFailed++;
                    }
                    
                    iTmp2++;
                }
            }
            
            for(Contact C: lsContactRecord) {
                if (C.ID_No__c != null && stContactSuccess.contains(C.Id)) {
                    mapContacts.put(C.ID_No__c, C);
                }
            }
            
            iCase = getCol('Cases__c', 'Name');
            iData = 0;
            strSN = '';
            mapRowSN = new Map<Integer, String>();
            
              for (i = startP; i <= endP; i++)
              {
                dataLine = dataAll[i];
                if (dataLine.size() > 51 && dataLine[iCase] != null && dataLine[iCase] != '') { // make sure correct data, only if case
                    strTmp = dataLine[iContact]; 
                    if (strTmp != null && mapContacts.get(strTmp) != null) // only if contact success
                    {
                        
                        strSN = dataLine[0]; // get serial number
                        mapRowSN.put(iData, strSN);
                        intRow = 0;
                        if (mapSNRow.get(strSN) != null) {
                            intRow = mapSNROw.get(strSN);
                        }
                        strErr = ''; // for skipped error
                        
                        strTmp2 = dataLine[iCase]; 
                        bolNew = true;
                        objCase = new Cases__c();
                        
                        if (strTmp2 != null && strTmp2 != '' && mapCases.get(strTmp2) != null) {
                            objCase = mapCases.get(strTmp2);
                            bolNew = false;
                        }
                        
                        objCase.Contact__c = mapContacts.get(strTmp).Id;
                        
                        // update fields
                        try {
                          for (String strF: mapCaseField.keySet()) {
                            iTmp = getCol('Cases__c', strF);
                            if (dataLine[iTmp] != null && dataLine[iTmp] != '' )
                            {
                                system.debug('DEBUG: ' + strF + ' = ' + dataLine[iTmp]);
                                if (stIntegerField.contains(strF)) {
                                    if (isValidNumber(dataLine[iTmp], true)) {
                                        objCase.put(strF, Integer.valueOf(dataLine[iTmp]));
                                    }
                                    else {
                                        strErr += 'Invalid number ' + dataLine[iTmp] + ' ;';
                                    }
                                }
                                else if (stDoubleField.contains(strF)) {
                                    if (isValidNumber(dataLine[iTmp], false)) {
                                        objCase.put(strF, Double.valueOf(dataLine[iTmp]));
                                    }
                                    else {
                                        strErr += 'Invalid number ' + dataLine[iTmp] + ' ;';
                                    }
                                }
                                else if (stDateField.contains(strF)) {
                                    system.debug('DEBUG: date ' + dataLine[iTmp]);
                                    objCase.put(strF, Date.valueOf(convertDate(dataLine[iTmp])));
                                }
                                else {
                                    objCase.put(strF, dataLine[iTmp]);
                                }
                            }
                            else {
                                objCase.put(strF, null);
                            }
                          }
                        }
                        catch (Exception e) {
                            // ApexPages.addMessages(e);
                            strWarning += 'Row ' + String.valueOf(i+2) + ' : ' + e.getMessage() + ' <br/>\n';
                        }
                        
                        lsCaseRecord.add(objCase);
                        iData++;
                        if (strErr != '') {
                            strWarning += 'Row ' + String.valueOf(i+2) + ' : ' + strErr + ' <br/>\n';
                        }
                    }
                }
              }
                
        
            // save cases
            srList = null;
            try {
                srList = Database.upsert(lsCaseRecord);
                // totalProceedCase += lsCaseRecord.size();
            }
            catch(DmlException e) {
                ApexPages.addMessages(e);
                
                strWarning += 'ERR on Case ' + e.getMessage() + '<br/>\n';
            }
            
            // todo, inform error when save case
            if (srList != null) {
                iTmp = 1;
                iTmp2 = 0;
                for(Database.UpsertResult sr: srList) {
                    iTmp++;
                    if (listErr != null) listErr.clear();
                    
                    if (sr.isSuccess()) {
                        // stContactSuccess.add(sr.getId());
                        totalProceedCase++;
                    }
                    else {
                        listErr = sr.getErrors();
                        
                        // check row number
                        strTmp = strTmp2 = '';
                        if (mapRowSN.get(iTmp2) != null) {
                            strTmp = mapRowSN.get(iTmp2); // SN
                            if (mapSNRow.get(strTmp) != null) {
                                strTmp2 = String.valueOf(mapSNRow.get(strTmp) + 2); // actual row (+2 because index start with 0, but data start at row 2)
                            }
                            
                        }
                        
                        
                        for(j = 0; j < listErr.size();j++) {
                            // strInfo += 'Row ' + String.valueOf(iTmp) + ': ' + listErr[j].getMessage() + '<br/>\n';
                            strInfo += 'Row (Case) ' + strTmp2 + ' [' + strTmp + ']: ' + listErr[j].getMessage() + '<br/>\n';
                        }
                        
                        // totalFailed++;
                    }
                    
                    iTmp2++;
                }
            }
            
        } // if totalData
        
    }
    
    public PageReference next()
    {
        proceed();
       return null;   
    }
    
    // check if a string is numeric (integer or double)
    public Boolean isValidNumber(String str, Boolean isInteger)
    {
        Decimal decTmp;
        Integer intTmp;
        Boolean bolOK = true;
        try {
            if (isInteger){
                intTmp = Integer.valueOf(str);
            }
            else {
                decTmp = Decimal.valueOf(str);
            }
        }
        catch (Exception e) {
            bolOK = false;
        }
        return bolOK;
    }
    
    // get column number from code
    public Integer getCol(String strObj, String strField)
    {
                
        Integer iResult = null;

        if (strObj == 'Contact' && mapContactField.get(strField) != null) {
            iResult = mapContactField.get(strField);
        }
        else if (strObj == 'Cases__c' && mapCaseField.get(strField) != null) {
            iResult = mapCaseField.get(strField);
        }

        return iResult;
    }
    
    // convert date from DD/MM/YYYY to YYYY-MM-DD
    public String convertDate(String strDate)
    {
        String strResult = strDate;
        String strYear;
        if (strDate != null && strDate != '')
        {
            String[] arrStr = strDate.split('/');
            
            if (arrStr.size() >= 3) {
                strYear = arrStr[2];
                if (strYear.length() == 2) strYear = '20' + strYear;
                strResult = strYear + '-' + arrStr[1] + '-' + arrStr[0];
            }
            
        }
        return strResult;
    }
    
    // to handle back button to return to Contact List
    public PageReference back(){
        return new ApexPages.Action('{!List}').invoke();
    } 
}