I'm getting this error from a class referenced by an Email Service. From what I understand, the error is kicked off when a reference is made to a list which exceeds the number of items in the list.

In this case, the class is referencing the attachments included in an email. Ultimately, it intends to re-save the attachment as a file in a SF record. Here are the lines which are causing the error. I will also include the entire class later in this post :

//Set file Name
 fileName  = fileStartName+pCR.Contact__r.Name +' )';
 version = Integer.valueOf(attachment.Name.split('V1.')[1].removeEnd('.csv').isNumeric() ? attachment.Name.split('V1.')[1].removeEnd('.csv') : '0');  
                            fileName +=  '.csv';

In the debug logs the line beginning with 'version' seems to be the line causing the error.

I am confused by the code so would really appreciate any input which you can provide on why this error is happening. I do know that the code will work some times. Thank you very much.

I have included the whole class here :

global Messaging.InboundEmailResult handleInboundEmail(Messaging.inboundEmail email,Messaging.InboundEnvelope envelop)
{
    
    Messaging.InboundEmailResult result = new Messaging.InboundEmailResult();
    
    //String to hold message
    String message = '';
    String fileStartName = '';
    String fileEndName = '';
    String fileName = '';
    
    Integer version = 0;
    
    //List to hold Error log records
    List<Error_Log__c> errorLogs = new List<Error_Log__c>();
    
    //Get From Address
    String fromAddress = email.FromAddress;
    
    //Get Contact
    Contact contactRecord;
    
    List<Contact> contacts = [SELECT Id , Name , AccountId FROM Contact WHERE Email =: fromAddress ORDER BY Name DESC LIMIT 1];
    
    if(contacts.size() > 0)
        contactRecord = contacts[0];    
    
    if (email.binaryAttachments != null && email.binaryAttachments.size() > 0) 
    {
        
        //Map to hold the Funder Contact Role Details with Funder
        Map<Id, Program_Contact_Role__c> mapPCRsWithProgram = new Map<Id, Program_Contact_Role__c>();
        
        //List to hold Content versions
        List<ContentVersion> contentVersions = new List<ContentVersion>();
        
        
       for(integer i =0, s = email.binaryattachments.size(); i < s; i++) 
       {


      if(email.binaryAttachments[i].mimeTypeSubType.equals('application/vnd.ms-excel') || email.binaryAttachments[i].mimeTypeSubType.equals('text/csv') ||email.binaryAttachments[i].filename.contains('.csv')) 
       
            {

            try
            {
                System.debug('Attachment matched a criteria');
                //Get Attachment details
                List<String> attachmentSplitsByRows = new List<String>();
                
                //Insatnce of attachemnts
                Attachment attachment = new Attachment();
                
                // Get attachment name and body
                attachment.Name = email.binaryAttachments[0].filename;
                attachment.Body = email.binaryAttachments[0].body;
                
                System.debug('Attachment Body '+(attachment.Body).toString());
                
                //Convert to string
                String attachmentBody = (attachment.Body).toString();
                attachmentBody = attachmentBody.unescapeCsv();
                
                //Split the data by new line 
                attachmentSplitsByRows = attachmentBody.split('\n');
                
                //Set to hold the Onbording Ids
                Set<Id> setOnbordingIds = new Set<Id>();
                
                //Map to hold the Onbording Record
                Map<Id, Program_Onboarding__c> mapProgramOnboardings = new Map<Id, Program_Onboarding__c>();
                
                //Set to hold the Program Onbording ids to check Funder is already approved or not 
                Set<Id> setOfProgOnboardingIds = new Set<Id>();
                
                //List of Milestone to create a new Milestone
                List<Milestone__c> milestones = new List<Milestone__c>();
                
                Boolean firstRow = true;
                
                //Loop over the Attachments
                for(String csvRow : attachmentSplitsByRows)
                {
                    
                    //Skip header row
                    if(!firstRow){
                        
                        //Get the onbording details
                        List<String> attachmentSplitByColumns = csvRow.split(',');
                        
                        //Add Onbording Id in set
                        setOnbordingIds.add(attachmentSplitByColumns[0]);
                    }
                    firstRow = false;
                }
                
                firstRow = true;
                
                //Check onbordings
                if(setOnbordingIds.size() > 0) {
                    
                    //Get Onboardings
                    mapProgramOnboardings = new Map<Id, Program_Onboarding__c>([Select Id, Supplier__c, Supplier__r.Supplier__c, Funder__c, Program__c From Program_Onboarding__c Where Id IN : setOnbordingIds]);
                    
                    //Get Milestones
                    for(Milestone__c ml : [Select Id , Onboarding__c FROM Milestone__c WHERE Onboarding__c IN: setOnbordingIds AND Milestone_Type__c =: Constants.PROGRAM_MILESTONE_MILESTONE_TYPE_APPROVED_BY_FUNDER])
                        setOfProgOnboardingIds.add(ml.Onboarding__c);
                    
                    //Set to hold the Program Details
                    Set<Id> setProgramIds = new Set<Id>();
                    
                    //Loop over the Onboardings
                    for(Program_Onboarding__c pO : mapProgramOnboardings.values())
                        setProgramIds.add(pO.Program__c);
                    
                    //Set file Name
                    fileStartName = 'Response - '+attachment.Name.split('.csv')[0].trim()+' - ( ';
                    
                    //Get Funder Program Contact Role
                    for(Program_Contact_Role__c pCR : [Select Id, Program_Name__c, Funder__c , Contact__c , Contact__r.Name From Program_Contact_Role__c Where Program_Name__c IN : setProgramIds AND Contact__r.Email =: fromAddress AND RecordTypeId =: Constants.PROGCONTACTROLE_RT_ID_FUNDER]){
                        mapPCRsWithProgram.put(pCR.Program_Name__c, pCR);
                        
                        //Set file Name
                        fileName  = fileStartName+pCR.Contact__r.Name +' )';
                        version = Integer.valueOf(attachment.Name.split('V1.')[1].removeEnd('.csv').isNumeric() ? attachment.Name.split('V1.')[1].removeEnd('.csv') : '0');  
                        fileName +=  '.csv';
                                                
                        //Insert File under Program
                        // convert from string to blob
                        Blob tempBlob = attachment.Body;
                        
                        // convert base64 encode from the blob
                        string csvFile = EncodingUtil.base64Encode(tempBlob);
                        
                        //Decoding base64Data
                        String base64Data = EncodingUtil.urlDecode(csvFile, 'UTF-8');
                        
                        ContentVersion contentVersionData = new ContentVersion();
                        contentVersionData.Title = fileName;
                        contentVersionData.PathOnClient = '/' + fileName;
                        contentVersionData.FirstPublishLocationId = pCR.Program_Name__c;
                        contentVersionData.VersionData = EncodingUtil.base64Decode(base64Data);
                        contentVersionData.IsMajorVersion = true;
                        
                        //Add content version
                        contentVersions.add(contentVersionData);
                        
                    }
                    
                }
                System.debug('attachmentSplitsByRows '+attachmentSplitsByRows[0].split(',').size());
                
                if(attachmentSplitsByRows.size()>0 && attachmentSplitsByRows[0].split(',').size() > 8){
                                    
                    //Loop over the Onbording details
                    for(String csvRow : attachmentSplitsByRows){
                        
                        //Skip header row
                        if(!firstRow){
                            
                            //Get the onbording details
                            List<String> attachmentSplitByColumns = csvRow.split(',');
                            
                            //Get last column
                            Integer lastColumn = attachmentSplitByColumns.size();
                            if(attachmentSplitByColumns.size() > 8){
                                
                                //Check Approved by funder is Yes or True then update program onboarding status to 'Trading Set Up - Pending Supplier'
                                if(attachmentSplitByColumns.size() > 8 && String.isNotBlank(attachmentSplitByColumns[0]) && !setOfProgOnboardingIds.contains(attachmentSplitByColumns[0]) && (attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('True') || attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('Yes'))){
                                    
                                    //Update onbording
                                    mapProgramOnboardings.get(attachmentSplitByColumns[0]).Status__c = Constants.ONBOARDING_STATUS_PENDING_SUPPLIER;
                                    
                                    //Add a new Milestone
                                    milestones.add(milestone(mapProgramOnboardings.get(attachmentSplitByColumns[0]), mapPCRsWithProgram, Constants.PROGRAM_MILESTONE_MILESTONE_TYPE_APPROVED_BY_FUNDER));
                                    
                                } else if(attachmentSplitByColumns.size() > 8 && String.isNotBlank(attachmentSplitByColumns[0]) && !setOfProgOnboardingIds.contains(attachmentSplitByColumns[0]) && (attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('False') || attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('No'))){
                                    
                                    //Update onbording
                                    mapProgramOnboardings.get(attachmentSplitByColumns[0]).Status__c = Constants.ONBOARDING_STATUS_BUYER_REVIEW;
                                    
                                    //Add a new Milestone
                                    milestones.add(milestone(mapProgramOnboardings.get(attachmentSplitByColumns[0]), mapPCRsWithProgram, Constants.PROGRAM_MILESTONE_MILESTONE_TYPE_BUYER_REVIEW_REQUESTED));
                                    
                                }else if(setOfProgOnboardingIds.contains(attachmentSplitByColumns[0])){
                                    
                                    message = 'Funder File is already processed.';
                                    
                                    if(mapProgramOnboardings.containsKey(attachmentSplitByColumns[0])){                              
                                        
                                        //Add error Log
                                        errorLogs.add(errorLog(mapProgramOnboardings.get(attachmentSplitByColumns[0]) , message , contactRecord));
                                    }
                                }else if(attachmentSplitByColumns.size() > 8 && (!attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('Yes') || !attachmentSplitByColumns[lastColumn-1].trim().equalsIgnoreCase('No'))){
                                    message = 'Funder replies back with '+attachmentSplitByColumns[lastColumn-1].trim()+' instead of Yes or No.';
                                    
                                    //Add error Log
                                    errorLogs.add(errorLog(mapProgramOnboardings.get(attachmentSplitByColumns[0]) , message , contactRecord));

                                }
                            }else{
                                    message = 'Funder replies back with blank value instead of Yes or No.';
                                    
                                    //Add error Log
                                    errorLogs.add(errorLog(mapProgramOnboardings.get(attachmentSplitByColumns[0]) , message , contactRecord));
                            }
                        }
                        firstRow = false;
                    }
                }else{
                    
                    message = 'Funder file formate is not correct , please check funder file.';
                    
                    //Add Error log
                    errorLogs.add(errorLog(null , message , contactRecord));
                    
                }
                
                //check size
                if(mapProgramOnboardings.size() > 0)
                    update mapProgramOnboardings.values();
                
                //Check milestone list
                if(milestones.size() > 0)
                    insert milestones;
                
                //Check content versions
                if(contentVersions.size() >0)
                    insert contentVersions;
            
            }catch(Exception ex){