Code to retrieve all reports in Salesforce

RetrieveAllReports.cls

//First query all ReportFolders in the org.
Map<Id,Folder> folderMap = new Map<Id,Folder>([SELECT 	Id,
							DeveloperName,
							NameSpacePrefix
							FROM Folder
							WHERE
							Type = 'Report']);

//Query all reports in the system.
List<Report> reportList = [SELECT FolderName,
			          DeveloperName,
			          OwnerId,
			          NameSpacePrefix
			          FROM Report
			          USING SCOPE everything];

List<String> reportNames = new List<String>();

for(Report reportObj: reportList){
	String reportName;
	//If a report is inside the folder then we should get the folder name also.
	//If report is in public folders then we should prefix with "unfiled$public"
	//We should also check for Managed package reports. If namspace is not blank then prepend foldername and reportname followed
	//by '__'

	if(folderMap.containsKey(reportObj.OwnerId)){
		if(String.isNotBlank(folderMap.get(reportObj.OwnerId).NameSpacePrefix)){
			reportName = folderMap.get(reportObj.OwnerId).NameSpacePrefix + '__' + folderMap.get(reportObj.OwnerId).DeveloperName;
		}else{
			reportName = folderMap.get(reportObj.OwnerId).DeveloperName;
		}

		if(String.isNotBlank(reportObj.NameSpacePrefix)){
			reportName = reportName + '/' + reportObj.NameSpacePrefix + '__' + reportObj.DeveloperName;
		}else{
			reportName = reportName + '/' + reportObj.DeveloperName;
		}

		reportNames.add(reportName);	
	}else{
		if(String.isNotBlank(reportObj.NameSpacePrefix)){
			reportName = 'unfiled$public/' + reportObj.NameSpacePrefix + '__' + reportObj.DeveloperName;
		}else{
			reportName = 'unfiled$public/' + reportObj.DeveloperName;
		}

		reportNames.add(reportName);
	}
    
}

System.debug(JSON.serialize(reportNames));
//Once all report names are printed, we can prepare package file and retrieve reports from Org.