Lightning Component:
<aura:component controller="Test">
  <aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
<div class ="card">
    <div class="card-heading context-dashboard">
        Report View
    </div>
    <div class="card-detail">
        <div id="chart"></div>
    </div>
</div>

({
doInit : function(component, event, helper) {
    var action = component.get("c.runReport");

    action.setCallback(this,function(response){
        var state = response.getState();
    if(state === "SUCCESS"){
        var reportData = JSON.parse(response.getReturnValue());
        console.log ("Return value" + JSON.stringify(response.getReturnValue()));
        var returnData = [];
        for(var i=0, j= reportData.groupingsDown.groupings.lenght; i<j; i++){
            var label = reportData.groupingsDown.groupings[i].label;
            var Key = reportData.groupingsDown.groupings[i].Key;
            var value= reportData.factMap[Key + '!T'].aggregates[0].value;
            returnData.push([label,value]);
        }
        var chart = c3.generate ({
            bindto :'#chart',
            data:{
                coloumns: returnData,
                type: 'pie'
            }
        });
    }
   });
$A.enqueueAction(action);
}

@AuraEnabled
public static String runReport(){
    Report rep = [SELECT Id, DeveloperName FROM Report where DeveloperName = 'Case' LIMIT 1];
    Reports.ReportResults results = Reports.ReportManager.runReport(rep.Id,true);
    return JSON.serialize(results);
}