<apex:form id="form">

    <apex:pageBlock title="Appointments Tables" id="TableDoctors">
        <apex:pageBlock >
            <apex:selectList value="{!selectedname}" size="1" multiselect="false" onChange="updateDoctors(this.value)">
                <h1>
                    Select a doctor name:
                </h1>
                <apex:selectOptions value="{!selectedDocnamefields}"/>
            </apex:selectList>
        </apex:pageBlock>

        <apex:pageBlock >
            <apex:commandButton action="{!URLFOR("/apex/DoctorCreate")}" value="Add new doctor"/>
        </apex:pageBlock>

        <apex:pageBlock >
            <apex:pageBlockSection title="Working hours">
                <apex:repeat value="{!Doctors}" var="d" rows="1">
                    <apex:outputField value="{!d.Doctor__r.Working_Hours_Start__c}"/>
                    <apex:outputField value="{!d.Doctor__r.Working_Hours_End__c}"/>
                </apex:repeat>
            </apex:pageBlockSection>
        </apex:pageBlock>

        <apex:pageBlock >
            <apex:selectList value="{!selectedPatientname}" size="1" multiselect="false" onChange="updatePatients(this.value)">
                <h1>
                    Select a Patient name:
                </h1>
                <apex:selectOptions value="{!selectedPatnamefields}" />
            </apex:selectList>
        </apex:pageBlock>

        <apex:pageBlock >
            <apex:commandButton action="{!URLFOR("/apex/PatientCreate")}" value="Add new patient"/>
        </apex:pageBlock>

        <apex:pageBlock >
            <apex:commandButton action="{!URLFOR("/apex/AppointmentCreatePage")}" value="Add new appointment"/>
        </apex:pageBlock>

        <apex:pageBlockTable value="{! doctors }" var="d" columns="5" id="TableDoctors" >

            <apex:column value="{! d.Doctor__c }" />
            <apex:column value="{! d.Doctor__r.Name }"/>
            <apex:column value="{! d.Patient__r.Name }"/>
            <apex:column value="{! d.Appointment_Date__c }"/>
            <apex:column value="{! d.Duration_in_minutes__c }"/>

        </apex:pageBlockTable>

        <apex:pageBlockButtons location="bottom">
            <apex:commandButton value="Previous" action="{!Previous}" rerender="TableDoctors" />
            <apex:commandButton value="Next" action="{!Next}" rerender="TableDoctors"/>
        </apex:pageBlockButtons>

        <apex:actionFunction name="updateDoctors" action="{!getDoctors}" rerender="TableDoctors" immediate="false">
            <apex:param name="selectedDoc" assignTo="{!selectedname}" value="" />
        </apex:actionFunction>

    </apex:pageBlock>

</apex:form>

public List<Appointment__c> Doctors   {get;set;}
public string selectedname{

    get{
        if(selectedname == null)
            selectedname ='Model API';
        return selectedname;
    }
    set;}

// Getting the name of the selected patient

Public List<Selectoption> getselectedDocnamefields(){
        List<Selectoption> Doctornamesel = new List<selectoption>();
        Doctornamesel.add(new selectOption('', '- None -'));
        for(Appointment__c Doc :[SELECT Id, Doctor__r.Name, Doctor__r.Working_Hours_Start__c, Doctor__r.Working_Hours_End__c, Patient__r.Name, Appointment_Date__c, Duration_in_minutes__c FROM Appointment__c Where Doctor__r.Name!=Null]){
            Doctornamesel.add(new selectoption(Doc.Doctor__r.id, Doc.Doctor__r.Name));
        }
        return Doctornamesel;
}

// List of doctors

public void getDoctors() {

    system.debug('SelectedName is: ' + selectedname);
    Doctors = [SELECT Doctor__r.Name, Doctor__r.Working_Hours_Start__c, Doctor__r.Working_Hours_End__c,  Patient__r.Name, Appointment_Date__c, Duration_in_minutes__c  FROM Appointment__c Where Doctor__c =: selectedname Limit :recordLimit OFFSET :offSetLimit];

}


public List<Appointment__c> Patients   {get;set;}
public string selectedPatientname{

    get{
        if(selectedPatientname == null)
        selectedPatientname ='Model API';
        return selectedPatientname;
    }
    set;}


// Getting the name of the selected patient

Public List<Selectoption> getselectedPatnamefields(){
    List<Selectoption> Patientnamesel = new List<selectoption>();
    Patientnamesel.add(new selectOption('', '- None -'));
    for(Appointment__c Pat :[SELECT Id, Patient__r.Name FROM Appointment__c Where Doctor__r.Name!=Null]){
        Patientnamesel.add(new selectoption(Pat.Patient__r.id, Pat.Patient__r.Name));
    }
    return Patientnamesel;
}


//  List of patient

public void getPatients() {

    system.debug('selectedPatientname is: ' + selectedPatientname);
    Patients = [SELECT Patient__r.Name  FROM Appointment__c Where Patient__c =: selectedPatientname ];

}

//Pagination


integer recordLimit = 20;
integer offSetLimit = 0;
integer index;

//Botton Next

public pagereference Next(){
    index = Doctors.size() - 1;
    if(Doctors.size()>0 && Doctors.size()<index)
    system.debug('Doctors'+ Doctors.size());
    offSetLimit = offSetLimit + 20;
    return null;
}

//Botton Previous
public pagereference Previous(){
    if(offSetLimit>0)
    offSetLimit = offSetLimit - 20;
    return null;
}