private String executeRequest(AbstractDataSource fileClassInstance, Configuration.MethodsID methodName, String relevation)
{
AbstractDataSource newFileClassInstance = fileClassInstance;
String response = null;
switch(methodName)
{
case Configuration.MethodsID.readLine: response = newFileClassInstance.readLine(); break;
case Configuration.MethodsID.appendRelevation: response = newFileClassInstance.appendRelevation(relevation); break;
case Configuration.MethodsID.showContent: response = newFileClassInstance.showContent(); break;
default: break;
}
return response;
}
/// <summary>
/// Checks the accessibility of a method by a requesting class
/// </summary>
/// <param name="requestingClass">The ID of the class requesting the service</param>
/// <param name="request">The ID of the requested service</param>
/// <returns>True if the method is accessible from the requesting class, false otherwise</returns>
private Boolean checkAccessibility(Configuration.ClassesID requestingClass, Configuration.MethodsID request)
{
Boolean accessibility = false;
switch (requestingClass)
{
case Configuration.ClassesID.WSN: if(WSN_MA.ContainsKey(request)) { accessibility = WSN_MA[request]; } break;
case Configuration.ClassesID.JournalingManager: if(journalingManager_MA.ContainsKey(request)) { accessibility = journalingManager_MA[request]; } break;
case Configuration.ClassesID.HistoryManager: if(historyManager_MA.ContainsKey(request)) { accessibility = historyManager_MA[request]; } break;
default: break;
}
return accessibility;
}
/// <summary>
/// Creates an instance of a subclass of AbstractDataSource based on the passed class ID
/// </summary>
/// <param name="classID">The ID of the requesting class</param>
/// <returns>An instance of a subclass of AbstractDataSource</returns>
private AbstractDataSource createClassInstanceFromClassID(Configuration.ClassesID classID)
{
AbstractDataSource classInstance = null;
switch(classID)
{
case Configuration.ClassesID.WSN: if(this.relevationFile == null)
{
this.relevationFile = new RelevationFile();
classInstance = this.relevationFile;
}
else
classInstance = this.relevationFile;
break;
case Configuration.ClassesID.JournalingManager: if(this.journalingFile == null)
{
this.journalingFile = new JournalingFile();
classInstance = this.journalingFile;
}
else
classInstance = this.journalingFile;
break;
case Configuration.ClassesID.HistoryManager: if(this.historyFile == null)
{
this.historyFile = new HistoryFile();
classInstance = this.historyFile;
}
else
classInstance = this.historyFile;
break;
default: break;
}
return classInstance;
}
/// <summary>
/// Each manager (WSN, JournalingManager, HistoryManager) invokes the method sendRequest() to perform an I/O operation on a file
/// passing its own class ID, the ID of the desired method and, optionally the string of the relevation to be appended.
/// sendRequest() first performs a check to verify that the requesting class is allowed to perform the requested method;
/// if true, it creates an instance of a subclass of AbstractDataSource (RelevationFile, JournalingFile or HistoryFile), based on the provided class ID
/// Eventually, it invokes the method executeRequest(), passing the just created instance, the ID of the requested method and the relevation string, if applicable.
/// </summary>
/// <param name="classID">The ID of the class requesting the operation</param>
/// <param name="methodID">The ID of the requested operation.</param>
/// <param name="relevation">The string of the relevation if the requested operation corresponds to appendRelevation</param>
public String sendRequest(Configuration.ClassesID classID, Configuration.MethodsID methodID, String relevation)
{
AbstractDataSource classInstance = null;
Configuration.MethodsID methodName = methodID;
String response = null;
Boolean accessibility = checkAccessibility(classID, methodID); // Checks the accessibility of the request by the requesting class
// If the operation is not accessible to the requesting class
if(!accessibility)
throw new System.InvalidOperationException("Cannot invoke this method:" + methodID.ToString() + "Operation not available.");
// Creates an instance of RelevationFile, JournalingFile or HistoryFile, depending od the provided class ID
classInstance = createClassInstanceFromClassID(classID);
// Executes the requested operation
response = executeRequest(classInstance, methodName, relevation);
return response;
}