package com.longluo.viewer;

import android.os.AsyncTask;

import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;

// Ideally this would be a subclass of AsyncTask, however the cancel() method is final, and cannot
// be overridden. I felt that having two different, but similar cancel methods was a bad idea.
public class CancellableAsyncTask<Params, Result> {
    private final AsyncTask<Params, Void, Result> asyncTask;
    private final CancellableTaskDefinition<Params, Result> ourTask;

    public void onPreExecute() {

    }

    public void onPostExecute(Result result) {

    }

    public CancellableAsyncTask(final CancellableTaskDefinition<Params, Result> task) {
        if (task == null)
            throw new IllegalArgumentException();

        this.ourTask = task;
        asyncTask = new AsyncTask<Params, Void, Result>() {
            @Override
            protected Result doInBackground(Params... params) {
                return task.doInBackground(params);
            }

            @Override
            protected void onPreExecute() {
                CancellableAsyncTask.this.onPreExecute();
            }

            @Override
            protected void onPostExecute(Result result) {
                CancellableAsyncTask.this.onPostExecute(result);
                task.doCleanup();
            }

            @Override
            protected void onCancelled(Result result) {
                task.doCleanup();
            }
        };
    }

    public void cancel() {
        this.asyncTask.cancel(true);
        ourTask.doCancel();

        try {
            this.asyncTask.get();
        } catch (InterruptedException e) {
        } catch (ExecutionException e) {
        } catch (CancellationException e) {
        }
    }

    public void execute(Params... params) {
        asyncTask.execute(params);
    }

}
