2 files changed, 123 insertions, 0 deletions
diff --git a/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/MyTask.java b/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/MyTask.java
new file mode 100644
index 0000000..d1de4fb
--- /dev/null
+++ b/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/MyTask.java
@@ -0,0 +1,48 @@
+package fr.epita.assistants.scheduler;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class MyTask<INPUT_TYPE, RETURN_TYPE> implements Task<RETURN_TYPE> {
+    
+    CompletableFuture<RETURN_TYPE> cpFuture;
+
+    public MyTask(CompletableFuture<RETURN_TYPE> cpFuture) {
+        this.cpFuture = cpFuture;
+    }
+
+    public static <RETURN_TYPE> Task<RETURN_TYPE> of(Supplier<RETURN_TYPE> actionSupplier) {
+        return new MyTask<>(CompletableFuture.supplyAsync(actionSupplier));
+    }
+
+    public static <RETURN_TYPE> Task<RETURN_TYPE> of(Supplier<RETURN_TYPE> actionSupplier, Executor executor) {
+        return new MyTask<>(CompletableFuture.supplyAsync(actionSupplier, executor));
+    }
+
+    @Override
+    public CompletableFuture<RETURN_TYPE> build() {
+        return cpFuture;
+    }
+
+    @Override
+    public Task<RETURN_TYPE> onErrorRecoverWith(Function<Throwable, RETURN_TYPE> recoveryFunction) {
+        return new MyTask<>(cpFuture.handle((result, exception) -> {
+            if (exception != null)
+                return recoveryFunction.apply(exception);
+            return result;
+        }));
+    }
+
+    @Override
+    public <NEW_RETURN_TYPE> Task<NEW_RETURN_TYPE> andThenDo(Function<RETURN_TYPE, NEW_RETURN_TYPE> action) {
+        return new MyTask<>(cpFuture.thenApply(action));
+    }
+
+    @Override
+    public Task<RETURN_TYPE> andThenWait(long number, TimeUnit timeUnit) {
+        return new MyTask<>(cpFuture.thenApplyAsync(i -> i, CompletableFuture.delayedExecutor(number, timeUnit)));
+    }
+}
diff --git a/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/Task.java b/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/Task.java
new file mode 100644
index 0000000..64c0c03
--- /dev/null
+++ b/graphs/java/scheduler/src/main/java/fr/epita/assistants/scheduler/Task.java
@@ -0,0 +1,75 @@
+package fr.epita.assistants.scheduler;
+
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+/**
+ * Represent a single task to be executed. Tasks can be chained using the andThenDo method.
+ *
+ * @param <RETURN_TYPE> The expected return type.
+ */
+public interface Task<RETURN_TYPE> {
+
+    /**
+     * Static initializer allowing the creation of a task instance with the given {@link Supplier}.
+     *
+     * @param actionSupplier The actual action to execute.
+     * @param <RETURN_TYPE>  The expected return type, inferred by the call chain.
+     * @return A {@link Task} instance.
+     */
+    static <RETURN_TYPE> Task<RETURN_TYPE> of(Supplier<RETURN_TYPE> actionSupplier) {
+        throw new UnsupportedOperationException("This default implementation should never be called, and should be" +
+                "implemented in classes that implement this interface");
+    }
+
+    /**
+     * Build the actual completable future according to this instance specifications.
+     *
+     * @return The built {@link CompletableFuture}.
+     */
+    CompletableFuture<RETURN_TYPE> build();
+
+    /**
+     * Execute a task and return its result.
+     *
+     * @return The result of the execution of this task.
+     */
+    default RETURN_TYPE execute() {
+        try {
+            return build().get();
+        } catch (InterruptedException | ExecutionException exception) {
+            throw new RuntimeException("Exception during task computing", exception);
+        }
+    }
+
+    /**
+     * Specify a function that provides a recovery value to use if the task fails.
+     *
+     * @param recoveryFunction The function that will be called with the exception - should any happen - in order to
+     *                         compute a recovery value.
+     * @return The updated task.
+     */
+    Task<RETURN_TYPE> onErrorRecoverWith(final Function<Throwable, RETURN_TYPE> recoveryFunction);
+
+    /**
+     * Chain a new task to be executed after the current one, taking the output of the current one as its input.
+     *
+     * @param action            The action to perform.
+     * @param <NEW_RETURN_TYPE> The return type of the task to create.
+     * @return The created task.
+     */
+    <NEW_RETURN_TYPE> Task<NEW_RETURN_TYPE> andThenDo(final Function<RETURN_TYPE, NEW_RETURN_TYPE> action);
+
+    /**
+     * Wait for the given number of timeUnit.
+     *
+     * @param number   The number of units to wait for.
+     * @param timeUnit The unit.
+     * @return The created task.
+     */
+    Task<RETURN_TYPE> andThenWait(final long number, final TimeUnit timeUnit);
+
+}