7 files changed, 494 insertions, 0 deletions

diff --git a/src/main/java/org/pacien/lemonad/attempt/Attempt.java b/src/main/java/org/pacien/lemonad/attempt/Attempt.java
new file mode 100644
index 0000000..fc437ad
--- /dev/null
+++ b/src/main/java/org/pacien/lemonad/attempt/Attempt.java
@@ -0,0 +1,129 @@
+/*
+ * lemonad - Some functional sweetness for Java
+ * Copyright (C) 2019  Pacien TRAN-GIRARD
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.pacien.lemonad.attempt;
+
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import lombok.NonNull;
+
+/**
+ * Wraps either a value from a success or an error from a failure.
+ *
+ * @param <R> the potential wrapped result type.
+ * @param <E> the potential error type.
+ * @author pacien
+ */
+public interface Attempt<R, E> {
+  /**
+   * @return whether the {@link Attempt} is successful.
+   */
+  boolean isSuccess();
+
+  /**
+   * @return whether the {@link Attempt} is failed.
+   */
+  boolean isFailure();
+
+  /**
+   * @return the result if this {@link Attempt} is a success.
+   * @throws java.util.NoSuchElementException if this {@link Attempt} is a failure.
+   */
+  R getResult();
+
+  /**
+   * @return the error if this {@link Attempt} is a failure.
+   * @throws java.util.NoSuchElementException if this {@link Attempt} is a success.
+   */
+  E getError();
+
+  /**
+   * @param resultConsumer a {@link Consumer} of result called if the {@link Attempt} is a success.
+   * @return the current {@link Attempt}
+   */
+  default Attempt<R, E> ifSuccess(@NonNull Consumer<? super R> resultConsumer) {
+    if (isSuccess()) resultConsumer.accept(getResult());
+    return this;
+  }
+
+  /**
+   * @param errorConsumer a {@link Consumer} of error called if the {@link Attempt} is a failure.
+   * @return the current {@link Attempt}
+   */
+  default Attempt<R, E> ifFailure(@NonNull Consumer<? super E> errorConsumer) {
+    if (isFailure()) errorConsumer.accept(getError());
+    return this;
+  }
+
+  /**
+   * @param mapper a function producing an {@link Attempt}, called with the current result if this {@link Attempt} is a success.
+   * @return this {@link Attempt} if it is a failure, or the produced one otherwise.
+   */
+  default <RR> Attempt<RR, E> mapResult(@NonNull Function<? super R, ? extends Attempt<? extends RR, ? extends E>> mapper) {
+    //noinspection unchecked
+    return (Attempt<RR, E>) (isSuccess() ? mapper.apply(getResult()) : this);
+  }
+
+  /**
+   * @param mapper a function producing an {@link Attempt}, called with the current error if this {@link Attempt} is a failure.
+   * @return this {@link Attempt} if it is a success, or the alternative {@link Attempt} retrieved from the supplier otherwise.
+   */
+  default <EE> Attempt<R, EE> mapFailure(@NonNull Function<? super E, ? extends Attempt<? extends R, ? extends EE>> mapper) {
+    //noinspection unchecked
+    return (Attempt<R, EE>) (isFailure() ? mapper.apply(getError()) : this);
+  }
+
+  /**
+   * @param mapper a function transforming an {@link Attempt}.
+   * @return the transformed {@link Attempt}
+   */
+  default <RR, EE> Attempt<RR, EE> flatMap(@NonNull Function<? super Attempt<? super R, ? super E>, ? extends Attempt<? extends RR, ? extends EE>> mapper) {
+    //noinspection unchecked
+    return (Attempt<RR, EE>) mapper.apply(this);
+  }
+
+  /**
+   * @param result the result of the {@link Attempt}.
+   * @return a successful {@link Attempt} wrapping the supplied result.
+   */
+  static <R, E> Attempt<R, E> success(R result) {
+    return new Success<>(result);
+  }
+
+  /**
+   * @param error the cause of the failure of the {@link Attempt}.
+   * @return a failed {@link Attempt} with the supplied error.
+   */
+  static <R, E> Attempt<R, E> failure(E error) {
+    return new Failure<>(error);
+  }
+
+  /**
+   * @param supplier a {@code Supplier} that may throw an {@link Throwable}.
+   * @return an {@link Attempt} wrapping either the result of the execution of the supplier or any thrown {@link Throwable}.
+   */
+  static <R, E extends Throwable> Attempt<R, E> attempt(@NonNull ThrowingSupplier<? extends R, ? extends E> supplier) {
+    try {
+      return success(supplier.get());
+    } catch (Throwable throwable) {
+      //noinspection unchecked
+      return (Attempt<R, E>) failure(throwable);
+    }
+  }
+}
diff --git a/src/main/java/org/pacien/lemonad/attempt/Failure.java b/src/main/java/org/pacien/lemonad/attempt/Failure.java
new file mode 100644
index 0000000..752e981
--- /dev/null
+++ b/src/main/java/org/pacien/lemonad/attempt/Failure.java
@@ -0,0 +1,42 @@
+/*
+ * lemonad - Some functional sweetness for Java
+ * Copyright (C) 2019  Pacien TRAN-GIRARD
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.pacien.lemonad.attempt;
+
+import java.util.NoSuchElementException;
+
+import lombok.Value;
+
+/**
+ * @author pacien
+ */
+@Value class Failure<R, E> implements Attempt<R, E> {
+  E error;
+
+  @Override public boolean isSuccess() {
+    return false;
+  }
+
+  @Override public boolean isFailure() {
+    return true;
+  }
+
+  @Override public R getResult() {
+    throw new NoSuchElementException();
+  }
+}
diff --git a/src/main/java/org/pacien/lemonad/attempt/Success.java b/src/main/java/org/pacien/lemonad/attempt/Success.java
new file mode 100644
index 0000000..928fbb1
--- /dev/null
+++ b/src/main/java/org/pacien/lemonad/attempt/Success.java
@@ -0,0 +1,42 @@
+/*
+ * lemonad - Some functional sweetness for Java
+ * Copyright (C) 2019  Pacien TRAN-GIRARD
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.pacien.lemonad.attempt;
+
+import java.util.NoSuchElementException;
+
+import lombok.Value;
+
+/**
+ * @author pacien
+ */
+@Value class Success<R, E> implements Attempt<R, E> {
+  R result;
+