/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.facebook.common.internal;

import android.util.Log;
import com.facebook.infer.annotation.Nullsafe;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.annotation.Nullable;

/**
 * Static utility methods pertaining to instances of {@link Throwable}.
 *
 * <p>See the Guava User Guide entry on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/ThrowablesExplained"> Throwables</a>.
 *
 * @author Kevin Bourrillion
 * @author Ben Yu
 * @since 1.0
 */
@Nullsafe(Nullsafe.Mode.STRICT)
public final class Throwables {
  private Throwables() {}

  /**
   * Propagates {@code throwable} exactly as-is, if and only if it is an instance of {@code
   * declaredType}. Example usage:
   *
   * <pre>
   *   try {
   *     someMethodThatCouldThrowAnything();
   *   } catch (IKnowWhatToDoWithThisException e) {
   *     handle(e);
   *   } catch (Throwable t) {
   *     Throwables.propagateIfInstanceOf(t, IOException.class);
   *     Throwables.propagateIfInstanceOf(t, SQLException.class);
   *     throw Throwables.propagate(t);
   *   }
   * </pre>
   */
  public static <X extends Throwable> void propagateIfInstanceOf(
      @Nullable Throwable throwable, Class<X> declaredType) throws X {
    // Check for null is needed to avoid frequent JNI calls to isInstance().
    if (throwable != null && declaredType.isInstance(throwable)) {
      throw declaredType.cast(throwable);
    }
  }

  /**
   * Propagates {@code throwable} exactly as-is, if and only if it is an instance of {@link
   * RuntimeException} or {@link Error}. Example usage:
   *
   * <pre>
   *   try {
   *     someMethodThatCouldThrowAnything();
   *   } catch (IKnowWhatToDoWithThisException e) {
   *     handle(e);
   *   } catch (Throwable t) {
   *     Throwables.propagateIfPossible(t);
   *     throw new RuntimeException("unexpected", t);
   *   }
   * </pre>
   */
  public static void propagateIfPossible(@Nullable Throwable throwable) {
    propagateIfInstanceOf(throwable, Error.class);
    propagateIfInstanceOf(throwable, RuntimeException.class);
  }

  /**
   * Propagates {@code throwable} exactly as-is, if and only if it is an instance of {@link
   * RuntimeException}, {@link Error}, or {@code declaredType}. Example usage:
   *
   * <pre>
   *   try {
   *     someMethodThatCouldThrowAnything();
   *   } catch (IKnowWhatToDoWithThisException e) {
   *     handle(e);
   *   } catch (Throwable t) {
   *     Throwables.propagateIfPossible(t, OtherException.class);
   *     throw new RuntimeException("unexpected", t);
   *   }
   * </pre>
   *
   * @param throwable the Throwable to possibly propagate
   * @param declaredType the single checked exception type declared by the calling method
   */
  public static <X extends Throwable> void propagateIfPossible(
      @Nullable Throwable throwable, Class<X> declaredType) throws X {
    propagateIfInstanceOf(throwable, declaredType);
    propagateIfPossible(throwable);
  }

  /**
   * Propagates {@code throwable} exactly as-is, if and only if it is an instance of {@link
   * RuntimeException}, {@link Error}, {@code declaredType1}, or {@code declaredType2}. In the
   * unlikely case that you have three or more declared checked exception types, you can handle them
   * all by invoking these methods repeatedly. See usage example in {@link
   * #propagateIfPossible(Throwable, Class)}.
   *
   * @param throwable the Throwable to possibly propagate
   * @param declaredType1 any checked exception type declared by the calling method
   * @param declaredType2 any other checked exception type declared by the calling method
   */
  public static <X1 extends Throwable, X2 extends Throwable> void propagateIfPossible(
      @Nullable Throwable throwable, Class<X1> declaredType1, Class<X2> declaredType2)
      throws X1, X2 {
    Preconditions.checkNotNull(declaredType2);
    propagateIfInstanceOf(throwable, declaredType1);
    propagateIfPossible(throwable, declaredType2);
  }

  /**
   * Propagates {@code throwable} as-is if it is an instance of {@link RuntimeException} or {@link
   * Error}, or else as a last resort, wraps it in a {@code RuntimeException} then propagates.
   *
   * <p>This method always throws an exception. The {@code RuntimeException} return type is only for
   * client code to make Java type system happy in case a return value is required by the enclosing
   * method. Example usage:
   *
   * <pre>
   *   T doSomething() {
   *     try {
   *       return someMethodThatCouldThrowAnything();
   *     } catch (IKnowWhatToDoWithThisException e) {
   *       return handle(e);
   *     } catch (Throwable t) {
   *       throw Throwables.propagate(t);
   *     }
   *   }
   * </pre>
   *
   * @param throwable the Throwable to propagate
   * @return nothing will ever be returned; this return type is only for your convenience, as
   *     illustrated in the example above
   */
  public static RuntimeException propagate(Throwable throwable) {
    propagateIfPossible(Preconditions.checkNotNull(throwable));
    throw new RuntimeException(throwable);
  }

  /**
   * Returns the innermost cause of {@code throwable}. The first throwable in a chain provides
   * context from when the error or exception was initially detected. Example usage:
   *
   * <pre>
   *   assertEquals("Unable to assign a customer id",
   *       Throwables.getRootCause(e).getMessage());
   * </pre>
   */
  public static Throwable getRootCause(Throwable throwable) {
    Throwable cause;
    while ((cause = throwable.getCause()) != null) {
      throwable = cause;
    }
    return throwable;
  }

  /**
   * Gets a {@code Throwable} cause chain as a list. The first entry in the list will be {@code
   * throwable} followed by its cause hierarchy. Note that this is a snapshot of the cause chain and
   * will not reflect any subsequent changes to the cause chain.
   *
   * <p>Here's an example of how it can be used to find specific types of exceptions in the cause
   * chain:
   *
   * <pre>
   * Iterables.filter(Throwables.getCausalChain(e), IOException.class));
   * </pre>
   *
   * @param throwable the non-null {@code Throwable} to extract causes from
   * @return an unmodifiable list containing the cause chain starting with {@code throwable}
   */
  public static List<Throwable> getCausalChain(Throwable throwable) {
    Preconditions.checkNotNull(throwable);
    List<Throwable> causes = new ArrayList<Throwable>(4);
    while (throwable != null) {
      causes.add(throwable);
      throwable = throwable.getCause();
    }
    return Collections.unmodifiableList(causes);
  }

  /**
   * Returns a string containing the result of {@link Throwable#toString() toString()}, followed by
   * the full, recursive stack trace of {@code throwable}. Note that you probably should not be
   * parsing the resulting string; if you need programmatic access to the stack frames, you can call
   * {@link Throwable#getStackTrace()}.
   */
  public static String getStackTraceAsString(Throwable throwable) {
    return Log.getStackTraceString(throwable);
  }
}
