react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/BaseJavaModule.java

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.react.bridge;

import com.fasterxml.jackson.core.JsonGenerator;

import com.facebook.infer.annotation.Assertions;
import com.facebook.systrace.Systrace;

import javax.annotation.Nullable;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

/**
 * Base class for Catalyst native modules whose implementations are written in Java. Default
 * implementations for {@link #initialize} and {@link #onCatalystInstanceDestroy} are provided for
 * convenience.  Subclasses which override these don't need to call {@code super} in case of
 * overriding those methods as implementation of those methods is empty.
 *
 * BaseJavaModules can be linked to Fragments' lifecycle events, {@link CatalystInstance} creation
 * and destruction, by being called on the appropriate method when a life cycle event occurs.
 *
 * Native methods can be exposed to JS with {@link ReactMethod} annotation. Those methods may
 * only use limited number of types for their arguments:
 * 1/ primitives (boolean, int, float, double
 * 2/ {@link String} mapped from JS string
 * 3/ {@link ReadableArray} mapped from JS Array
 * 4/ {@link ReadableMap} mapped from JS Object
 * 5/ {@link Callback} mapped from js function and can be used only as a last parameter or in the
 * case when it express success & error callback pair as two last arguments respecively.
 *
 * All methods exposed as native to JS with {@link ReactMethod} annotation must return
 * {@code void}.
 *
 * Please note that it is not allowed to have multiple methods annotated with {@link ReactMethod}
 * with the same name.
 */
public abstract class BaseJavaModule implements NativeModule {
  // taken from Libraries/Utilities/MessageQueue.js
  static final public String METHOD_TYPE_REMOTE = "remote";
  static final public String METHOD_TYPE_REMOTE_ASYNC = "remoteAsync";

  private static abstract class ArgumentExtractor<T> {
    public int getJSArgumentsNeeded() {
      return 1;
    }

    public abstract @Nullable T extractArgument(
        CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex);
  }

  static final private ArgumentExtractor<Boolean> ARGUMENT_EXTRACTOR_BOOLEAN =
      new ArgumentExtractor<Boolean>() {
        @Override
        public Boolean extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return jsArguments.getBoolean(atIndex);
        }
      };

  static final private ArgumentExtractor<Double> ARGUMENT_EXTRACTOR_DOUBLE =
      new ArgumentExtractor<Double>() {
        @Override
        public Double extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return jsArguments.getDouble(atIndex);
        }
      };

  static final private ArgumentExtractor<Float> ARGUMENT_EXTRACTOR_FLOAT =
      new ArgumentExtractor<Float>() {
        @Override
        public Float extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return (float) jsArguments.getDouble(atIndex);
        }
      };

  static final private ArgumentExtractor<Integer> ARGUMENT_EXTRACTOR_INTEGER =
      new ArgumentExtractor<Integer>() {
        @Override
        public Integer extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return (int) jsArguments.getDouble(atIndex);
        }
      };

  static final private ArgumentExtractor<String> ARGUMENT_EXTRACTOR_STRING =
      new ArgumentExtractor<String>() {
        @Override
        public String extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return jsArguments.getString(atIndex);
        }
      };

  static final private ArgumentExtractor<ReadableNativeArray> ARGUMENT_EXTRACTOR_ARRAY =
      new ArgumentExtractor<ReadableNativeArray>() {
        @Override
        public ReadableNativeArray extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return jsArguments.getArray(atIndex);
        }
      };

  static final private ArgumentExtractor<ReadableMap> ARGUMENT_EXTRACTOR_MAP =
      new ArgumentExtractor<ReadableMap>() {
        @Override
        public ReadableMap extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          return jsArguments.getMap(atIndex);
        }
      };

  static final private ArgumentExtractor<Callback> ARGUMENT_EXTRACTOR_CALLBACK =
      new ArgumentExtractor<Callback>() {
        @Override
        public @Nullable Callback extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          if (jsArguments.isNull(atIndex)) {
            return null;
          } else {
            int id = (int) jsArguments.getDouble(atIndex);
            return new CallbackImpl(catalystInstance, id);
          }
        }
      };

  static final private ArgumentExtractor<Promise> ARGUMENT_EXTRACTOR_PROMISE =
      new ArgumentExtractor<Promise>() {
        @Override
        public int getJSArgumentsNeeded() {
          return 2;
        }

        @Override
        public Promise extractArgument(
            CatalystInstance catalystInstance, ReadableNativeArray jsArguments, int atIndex) {
          Callback resolve = ARGUMENT_EXTRACTOR_CALLBACK
              .extractArgument(catalystInstance, jsArguments, atIndex);
          Callback reject = ARGUMENT_EXTRACTOR_CALLBACK
              .extractArgument(catalystInstance, jsArguments, atIndex + 1);
          return new PromiseImpl(resolve, reject);
        }
      };

  private class JavaMethod implements NativeMethod {

    private Method mMethod;
    private final ArgumentExtractor[] mArgumentExtractors;
    private final Object[] mArguments;
    private String mType = METHOD_TYPE_REMOTE;
    private final int mJSArgumentsNeeded;

    public JavaMethod(Method method) {
      mMethod = method;
      Class[] parameterTypes = method.getParameterTypes();
      mArgumentExtractors = buildArgumentExtractors(parameterTypes);
      // Since native methods are invoked from a message queue executed on a single thread, it is
      // save to allocate only one arguments object per method that can be reused across calls
      mArguments = new Object[parameterTypes.length];
      mJSArgumentsNeeded = calculateJSArgumentsNeeded();
    }

    private ArgumentExtractor[] buildArgumentExtractors(Class[] paramTypes) {
      ArgumentExtractor[] argumentExtractors = new ArgumentExtractor[paramTypes.length];
      for (int i = 0; i < paramTypes.length; i += argumentExtractors[i].getJSArgumentsNeeded()) {
        Class argumentClass = paramTypes[i];
        if (argumentClass == Boolean.class || argumentClass == boolean.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_BOOLEAN;
        } else if (argumentClass == Integer.class || argumentClass == int.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_INTEGER;
        } else if (argumentClass == Double.class || argumentClass == double.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_DOUBLE;
        } else if (argumentClass == Float.class || argumentClass == float.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_FLOAT;
        } else if (argumentClass == String.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_STRING;
        } else if (argumentClass == Callback.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_CALLBACK;
        } else if (argumentClass == Promise.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_PROMISE;
          Assertions.assertCondition(
              i == paramTypes.length - 1, "Promise must be used as last parameter only");
          mType = METHOD_TYPE_REMOTE_ASYNC;
        } else if (argumentClass == ReadableMap.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_MAP;
        } else if (argumentClass == ReadableArray.class) {
          argumentExtractors[i] = ARGUMENT_EXTRACTOR_ARRAY;
        } else {
          throw new RuntimeException(
              "Got unknown argument class: " + argumentClass.getSimpleName());
        }
      }
      return argumentExtractors;
    }

    private int calculateJSArgumentsNeeded() {
      int n = 0;
      for (ArgumentExtractor extractor : mArgumentExtractors) {
        n += extractor.getJSArgumentsNeeded();
      }
      return n;
    }

    private String getAffectedRange(int startIndex, int jsArgumentsNeeded) {
      return jsArgumentsNeeded > 1 ?
          "" + startIndex + "-" + (startIndex + jsArgumentsNeeded - 1) : "" + startIndex;
    }

    @Override
    public void invoke(CatalystInstance catalystInstance, ReadableNativeArray parameters) {
      Systrace.beginSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE, "callJavaModuleMethod");
      try {
        if (mJSArgumentsNeeded != parameters.size()) {
          throw new NativeArgumentsParseException(
              BaseJavaModule.this.getName() + "." + mMethod.getName() + " got " +
              parameters.size() + " arguments, expected " + mJSArgumentsNeeded);
        }

        int i = 0, jsArgumentsConsumed = 0;
        try {
          for (; i < mArgumentExtractors.length; i++) {
            mArguments[i] = mArgumentExtractors[i].extractArgument(
                catalystInstance, parameters, jsArgumentsConsumed);
            jsArgumentsConsumed += mArgumentExtractors[i].getJSArgumentsNeeded();
          }
        } catch (UnexpectedNativeTypeException e) {
          throw new NativeArgumentsParseException(
              e.getMessage() + " (constructing arguments for " + BaseJavaModule.this.getName() +
              "." + mMethod.getName() + " at argument index " +
              getAffectedRange(jsArgumentsConsumed, mArgumentExtractors[i].getJSArgumentsNeeded()) +
              ")",
              e);
        }

        try {
          mMethod.invoke(BaseJavaModule.this, mArguments);
        } catch (IllegalArgumentException ie) {
          throw new RuntimeException(
              "Could not invoke " + BaseJavaModule.this.getName() + "." + mMethod.getName(), ie);
        } catch (IllegalAccessException iae) {
          throw new RuntimeException(
              "Could not invoke " + BaseJavaModule.this.getName() + "." + mMethod.getName(), iae);
        } catch (InvocationTargetException ite) {
          // Exceptions thrown from native module calls end up wrapped in InvocationTargetException
          // which just make traces harder to read and bump out useful information
          if (ite.getCause() instanceof RuntimeException) {
            throw (RuntimeException) ite.getCause();
          }
          throw new RuntimeException(
              "Could not invoke " + BaseJavaModule.this.getName() + "." + mMethod.getName(), ite);
        }
      } finally {
        Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
      }
    }

    /**
     * Determines how the method is exported in JavaScript:
     * METHOD_TYPE_REMOTE for regular methods
     * METHOD_TYPE_REMOTE_ASYNC for methods that return a promise object to the caller.
     */
    @Override
    public String getType() {
      return mType;
    }
  }

  @Override
  public final Map<String, NativeMethod> getMethods() {
    Map<String, NativeMethod> methods = new HashMap<String, NativeMethod>();
    Method[] targetMethods = getClass().getDeclaredMethods();
    for (int i = 0; i < targetMethods.length; i++) {
      Method targetMethod = targetMethods[i];
      if (targetMethod.getAnnotation(ReactMethod.class) != null) {
        String methodName = targetMethod.getName();
        if (methods.containsKey(methodName)) {
          // We do not support method overloading since js sees a function as an object regardless
          // of number of params.
          throw new IllegalArgumentException(
              "Java Module " + getName() + " method name already registered: " + methodName);
          }
        methods.put(methodName, new JavaMethod(targetMethod));
      }
    }
    return methods;
  }

  /**
   * @return a map of constants this module exports to JS. Supports JSON types.
   */
  public @Nullable Map<String, Object> getConstants() {
    return null;
  }

  @Override
  public final void writeConstantsField(JsonGenerator jg, String fieldName) throws IOException {
    Map<String, Object> constants = getConstants();
    if (constants == null || constants.isEmpty()) {
      return;
    }

    jg.writeObjectFieldStart(fieldName);
    for (Map.Entry<String, Object> constant : constants.entrySet()) {
      JsonGeneratorHelper.writeObjectField(
        jg,
        constant.getKey(),
        constant.getValue());
    }
    jg.writeEndObject();
  }

  @Override
  public void initialize() {
    // do nothing
  }

  @Override
  public boolean canOverrideExistingModule() {
    return false;
  }

  @Override
  public void onCatalystInstanceDestroy() {
    // do nothing
  }
}