/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * 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 android.signature.cts;

import android.util.Log;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;

public class DexMemberChecker {
    public static final String TAG = "DexMemberChecker";

    public interface Observer {
        void classAccessible(boolean accessible, DexMember member);
        void fieldAccessibleViaReflection(boolean accessible, DexField field);
        void fieldAccessibleViaJni(boolean accessible, DexField field);
        void methodAccessibleViaReflection(boolean accessible, DexMethod method);
        void methodAccessibleViaJni(boolean accessible, DexMethod method);
    }

    public static void init() {
        System.loadLibrary("cts_dexchecker");
    }

    private static void call_VMDebug_allowHiddenApiReflectionFrom(Class<?> klass) throws Exception {
      Method method = null;

      try {
        Class<?> vmdebug = Class.forName("dalvik.system.VMDebug");
        method = vmdebug.getDeclaredMethod("allowHiddenApiReflectionFrom", Class.class);
      } catch (Exception ex) {
        // Could not find the method. Report the problem as a RuntimeException.
        throw new RuntimeException(ex);
      }

      try {
        method.invoke(null, klass);
      } catch (InvocationTargetException ex) {
        // Rethrow the original exception.
        Throwable cause = ex.getCause();
        // Please the compiler's 'throws' static analysis.
        if (cause instanceof Exception) {
          throw (Exception) cause;
        } else {
          throw (Error) cause;
        }
      }
    }

    public static boolean requestExemptionFromHiddenApiChecks() throws Exception {
      try {
        call_VMDebug_allowHiddenApiReflectionFrom(DexMemberChecker.class);
        return true;
      } catch (SecurityException ex) {
        return false;
      }
    }

    public static void checkSingleMember(DexMember dexMember, DexMemberChecker.Observer observer) {
        checkSingleMember(dexMember, /* reflection= */ true, /* jni= */ true, observer);
    }

    public static void checkSingleMember(DexMember dexMember, boolean reflection, boolean jni,
            DexMemberChecker.Observer observer) {
        Class<?> klass = findClass(dexMember);
        if (klass == null) {
            // Class not found. Therefore its members are not visible.
            observer.classAccessible(false, dexMember);
            return;
        }
        observer.classAccessible(true, dexMember);

        if (dexMember instanceof DexField) {
            DexField field = (DexField) dexMember;
            if (reflection) {
                observer.fieldAccessibleViaReflection(
                        hasMatchingField_Reflection(klass, field),
                        field);
            }
            if (jni) {
                try {
                    observer.fieldAccessibleViaJni(hasMatchingField_JNI(klass, field), field);
                } catch (ClassNotFoundException | ExceptionInInitializerError | UnsatisfiedLinkError
                        | NoClassDefFoundError e) {
                    if ((e instanceof NoClassDefFoundError)
                            && !(e.getCause() instanceof ExceptionInInitializerError)
                            && !(e.getCause() instanceof UnsatisfiedLinkError)) {
                        throw (NoClassDefFoundError) e;
                    }

                    // Could not initialize the class. Skip JNI test.
                    Log.w(TAG, "JNI failed for " + dexMember.toString(), e);
                }
            }
        } else if (dexMember instanceof DexMethod) {
            DexMethod method = (DexMethod) dexMember;
            if (reflection) {
                try {
                    observer.methodAccessibleViaReflection(
                            hasMatchingMethod_Reflection(klass, method), method);
                } catch (ClassNotFoundException e) {
                    Log.w(TAG, "Failed resolution of " + dexMember.toString(), e);
                }
            }
            if (jni) {
                try {
                    observer.methodAccessibleViaJni(hasMatchingMethod_JNI(klass, method), method);
                } catch (ExceptionInInitializerError | UnsatisfiedLinkError
                        | NoClassDefFoundError e) {
                    if ((e instanceof NoClassDefFoundError)
                            && !(e.getCause() instanceof ExceptionInInitializerError)
                            && !(e.getCause() instanceof UnsatisfiedLinkError)) {
                        throw e;
                    }

                    // Could not initialize the class. Skip JNI test.
                    Log.w(TAG, "JNI failed for " + dexMember.toString(), e);
                }
            }
        } else {
            throw new IllegalStateException("Unexpected type of dex member");
        }
    }

    private static boolean typesMatch(Class<?>[] classes, List<String> typeNames) {
        if (classes.length != typeNames.size()) {
            return false;
        }
        for (int i = 0; i < classes.length; ++i) {
            if (!classes[i].getTypeName().equals(typeNames.get(i))) {
                return false;
            }
        }
        return true;
    }

    private static Class<?> findClass(DexMember dexMember) {
        try {
            // Try to find the class. Do not initialize it - we do not want to run
            // static initializers.
            return Class.forName(dexMember.getJavaClassName(), /* initialize */ false,
                DexMemberChecker.class.getClassLoader());
        } catch (ClassNotFoundException ex) {
            return null;
        }
    }

    private static boolean hasMatchingField_Reflection(Class<?> klass, DexField dexField) {
        try {
            klass.getDeclaredField(dexField.getName());
            return true;
        } catch (NoSuchFieldException ex) {
            return false;
        } catch (NoClassDefFoundError ex) {
            // The field has a type that cannot be loaded.
            return true;
        }
    }

    private static boolean hasMatchingField_JNI(Class<?> klass, DexField dexField)
            throws ClassNotFoundException {
        // If we fail to resolve the type of the field, we will throw a ClassNotFoundException.
        DexMember.typeToClass(dexField.getDexType());

        try {
            Field ifield = getField_JNI(klass, dexField.getName(), dexField.getDexType());
            if (ifield.getDeclaringClass() == klass) {
              return true;
            }
        } catch (NoSuchFieldError e) {
            // Not found.
        }

        try {
            Field sfield = getStaticField_JNI(klass, dexField.getName(), dexField.getDexType());
            if (sfield.getDeclaringClass() == klass) {
              return true;
            }
        } catch (NoSuchFieldError e) {
            // Not found.
        }

        return false;
    }

    private static boolean hasMatchingMethod_Reflection(Class<?> klass, DexMethod dexMethod)
                throws ClassNotFoundException {
        // If we fail to resolve all parameters or return type, we will throw
        // ClassNotFoundException.
        Class<?>[] parameterClasses = dexMethod.getJavaParameterClasses();
        Class<?> returnClass = DexMember.typeToClass(dexMethod.getDexType());

        if (dexMethod.isConstructor()) {
            try {
                if (klass.getDeclaredConstructor(parameterClasses) != null) {
                    return true;
                }
            } catch (NoSuchMethodException e) {
              return false;
            }
        } else if (!dexMethod.isStaticConstructor()) {
            List<String> methodParams = dexMethod.getJavaParameterTypes();
            String methodReturnType = dexMethod.getJavaType();
            try {
                // First try with getDeclaredMethods, hoping all parameter and return types can be
                // resolved.
                for (Method method : klass.getDeclaredMethods()) {
                    if (method.getName().equals(dexMethod.getName())
                            && method.getReturnType().getTypeName().equals(methodReturnType)
                            && typesMatch(method.getParameterTypes(), methodParams)) {
                        return true;
                    }
                }
            } catch (NoClassDefFoundError ncdfe) {
                // Try with getMethods, which does not check parameter and return types are
                // resolved, but only returns public methods.
                for (Method method : klass.getMethods()) {
                    if (method.getName().equals(dexMethod.getName())
                            && method.getClass() == klass
                            && method.getReturnType().getTypeName().equals(methodReturnType)
                            && typesMatch(method.getParameterTypes(), methodParams)) {
                        return true;
                    }
                }
                // Last chance, try with getDeclaredMethod.
                try {
                    Method m = klass.getDeclaredMethod(dexMethod.getName(), parameterClasses);
                    if (m.getReturnType().getTypeName().equals(dexMethod.getJavaType())) {
                        return true;
                    }
                    // This means we found a method with a different return type. We cannot make
                    // any conclusion here: the method may exisit or not. However, given we have
                    // not found the method through getMethods and getDeclaredMethods, we know
                    // this method won't be accessible through reflection.
                } catch (NoSuchMethodException nsme) {
                  return false;
                }
            }
        }
        return false;
    }

    private static boolean hasMatchingMethod_JNI(Class<?> klass, DexMethod dexMethod) {
        try {
            Executable imethod = getMethod_JNI(
                klass, dexMethod.getName(), dexMethod.getDexSignature());
            if (imethod.getDeclaringClass() == klass) {
                return true;
            }
        } catch (NoSuchMethodError e) {
            // Not found.
        }

        if (!dexMethod.isConstructor()) {
            try {
                Executable smethod =
                    getStaticMethod_JNI(klass, dexMethod.getName(), dexMethod.getDexSignature());
                if (smethod.getDeclaringClass() == klass) {
                    return true;
                }
            } catch (NoSuchMethodError e) {
                // Not found.
            }
        }

        return false;
    }

    private static native Field getField_JNI(Class<?> klass, String name, String type);
    private static native Field getStaticField_JNI(Class<?> klass, String name, String type);
    private static native Executable getMethod_JNI(Class<?> klass, String name, String signature);
    private static native Executable getStaticMethod_JNI(Class<?> klass, String name,
            String signature);

}