First integration of libgit2 in the Android App

This will allow us to remove the jgit dependency. JGit is annoying
because we have to use an old version in order to support older API
versions. Additionally, there are some subtle differences in their
implementation.

Finally, for iOS and desktop we will be using libgit2, so we may as well
use the same stack on Android.

android/app/build.gradle

@@ -44,13 +44,21 @@ android {
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
-        /*
+
         externalNativeBuild {
             cmake {
                 cppFlags ""
             }
         }
-        */
+        ndk {
+            abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
+        }
+        sourceSets {
+            main {
+                jniLibs.srcDirs = ['libs']
+                java.srcDirs = ['src']
+            }
+        }
     }
 
     signingConfigs {
@@ -66,13 +74,19 @@ android {
             signingConfig signingConfigs.release
         }
     }
-    /*
+
     externalNativeBuild {
         cmake {
             path "src/main/cpp/CMakeLists.txt"
         }
     }
-    */
+
+    dexOptions {
+        incremental true
+        preDexLibraries true
+        jumboMode true
+        javaMaxHeapSize "12g"
+    }
 }
 
 flutter {

android/app/src/main/cpp/CMakeLists.txt

@@ -1,6 +1,57 @@
 cmake_minimum_required(VERSION 3.4.1)
 
+macro(print_all_variables)
+    message(STATUS "print_all_variables------------------------------------------{")
+    get_cmake_property(_variableNames VARIABLES)
+    foreach (_variableName ${_variableNames})
+        message(STATUS "${_variableName}=${${_variableName}}")
+    endforeach ()
+    message(STATUS "print_all_variables------------------------------------------}")
+endmacro()
 
-add_library( native-lib
-             SHARED
-             native-lib.cpp )
+
+set(lib_src_DIR ${CMAKE_SOURCE_DIR}/../../../libs/${ANDROID_ABI})
+include_directories(${lib_src_DIR}/include)
+
+add_library(openssl-lib
+        STATIC
+        IMPORTED)
+
+set_target_properties(openssl-lib
+        PROPERTIES IMPORTED_LOCATION
+        ${lib_src_DIR}/lib/libssl.a)
+
+
+add_library(crypto-lib
+        STATIC
+        IMPORTED)
+
+set_target_properties(crypto-lib
+        PROPERTIES IMPORTED_LOCATION
+        ${lib_src_DIR}/lib/libcrypto.a)
+
+
+add_library(ssh2-lib
+        STATIC
+        IMPORTED)
+
+set_target_properties(ssh2-lib
+        PROPERTIES IMPORTED_LOCATION
+        ${lib_src_DIR}/lib/libssh2.a)
+
+
+add_library(git2-lib
+        STATIC
+        IMPORTED)
+
+set_target_properties(git2-lib
+        PROPERTIES IMPORTED_LOCATION
+        ${lib_src_DIR}/lib/libgit2.a)
+
+add_library(native-lib
+        SHARED
+        native-lib.cpp)
+
+# The order of these libraries is super dooper important
+# Otherwise you'll get linker errors
+target_link_libraries(native-lib git2-lib ssh2-lib openssl-lib crypto-lib)

android/app/src/main/cpp/native-lib.cpp

@@ -1,10 +1,36 @@
 #include <jni.h>
 #include <string>
+#include <stdlib.h>
+
+#include <openssl/err.h>
+#include <openssl/crypto.h>
+#include <libssh2.h>
+#include <git2.h>
 
 extern "C" JNIEXPORT jstring JNICALL
 Java_io_gitjournal_gitjournal_MainActivity_stringFromJNI(
-        JNIEnv* env,
+        JNIEnv *env,
         jobject /* this */) {
-    std::string hello = "Hello from C++";
+
+    ERR_load_crypto_strings();
+    const char *openssl_version = OpenSSL_version(0);
+    const char *ssh2_version = libssh2_version(0);
+
+    std::string hello = "Hello from C++: ";
+    hello += openssl_version;
+    hello += " SSH Version: ";
+    hello += ssh2_version;
+
+    //git_libgit2_init();
+    int major;
+    int minor;
+    int patch;
+    git_libgit2_version(&major, &minor, &patch);
+
+    hello += " Git version: ";
+    char n_str[20];
+    sprintf(n_str, "%d.%d.%d", major, minor, patch);
+    hello += n_str;
+
     return env->NewStringUTF(hello.c_str());
 }

android/app/src/main/java/io/gitjournal/gitjournal/MainActivity.java

@@ -21,15 +21,15 @@ import io.flutter.util.PathUtils;
 // For MethodChannel
 
 public class MainActivity extends FlutterActivity implements MethodCallHandler {
-    //static {
-    //    System.loadLibrary("native-lib");
-    //}
+    static {
+        System.loadLibrary("native-lib");
+    }
 
     /**
      * A native method that is implemented by the 'native-lib' native library,
      * which is packaged with this application.
      */
-    //public native String stringFromJNI();
+    public native String stringFromJNI();
 
 
     private static final String CHANNEL_NAME = "gitjournal.io/git";
@@ -37,7 +37,7 @@ public class MainActivity extends FlutterActivity implements MethodCallHandler {
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
-        //Log.d("VISH", stringFromJNI());
+        Log.d("VISH", stringFromJNI());
 
         super.onCreate(savedInstanceState);
         GeneratedPluginRegistrant.registerWith(this);