Fix #8 - Fix Marvel Api Authorization

data/build.gradle

@@ -54,6 +54,8 @@ dependencies {
     // Retrofit & OkHttp
     implementation 'com.squareup.retrofit2:retrofit:2.3.0'
     implementation 'com.squareup.retrofit2:converter-gson:2.3.0'
+    implementation 'com.squareup.okhttp3:okhttp:3.8.1'
+    implementation 'com.squareup.okhttp3:logging-interceptor:3.8.1'
 
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'com.android.support.test:runner:1.0.1'

data/src/main/java/com/puzzlebench/cmk/data/service/CharacterServicesImpl.kt

@@ -7,7 +7,7 @@ import com.puzzlebench.cmk.domain.service.CharacterServices
 import io.reactivex.Observable
 
 
-class CharacterServicesImpl(private val api: MarvelResquestGenerator = MarvelResquestGenerator(), private val mapper: CharacterMapperService = CharacterMapperService()) : CharacterServices {
+class CharacterServicesImpl(private val api: MarvelRequestGenerator = MarvelRequestGenerator(), private val mapper: CharacterMapperService = CharacterMapperService()) : CharacterServices {
     override fun getCharacters(): Observable<List<Character>> {
         return Observable.create { subscriber ->
             val callResponse = api.createService(MarvelApi::class.java).getCharacter()

data/src/main/java/com/puzzlebench/cmk/data/service/MarvelRequestGenerator.kt

@@ -0,0 +1,72 @@
+package com.puzzlebench.cmk.data.service
+
+import com.puzzlebench.cmk.data.BuildConfig
+import okhttp3.OkHttpClient
+import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+import java.security.NoSuchAlgorithmException
+
+
+class MarvelRequestGenerator {
+    private val QUERY_PARAMETER_KEY_HASH = "hash"
+    private val QUERY_PARAMETER_KEY_API_KEY = "apikey"
+    private val QUERY_PARAMETER_KEY_TS = "ts"
+    private val builder = Retrofit.Builder()
+            .baseUrl(BuildConfig.MARVEL_BASE_URL)
+            .addConverterFactory(GsonConverterFactory.create())
+
+    private fun getHttpClient() : OkHttpClient {
+        // TODO: add proper environment configuration
+        return OkHttpClient.Builder()
+                .addInterceptor { chain ->
+                    val defaultRequest = chain.request()
+                    val timestamp = System.currentTimeMillis().toString()
+                    val defaultHttpUrl = defaultRequest.url()
+                    val httpUrl = defaultHttpUrl.newBuilder()
+                            .addQueryParameter(QUERY_PARAMETER_KEY_API_KEY, BuildConfig.PUBLIC_API_KEY_VALUE)
+                            .addQueryParameter(
+                                    QUERY_PARAMETER_KEY_HASH,
+                                    md5(timestamp + BuildConfig.PRIVATE_API_KEY_VALUE + BuildConfig.PUBLIC_API_KEY_VALUE)
+                            )
+                            .addQueryParameter(QUERY_PARAMETER_KEY_TS, timestamp)
+                            .build()
+
+                    val requestBuilder = defaultRequest.newBuilder().url(httpUrl)
+                    chain.proceed(requestBuilder.build())
+                }
+                .addInterceptor(HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY))
+                .build()
+    }
+
+    fun <S> createService(serviceClass: Class<S>): S {
+        val retrofit = builder.client(getHttpClient()).build()
+        return retrofit.create(serviceClass)
+    }
+
+    fun md5(s: String): String {
+        val MD5 = "MD5"
+        try {
+            // Create MD5 Hash
+            val digest = java.security.MessageDigest
+                    .getInstance(MD5)
+            digest.update(s.toByteArray())
+            val messageDigest = digest.digest()
+
+            // Create Hex String
+            val hexString = StringBuilder()
+            for (aMessageDigest in messageDigest) {
+                var h = Integer.toHexString(0xFF and aMessageDigest.toInt())
+                while (h.length < 2)
+                    h = "0$h"
+                hexString.append(h)
+            }
+            return hexString.toString()
+
+        } catch (e: NoSuchAlgorithmException) {
+            e.printStackTrace()
+        }
+
+        return ""
+    }
+}