Downloading extensions from Github Repo. (#1101)

Downloading extensions from Github Repo.

app/src/main/java/eu/kanade/tachiyomi/extension/model/Extension.kt

@@ -0,0 +1,36 @@
+package eu.kanade.tachiyomi.extension.model
+
+import eu.kanade.tachiyomi.source.Source
+
+sealed class Extension {
+
+    abstract val name: String
+    abstract val pkgName: String
+    abstract val versionName: String
+    abstract val versionCode: Int
+    abstract val lang: String?
+
+    data class Installed(override val name: String,
+                         override val pkgName: String,
+                         override val versionName: String,
+                         override val versionCode: Int,
+                         val sources: List<Source>,
+                         override val lang: String,
+                         val hasUpdate: Boolean = false) : Extension()
+
+    data class Available(override val name: String,
+                         override val pkgName: String,
+                         override val versionName: String,
+                         override val versionCode: Int,
+                         override val lang: String,
+                         val apkName: String,
+                         val iconUrl: String) : Extension()
+
+    data class Untrusted(override val name: String,
+                         override val pkgName: String,
+                         override val versionName: String,
+                         override val versionCode: Int,
+                         val signatureHash: String,
+                         override val lang: String? = null) : Extension()
+
+}

app/src/main/java/eu/kanade/tachiyomi/extension/model/InstallStep.kt

@@ -0,0 +1,9 @@
+package eu.kanade.tachiyomi.extension.model
+
+enum class InstallStep {
+    Pending, Downloading, Installing, Installed, Error;
+
+    fun isCompleted(): Boolean {
+        return this == Installed || this == Error
+    }
+}

app/src/main/java/eu/kanade/tachiyomi/extension/model/LoadResult.kt

@@ -0,0 +1,10 @@
+package eu.kanade.tachiyomi.extension.model
+
+sealed class LoadResult {
+
+    class Success(val extension: Extension.Installed) : LoadResult()
+    class Untrusted(val extension: Extension.Untrusted) : LoadResult()
+    class Error(val message: String? = null) : LoadResult() {
+        constructor(exception: Throwable) : this(exception.message)
+    }
+}