Add adapter for parsing atom feed

api/src/androidTest/assets/localfeed/atom/atom_feed.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en-US">
+    <id>tag:github.com,2008:/readrops/Readrops/commits/develop</id>
+    <link type="text/html" rel="alternate" href="https://github.com/readrops/Readrops/commits/develop"/>
+    <link type="application/atom+xml" rel="self" href="https://github.com/readrops/Readrops/commits/develop.atom"/>
+    <title>Recent Commits to Readrops:develop</title>
+    <updated>2020-09-06T21:09:59Z</updated>
+    <subtitle>Here is a subtitle</subtitle>
+</feed>

api/src/androidTest/java/com/readrops/api/localfeed/atom/ATOMFeedAdapterTest.kt

@@ -0,0 +1,28 @@
+package com.readrops.api.localfeed.atom
+
+import android.content.Context
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry
+import junit.framework.TestCase.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+
+@RunWith(AndroidJUnit4::class)
+class ATOMFeedAdapterTest {
+
+    private val context: Context = InstrumentationRegistry.getInstrumentation().context
+
+    private val adapter = ATOMFeedAdapter()
+
+    @Test
+    fun normalCasesTest() {
+        val stream = context.assets.open("localfeed/atom/atom_feed.xml")
+
+        val feed = adapter.fromXml(stream)
+
+        assertEquals(feed.name, "Recent Commits to Readrops:develop")
+        assertEquals(feed.url, "https://github.com/readrops/Readrops/commits/develop.atom")
+        assertEquals(feed.siteUrl, "https://github.com/readrops/Readrops/commits/develop")
+        assertEquals(feed.description, "Here is a subtitle")
+    }
+}

api/src/main/java/com/readrops/api/localfeed/XmlAdapter.kt

@@ -1,5 +1,6 @@
 package com.readrops.api.localfeed
 
+import com.readrops.api.localfeed.atom.ATOMFeedAdapter
 import com.readrops.api.localfeed.rss.RSSFeedAdapter
 import com.readrops.api.localfeed.rss.RSSItemsAdapter
 import com.readrops.db.entities.Feed
@@ -14,6 +15,7 @@ interface XmlAdapter<T> {
         fun xmlFeedAdapterFactory(type: LocalRSSHelper.RSSType): XmlAdapter<Feed> {
             return when (type) {
                 LocalRSSHelper.RSSType.RSS_2 -> RSSFeedAdapter()
+                LocalRSSHelper.RSSType.ATOM -> ATOMFeedAdapter()
                 else -> throw Exception("Unknown RSS type : $type")
             }
         }

api/src/main/java/com/readrops/api/localfeed/atom/ATOMFeedAdapter.kt

@@ -0,0 +1,52 @@
+package com.readrops.api.localfeed.atom
+
+import com.gitlab.mvysny.konsumexml.Konsumer
+import com.gitlab.mvysny.konsumexml.Names
+import com.gitlab.mvysny.konsumexml.allChildrenAutoIgnore
+import com.gitlab.mvysny.konsumexml.konsumeXml
+import com.readrops.api.localfeed.XmlAdapter
+import com.readrops.api.utils.ParseException
+import com.readrops.api.utils.nonNullText
+import com.readrops.api.utils.nullableText
+import com.readrops.db.entities.Feed
+import java.io.InputStream
+
+class ATOMFeedAdapter : XmlAdapter<Feed> {
+
+    override fun fromXml(inputStream: InputStream): Feed {
+        val konsume = inputStream.konsumeXml()
+        val feed = Feed()
+
+        return try {
+            konsume.child("feed") {
+                allChildrenAutoIgnore(names) {
+                    with(feed) {
+                        when (tagName) {
+                            "title" -> name = nonNullText()
+                            "link" -> parseLink(this@allChildrenAutoIgnore, feed)
+                            "subtitle" -> description = nullableText()
+                        }
+                    }
+                }
+            }
+
+            konsume.close()
+            feed
+        } catch (e: Exception) {
+            throw ParseException(e.message)
+        }
+    }
+
+    private fun parseLink(konsume: Konsumer, feed: Feed) {
+        val rel = konsume.attributes["rel"]
+
+        if (rel == "self")
+            feed.url = konsume.attributes["href"]
+        else if (rel == "alternate")
+            feed.siteUrl = konsume.attributes["href"]
+    }
+
+    companion object {
+        val names = Names.of("title", "link", "subtitle")
+    }
+}