Add JSON Feed support

rssparser/build.gradle.kts

@@ -1,5 +1,6 @@
 plugins {
     id("java-library")
+    id("com.google.devtools.ksp") version libs.versions.ksp
     alias(libs.plugins.jetbrains.kotlin.jvm)
 }
 
@@ -12,6 +13,9 @@ dependencies {
     implementation(libs.okhttp.client)
     implementation(libs.kotlinx.coroutines.core)
     implementation(libs.jsoup)
+    implementation(libs.moshi)
+    implementation(libs.moshi.converter)
+    ksp(libs.moshi.kotlin.codegen)
     testImplementation(kotlin("test"))
     testImplementation(kotlin("test-common"))
     testImplementation(kotlin("test-annotations-common"))

rssparser/src/main/kotlin/com/prof18/rssparser/RssParser.kt

@@ -1,51 +1,44 @@
 package com.prof18.rssparser
 
-import com.prof18.rssparser.exception.RssParsingException
-import com.prof18.rssparser.internal.XmlFetcher
-import com.prof18.rssparser.internal.XmlParser
+import com.prof18.rssparser.internal.Fetcher
+import com.prof18.rssparser.internal.Parser
+import com.prof18.rssparser.internal.ParserInput
 import com.prof18.rssparser.model.RssChannel
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.withContext
 import kotlin.coroutines.CoroutineContext
 
 class RssParser internal constructor(
-    private val xmlFetcher: XmlFetcher,
-    private val xmlParser: XmlParser,
+    private val fetcher: Fetcher,
+    private val parser: Parser,
 ) {
-
     private val coroutineContext: CoroutineContext =
         SupervisorJob() + Dispatchers.Default
 
     internal interface Builder {
-        /**
-         * Creates a [RssParser] object
-         */
         fun build(): RssParser
     }
 
     /**
      * Downloads and parses an RSS feed from an [url] and returns an [RssChannel].
-     *
-     * If the parsing fails because the XML is malformed, it will re-download the XML as a string,
-     * clean it up and try to parse it again. If it fails again, it will throw an [RssParsingException].
      */
     suspend fun getRssChannel(url: String): RssChannel = withContext(coroutineContext) {
-        val parserInput = xmlFetcher.fetchXml(url)
-        return@withContext try {
-            xmlParser.parseXML(parserInput)
-        } catch (_: RssParsingException) {
-            val xmlAsString = xmlFetcher.fetchXmlAsString(url)
-            val input = xmlParser.generateParserInputFromString(xmlAsString)
-            xmlParser.parseXML(input)
-        }
+        val parserInput = fetcher.fetch(url)
+        return@withContext parser.parse(parserInput)
     }
 
     /**
      * Parses an RSS feed provided by [rawRssFeed] and returns an [RssChannel]
      */
     suspend fun parse(rawRssFeed: String): RssChannel = withContext(coroutineContext) {
-        val parserInput = xmlParser.generateParserInputFromString(rawRssFeed)
-        return@withContext xmlParser.parseXML(parserInput)
+        val parserInput = generateParserInputFromString(rawRssFeed)
+        return@withContext parser.parse(parserInput)
+    }
+
+    private fun generateParserInputFromString(rawRssFeed: String): ParserInput {
+        val cleanedXml = rawRssFeed.trim()
+        val inputStream = cleanedXml.byteInputStream(Charsets.UTF_8)
+        return ParserInput.from(inputStream)
     }
 }

rssparser/src/main/kotlin/com/prof18/rssparser/RssParserBuilder.kt

@@ -1,7 +1,7 @@
 package com.prof18.rssparser
 
-import com.prof18.rssparser.internal.DefaultXmlFetcher
-import com.prof18.rssparser.internal.DefaultXmlParser
+import com.prof18.rssparser.internal.DefaultFetcher
+import com.prof18.rssparser.internal.DefaultParser
 import kotlinx.coroutines.Dispatchers
 import okhttp3.Call
 import okhttp3.OkHttpClient
@@ -23,11 +23,10 @@ class RssParserBuilder(
     override fun build(): RssParser {
         val client = callFactory
         return RssParser(
-            xmlFetcher = DefaultXmlFetcher(
+            fetcher = DefaultFetcher(
                 callFactory = client,
             ),
-            xmlParser = DefaultXmlParser(
-                charset = charset,
+            parser = DefaultParser(
                 dispatcher = Dispatchers.IO,
             ),
         )

rssparser/src/main/kotlin/com/prof18/rssparser/internal/DefaultFetcher.kt

@@ -0,0 +1,54 @@
+package com.prof18.rssparser.internal
+
+import com.prof18.rssparser.exception.HttpException
+import kotlinx.coroutines.suspendCancellableCoroutine
+import okhttp3.Call
+import okhttp3.Callback
+import okhttp3.Request
+import okhttp3.Response
+import java.io.IOException
+import java.io.InputStream
+import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
+
+internal class DefaultFetcher(
+    private val callFactory: Call.Factory,
+) : Fetcher {
+    override suspend fun fetch(url: String): ParserInput {
+        val request = createRequest(url)
+        return callFactory.newCall(request).awaitForInputStream()
+    }
+
+    private fun createRequest(url: String): Request =
+        Request.Builder()
+            .url(url)
+            .build()
+
+    private suspend fun Call.awaitForInputStream(): ParserInput =
+        suspendCancellableCoroutine { continuation ->
+            continuation.invokeOnCancellation {
+                cancel()
+            }
+
+            enqueue(object : Callback {
+                override fun onResponse(call: Call, response: Response) {
+                    if (response.isSuccessful) {
+                        val body = requireNotNull(response.body)
+                        continuation.resume(
+                            ParserInput(body.bytes())
+                        )
+                    } else {
+                        val exception = HttpException(
+                            code = response.code,
+                            message = response.message,
+                        )
+                        continuation.resumeWithException(exception)
+                    }
+                }
+
+                override fun onFailure(call: Call, e: IOException) {
+                    continuation.resumeWithException(e)
+                }
+            })
+        }
+}

rssparser/src/main/kotlin/com/prof18/rssparser/internal/DefaultParser.kt

@@ -0,0 +1,91 @@
+package com.prof18.rssparser.internal
+
+import com.prof18.rssparser.exception.RssParsingException
+import com.prof18.rssparser.internal.atom.AtomFeedHandler
+import com.prof18.rssparser.internal.atom.AtomKeyword
+import com.prof18.rssparser.internal.json.JsonFeedHandler
+import com.prof18.rssparser.internal.json.models.Feed
+import com.prof18.rssparser.internal.rdf.RdfFeedHandler
+import com.prof18.rssparser.internal.rdf.RdfKeyword
+import com.prof18.rssparser.internal.rss.RssFeedHandler
+import com.prof18.rssparser.internal.rss.RssKeyword
+import com.prof18.rssparser.model.RssChannel
+import com.squareup.moshi.Moshi
+import com.squareup.moshi.adapter
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+import okio.IOException
+import okio.buffer
+import okio.source
+import org.jsoup.Jsoup
+import org.jsoup.nodes.Document
+import org.jsoup.parser.Parser as JsoupParser
+
+internal class DefaultParser(
+    private val dispatcher: CoroutineDispatcher,
+) : Parser {
+    override suspend fun parse(input: ParserInput): RssChannel {
+        return withContext(dispatcher) {
+
+            val handler = findHandler(input)
+
+            if (handler == null) {
+                throw RssParsingException(
+                    message = "Could not find top-level RSS node",
+                    cause = null
+                )
+            }
+
+            handler.build()
+
+        }
+    }
+
+    private fun findHandler(input: ParserInput): FeedHandler? {
+        val document = tryXmlParse(input) ?: return null
+
+        val handler = document.children().firstNotNullOfOrNull { node ->
+            when (node.tagName()) {
+                RssKeyword.Rss.value -> {
+                    RssFeedHandler(document)
+                }
+
+                AtomKeyword.Atom.value -> {
+                    AtomFeedHandler(node)
+                }
+
+                RdfKeyword.Rdf.value -> {
+                    RdfFeedHandler(node)
+                }
+
+                else -> tryParseJson(input)
+            }
+        }
+
+        return handler ?: tryParseJson(input)
+    }
+}
+
+private fun tryXmlParse(input: ParserInput): Document? {
+    return try {
+        Jsoup.parse(input.inputStream(), null, "", JsoupParser.xmlParser())
+    } catch (e: IOException) {
+        null
+    }
+}
+
+@OptIn(ExperimentalStdlibApi::class)
+private fun tryParseJson(input: ParserInput): FeedHandler? {
+    return try {
+        val moshi = Moshi
+            .Builder()
+            .build()
+
+        val feed = moshi.adapter<Feed>()
+            .fromJson(input.inputStream().source().buffer()) ?: return null
+
+        JsonFeedHandler(feed)
+    } catch (e: IOException) {
+        null
+    }
+}