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package org.terst.feedreader.data
import android.util.Xml
import org.xmlpull.v1.XmlPullParser
import java.io.InputStream
import java.time.OffsetDateTime
import java.time.ZonedDateTime
import java.time.format.DateTimeFormatter
import java.time.format.DateTimeFormatterBuilder
import java.time.temporal.ChronoField
import java.util.Locale
data class ParsedItem(
val guid: String?,
val title: String,
val link: String,
val author: String?,
val publishedAt: Long?,
val contentHtml: String?
)
data class ParsedFeed(
val title: String,
val siteUrl: String?,
val items: List<ParsedItem>
)
/**
* Hand-rolled RSS 2.0 + Atom parser -- deliberately not a third-party library
* (rome, etc.), per the "simple design" scope: only the fields this app
* actually uses (title/link/guid/author/date/content), nothing else.
*/
object FeedParser {
fun parse(input: InputStream): ParsedFeed {
val parser = Xml.newPullParser()
parser.setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, false)
parser.setInput(input, null)
// Peek the root element to decide which dialect we're in.
var eventType = parser.eventType
while (eventType != XmlPullParser.START_TAG) {
eventType = parser.next()
}
return when (parser.name.lowercase()) {
"rss" -> parseRss(parser)
"feed" -> parseAtom(parser)
else -> throw IllegalArgumentException("Unrecognized feed root element: ${parser.name}")
}
}
private fun parseRss(parser: XmlPullParser): ParsedFeed {
var feedTitle = ""
var siteUrl: String? = null
val items = mutableListOf<ParsedItem>()
var eventType = parser.next()
var depth = 1
// Track whether we're directly inside <channel> (title/link there) vs inside an <item>.
var inItem = false
var itemGuid: String? = null
var itemTitle = ""
var itemLink = ""
var itemAuthor: String? = null
var itemDate: Long? = null
var itemContent: String? = null
var itemDescription: String? = null
while (eventType != XmlPullParser.END_DOCUMENT && depth > 0) {
when (eventType) {
XmlPullParser.START_TAG -> {
depth++
when (parser.name.lowercase()) {
"item" -> {
inItem = true
itemGuid = null; itemTitle = ""; itemLink = ""; itemAuthor = null
itemDate = null; itemContent = null; itemDescription = null
}
"title" -> {
val text = parser.nextText()
if (inItem) itemTitle = text else feedTitle = text
}
"link" -> {
val text = parser.nextText()
if (inItem) itemLink = text else if (siteUrl == null) siteUrl = text
}
"guid" -> if (inItem) itemGuid = parser.nextText()
"author" -> if (inItem) itemAuthor = parser.nextText()
"dc:creator" -> if (inItem) itemAuthor = parser.nextText()
"pubdate" -> if (inItem) itemDate = parseRfc822Date(parser.nextText())
"content:encoded" -> if (inItem) itemContent = parser.nextText()
"description" -> if (inItem) itemDescription = parser.nextText()
}
}
XmlPullParser.END_TAG -> {
depth--
if (parser.name.lowercase() == "item") {
inItem = false
items += ParsedItem(
guid = itemGuid ?: itemLink.ifBlank { null },
title = itemTitle,
link = itemLink,
author = itemAuthor,
publishedAt = itemDate,
contentHtml = itemContent ?: itemDescription
)
}
}
}
if (depth > 0) eventType = parser.next()
}
return ParsedFeed(feedTitle, siteUrl, items)
}
private fun parseAtom(parser: XmlPullParser): ParsedFeed {
var feedTitle = ""
var siteUrl: String? = null
val items = mutableListOf<ParsedItem>()
var eventType = parser.next()
var depth = 1
var inEntry = false
var entryId: String? = null
var entryTitle = ""
var entryLink = ""
var entryAuthor: String? = null
var entryDate: Long? = null
var entryContent: String? = null
var entrySummary: String? = null
while (eventType != XmlPullParser.END_DOCUMENT && depth > 0) {
when (eventType) {
XmlPullParser.START_TAG -> {
depth++
when (parser.name.lowercase()) {
"entry" -> {
inEntry = true
entryId = null; entryTitle = ""; entryLink = ""; entryAuthor = null
entryDate = null; entryContent = null; entrySummary = null
}
"title" -> {
val text = parser.nextText()
if (inEntry) entryTitle = text else feedTitle = text
}
"link" -> {
val rel = parser.getAttributeValue(null, "rel")
val href = parser.getAttributeValue(null, "href")
if (href != null && (rel == null || rel == "alternate")) {
if (inEntry) entryLink = href else if (siteUrl == null) siteUrl = href
}
}
"id" -> if (inEntry) entryId = parser.nextText()
"name" -> if (inEntry && entryAuthor == null) entryAuthor = parser.nextText()
"updated" -> if (inEntry) entryDate = parseIso8601Date(parser.nextText())
"published" -> if (inEntry) entryDate = parseIso8601Date(parser.nextText()) ?: entryDate
"content" -> if (inEntry) entryContent = parser.nextText()
"summary" -> if (inEntry) entrySummary = parser.nextText()
}
}
XmlPullParser.END_TAG -> {
depth--
if (parser.name.lowercase() == "entry") {
inEntry = false
items += ParsedItem(
guid = entryId ?: entryLink.ifBlank { null },
title = entryTitle,
link = entryLink,
author = entryAuthor,
publishedAt = entryDate,
contentHtml = entryContent ?: entrySummary
)
}
}
}
if (depth > 0) eventType = parser.next()
}
return ParsedFeed(feedTitle, siteUrl, items)
}
private val rfc822Formatters = listOf(
DateTimeFormatter.RFC_1123_DATE_TIME,
DateTimeFormatterBuilder()
.appendPattern("EEE, d MMM yyyy HH:mm:ss ")
.optionalStart().appendPattern("zzz").optionalEnd()
.optionalStart().appendOffset("+HHMM", "+0000").optionalEnd()
.parseDefaulting(ChronoField.OFFSET_SECONDS, 0)
.toFormatter(Locale.US)
)
private fun parseRfc822Date(raw: String): Long? {
val trimmed = raw.trim()
for (formatter in rfc822Formatters) {
try {
return ZonedDateTime.parse(trimmed, formatter).toInstant().toEpochMilli()
} catch (_: Exception) {
// try the next formatter
}
}
return null
}
private fun parseIso8601Date(raw: String): Long? = try {
OffsetDateTime.parse(raw.trim()).toInstant().toEpochMilli()
} catch (_: Exception) {
null
}
}
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