feat: preview PDF links inline with first-page thumbnail and full pager

Adds MediaUrlPdf / PdfSegment to the rich-text pipeline so PDF URLs
(detected by .pdf extension, NIP-92 imeta m tag, or application/pdf
Content-Type) render a card showing the first page, filename, and page
count. Tapping opens a full-screen HorizontalPager over every page
rendered on demand with PdfRenderer. Long-press surfaces the existing
share menu. Uses only the built-in Android PdfRenderer; no new
dependencies. Desktop continues to fall back to a clickable link.

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/MediaContentModels.kt

@@ -68,6 +68,17 @@ class EncryptedMediaUrlImage(
     val encryptionNonce: ByteArray,
 ) : MediaUrlImage(url, description, hash, blurhash, dim, uri, contentWarning, mimeType)
 
+@Immutable
+open class MediaUrlPdf(
+    url: String,
+    description: String? = null,
+    hash: String? = null,
+    blurhash: String? = null,
+    dim: DimensionTag? = null,
+    uri: String? = null,
+    mimeType: String? = null,
+) : MediaUrlContent(url, description, hash, dim, blurhash, uri, mimeType)
+
 @Immutable
 open class MediaUrlVideo(
     url: String,

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/RichTextParser.kt

@@ -58,17 +58,21 @@ class RichTextParser {
 
         val isImage: Boolean
         val isVideo: Boolean
+        val isPdf: Boolean
 
         if (contentType != null) {
             isImage = contentType.startsWith("image/")
             isVideo = contentType.startsWith("video/") || contentType.startsWith("audio/")
+            isPdf = contentType.startsWith("application/pdf")
         } else if (fullUrl.startsWith("data:")) {
             isImage = fullUrl.startsWith("data:image/")
             isVideo = fullUrl.startsWith("data:video/") || fullUrl.startsWith("data:audio/")
+            isPdf = fullUrl.startsWith("data:application/pdf")
         } else {
             val removedParamsFromUrl = removeQueryParamsForExtensionComparison(fullUrl)
             isImage = imageExtensions.any { removedParamsFromUrl.endsWith(it) }
             isVideo = videoExtensions.any { removedParamsFromUrl.endsWith(it) }
+            isPdf = pdfExtensions.any { removedParamsFromUrl.endsWith(it) }
         }
 
         return if (isImage) {
@@ -93,6 +97,16 @@ class RichTextParser {
                 uri = callbackUri,
                 mimeType = contentType,
             )
+        } else if (isPdf) {
+            MediaUrlPdf(
+                url = fullUrl,
+                description = description ?: frags[AltTag.TAG_NAME] ?: tags[AltTag.TAG_NAME]?.firstOrNull(),
+                hash = frags[HashSha256Tag.TAG_NAME] ?: tags[HashSha256Tag.TAG_NAME]?.firstOrNull(),
+                blurhash = frags[BlurhashTag.TAG_NAME] ?: tags[BlurhashTag.TAG_NAME]?.firstOrNull(),
+                dim = frags[DimensionTag.TAG_NAME]?.let { DimensionTag.parse(it) } ?: tags[DimensionTag.TAG_NAME]?.firstOrNull()?.let { DimensionTag.parse(it) },
+                uri = callbackUri,
+                mimeType = contentType,
+            )
         } else {
             null
         }
@@ -158,6 +172,7 @@ class RichTextParser {
 
         val imageUrls = mediaForPager.filterValues { it is MediaUrlImage }.keys
         val videoUrls = mediaForPager.filterValues { it is MediaUrlVideo }.keys
+        val pdfUrls = mediaForPager.filterValues { it is MediaUrlPdf }.keys
 
         val emojiMap = CustomEmoji.createEmojiMap(tags.lists)
 
@@ -165,7 +180,7 @@ class RichTextParser {
 
         val newContent = fixMissingSpaces(content, allUrls)
 
-        val segments = findTextSegments(newContent, imageUrls, videoUrls, urlSet, emojiMap, tags)
+        val segments = findTextSegments(newContent, imageUrls, videoUrls, pdfUrls, urlSet, emojiMap, tags)
 
         val mediaForPagerWithBase64 =
             mediaForPager +
@@ -197,6 +212,7 @@ class RichTextParser {
         content: String,
         images: Set<String>,
         videos: Set<String>,
+        pdfs: Set<String>,
         urls: Urls,
         emojis: Map<String, String>,
         tags: ImmutableListOfLists<String>,
@@ -211,7 +227,7 @@ class RichTextParser {
 
             val segments = ArrayList<Segment>(wordList.size)
             wordList.forEach { word ->
-                segments.add(wordIdentifier(word, images, videos, urls, emojis, tags))
+                segments.add(wordIdentifier(word, images, videos, pdfs, urls, emojis, tags))
             }
 
             paragraphSegments.add(ParagraphState(segments.toPersistentList(), isRTL))
@@ -262,6 +278,7 @@ class RichTextParser {
         word: String,
         images: Set<String>,
         videos: Set<String>,
+        pdfs: Set<String>,
         urls: Urls,
         emojis: Map<String, String>,
         tags: ImmutableListOfLists<String>,
@@ -288,6 +305,14 @@ class RichTextParser {
             }
         }
 
+        if (pdfs.contains(word)) {
+            return if (urls.withoutScheme.contains(word)) {
+                PdfSegment("https://$word")
+            } else {
+                PdfSegment(word)
+            }
+        }
+
         if (urls.withoutScheme.contains(word)) return SchemelessUrlSegment(word)
 
         if (urls.withScheme.contains(word)) return LinkSegment(word)
@@ -377,9 +402,11 @@ class RichTextParser {
 
         val imageExt = listOf("png", "jpg", "gif", "bmp", "jpeg", "webp", "svg", "avif")
         val videoExt = listOf("mp4", "avi", "wmv", "mpg", "amv", "webm", "mov", "mp3", "m3u8", "ogg", "wav", "flac", "aac", "opus", "m4a")
+        val pdfExt = listOf("pdf")
 
         val imageExtensions = imageExt + imageExt.map { it.uppercase() }
         val videoExtensions = videoExt + videoExt.map { it.uppercase() }
+        val pdfExtensions = pdfExt + pdfExt.map { it.uppercase() }
 
         val tagIndex = Regex("\\#\\[([0-9]+)\\](.*)")
         val hashTagsPattern: Regex =
@@ -421,6 +448,11 @@ class RichTextParser {
             return videoExtensions.any { removedParamsFromUrl.endsWith(it) }
         }
 
+        fun isPdfUrl(url: String): Boolean {
+            val removedParamsFromUrl = removeQueryParamsForExtensionComparison(url)
+            return pdfExtensions.any { removedParamsFromUrl.endsWith(it) }
+        }
+
         fun isValidURL(url: String?): Boolean =
             try {
                 if (url != null) {
@@ -496,4 +528,6 @@ val mimeTypeMap: Map<String, String> =
         "m4a" to "audio/mp4",
         "aac" to "audio/aac",
         "flac" to "audio/flac",
+        // Documents
+        "pdf" to "application/pdf",
     )

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/richtext/RichTextParserSegments.kt

@@ -62,6 +62,11 @@ class VideoSegment(
     segment: String,
 ) : Segment(segment)
 
+@Immutable
+class PdfSegment(
+    segment: String,
+) : Segment(segment)
+
 @Immutable
 class LinkSegment(
     segment: String,