feat(chat): add rich text support (starting with clickable URLs)

apps/flipcash/shared/chat-ui/build.gradle.kts

@@ -18,4 +18,6 @@ dependencies {
     implementation(libs.androidx.paging.runtime)
     implementation(libs.compose.paging)
     implementation(project(":apps:flipcash:shared:theme"))
+
+    testImplementation(libs.robolectric)
 }

apps/flipcash/shared/chat-ui/src/main/kotlin/com/flipcash/shared/chat/ui/MessageBubble.kt

@@ -32,7 +32,9 @@ import androidx.compose.ui.graphics.Shape
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalInspectionMode
 import androidx.compose.ui.res.stringResource
+import androidx.compose.ui.text.SpanStyle
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextDecoration
 import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.tooling.preview.PreviewWrapper
 import androidx.compose.ui.unit.Dp
@@ -113,9 +115,17 @@ private fun TextBubble(
     modifier: Modifier = Modifier,
 ) {
     Bubble(isFromSelf, position, maxWidth, modifier) {
+        val linkStyle = SpanStyle(
+            color = CodeTheme.colors.textMain,
+            textDecoration = TextDecoration.Underline,
+        )
+        val richText = rememberRichText(
+            text = text,
+            annotators = listOf(UrlAnnotator(linkStyle)),
+        )
         SelectionContainer {
             Text(
-                text = text,
+                text = richText,
                 style = CodeTheme.typography.textMedium.copy(
                     fontWeight = FontWeight.Medium
                 ),
@@ -380,6 +390,18 @@ private fun Preview_TextBubble_Incoming() {
     )
 }
 
+@Preview
+@PreviewWrapper(FlipcashThemeWrapper::class)
+@Composable
+private fun Preview_TextBubble_WithLink() {
+    TextBubble(
+        text = "Check out https://flipcash.app for more info!",
+        isFromSelf = false,
+        position = BubblePosition.Solo,
+        maxWidth = 300.dp,
+    )
+}
+
 @Preview
 @PreviewWrapper(FlipcashThemeWrapper::class)
 @Composable

apps/flipcash/shared/chat-ui/src/main/kotlin/com/flipcash/shared/chat/ui/RichText.kt

@@ -0,0 +1,43 @@
+package com.flipcash.shared.chat.ui
+
+import android.util.Patterns
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.LinkAnnotation
+import androidx.compose.ui.text.SpanStyle
+import androidx.compose.ui.text.TextLinkStyles
+import androidx.compose.ui.text.buildAnnotatedString
+
+fun interface SpanAnnotator {
+    fun AnnotatedString.Builder.annotate(text: String)
+}
+
+class UrlAnnotator(private val linkStyle: SpanStyle) : SpanAnnotator {
+    override fun AnnotatedString.Builder.annotate(text: String) {
+        val matcher = Patterns.WEB_URL.matcher(text)
+        while (matcher.find()) {
+            val url = matcher.group() ?: continue
+            val resolved = if (!url.startsWith("http")) "https://$url" else url
+            addLink(
+                LinkAnnotation.Url(
+                    url = resolved,
+                    styles = TextLinkStyles(style = linkStyle),
+                ),
+                start = matcher.start(),
+                end = matcher.end(),
+            )
+        }
+    }
+}
+
+@Composable
+fun rememberRichText(
+    text: String,
+    annotators: List<SpanAnnotator>,
+): AnnotatedString = remember(text, annotators) {
+    buildAnnotatedString {
+        append(text)
+        annotators.forEach { with(it) { annotate(text) } }
+    }
+}

apps/flipcash/shared/chat-ui/src/test/kotlin/com/flipcash/shared/chat/ui/UrlAnnotatorTest.kt

@@ -0,0 +1,91 @@
+package com.flipcash.shared.chat.ui
+
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.LinkAnnotation
+import androidx.compose.ui.text.SpanStyle
+import androidx.compose.ui.text.buildAnnotatedString
+import androidx.compose.ui.text.style.TextDecoration
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE)
+class UrlAnnotatorTest {
+
+    private val linkStyle = SpanStyle(
+        color = Color.Blue,
+        textDecoration = TextDecoration.Underline,
+    )
+    private val annotator = UrlAnnotator(linkStyle)
+
+    private fun annotate(text: String) = buildAnnotatedString {
+        append(text)
+        with(annotator) { annotate(text) }
+    }
+
+    @Test
+    fun `annotates https URL at correct offsets`() {
+        val text = "Visit https://example.com today"
+        val result = annotate(text)
+
+        val links = result.getLinkAnnotations(0, result.length)
+        assertEquals(1, links.size)
+
+        val link = links.first()
+        assertEquals(6, link.start)
+        assertEquals(25, link.end)
+
+        val annotation = link.item as LinkAnnotation.Url
+        assertEquals("https://example.com", annotation.url)
+    }
+
+    @Test
+    fun `annotates http URL without adding https`() {
+        val text = "Go to http://example.com now"
+        val result = annotate(text)
+
+        val links = result.getLinkAnnotations(0, result.length)
+        assertEquals(1, links.size)
+
+        val annotation = links.first().item as LinkAnnotation.Url
+        assertEquals("http://example.com", annotation.url)
+    }
+
+    @Test
+    fun `prepends https for bare domain`() {
+        val text = "Check example.com out"
+        val result = annotate(text)
+
+        val links = result.getLinkAnnotations(0, result.length)
+        assertEquals(1, links.size)
+
+        val annotation = links.first().item as LinkAnnotation.Url
+        assertEquals("https://example.com", annotation.url)
+    }
+
+    @Test
+    fun `annotates multiple URLs`() {
+        val text = "See https://a.com and https://b.com"
+        val result = annotate(text)
+
+        val links = result.getLinkAnnotations(0, result.length)
+        assertEquals(2, links.size)
+
+        val urls = links.map { (it.item as LinkAnnotation.Url).url }
+        assertTrue("https://a.com" in urls)
+        assertTrue("https://b.com" in urls)
+    }
+
+    @Test
+    fun `no annotations for plain text`() {
+        val text = "Just a plain message"
+        val result = annotate(text)
+
+        val links = result.getLinkAnnotations(0, result.length)
+        assertTrue(links.isEmpty())
+    }
+}