Fix hashtags matching on note content

PrimalHQ · Aug 29, 2023 · 57919f8 · 57919f8
1 parent 46d9163
commit 57919f8
Show file tree

Hide file tree

Showing 3 changed files with 137 additions and 39 deletions.
diff --git a/app/src/main/kotlin/net/primal/android/core/compose/feed/FeedPostContent.kt b/app/src/main/kotlin/net/primal/android/core/compose/feed/FeedPostContent.kt
@@ -40,6 +40,7 @@ import net.primal.android.core.compose.feed.model.NostrResourceUi
 import net.primal.android.core.compose.media.model.MediaResourceUi
 import net.primal.android.core.ext.calculateImageSize
 import net.primal.android.core.ext.findNearestOrNull
+import net.primal.android.core.utils.HashtagMatcher
 import net.primal.android.core.utils.parseHashtags
 import net.primal.android.feed.db.ReferencedPost
 import net.primal.android.feed.db.ReferencedUser
@@ -145,53 +146,57 @@ fun FeedPostContent(
 
             refinedUrlResources.map { it.url }.forEach {
                 val startIndex = refinedContent.indexOf(it)
-                val endIndex = startIndex + it.length
-                addStyle(
-                    style = SpanStyle(color = primaryColor),
-                    start = startIndex,
-                    end = endIndex,
-                )
-                addStringAnnotation(
-                    tag = URL_ANNOTATION_TAG,
-                    annotation = it,
-                    start = startIndex,
-                    end = endIndex,
-                )
+                if (startIndex >= 0) {
+                    val endIndex = startIndex + it.length
+                    addStyle(
+                        style = SpanStyle(color = primaryColor),
+                        start = startIndex,
+                        end = endIndex,
+                    )
+                    addStringAnnotation(
+                        tag = URL_ANNOTATION_TAG,
+                        annotation = it,
+                        start = startIndex,
+                        end = endIndex,
+                    )
+                }
             }
 
             referencedUserResources.forEach {
                 checkNotNull(it.referencedUser)
                 val displayHandle = it.referencedUser.displayHandle
                 val startIndex = refinedContent.indexOf(displayHandle)
-                val endIndex = startIndex + displayHandle.length
-                addStyle(
-                    style = SpanStyle(color = primaryColor),
-                    start = startIndex,
-                    end = endIndex,
-                )
-                addStringAnnotation(
-                    tag = PROFILE_ID_ANNOTATION_TAG,
-                    annotation = it.referencedUser.userId,
-                    start = startIndex,
-                    end = endIndex,
-                )
+                if (startIndex >= 0) {
+                    val endIndex = startIndex + displayHandle.length
+                    addStyle(
+                        style = SpanStyle(color = primaryColor),
+                        start = startIndex,
+                        end = endIndex,
+                    )
+                    addStringAnnotation(
+                        tag = PROFILE_ID_ANNOTATION_TAG,
+                        annotation = it.referencedUser.userId,
+                        start = startIndex,
+                        end = endIndex,
+                    )
+                }
             }
 
-            hashtags.forEach {
-                val startIndex = refinedContent.indexOf(it)
-                val endIndex = startIndex + it.length
-                addStyle(
-                    style = SpanStyle(color = primaryColor),
-                    start = startIndex,
-                    end = endIndex,
-                )
-                addStringAnnotation(
-                    tag = HASHTAG_ANNOTATION_TAG,
-                    annotation = it,
-                    start = startIndex,
-                    end = endIndex,
-                )
-            }
+            HashtagMatcher(content = refinedContent, hashtags = hashtags)
+                .matches()
+                .forEach {
+                    addStyle(
+                        style = SpanStyle(color = primaryColor),
+                        start = it.startIndex,
+                        end = it.endIndex,
+                    )
+                    addStringAnnotation(
+                        tag = HASHTAG_ANNOTATION_TAG,
+                        annotation = it.value,
+                        start = it.startIndex,
+                        end = it.endIndex,
+                    )
+                }
         }
     }
 

diff --git a/app/src/main/kotlin/net/primal/android/core/utils/HashtagMatcher.kt b/app/src/main/kotlin/net/primal/android/core/utils/HashtagMatcher.kt
@@ -0,0 +1,47 @@
+package net.primal.android.core.utils
+
+class HashtagMatcher(
+    content: String,
+    hashtags: List<String>,
+) {
+
+    private val matches: MutableList<HashtagMatch> = mutableListOf()
+    fun matches(): List<HashtagMatch> = matches
+
+    private fun containsIndex(index: Int) = matches.find { it.startIndex == index } != null
+
+    private fun String.indexOfNotMatchedBefore(hashtag: String): Int? {
+        var startIndex = 0
+        var foundIndex: Int? = -1
+        while (foundIndex == -1) {
+            val indexOf  = this.indexOf(hashtag, startIndex = startIndex)
+            when {
+                indexOf == -1 -> foundIndex = null
+                containsIndex(index = indexOf) -> startIndex = indexOf + 1
+                else -> foundIndex = indexOf
+            }
+        }
+        return foundIndex
+    }
+
+    init {
+        hashtags.forEach {
+            val startIndex = content.indexOfNotMatchedBefore(hashtag = it)
+            if (startIndex != null) {
+                matches.add(
+                    HashtagMatch(
+                        value = it,
+                        startIndex = startIndex,
+                        endIndex = startIndex + it.length,
+                    )
+                )
+            }
+        }
+    }
+}
+
+data class HashtagMatch(
+    val value: String,
+    val startIndex: Int,
+    val endIndex: Int,
+)
diff --git a/app/src/test/kotlin/net/primal/android/core/utils/HashtagMatcherTest.kt b/app/src/test/kotlin/net/primal/android/core/utils/HashtagMatcherTest.kt
@@ -0,0 +1,46 @@
+package net.primal.android.core.utils
+
+import io.kotest.matchers.collections.shouldContain
+import io.kotest.matchers.collections.shouldContainAll
+import io.kotest.matchers.collections.shouldNotContain
+import org.junit.Test
+
+class HashtagMatcherTest {
+
+    @Test
+    fun `matches should match all known hashtags`() {
+        val hashtags = listOf("#TextureTuesday", "#Texture", "#Details", "#Photography")
+        val matcher = HashtagMatcher(
+            content = "Rusty iron chain on gray gravel. #TextureTuesday #Texture #Details #Photography",
+            hashtags = hashtags,
+        )
+
+        val actual = matcher.matches().map { it.value }
+        actual.shouldContainAll(hashtags)
+    }
+
+    @Test
+    fun `matches should match hashtags which are contained in other hashtags`() {
+        val hashtags = listOf("#TextureTuesday", "#Texture", "#Zapathon", "#Zap")
+        val matcher = HashtagMatcher(
+            content = "Rusty iron chain on gray gravel. #TextureTuesday #Texture #Zap #Zapathon",
+            hashtags = hashtags,
+        )
+
+        val actual = matcher.matches().map { it.value }
+        actual.shouldContainAll(hashtags)
+    }
+
+    @Test
+    fun `matches should not match unknown hashtags`() {
+        val hashtags = listOf("#Hiking", "#Trails")
+        val matcher = HashtagMatcher(
+            content = "The #Hiking Trails is available in Art prints with or without frame.",
+            hashtags = hashtags,
+        )
+
+        val actual = matcher.matches().map { it.value }
+        actual.shouldContain(hashtags.first())
+        actual.shouldNotContain(hashtags.last())
+    }
+}