Fixes Emoji Joining issues.

app/src/main/java/com/vitorpamplona/amethyst/service/StringUtils.kt

@@ -1,10 +1,11 @@
 package com.vitorpamplona.amethyst.service
 
 fun String.isUTF16Char(pos: Int): Boolean {
+    println("Test $pos ${Character.charCount(this.codePointAt(pos))}")
     return Character.charCount(this.codePointAt(pos)) == 2
 }
 
-fun String.firstFullChar(): String {
+fun String.firstFullCharOld(): String {
     return when (this.length) {
         0, 1 -> return this
         2, 3 -> return if (isUTF16Char(0)) this.take(2) else this.take(1)
@@ -21,3 +22,57 @@ fun String.firstFullChar(): String {
         }
     }
 }
+
+fun String.firstFullChar(): String {
+    var isInJoin = false
+    var start = 0
+    var previousCharLength = 0
+    var next: Int
+    var codePoint: Int
+
+    var i = 0
+
+    while (i < this.length) {
+        codePoint = codePointAt(i)
+
+        // Skips if it starts with the join char 0x200D
+        if (codePoint == 0x200D && previousCharLength == 0) {
+            next = offsetByCodePoints(i, 1)
+            start = next
+        } else {
+            // If join, searches for the next char
+            if (codePoint == 0x200D) {
+                isInJoin = true
+            } else {
+                // stops when two chars are not joined together
+                if ((previousCharLength > 0) && (!isInJoin) && Character.charCount(codePoint) == 1) {
+                    break
+                }
+
+                isInJoin = false
+            }
+
+            // next char to evaluate
+            next = offsetByCodePoints(i, 1)
+            previousCharLength += (next - i)
+        }
+
+        i = next
+    }
+
+    // if ends in join, then seachers backwards until a char is found.
+    if (isInJoin) {
+        i = previousCharLength - 1
+        while (i > 0) {
+            if (this[i].code == 0x200D) {
+                previousCharLength -= 1
+            } else {
+                break
+            }
+
+            i -= 1
+        }
+    }
+
+    return substring(start, start + previousCharLength)
+}

app/src/test/java/com/vitorpamplona/amethyst/CharsetTest.kt

@@ -11,12 +11,12 @@ class CharsetTest {
     }
 
     @Test
-    fun testUTF16Char() {
+    fun testUTF16JoinChar() {
         Assert.assertEquals("\uD83C\uDF48", "\uD83C\uDF48Hi".firstFullChar())
     }
 
     @Test
-    fun testUTF32Char() {
+    fun testUTF32JoinChar() {
         Assert.assertEquals("\uD83E\uDDD1\uD83C\uDFFE", "\uD83E\uDDD1\uD83C\uDFFEHi".firstFullChar())
     }
 
@@ -34,4 +34,19 @@ class CharsetTest {
     fun testSpecialChars() {
         Assert.assertEquals("=", "=x".firstFullChar())
     }
+
+    @Test
+    fun test5CharEmoji() {
+        Assert.assertEquals("\uD83D\uDC68\u200D\uD83D\uDCBB", "\uD83D\uDC68\u200D\uD83D\uDCBBadsfasdf".firstFullChar())
+    }
+
+    @Test
+    fun testFamily() {
+        Assert.assertEquals("\uD83D\uDC68\u200d\uD83D\uDC69\u200d\uD83D\uDC67\u200d\uD83D\uDC67", "\uD83D\uDC68\u200D\uD83D\uDC69\u200D\uD83D\uDC67\u200D\uD83D\uDC67adsfasdf".firstFullChar())
+    }
+
+    @Test
+    fun testTeacher() {
+        Assert.assertEquals("\uD83E\uDDD1\uD83C\uDFFF\u200D\uD83C\uDFEB", "\uD83E\uDDD1\uD83C\uDFFF\u200D\uD83C\uDFEBasdf".firstFullChar())
+    }
 }