test(richtext): guard math/link/image/hashtag adjacency

Pins that a MathSegment covers only its $-delimited span (not the paragraph), that space-separated hashtags, URLs and images next to math stay independently detected, that `$x$.` keeps its trailing period while a following hashtag remains its own segment, and that currency `$5` doesn't pair with a later equation. Also documents the glued (no-space) edge cases.
2026-10-06 19:53:08 +00:00 · 2026-06-08 21:27:15 +00:00
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+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.richtext
+
+import com.vitorpamplona.amethyst.commons.model.EmptyTagList
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * Guards that math extraction stays inside its `$`-delimiters and doesn't disturb
+ * neighbouring links / images / hashtags when separated by a space (the normal
+ * case), and documents the glued (no-space) edge behaviour.
+ */
+class RichTextParserMathAdjacencyTest {
+    // Kotlin uses `$` for string templates; a constant keeps the test strings readable.
+    private val d = "$"
+
+    private fun parse(content: String) = RichTextParser().parseText(content, EmptyTagList, null).paragraphs.flatMap { it.words }
+
+    @Test
+    fun mathSegmentIsJustTheSpanNotTheParagraph() {
+        val content = "before ${d}x_1 + y$d after more words here"
+        val math = parse(content).filterIsInstance<MathSegment>().single()
+        assertEquals("${d}x_1 + y$d", math.segmentText)
+        assertEquals("x_1 + y", math.latex)
+    }
+
+    @Test
+    fun spaceSeparatedHashtagUrlAndMathAreAllDetected() {
+        val content = "#physics the law ${d}E=mc^2$d see https://nostr.com today"
+        val words = parse(content)
+        assertEquals(1, words.filterIsInstance<HashTagSegment>().size)
+        assertEquals(1, words.filterIsInstance<MathSegment>().size)
+        assertEquals(1, words.filterIsInstance<LinkSegment>().size)
+        assertEquals("physics", words.filterIsInstance<HashTagSegment>().single().hashtag)
+        assertEquals("E=mc^2", words.filterIsInstance<MathSegment>().single().latex)
+        assertEquals("https://nostr.com", words.filterIsInstance<LinkSegment>().single().segmentText)
+    }
+
+    @Test
+    fun imageNextToMathStaysAnImage() {
+        val content = "${d}a^2$d https://i.imgur.com/abc.jpg done"
+        val words = parse(content)
+        assertEquals(1, words.filterIsInstance<MathSegment>().size)
+        assertEquals(1, words.filterIsInstance<ImageSegment>().size)
+        assertEquals("https://i.imgur.com/abc.jpg", words.filterIsInstance<ImageSegment>().single().segmentText)
+    }
+
+    @Test
+    fun mathEndingSentenceThenHashtag() {
+        // `$x$.` keeps the period as trailing; the hashtag after the space is its own segment.
+        val content = "result ${d}x=0$d. #done"
+        val words = parse(content)
+        val math = words.filterIsInstance<MathSegment>().single()
+        assertEquals("x=0", math.latex)
+        assertEquals(".", math.trailing)
+        assertEquals("done", words.filterIsInstance<HashTagSegment>().single().hashtag)
+    }
+
+    // ---- glued (no-space) adjacency: documents the known limitation ----
+
+    @Test
+    fun hashtagGluedAfterMathBecomesTrailingText() {
+        // `$x$#tag` with no space: the hashtag is absorbed as trailing punctuation
+        // and is NOT a clickable hashtag. Acceptable edge case.
+        val content = "eq ${d}x$d#tag"
+        val words = parse(content)
+        val math = words.filterIsInstance<MathSegment>().single()
+        assertEquals("x", math.latex)
+        assertEquals("#tag", math.trailing)
+        assertTrue(words.none { it is HashTagSegment })
+    }
+
+    @Test
+    fun mathGluedAfterHashtagDoesNotRenderAsMath() {
+        // `#tag$x$` with no space: the `#` token wins; the math stays literal text.
+        val content = "see #tag${d}x$d here"
+        val words = parse(content)
+        assertTrue(words.none { it is MathSegment })
+        assertEquals("tag", words.filterIsInstance<HashTagSegment>().single().hashtag)
+    }
+
+    @Test
+    fun currencyBeforeRealEquationDoesNotSwallow() {
+        // `$5` must not pair with the later equation's `$`.
+        val content = "costs ${d}5 but the formula ${d}x=1$d holds"
+        assertEquals("x=1", parse(content).filterIsInstance<MathSegment>().single().latex)
+    }
+}