android/app/src/test/java/com/fabledsword/minstrel/theme/BundledFontsTest.kt

@@ -0,0 +1,125 @@
+package com.fabledsword.minstrel.theme
+
+import org.junit.jupiter.api.Test
+import java.io.File
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+/**
+ * Guards that the typefaces ship inside the APK instead of being fetched at
+ * runtime.
+ *
+ * Until 2026-09-09 these were resolved through the Play Services font
+ * provider. That needs a network the deployed app is not guaranteed, and a
+ * provider that devices without Play Services do not have at all. Both
+ * failures are silent — text just renders in the platform default, which
+ * reads as a styling regression rather than a missing dependency.
+ *
+ * Expectations are read out of Typography.kt itself rather than hardcoded, so
+ * this cannot drift away from what the app actually declares: adding a face
+ * without vendoring its file fails here, and so does changing a declared
+ * weight without refetching the matching static instance.
+ */
+class BundledFontsTest {
+    @Test
+    fun `typography builds its families from bundled resources`() {
+        val source = typographySource()
+        assertTrue(
+            source.contains("R.font."),
+            "Typography.kt should build its families from res/font resources",
+        )
+        FORBIDDEN.forEach { symbol ->
+            assertTrue(
+                !source.contains(symbol),
+                "Typography.kt must not reference $symbol — fonts are bundled, not fetched",
+            )
+        }
+    }
+
+    @Test
+    fun `every declared face is vendored as TrueType at its declared weight`() {
+        val declared = FACE_PATTERN.findAll(typographySource()).toList()
+        assertTrue(
+            declared.isNotEmpty(),
+            "no Font(R.font.…, FontWeight.W…) declarations found — the guard would pass vacuously",
+        )
+
+        declared.forEach { match ->
+            val (name, weight) = match.destructured
+            val file = File(appDir(), "src/main/res/font/$name.ttf")
+            assertTrue(file.isFile, "res/font/$name.ttf is missing — run tools/vendor-fonts.py")
+
+            val bytes = file.readBytes()
+            assertTrue(
+                bytes.copyOfRange(0, TTF_MAGIC.size).contentEquals(TTF_MAGIC),
+                "$name.ttf is not TrueType — res/font cannot load a woff2 or an eot",
+            )
+            // The decisive check. Google's css2 endpoint silently collapses a
+            // multi-weight request to 400 for legacy clients, so Medium can
+            // come back as Regular: a valid TrueType file that renders at the
+            // wrong weight everywhere. usWeightClass is the only field that
+            // tells the two apart.
+            assertEquals(
+                weight.toInt(),
+                weightClass(bytes),
+                "$name.ttf carries a different OS/2 usWeightClass than the FontWeight declared beside it",
+            )
+        }
+    }
+
+    /** Typography.kt with comments removed, so prose naming the forbidden
+     *  symbols cannot satisfy — or trip — the absence check above. */
+    private fun typographySource(): String =
+        File(appDir(), TYPOGRAPHY)
+            .readText()
+            .replace(BLOCK_COMMENT, "")
+            .replace(LINE_COMMENT, "")
+
+    /** Gradle's working directory for tests is the module dir, but don't rely
+     *  on it: walk up until the module is found, and say so if it isn't. */
+    private fun appDir(): File {
+        var dir: File? = File("").absoluteFile
+        while (dir != null) {
+            if (File(dir, TYPOGRAPHY).isFile) return dir
+            if (File(dir, "app/$TYPOGRAPHY").isFile) return File(dir, "app")
+            dir = dir.parentFile
+        }
+        error("could not locate the app module from ${File("").absolutePath}")
+    }
+
+    private fun weightClass(bytes: ByteArray): Int {
+        val tables = readU16(bytes, NUM_TABLES)
+        for (i in 0 until tables) {
+            val record = TABLE_DIRECTORY + i * TABLE_RECORD
+            if (String(bytes, record, TAG_LENGTH, Charsets.US_ASCII) == "OS/2") {
+                return readU16(bytes, readU32(bytes, record + OFFSET_FIELD) + WEIGHT_FIELD)
+            }
+        }
+        error("no OS/2 table in the font")
+    }
+
+    private fun readU16(bytes: ByteArray, at: Int): Int =
+        ((bytes[at].toInt() and BYTE_MASK) shl Byte.SIZE_BITS) or (bytes[at + 1].toInt() and BYTE_MASK)
+
+    private fun readU32(bytes: ByteArray, at: Int): Int =
+        (readU16(bytes, at) shl Short.SIZE_BITS) or readU16(bytes, at + 2)
+
+    private companion object {
+        const val TYPOGRAPHY = "src/main/java/com/fabledsword/minstrel/theme/Typography.kt"
+
+        val FORBIDDEN = listOf("GoogleFont", "googlefonts")
+        val FACE_PATTERN = Regex("""R\.font\.(\w+)\s*,\s*FontWeight\.W(\d+)""")
+        val BLOCK_COMMENT = Regex("""/\*[\s\S]*?\*/""")
+        val LINE_COMMENT = Regex("""//.*""")
+        val TTF_MAGIC = byteArrayOf(0x00, 0x01, 0x00, 0x00)
+
+        // Offsets into the TrueType table directory, per the OpenType spec.
+        const val NUM_TABLES = 4
+        const val TABLE_DIRECTORY = 12
+        const val TABLE_RECORD = 16
+        const val TAG_LENGTH = 4
+        const val OFFSET_FIELD = 8
+        const val WEIGHT_FIELD = 4
+        const val BYTE_MASK = 0xFF
+    }
+}