Fixes #14409

app/src/main/java/org/thoughtcrime/securesms/components/registration/VerificationCodeViewCompose.kt

@@ -0,0 +1,179 @@
+/*
+ * Copyright 2025 Signal Messenger, LLC
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+package org.thoughtcrime.securesms.components.registration
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.BoxWithConstraints
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.derivedStateOf
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalDensity
+import androidx.compose.ui.platform.LocalFocusManager
+import androidx.compose.ui.text.AnnotatedString
+import androidx.compose.ui.text.TextStyle
+import androidx.compose.ui.text.rememberTextMeasurer
+import androidx.compose.ui.text.style.TextAlign
+import androidx.compose.ui.tooling.preview.PreviewFontScale
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import org.signal.core.ui.compose.theme.SignalTheme
+
+private const val DEFAULT_CODE_LENGTH: Int = 6
+private val BOX_SPACING = 4.dp
+private val MIN_BOX_WIDTH = 24.dp
+private val SEPARATOR_FONT_SIZE = 28.sp
+private val BOX_CORNER_RADIUS = 4.dp
+private val BOTTOM_ACCENT_HEIGHT = 2.dp
+private const val DASH_INSERT_INDEX: Int = 2
+private const val DASH_MIN_CODE_LENGTH: Int = 3
+private const val BOX_HEIGHT_NUMERATOR: Float = 7f
+private const val BOX_HEIGHT_DENOMINATOR: Float = 6f
+
+@Composable
+fun VerificationCodeViewCompose(
+  codeLength: Int = DEFAULT_CODE_LENGTH,
+  onCodeComplete: (String) -> Unit,
+  codeState: List<String>
+) {
+  val focusManager = LocalFocusManager.current
+
+  val firstEmptyIndex by remember(codeState, codeLength) { derivedStateOf { nextEmptyIndex(codeState, codeLength) } }
+  var focusedIndex by remember { mutableStateOf(firstEmptyIndex) }
+
+  val onComplete by rememberUpdatedState(onCodeComplete)
+
+  val codeString by remember(codeState) { derivedStateOf { codeState.joinToString("") } }
+
+  LaunchedEffect(firstEmptyIndex) { focusManager.clearFocus() }
+
+  LaunchedEffect(codeString) {
+    focusedIndex = nextEmptyIndex(codeState, codeLength)
+
+    if (codeState.all { it.length == 1 }) {
+      onComplete(codeString)
+      focusManager.clearFocus()
+    }
+  }
+
+  SignalTheme {
+    val boxSpacing = BOX_SPACING
+
+    BoxWithConstraints {
+      // Use the full maxWidth so there are no absolute start/end margins.
+      val availableWidth = this.maxWidth
+
+      val textMeasurer = rememberTextMeasurer()
+      val density = LocalDensity.current
+      val separatorWidth = remember(textMeasurer, density) {
+        val layout = textMeasurer.measure(AnnotatedString("-"), style = TextStyle(fontSize = SEPARATOR_FONT_SIZE))
+        density.run { layout.size.width.toDp() }
+      }
+
+      val hasSeparator = codeLength > DASH_MIN_CODE_LENGTH
+      val elementsCount = if (hasSeparator) codeLength + 1 else codeLength
+      val totalGaps = (elementsCount - 1)
+      val totalSpacing = boxSpacing * totalGaps
+
+      val availableForBoxes = availableWidth - totalSpacing - if (hasSeparator) separatorWidth else 0.dp
+      val computedBoxWidth = availableForBoxes / codeLength
+      val boxWidth = computedBoxWidth.coerceAtLeast(MIN_BOX_WIDTH)
+      val boxHeight = boxWidth * BOX_HEIGHT_NUMERATOR / BOX_HEIGHT_DENOMINATOR
+
+      Row(
+        modifier = Modifier.fillMaxWidth(),
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(boxSpacing, Alignment.CenterHorizontally)
+      ) {
+        for (i in 0 until codeLength) {
+          val char = codeState.getOrNull(i) ?: ""
+          val isFocused = focusedIndex == i
+
+          DigitCell(
+            char = char,
+            isFocused = isFocused,
+            boxWidth = boxWidth,
+            boxHeight = boxHeight,
+            onClick = { focusedIndex = i }
+          )
+
+          if (i == DASH_INSERT_INDEX && hasSeparator) {
+            Text(
+              text = "-",
+              style = TextStyle(fontSize = SEPARATOR_FONT_SIZE, color = MaterialTheme.colorScheme.onSurfaceVariant),
+              modifier = Modifier
+            )
+          }
+        }
+      }
+    }
+  }
+}
+
+@Composable
+private fun DigitCell(
+  char: String,
+  isFocused: Boolean,
+  boxWidth: Dp,
+  boxHeight: Dp,
+  onClick: () -> Unit
+) {
+  Box(
+    modifier = Modifier
+      .size(width = boxWidth, height = boxHeight)
+      .clickable { onClick() }
+      .background(MaterialTheme.colorScheme.surfaceVariant, RoundedCornerShape(topStart = BOX_CORNER_RADIUS, topEnd = BOX_CORNER_RADIUS, bottomEnd = 0.dp, bottomStart = 0.dp)),
+    contentAlignment = Alignment.Center
+  ) {
+    if (char.isEmpty()) {
+      Text("•", style = MaterialTheme.typography.bodyLarge.copy(color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = 0.5f)), textAlign = TextAlign.Center)
+    } else {
+      Text(char, style = MaterialTheme.typography.bodyLarge.copy(color = MaterialTheme.colorScheme.onSurfaceVariant), textAlign = TextAlign.Center)
+    }
+
+    Box(
+      modifier = Modifier
+        .align(Alignment.BottomCenter)
+        .height(BOTTOM_ACCENT_HEIGHT)
+        .fillMaxWidth()
+        .background(MaterialTheme.colorScheme.primary.copy(alpha = if (isFocused) 1f else 0f))
+    )
+  }
+}
+
+private fun nextEmptyIndex(codeState: List<String>, codeLength: Int): Int {
+  val idx = codeState.indexOfFirst { it.isEmpty() }
+  return if (idx == -1) codeLength - 1 else idx
+}
+
+@PreviewFontScale
+@Composable
+fun VerificationCodeViewComposePreview() {
+  SignalTheme {
+    VerificationCodeViewCompose(
+      codeLength = DEFAULT_CODE_LENGTH,
+      codeState = listOf("1", "5", "6", "", "", ""),
+      onCodeComplete = {}
+    )
+  }
+}