feat: import Chinese-localized Buzz source snapshot

Signed-off-by: cls_宁波本机 <908705107@qq.com>

mobile/android/.gitignore

@@ -0,0 +1,15 @@
+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+.cxx/
+/worktree.properties
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/to/reference-keystore
+key.properties
+**/*.keystore
+**/*.jks

mobile/android/app/build.gradle.kts

@@ -0,0 +1,176 @@
+import java.util.Properties
+
+plugins {
+    id("com.android.application")
+    id("kotlin-android")
+    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
+    id("dev.flutter.flutter-gradle-plugin")
+}
+
+val uploadKeystorePath = providers.environmentVariable("BUZZ_ANDROID_UPLOAD_KEYSTORE_PATH").orNull
+val uploadKeystorePassword = providers.environmentVariable("BUZZ_ANDROID_UPLOAD_KEYSTORE_PASSWORD").orNull
+val uploadKeyAlias = providers.environmentVariable("BUZZ_ANDROID_UPLOAD_KEY_ALIAS").orNull
+val uploadKeyPassword = providers.environmentVariable("BUZZ_ANDROID_UPLOAD_KEY_PASSWORD").orNull
+val uploadSigningValues =
+    mapOf(
+        "BUZZ_ANDROID_UPLOAD_KEYSTORE_PATH" to uploadKeystorePath,
+        "BUZZ_ANDROID_UPLOAD_KEYSTORE_PASSWORD" to uploadKeystorePassword,
+        "BUZZ_ANDROID_UPLOAD_KEY_ALIAS" to uploadKeyAlias,
+        "BUZZ_ANDROID_UPLOAD_KEY_PASSWORD" to uploadKeyPassword,
+    )
+val missingUploadSigningValues = uploadSigningValues.filterValues { it.isNullOrBlank() }.keys
+val hasUploadSigning = missingUploadSigningValues.isEmpty()
+
+// Worktree-aware debug identity (gitignored, written by
+// scripts/mobile-worktree-overrides.sh): debug builds from a git worktree get a
+// branch-labelled app name and a unique applicationId suffix so builds from
+// multiple worktrees install side by side. Release builds never read this.
+val worktreePropsFile = rootProject.file("worktree.properties")
+val worktreeProps =
+    Properties().apply {
+        if (worktreePropsFile.isFile) worktreePropsFile.inputStream().use { load(it) }
+    }
+val worktreeLabel = worktreeProps.getProperty("label")?.takeIf { it.isNotBlank() }
+if (worktreeLabel != null && !worktreeLabel.matches(Regex("""[A-Za-z0-9._-]+"""))) {
+    throw GradleException(
+        "worktree.properties label must match [A-Za-z0-9._-]+ (safe for string " +
+            "resources), got: " + worktreeLabel,
+    )
+}
+val worktreeIdSuffix =
+    worktreeProps.getProperty("applicationIdSuffix")?.takeIf { it.isNotBlank() }
+if (worktreeIdSuffix != null && !worktreeIdSuffix.matches(Regex("""\.[a-z][a-z0-9_]*"""))) {
+    throw GradleException(
+        "worktree.properties applicationIdSuffix must match \\.[a-z][a-z0-9_]*, got: " +
+            worktreeIdSuffix,
+    )
+}
+
+// Release signing modes:
+//   - "upload-keystore" (default): sign with the CI-vended upload keystore;
+//     release builds fail loudly when any credential is missing.
+//   - "external": deliberately produce an UNSIGNED release bundle for a
+//     pipeline that signs through the central APK Signer service (Cashkite,
+//     BOT-1234). No keystore material may be present in this mode.
+val releaseSigningMode =
+    providers.environmentVariable("BUZZ_ANDROID_RELEASE_SIGNING").orNull ?: "upload-keystore"
+val externalReleaseSigning = releaseSigningMode == "external"
+if (releaseSigningMode !in setOf("upload-keystore", "external")) {
+    throw GradleException(
+        "BUZZ_ANDROID_RELEASE_SIGNING must be \"upload-keystore\" or \"external\", got: " +
+            releaseSigningMode,
+    )
+}
+if (externalReleaseSigning && uploadSigningValues.values.any { !it.isNullOrBlank() }) {
+    throw GradleException(
+        "BUZZ_ANDROID_RELEASE_SIGNING=external must not be combined with " +
+            "BUZZ_ANDROID_UPLOAD_* credentials; unset one of them.",
+    )
+}
+
+android {
+    namespace = "xyz.block.buzz.mobile"
+    compileSdk = flutter.compileSdkVersion
+    ndkVersion = flutter.ndkVersion
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+
+    kotlinOptions {
+        jvmTarget = JavaVersion.VERSION_17.toString()
+    }
+
+    defaultConfig {
+        applicationId = "xyz.block.buzz.mobile"
+        // You can update the following values to match your application needs.
+        // For more information, see: https://flutter.dev/to/review-gradle-config.
+        minSdk = flutter.minSdkVersion
+        targetSdk = flutter.targetSdkVersion
+        versionCode = flutter.versionCode
+        versionName = flutter.versionName
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        resValue("string", "app_name", "Buzz")
+    }
+
+    signingConfigs {
+        if (hasUploadSigning) {
+            create("upload") {
+                storeFile = file(requireNotNull(uploadKeystorePath))
+                storePassword = uploadKeystorePassword
+                keyAlias = uploadKeyAlias
+                keyPassword = uploadKeyPassword
+            }
+        }
+    }
+
+    buildTypes {
+        debug {
+            // Only debug builds take the worktree identity; release/profile
+            // keep the production applicationId and label.
+            if (worktreeIdSuffix != null) {
+                applicationIdSuffix = worktreeIdSuffix
+            }
+            if (worktreeLabel != null) {
+                resValue("string", "app_name", "Buzz ($worktreeLabel)")
+            }
+        }
+        release {
+            if (hasUploadSigning) {
+                signingConfig = signingConfigs.getByName("upload")
+            }
+        }
+    }
+}
+
+dependencies {
+    testImplementation(kotlin("test"))
+
+    androidTestImplementation(kotlin("test"))
+    androidTestImplementation("androidx.test.ext:junit:1.3.0")
+    androidTestImplementation("androidx.test:runner:1.7.0")
+}
+
+gradle.taskGraph.whenReady {
+    val buildsRelease = allTasks.any { task ->
+        task.project == project && task.name in setOf("assembleRelease", "bundleRelease")
+    }
+    if (buildsRelease && externalReleaseSigning) {
+        // External signing: the unsigned bundle goes to the central APK
+        // Signer. All keystore checks are intentionally skipped; the
+        // guard above already rejected any BUZZ_ANDROID_UPLOAD_* values.
+        return@whenReady
+    }
+    if (buildsRelease && !hasUploadSigning) {
+        throw GradleException(
+            "Release builds require Android upload signing credentials. Missing: " +
+                missingUploadSigningValues.sorted().joinToString(", ") +
+                ". For central APK Signer pipelines set BUZZ_ANDROID_RELEASE_SIGNING=external.",
+        )
+    }
+    if (buildsRelease) {
+        val configuredKeystore = File(requireNotNull(uploadKeystorePath))
+        if (!configuredKeystore.isAbsolute) {
+            throw GradleException(
+                "BUZZ_ANDROID_UPLOAD_KEYSTORE_PATH must be absolute: $configuredKeystore",
+            )
+        }
+        val keystore = file(configuredKeystore)
+        val repositoryRoot = rootProject.projectDir.parentFile.parentFile.canonicalFile
+        if (keystore.canonicalFile.toPath().startsWith(repositoryRoot.toPath())) {
+            throw GradleException(
+                "BUZZ_ANDROID_UPLOAD_KEYSTORE_PATH must be outside the repository: $keystore",
+            )
+        }
+        if (!keystore.isFile || !keystore.canRead()) {
+            throw GradleException(
+                "BUZZ_ANDROID_UPLOAD_KEYSTORE_PATH is not a readable file: $keystore",
+            )
+        }
+    }
+}
+
+flutter {
+    source = "../.."
+}

mobile/android/app/src/androidTest/kotlin/xyz/block/buzz/mobile/AndroidImageProcessorTest.kt

@@ -0,0 +1,188 @@
+package xyz.block.buzz.mobile
+
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import android.graphics.Color
+import android.os.Build
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Test
+import org.junit.runner.RunWith
+import kotlin.math.abs
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertTrue
+
+@RunWith(AndroidJUnit4::class)
+class AndroidImageProcessorTest {
+    companion object {
+        private val ALLOWED_PNG_CHUNKS = setOf(
+            "IHDR", "PLTE", "IDAT", "IEND", "cHRM", "gAMA", "sBIT", "sRGB", "bKGD", "hIST", "tRNS", "sPLT",
+            "acTL", "fcTL", "fdAT",
+        )
+    }
+
+    @Test
+    fun supportedApiCanProcessImagesWithoutNewerPlatformApis() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) return
+
+        val sourceBytes = fixtureBytes("bitmap-srgb.png")
+        val processed = assertNotNull(AndroidImageProcessor.decodeSrgbBitmap(sourceBytes))
+        assertEquals(Bitmap.Config.ARGB_8888, processed.config)
+
+        val scrubbed = assertNotNull(
+            AndroidImageProcessor.encodeAndScrub(processed, Bitmap.CompressFormat.PNG),
+        )
+        val chunkTypes = pngChunkTypes(scrubbed)
+        assertEquals("IHDR", chunkTypes.first())
+        assertEquals("IEND", chunkTypes.last())
+        assertTrue(chunkTypes.all { it in ALLOWED_PNG_CHUNKS })
+        assertPngPixelsPreserved(sourceBytes, scrubbed)
+    }
+
+    @Test
+    fun transparentPngPixelsSurviveSrgbProcessing() {
+        val sourceBytes = fixtureBytes("bitmap-srgb.png")
+        val source = assertNotNull(BitmapFactory.decodeByteArray(sourceBytes, 0, sourceBytes.size))
+        val processed = assertNotNull(AndroidImageProcessor.decodeSrgbBitmap(sourceBytes))
+        assertTrue(processed.hasAlpha())
+
+        val scrubbed = assertNotNull(
+            AndroidImageProcessor.encodeAndScrub(processed, Bitmap.CompressFormat.PNG),
+        )
+        assertPngPixelsPreserved(sourceBytes, scrubbed)
+        assertEquals(128, Color.alpha(source.getPixel(0, 1)))
+        assertEquals(64, Color.alpha(source.getPixel(1, 1)))
+        assertEquals(0, Color.alpha(source.getPixel(2, 1)))
+    }
+
+    @Test
+    fun displayP3InputIsConvertedToSrgbBeforeEncodedMetadataIsScrubbed() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) return
+
+        val sourceBytes = fixtureBytes("bitmap-display-p3.png")
+        val source = assertNotNull(BitmapFactory.decodeByteArray(sourceBytes, 0, sourceBytes.size))
+        assertEquals(android.graphics.ColorSpace.get(android.graphics.ColorSpace.Named.DISPLAY_P3), source.colorSpace)
+        val expectedSrgbPixel = source.getColor(0, 0).convert(
+            android.graphics.ColorSpace.get(android.graphics.ColorSpace.Named.SRGB),
+        )
+
+        val srgbBitmap = assertNotNull(AndroidImageProcessor.decodeSrgbBitmap(sourceBytes))
+        assertEquals(android.graphics.ColorSpace.get(android.graphics.ColorSpace.Named.SRGB), srgbBitmap.colorSpace)
+        assertEquals(Bitmap.Config.ARGB_8888, srgbBitmap.config)
+        assertColorClose(expectedSrgbPixel, srgbBitmap.getColor(0, 0), tolerance = 1.0f / 255.0f)
+
+        for ((format, tolerance) in listOf(
+            Bitmap.CompressFormat.PNG to (1.0f / 255.0f),
+            Bitmap.CompressFormat.JPEG to (2.0f / 255.0f),
+        )) {
+            val scrubbed = assertNotNull(AndroidImageProcessor.encodeAndScrub(srgbBitmap, format))
+            when (format) {
+                Bitmap.CompressFormat.PNG -> {
+                    assertEquals(listOf("IHDR", "sRGB", "sBIT", "IDAT", "IEND"), pngChunkTypes(scrubbed))
+                }
+                Bitmap.CompressFormat.JPEG -> {
+                    assertEquals(listOf(0xE0), jpegMetadataMarkers(scrubbed))
+                }
+                else -> error("Unexpected format: $format")
+            }
+
+            val decodedOutput = assertNotNull(BitmapFactory.decodeByteArray(scrubbed, 0, scrubbed.size))
+            assertEquals(
+                android.graphics.ColorSpace.get(android.graphics.ColorSpace.Named.SRGB),
+                decodedOutput.colorSpace,
+            )
+            assertColorClose(expectedSrgbPixel, decodedOutput.getColor(0, 0), tolerance)
+        }
+    }
+
+    private fun assertPngPixelsPreserved(expectedBytes: ByteArray, actualBytes: ByteArray) {
+        val expected = assertNotNull(BitmapFactory.decodeByteArray(expectedBytes, 0, expectedBytes.size))
+        val actual = assertNotNull(BitmapFactory.decodeByteArray(actualBytes, 0, actualBytes.size))
+        assertEquals(expected.width, actual.width)
+        assertEquals(expected.height, actual.height)
+        for (y in 0 until expected.height) {
+            for (x in 0 until expected.width) {
+                assertEquals(
+                    expected.getPixel(x, y),
+                    actual.getPixel(x, y),
+                    "pixel ($x, $y)",
+                )
+            }
+        }
+    }
+
+    private fun fixtureBytes(name: String): ByteArray {
+        return requireNotNull(javaClass.getResourceAsStream("/fixtures/android/$name")) {
+            "Missing fixture: $name"
+        }.use { it.readBytes() }
+    }
+
+    private fun assertColorClose(expected: Color, actual: Color, tolerance: Float) {
+        val expectedComponents = expected.components
+        val actualComponents = actual.convert(expected.colorSpace).components
+        for (index in expectedComponents.indices) {
+            assertTrue(
+                abs(expectedComponents[index] - actualComponents[index]) <= tolerance,
+                "component $index: expected ${expectedComponents[index]}, got ${actualComponents[index]}",
+            )
+        }
+    }
+
+    private fun pngChunkTypes(bytes: ByteArray): List<String> {
+        val result = mutableListOf<String>()
+        var offset = 8
+        while (offset < bytes.size) {
+            require(bytes.size - offset >= 12)
+            val payloadLength = readUnsignedInt(bytes, offset)
+            val type = bytes.decodeToString(offset + 4, offset + 8)
+            result += type
+            offset += payloadLength + 12
+            if (type == "IEND") {
+                assertEquals(bytes.size, offset)
+                return result
+            }
+        }
+        error("PNG is missing IEND")
+    }
+
+    private fun jpegMetadataMarkers(bytes: ByteArray): List<Int> {
+        val result = mutableListOf<Int>()
+        var offset = 2
+        var inScan = false
+        while (offset < bytes.size) {
+            if (inScan && bytes[offset] != 0xFF.toByte()) {
+                offset += 1
+                continue
+            }
+            require(bytes[offset] == 0xFF.toByte())
+            while (offset < bytes.size && bytes[offset] == 0xFF.toByte()) {
+                offset += 1
+            }
+            require(offset < bytes.size)
+            val marker = bytes[offset].toInt() and 0xFF
+            offset += 1
+            if (inScan && marker == 0x00) continue
+            if (marker in 0xD0..0xD7 || marker == 0x01) continue
+            if (marker == 0xD9) {
+                assertEquals(bytes.size, offset)
+                return result
+            }
+            val segmentLength = readUnsignedShort(bytes, offset)
+            if (marker in 0xE0..0xEF || marker == 0xFE) result += marker
+            offset += segmentLength
+            inScan = marker == 0xDA
+        }
+        error("JPEG is missing EOI")
+    }
+
+    private fun readUnsignedShort(bytes: ByteArray, offset: Int): Int {
+        return ((bytes[offset].toInt() and 0xFF) shl 8) or (bytes[offset + 1].toInt() and 0xFF)
+    }
+
+    private fun readUnsignedInt(bytes: ByteArray, offset: Int): Int {
+        return ((bytes[offset].toInt() and 0xFF) shl 24) or
+            ((bytes[offset + 1].toInt() and 0xFF) shl 16) or
+            ((bytes[offset + 2].toInt() and 0xFF) shl 8) or
+            (bytes[offset + 3].toInt() and 0xFF)
+    }
+}

mobile/android/app/src/debug/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- The INTERNET permission is required for development. Specifically,
+         the Flutter tool needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

mobile/android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,71 @@
+<manifest
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.CAMERA" />
+    <uses-permission
+        android:name="android.permission.READ_EXTERNAL_STORAGE"
+        android:maxSdkVersion="32"
+        tools:replace="android:maxSdkVersion" />
+    <uses-permission
+        android:name="android.permission.WRITE_EXTERNAL_STORAGE"
+        android:maxSdkVersion="28" />
+    <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
+    <uses-permission android:name="android.permission.READ_MEDIA_VIDEO" />
+    <uses-permission android:name="android.permission.READ_MEDIA_VISUAL_USER_SELECTED" />
+    <application
+        android:label="@string/app_name"
+        android:name="${applicationName}"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:launchMode="singleTop"
+            android:taskAffinity=""
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+            <!-- Handle buzz:// deep links (e.g. buzz://message?channel=…&id=…). -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW"/>
+                <category android:name="android.intent.category.DEFAULT"/>
+                <category android:name="android.intent.category.BROWSABLE"/>
+                <data android:scheme="buzz"/>
+            </intent-filter>
+            <!-- Disable Flutter's built-in deeplink handler; app_links owns
+                 incoming URLs so they can be routed with app state in Dart. -->
+            <meta-data
+                android:name="flutter_deeplinking_enabled"
+                android:value="false" />
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+    <!-- Required to query activities that can process text, see:
+         https://developer.android.com/training/package-visibility and
+         https://developer.android.com/reference/android/content/Intent#ACTION_PROCESS_TEXT.
+
+         In particular, this is used by the Flutter engine in io.flutter.plugin.text.ProcessTextPlugin. -->
+    <queries>
+        <intent>
+            <action android:name="android.intent.action.PROCESS_TEXT"/>
+            <data android:mimeType="text/plain"/>
+        </intent>
+    </queries>
+</manifest>

mobile/android/app/src/main/kotlin/xyz/block/buzz/mobile/AndroidMediaSanitizer.kt

@@ -0,0 +1,160 @@
+package xyz.block.buzz.mobile
+
+import java.io.ByteArrayOutputStream
+import java.nio.charset.StandardCharsets
+
+internal object AndroidMediaSanitizer {
+    private val pngSignature = byteArrayOf(
+        0x89.toByte(), 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A,
+    )
+    private val allowedPngAncillaryChunks = setOf(
+        "cHRM", "gAMA", "sBIT", "sRGB", "bKGD", "hIST", "tRNS", "sPLT", "acTL", "fcTL", "fdAT",
+    )
+
+    fun scrubPng(bytes: ByteArray): ByteArray {
+        require(bytes.size >= pngSignature.size && bytes.copyOfRange(0, pngSignature.size).contentEquals(pngSignature)) {
+            "Invalid PNG signature"
+        }
+
+        val output = ByteArrayOutputStream(bytes.size)
+        output.write(pngSignature)
+        var offset = pngSignature.size
+        while (offset < bytes.size) {
+            require(bytes.size - offset >= PNG_CHUNK_OVERHEAD) { "Truncated PNG chunk" }
+            val payloadLength = readUnsignedIntBigEndian(bytes, offset)
+            require(payloadLength <= bytes.size.toLong() - offset - PNG_CHUNK_OVERHEAD) {
+                "Invalid PNG chunk length"
+            }
+            val chunkLength = payloadLength.toInt() + PNG_CHUNK_OVERHEAD
+            val typeStart = offset + 4
+            val type = String(bytes, typeStart, 4, StandardCharsets.US_ASCII)
+            val isAncillary = bytes[typeStart].toInt() and 0x20 != 0
+            if (!isAncillary || type in allowedPngAncillaryChunks) {
+                output.write(bytes, offset, chunkLength)
+            }
+            offset += chunkLength
+            if (type == "IEND") {
+                return output.toByteArray()
+            }
+        }
+
+        throw IllegalArgumentException("PNG is missing IEND")
+    }
+
+    fun scrubJpeg(bytes: ByteArray): ByteArray {
+        require(
+            bytes.size >= 2 &&
+                bytes[0] == 0xFF.toByte() &&
+                (bytes[1].toInt() and 0xFF) == JPEG_SOI,
+        ) {
+            "Invalid JPEG signature"
+        }
+
+        val output = ByteArrayOutputStream(bytes.size)
+        output.write(byteArrayOf(0xFF.toByte(), JPEG_SOI.toByte()))
+        var offset = 2
+        var inScan = false
+        while (offset < bytes.size) {
+            if (inScan && bytes[offset] != 0xFF.toByte()) {
+                val nextMarker = bytes.indexOf(0xFF.toByte(), offset).let { if (it == -1) bytes.size else it }
+                output.write(bytes, offset, nextMarker - offset)
+                offset = nextMarker
+                continue
+            }
+            require(bytes[offset] == 0xFF.toByte()) { "Invalid JPEG marker" }
+
+            val markerStart = offset
+            while (offset < bytes.size && bytes[offset] == 0xFF.toByte()) {
+                offset += 1
+            }
+            require(offset < bytes.size) { "Truncated JPEG marker" }
+
+            val marker = bytes[offset].toInt() and 0xFF
+            offset += 1
+            if (inScan && marker == 0x00) {
+                output.write(bytes, markerStart, offset - markerStart)
+                continue
+            }
+            if (marker in JPEG_RESTART_MARKERS || marker == JPEG_TEMP) {
+                output.write(bytes, markerStart, offset - markerStart)
+                continue
+            }
+            if (marker == JPEG_EOI) {
+                output.write(bytes, markerStart, offset - markerStart)
+                return output.toByteArray()
+            }
+            require(marker != JPEG_SOI && bytes.size - offset >= 2) { "Invalid JPEG segment" }
+
+            val segmentLength = readUnsignedShortBigEndian(bytes, offset)
+            require(segmentLength >= 2 && segmentLength <= bytes.size - offset) { "Invalid JPEG segment length" }
+            val segmentEnd = offset + segmentLength
+            if (shouldKeepJpegSegment(marker, bytes, offset + 2, segmentEnd)) {
+                output.write(bytes, markerStart, segmentEnd - markerStart)
+            }
+            offset = segmentEnd
+            inScan = marker == JPEG_SOS
+        }
+
+        throw IllegalArgumentException("JPEG is missing EOI")
+    }
+
+    private fun shouldKeepJpegSegment(
+        marker: Int,
+        bytes: ByteArray,
+        payloadStart: Int,
+        payloadEnd: Int,
+    ): Boolean {
+        val payloadLength = payloadEnd - payloadStart
+        return when (marker) {
+            JPEG_APP0 -> {
+                if (payloadLength < 14 || !bytes.matchesAscii(payloadStart, "JFIF\u0000")) {
+                    false
+                } else {
+                    val thumbnailWidth = bytes[payloadStart + 12].toInt() and 0xFF
+                    val thumbnailHeight = bytes[payloadStart + 13].toInt() and 0xFF
+                    payloadLength == 14 + 3 * thumbnailWidth * thumbnailHeight
+                }
+            }
+            JPEG_APP14 -> payloadLength == 12 && bytes.matchesAscii(payloadStart, "Adobe")
+            in JPEG_FORBIDDEN_APP_MARKERS, JPEG_APP15, JPEG_COMMENT -> false
+            else -> true
+        }
+    }
+
+    private fun readUnsignedShortBigEndian(bytes: ByteArray, offset: Int): Int {
+        require(bytes.size - offset >= 2) { "Truncated two-byte integer" }
+        return (bytes[offset].toInt() and 0xFF shl 8) or (bytes[offset + 1].toInt() and 0xFF)
+    }
+
+    private fun readUnsignedIntBigEndian(bytes: ByteArray, offset: Int): Long {
+        require(bytes.size - offset >= 4) { "Truncated four-byte integer" }
+        return (bytes[offset].toLong() and 0xFF shl 24) or
+            (bytes[offset + 1].toLong() and 0xFF shl 16) or
+            (bytes[offset + 2].toLong() and 0xFF shl 8) or
+            (bytes[offset + 3].toLong() and 0xFF)
+    }
+
+    private fun ByteArray.matchesAscii(offset: Int, value: String): Boolean {
+        val expected = value.toByteArray(StandardCharsets.US_ASCII)
+        return size - offset >= expected.size && expected.indices.all { this[offset + it] == expected[it] }
+    }
+
+    private fun ByteArray.indexOf(value: Byte, startIndex: Int): Int {
+        for (index in startIndex until size) {
+            if (this[index] == value) return index
+        }
+        return -1
+    }
+
+    private const val PNG_CHUNK_OVERHEAD = 12
+    private const val JPEG_SOI = 0xD8
+    private const val JPEG_EOI = 0xD9
+    private const val JPEG_SOS = 0xDA
+    private const val JPEG_TEMP = 0x01
+    private const val JPEG_APP0 = 0xE0
+    private const val JPEG_APP14 = 0xEE
+    private const val JPEG_APP15 = 0xEF
+    private const val JPEG_COMMENT = 0xFE
+    private val JPEG_RESTART_MARKERS = 0xD0..0xD7
+    private val JPEG_FORBIDDEN_APP_MARKERS = 0xE1..0xED
+}

mobile/android/app/src/main/kotlin/xyz/block/buzz/mobile/MainActivity.kt

@@ -0,0 +1,347 @@
+package xyz.block.buzz.mobile
+
+import android.graphics.Bitmap
+import android.graphics.BitmapFactory
+import android.graphics.Canvas
+import android.graphics.ColorSpace
+import android.graphics.ImageDecoder
+import android.media.MediaExtractor
+import android.media.MediaMetadataRetriever
+import android.media.MediaMuxer
+import android.os.Build
+import androidx.annotation.RequiresApi
+import io.flutter.embedding.android.FlutterActivity
+import io.flutter.embedding.engine.FlutterEngine
+import io.flutter.plugin.common.MethodChannel
+import java.io.ByteArrayOutputStream
+import java.io.File
+import java.nio.ByteBuffer
+import java.util.UUID
+
+internal object AndroidImageProcessor {
+    fun decodeSrgbBitmap(bytes: ByteArray): Bitmap? {
+        return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            decodeSrgbBitmapWithColorManagement(bytes)
+        } else {
+            BitmapFactory.decodeByteArray(bytes, 0, bytes.size)
+        }
+    }
+
+    @RequiresApi(Build.VERSION_CODES.O)
+    private fun decodeSrgbBitmapWithColorManagement(bytes: ByteArray): Bitmap? {
+        val decoded = decodeColorManagedBitmap(bytes) ?: return null
+        val srgb = ColorSpace.get(ColorSpace.Named.SRGB)
+        if (decoded.config == Bitmap.Config.ARGB_8888 && decoded.colorSpace == srgb) return decoded
+
+        val srgbBitmap = Bitmap.createBitmap(
+            decoded.width,
+            decoded.height,
+            Bitmap.Config.ARGB_8888,
+            decoded.hasAlpha(),
+            srgb,
+        )
+        Canvas(srgbBitmap).drawBitmap(decoded, 0f, 0f, null)
+        return srgbBitmap
+    }
+
+    @RequiresApi(Build.VERSION_CODES.O)
+    private fun decodeColorManagedBitmap(bytes: ByteArray): Bitmap? {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            runCatching {
+                val source = ImageDecoder.createSource(ByteBuffer.wrap(bytes))
+                ImageDecoder.decodeBitmap(source) { decoder, _, _ ->
+                    decoder.allocator = ImageDecoder.ALLOCATOR_SOFTWARE
+                    decoder.setTargetColorSpace(ColorSpace.get(ColorSpace.Named.SRGB))
+                }
+            }.getOrNull()?.let { return it }
+        }
+
+        val options = BitmapFactory.Options().apply {
+            inPreferredColorSpace = ColorSpace.get(ColorSpace.Named.SRGB)
+        }
+        return BitmapFactory.decodeByteArray(bytes, 0, bytes.size, options)
+    }
+
+    fun encodeAndScrub(
+        bitmap: Bitmap,
+        format: Bitmap.CompressFormat,
+    ): ByteArray? {
+        val output = ByteArrayOutputStream()
+        if (!bitmap.compress(format, 100, output)) return null
+
+        return when (format) {
+            Bitmap.CompressFormat.PNG -> AndroidMediaSanitizer.scrubPng(output.toByteArray())
+            Bitmap.CompressFormat.JPEG -> AndroidMediaSanitizer.scrubJpeg(output.toByteArray())
+            else -> error("Unsupported upload image format: $format")
+        }
+    }
+}
+
+class MainActivity : FlutterActivity() {
+    private var mediaUploadChannel: MethodChannel? = null
+
+    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
+        super.configureFlutterEngine(flutterEngine)
+
+        mediaUploadChannel = MethodChannel(
+            flutterEngine.dartExecutor.binaryMessenger,
+            MEDIA_UPLOAD_CHANNEL,
+        ).also { channel ->
+            channel.setMethodCallHandler { call, result ->
+                when (call.method) {
+                    SANITIZE_IMAGE_FOR_UPLOAD_METHOD -> {
+                        handleSanitizeImageForUpload(call.arguments, result)
+                    }
+                    TRANSCODE_IMAGE_TO_JPEG_METHOD -> {
+                        handleTranscodeImageToJpeg(call.arguments, result)
+                    }
+                    TRANSCODE_VIDEO_TO_MP4_METHOD -> {
+                        handleTranscodeVideoToMp4(call.arguments, result)
+                    }
+                    GENERATE_VIDEO_POSTER_METHOD -> {
+                        handleGenerateVideoPoster(call.arguments, result)
+                    }
+                    REQUIRES_LEGACY_MEDIA_STORAGE_PERMISSION_METHOD -> {
+                        result.success(Build.VERSION.SDK_INT <= Build.VERSION_CODES.P)
+                    }
+                    else -> result.notImplemented()
+                }
+            }
+        }
+    }
+
+    private fun handleSanitizeImageForUpload(
+        arguments: Any?,
+        result: MethodChannel.Result,
+    ) {
+        val payload = arguments as? Map<*, *> ?: run {
+            invalidArguments(result, "Expected image bytes and mime type.")
+            return
+        }
+        val bytes = payload["bytes"] as? ByteArray ?: run {
+            invalidArguments(result, "Expected raw image bytes.")
+            return
+        }
+        val mimeType = payload["mimeType"] as? String ?: run {
+            invalidArguments(result, "Expected image mime type.")
+            return
+        }
+
+        val format = sanitizeCompressFormatFor(mimeType)
+        if (format == null) {
+            result.error(
+                "sanitize_failed",
+                "Unable to sanitize picked image.",
+                mimeType,
+            )
+            return
+        }
+
+        transformImageBytes(
+            bytes = bytes,
+            result = result,
+            format = format,
+            errorCode = "sanitize_failed",
+            encodeFailureMessage = "Unable to sanitize picked image.",
+            errorDetails = mimeType,
+        )
+    }
+
+    private fun handleTranscodeImageToJpeg(
+        arguments: Any?,
+        result: MethodChannel.Result,
+    ) {
+        val bytes = arguments as? ByteArray ?: run {
+            invalidArguments(result, "Expected raw image bytes.")
+            return
+        }
+
+        transformImageBytes(
+            bytes = bytes,
+            result = result,
+            format = Bitmap.CompressFormat.JPEG,
+            errorCode = "transcode_failed",
+            encodeFailureMessage = "Unable to convert picked image to JPEG.",
+        )
+    }
+
+    private fun sanitizeCompressFormatFor(
+        mimeType: String,
+    ): Bitmap.CompressFormat? {
+        return when (mimeType) {
+            "image/jpeg" -> Bitmap.CompressFormat.JPEG
+            "image/png", "image/webp" -> Bitmap.CompressFormat.PNG
+            else -> null
+        }
+    }
+
+    private fun transformImageBytes(
+        bytes: ByteArray,
+        result: MethodChannel.Result,
+        format: Bitmap.CompressFormat,
+        errorCode: String,
+        encodeFailureMessage: String,
+        errorDetails: Any? = null,
+    ) {
+        val bitmap = AndroidImageProcessor.decodeSrgbBitmap(bytes) ?: run {
+            result.error(
+                errorCode,
+                "Unable to decode picked image.",
+                null,
+            )
+            return
+        }
+
+        val transformedBytes = try {
+            AndroidImageProcessor.encodeAndScrub(bitmap, format)
+        } catch (_: IllegalArgumentException) {
+            null
+        } ?: run {
+            result.error(
+                errorCode,
+                encodeFailureMessage,
+                errorDetails,
+            )
+            return
+        }
+
+        result.success(transformedBytes)
+    }
+
+    private fun handleTranscodeVideoToMp4(
+        arguments: Any?,
+        result: MethodChannel.Result,
+    ) {
+        val sourcePath = arguments as? String ?: run {
+            invalidArguments(result, "Expected source file path as String.")
+            return
+        }
+
+        Thread {
+            val outputFile = File(cacheDir, "${UUID.randomUUID()}.mp4")
+            var muxer: MediaMuxer? = null
+            val extractor = MediaExtractor()
+            try {
+                extractor.setDataSource(sourcePath)
+                muxer = MediaMuxer(outputFile.absolutePath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4)
+
+                val trackIndices = mutableMapOf<Int, Int>()
+                var copiedVideo = false
+                var copiedAudio = false
+                for (i in 0 until extractor.trackCount) {
+                    val format = extractor.getTrackFormat(i)
+                    val mime = format.getString(android.media.MediaFormat.KEY_MIME) ?: continue
+                    val isVideo = mime.startsWith("video/")
+                    val isAudio = mime.startsWith("audio/")
+                    if ((!isVideo && !isAudio) || (isVideo && copiedVideo) || (isAudio && copiedAudio)) {
+                        continue
+                    }
+                    val newIndex = muxer.addTrack(format)
+                    trackIndices[i] = newIndex
+                    extractor.selectTrack(i)
+                    copiedVideo = copiedVideo || isVideo
+                    copiedAudio = copiedAudio || isAudio
+                }
+
+                muxer.start()
+                val buffer = ByteBuffer.allocate(1024 * 1024) // 1MB buffer
+                val bufferInfo = android.media.MediaCodec.BufferInfo()
+
+                while (true) {
+                    val sampleSize = extractor.readSampleData(buffer, 0)
+                    if (sampleSize < 0) break
+                    val muxerTrack = trackIndices[extractor.sampleTrackIndex]
+                    if (muxerTrack == null) {
+                        extractor.advance()
+                        continue
+                    }
+                    bufferInfo.offset = 0
+                    bufferInfo.size = sampleSize
+                    bufferInfo.presentationTimeUs = extractor.sampleTime
+                    bufferInfo.flags = extractor.sampleFlags
+                    muxer.writeSampleData(muxerTrack, buffer, bufferInfo)
+                    extractor.advance()
+                }
+
+                muxer.stop()
+                result.success(outputFile.absolutePath)
+            } catch (e: Exception) {
+                outputFile.delete()
+                result.error(
+                    "transcode_failed",
+                    e.message ?: "Video transcoding failed.",
+                    null,
+                )
+            } finally {
+                try { muxer?.release() } catch (_: Exception) {}
+                extractor.release()
+            }
+        }.start()
+    }
+
+    private fun handleGenerateVideoPoster(
+        arguments: Any?,
+        result: MethodChannel.Result,
+    ) {
+        val sourcePath = arguments as? String ?: run {
+            invalidArguments(result, "Expected source file path as String.")
+            return
+        }
+
+        Thread {
+            val retriever = MediaMetadataRetriever()
+            try {
+                retriever.setDataSource(sourcePath)
+                val source = retriever.getFrameAtTime(
+                    0,
+                    MediaMetadataRetriever.OPTION_CLOSEST_SYNC,
+                ) ?: retriever.getFrameAtTime(
+                    100_000,
+                    MediaMetadataRetriever.OPTION_CLOSEST_SYNC,
+                ) ?: throw IllegalArgumentException("Unable to decode a video frame.")
+                val scale = minOf(1f, 720f / maxOf(source.width, source.height))
+                val frame = if (scale < 1f) {
+                    Bitmap.createScaledBitmap(
+                        source,
+                        (source.width * scale).toInt(),
+                        (source.height * scale).toInt(),
+                        true,
+                    ).also { source.recycle() }
+                } else {
+                    source
+                }
+                val bytes = AndroidImageProcessor.encodeAndScrub(
+                    frame,
+                    Bitmap.CompressFormat.JPEG,
+                ) ?: throw IllegalArgumentException("Unable to encode a video preview.")
+                frame.recycle()
+                result.success(bytes)
+            } catch (e: Exception) {
+                result.error(
+                    "poster_failed",
+                    "Unable to create a video preview.",
+                    e.message,
+                )
+            } finally {
+                retriever.release()
+            }
+        }.start()
+    }
+
+    private fun invalidArguments(
+        result: MethodChannel.Result,
+        message: String,
+    ) {
+        result.error("invalid_arguments", message, null)
+    }
+
+    companion object {
+        private const val MEDIA_UPLOAD_CHANNEL = "buzz/media_upload"
+        private const val SANITIZE_IMAGE_FOR_UPLOAD_METHOD = "sanitizeImageForUpload"
+        private const val TRANSCODE_IMAGE_TO_JPEG_METHOD = "transcodeImageToJpeg"
+        private const val TRANSCODE_VIDEO_TO_MP4_METHOD = "transcodeVideoToMp4"
+        private const val GENERATE_VIDEO_POSTER_METHOD = "generateVideoPoster"
+        private const val REQUIRES_LEGACY_MEDIA_STORAGE_PERMISSION_METHOD =
+            "requiresLegacyMediaStoragePermission"
+    }
+}

mobile/android/app/src/main/res/drawable-v21/launch_background.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@android:color/black" />
+
+    <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item>
+</layer-list>

mobile/android/app/src/main/res/drawable/ic_launcher_foreground_inset.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<inset xmlns:android="http://schemas.android.com/apk/res/android"
+    android:drawable="@mipmap/ic_launcher_foreground"
+    android:inset="10%" />

mobile/android/app/src/main/res/drawable/launch_background.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="@android:color/black" />
+
+    <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item>
+</layer-list>

mobile/android/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+  <foreground android:drawable="@drawable/ic_launcher_foreground_inset"/>
+  <background android:drawable="@color/ic_launcher_background"/>
+</adaptive-icon>

mobile/android/app/src/main/res/values-night/styles.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is on -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             the Flutter engine draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Black.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

mobile/android/app/src/main/res/values/ic_launcher_background.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+  <color name="ic_launcher_background">#000</color>
+</resources>

mobile/android/app/src/main/res/values/styles.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Theme applied to the Android Window while the process is starting when the OS's Dark Mode setting is off -->
+    <style name="LaunchTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <!-- Show a splash screen on the activity. Automatically removed when
+             the Flutter engine draws its first frame -->
+        <item name="android:windowBackground">@drawable/launch_background</item>
+    </style>
+    <!-- Theme applied to the Android Window as soon as the process has started.
+         This theme determines the color of the Android Window while your
+         Flutter UI initializes, as well as behind your Flutter UI while its
+         running.
+
+         This Theme is only used starting with V2 of Flutter's Android embedding. -->
+    <style name="NormalTheme" parent="@android:style/Theme.Light.NoTitleBar">
+        <item name="android:windowBackground">?android:colorBackground</item>
+    </style>
+</resources>

mobile/android/app/src/profile/AndroidManifest.xml

@@ -0,0 +1,7 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- The INTERNET permission is required for development. Specifically,
+         the Flutter tool needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

mobile/android/app/src/test/kotlin/xyz/block/buzz/mobile/AndroidMediaSanitizerTest.kt

@@ -0,0 +1,128 @@
+package xyz.block.buzz.mobile
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+class AndroidMediaSanitizerTest {
+    @Test
+    fun `scrubPng keeps canonical sRGB output unchanged`() {
+        val fixture = fixtureBytes("bitmap-srgb.png")
+
+        val sanitized = AndroidMediaSanitizer.scrubPng(fixture)
+
+        assertContentEquals(fixture, sanitized)
+        assertEquals(listOf("IHDR", "sRGB", "sBIT", "IDAT", "IEND"), pngChunkTypes(sanitized))
+    }
+
+    @Test
+    fun `scrubPng removes Display P3 profile and trailing data`() {
+        val fixture = fixtureBytes("bitmap-display-p3.png")
+        val withTrailingData = fixture + "hidden location".encodeToByteArray()
+
+        val sanitized = AndroidMediaSanitizer.scrubPng(withTrailingData)
+
+        assertEquals(listOf("IHDR", "sBIT", "IDAT", "IEND"), pngChunkTypes(sanitized))
+    }
+
+    @Test
+    fun `scrubJpeg removes Android ICC profile and trailing data`() {
+        for (fixtureName in listOf("bitmap-srgb.jpg", "bitmap-display-p3.jpg")) {
+            val fixture = fixtureBytes(fixtureName)
+            val withTrailingData = fixture + "hidden location".encodeToByteArray()
+
+            val sanitized = AndroidMediaSanitizer.scrubJpeg(withTrailingData)
+
+            assertEquals(listOf(0xE0), jpegMetadataMarkers(sanitized), fixtureName)
+        }
+    }
+
+    @Test
+    fun `scrubbers fail closed for malformed containers`() {
+        assertFailsWith<IllegalArgumentException> {
+            AndroidMediaSanitizer.scrubPng(byteArrayOf(0x89.toByte(), 0x50, 0x4E, 0x47))
+        }
+        assertFailsWith<IllegalArgumentException> {
+            AndroidMediaSanitizer.scrubJpeg(byteArrayOf(0xFF.toByte(), 0xD8.toByte(), 0xFF.toByte()))
+        }
+        assertFailsWith<IllegalArgumentException> {
+            AndroidMediaSanitizer.scrubJpeg(
+                byteArrayOf(
+                    0xFF.toByte(),
+                    0xD8.toByte(),
+                    0xFF.toByte(),
+                    0xD8.toByte(),
+                    0x00,
+                    0x02,
+                    0xFF.toByte(),
+                    0xD9.toByte(),
+                ),
+            )
+        }
+    }
+
+    private fun fixtureBytes(name: String): ByteArray {
+        return requireNotNull(javaClass.getResourceAsStream("/fixtures/android/$name")) {
+            "Missing fixture: $name"
+        }.use { it.readBytes() }
+    }
+
+    private fun pngChunkTypes(bytes: ByteArray): List<String> {
+        val result = mutableListOf<String>()
+        var offset = 8
+        while (offset < bytes.size) {
+            require(bytes.size - offset >= 12)
+            val payloadLength = readUnsignedInt(bytes, offset)
+            val type = bytes.decodeToString(offset + 4, offset + 8)
+            result += type
+            offset += payloadLength + 12
+            if (type == "IEND") {
+                assertEquals(bytes.size, offset)
+                return result
+            }
+        }
+        error("PNG is missing IEND")
+    }
+
+    private fun jpegMetadataMarkers(bytes: ByteArray): List<Int> {
+        val result = mutableListOf<Int>()
+        var offset = 2
+        var inScan = false
+        while (offset < bytes.size) {
+            if (inScan && bytes[offset] != 0xFF.toByte()) {
+                offset += 1
+                continue
+            }
+            require(bytes[offset] == 0xFF.toByte())
+            while (offset < bytes.size && bytes[offset] == 0xFF.toByte()) {
+                offset += 1
+            }
+            require(offset < bytes.size)
+            val marker = bytes[offset].toInt() and 0xFF
+            offset += 1
+            if (inScan && marker == 0x00) continue
+            if (marker in 0xD0..0xD7 || marker == 0x01) continue
+            if (marker == 0xD9) {
+                assertEquals(bytes.size, offset)
+                return result
+            }
+            val segmentLength = readUnsignedShort(bytes, offset)
+            if (marker in 0xE0..0xEF || marker == 0xFE) result += marker
+            offset += segmentLength
+            inScan = marker == 0xDA
+        }
+        error("JPEG is missing EOI")
+    }
+
+    private fun readUnsignedShort(bytes: ByteArray, offset: Int): Int {
+        return ((bytes[offset].toInt() and 0xFF) shl 8) or (bytes[offset + 1].toInt() and 0xFF)
+    }
+
+    private fun readUnsignedInt(bytes: ByteArray, offset: Int): Int {
+        return ((bytes[offset].toInt() and 0xFF) shl 24) or
+            ((bytes[offset + 1].toInt() and 0xFF) shl 16) or
+            ((bytes[offset + 2].toInt() and 0xFF) shl 8) or
+            (bytes[offset + 3].toInt() and 0xFF)
+    }
+}

mobile/android/build.gradle.kts

@@ -0,0 +1,24 @@
+allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+val newBuildDir: Directory =
+    rootProject.layout.buildDirectory
+        .dir("../../build")
+        .get()
+rootProject.layout.buildDirectory.value(newBuildDir)
+
+subprojects {
+    val newSubprojectBuildDir: Directory = newBuildDir.dir(project.name)
+    project.layout.buildDirectory.value(newSubprojectBuildDir)
+}
+subprojects {
+    project.evaluationDependsOn(":app")
+}
+
+tasks.register<Delete>("clean") {
+    delete(rootProject.layout.buildDirectory)
+}

mobile/android/gradle.properties

@@ -0,0 +1,2 @@
+org.gradle.jvmargs=-Xmx8G -XX:MaxMetaspaceSize=4G -XX:ReservedCodeCacheSize=512m -XX:+HeapDumpOnOutOfMemoryError
+android.useAndroidX=true

mobile/android/gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,5 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.5-all.zip

mobile/android/settings.gradle.kts

@@ -0,0 +1,26 @@
+pluginManagement {
+    val flutterSdkPath =
+        run {
+            val properties = java.util.Properties()
+            file("local.properties").inputStream().use { properties.load(it) }
+            val flutterSdkPath = properties.getProperty("flutter.sdk")
+            require(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
+            flutterSdkPath
+        }
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id("dev.flutter.flutter-plugin-loader") version "1.0.0"
+    id("com.android.application") version "8.11.2" apply false
+    id("org.jetbrains.kotlin.android") version "2.2.21" apply false
+}
+
+include(":app")