feat(settings): in-app update from About tab (issue #867) (#875)

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/config/ServerStoreState.kt

@@ -24,4 +24,8 @@ data class ServerStoreState(
     // App display language. "system" = follow device locale; otherwise a BCP-47
     // language code such as "en" or "ko". Applied via ContextWrapper in MainActivity.
     val appLanguage: String = "system",
+    // App version the silent update check (issue #867) last completed for.
+    // Null / mismatched with BuildConfig.VERSION_NAME → the About tab runs
+    // its one-time check again (re-check on app version bump).
+    val updateCheckDoneForVersion: String? = null,
 )

app/src/main/java/com/m57/hermescontrol/data/local/AuthManager.kt

@@ -623,4 +623,13 @@ object AuthManager {
     fun setTypingEffectDelayMs(delayMs: Int) {
         serverStore.update { it.copy(typingEffectDelayMs = delayMs) }
     }
+
+    // ── In-app update check (issue #867) ─────────────────────────────────
+
+    /** App version the silent update check last completed for (null = never). */
+    fun getUpdateCheckDoneForVersion(): String? = serverStore.getLatestState().updateCheckDoneForVersion
+
+    fun setUpdateCheckDoneForVersion(version: String) {
+        serverStore.update { it.copy(updateCheckDoneForVersion = version) }
+    }
 }

app/src/main/java/com/m57/hermescontrol/data/update/AppUpdateChecker.kt

@@ -0,0 +1,143 @@
+package com.m57.hermescontrol.data.update
+
+import com.m57.hermescontrol.data.remote.OkHttpProvider
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.Serializable
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import java.io.File
+import java.io.IOException
+
+/**
+ * Latest release metadata from the GitHub releases API (issue #867) — the
+ * in-app self-update source. Fields map to the JSON via the app's shared
+ * snake_case [OkHttpProvider.json].
+ */
+@Serializable
+data class UpdateInfo(
+    val tagName: String = "",
+    val assets: List<Asset> = emptyList(),
+) {
+    @Serializable
+    data class Asset(
+        val name: String = "",
+        val size: Long = 0L,
+        val browserDownloadUrl: String = "",
+    )
+
+    /** The release APK asset — release.yml ships `hermes-mobile-<tag>.apk`. */
+    val apkAsset: Asset?
+        get() = assets.firstOrNull { it.name.endsWith(".apk", ignoreCase = true) }
+}
+
+/** Strip a leading 'v' from a release tag ("v1.21.0" → "1.21.0"). */
+fun normalizedVersion(tag: String): String = tag.trim().removePrefix("v")
+
+/**
+ * True when [latest] is strictly newer than [current]. Numeric dot-segment
+ * comparison ("1.21.0" > "1.2"). Non-numeric suffixes (e.g. "1.0-dev")
+ * compare as 0; an unparseable version never claims an update exists.
+ */
+fun isNewerVersion(
+    latest: String,
+    current: String,
+): Boolean {
+    val a = versionSegments(latest) ?: return false
+    val b = versionSegments(current) ?: return false
+    for (i in 0 until maxOf(a.size, b.size)) {
+        val x = a.getOrElse(i) { 0 }
+        val y = b.getOrElse(i) { 0 }
+        if (x != y) return x > y
+    }
+    return false
+}
+
+private fun versionSegments(version: String): List<Int>? {
+    val cleaned = normalizedVersion(version)
+    if (cleaned.isBlank()) return null
+    return cleaned.split('.').map { segment ->
+        // Leading numeric portion of each segment: "0-dev" → 0, "21" → 21.
+        segment.takeWhile { it.isDigit() }.toIntOrNull() ?: 0
+    }
+}
+
+/**
+ * Talks to the GitHub releases API and downloads the release APK (issue
+ * #867). Network methods are `open` so tests can fake them; the pure logic
+ * ([isNewerVersion], [parseUpdateInfo]) lives top-level for direct unit
+ * tests.
+ */
+open class AppUpdateChecker(
+    private val client: OkHttpClient = OkHttpProvider.base,
+) {
+    /**
+     * Fetch the latest release metadata. Returns null when there is no
+     * release yet (404) or the body can't be parsed. Throws [IOException]
+     * on network failure so the caller can surface a friendly error.
+     */
+    open suspend fun fetchLatestRelease(): UpdateInfo? =
+        withContext(Dispatchers.IO) {
+            val request =
+                Request
+                    .Builder()
+                    .url("https://api.github.com/repos/Hy4ri/hermes-mobile/releases/latest")
+                    .header("Accept", "application/vnd.github+json")
+                    .build()
+            client.newCall(request).execute().use { response ->
+                if (!response.isSuccessful) return@use null
+                val body = response.body?.string().orEmpty()
+                parseUpdateInfo(body)
+            }
+        }
+
+    /**
+     * Stream a release APK asset to [dest], reporting progress 0..1 via
+     * [onProgress]. True on success; false (with the partial file deleted)
+     * on any HTTP or I/O failure.
+     */
+    open suspend fun downloadApk(
+        url: String,
+        dest: File,
+        onProgress: (Float) -> Unit,
+    ): Boolean =
+        withContext(Dispatchers.IO) {
+            val request = Request.Builder().url(url).build()
+            try {
+                client.newCall(request).execute().use { response ->
+                    if (!response.isSuccessful) return@withContext false
+                    val body = response.body ?: return@withContext false
+                    val total = body.contentLength()
+                    dest.outputStream().use { out ->
+                        val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
+                        var read = 0L
+                        body.byteStream().use { input ->
+                            while (true) {
+                                val n = input.read(buffer)
+                                if (n == -1) break
+                                out.write(buffer, 0, n)
+                                read += n
+                                if (total > 0) {
+                                    onProgress((read.toFloat() / total.toFloat()).coerceIn(0f, 1f))
+                                }
+                            }
+                        }
+                    }
+                    true
+                }
+            } catch (e: Exception) {
+                dest.delete()
+                false
+            }
+        }
+
+    private companion object {
+        const val DEFAULT_BUFFER_SIZE = 8192
+    }
+}
+
+/** Parse a GitHub `releases/latest` JSON body into [UpdateInfo], or null. */
+fun parseUpdateInfo(json: String): UpdateInfo? =
+    runCatching {
+        OkHttpProvider.json.decodeFromString<UpdateInfo>(json)
+    }.getOrNull()