feat(android): add ProfileMigrations scaffold + safety export on upgrade

Author: Hidden-Node

android/app/src/main/java/com/gooserelay/gooserelayvpn/data/local/AppDatabase.kt

@@ -19,7 +19,9 @@ abstract class AppDatabase : RoomDatabase() {
                     context.applicationContext,
                     AppDatabase::class.java,
                     "gooserelay_vpn.db"
-                ).fallbackToDestructiveMigration().build().also { INSTANCE = it }
+                )
+                    .addMigrations(*ProfileMigrations.ALL)
+                    .build().also { INSTANCE = it }
             }
         }
     }

android/app/src/main/java/com/gooserelay/gooserelayvpn/data/local/ProfileDao.kt

@@ -23,6 +23,9 @@ interface ProfileDao {
     @Query("SELECT * FROM profiles ORDER BY createdAt DESC LIMIT 1")
     suspend fun getNewestProfile(): ProfileEntity?
 
+    @Query("SELECT * FROM profiles")
+    suspend fun getAllOnce(): List<ProfileEntity>
+
     @Insert(onConflict = OnConflictStrategy.REPLACE)
     suspend fun insertProfile(profile: ProfileEntity): Long
 

android/app/src/main/java/com/gooserelay/gooserelayvpn/data/local/ProfileMigrations.kt

@@ -0,0 +1,92 @@
+package com.gooserelay.gooserelayvpn.data.local
+
+import android.content.Context
+import androidx.room.migration.Migration
+import androidx.room.Room
+import androidx.room.RoomDatabase
+import androidx.sqlite.db.SupportSQLiteDatabase
+import com.google.gson.Gson
+import com.google.gson.JsonObject
+import java.io.File
+
+/**
+ * Central place for Room migrations. Each Migration(N, N+1) lives here.
+ *
+ * Convention: every migration that risks user data MUST be preceded by
+ * an on-upgrade export of the current profile table to
+ * `cacheDir/profiles_backup_<fromVersion>_to_<toVersion>_<timestamp>.json`
+ * before the schema change. See [SafetyExportMigration].
+ */
+object ProfileMigrations {
+
+    private val gson = Gson()
+
+    /**
+     * Run before [delegate] applies its schema change. Reads every profile
+     * from the v`from` schema and writes a JSON snapshot to the app's cache
+     * directory. If the export fails, the migration is NOT applied and an
+     * [IllegalStateException] is thrown so the user sees a crash instead
+     * of silent data loss.
+     */
+    class SafetyExportMigration(
+        private val context: Context,
+        private val from: Int,
+        private val to: Int,
+        private val delegate: Migration
+    ) : Migration(from, to) {
+
+        override fun migrate(db: SupportSQLiteDatabase) {
+            exportCurrentProfiles(db)
+            delegate.migrate(db)
+        }
+
+        private fun exportCurrentProfiles(db: SupportSQLiteDatabase) {
+            val cursor = db.query("SELECT * FROM profiles")
+            val rows = mutableListOf<JsonObject>()
+            cursor.use { c ->
+                while (c.moveToNext()) {
+                    val obj = JsonObject()
+                    // Column order matches ProfileEntity field order at v3.
+                    // Use column names defensively — older schema snapshots
+                    // may differ.
+                    fun col(name: String): String =
+                        c.getString(c.getColumnIndexOrThrow(name))
+                    obj.apply {
+                        addProperty("id", c.getLong(c.getColumnIndexOrThrow("id")))
+                        addProperty("name", col("name"))
+                        addProperty("debugTiming", c.getInt(c.getColumnIndexOrThrow("debugTiming")) != 0)
+                        addProperty("socksHost", col("socksHost"))
+                        addProperty("socksPort", c.getInt(c.getColumnIndexOrThrow("socksPort")))
+                        addProperty("socksUser", col("socksUser"))
+                        addProperty("socksPass", col("socksPass"))
+                        addProperty("googleHost", col("googleHost"))
+                        addProperty("sniJson", col("sniJson"))
+                        addProperty("scriptKeysText", col("scriptKeysText"))
+                        addProperty("tunnelKey", col("tunnelKey"))
+                        addProperty("coalesceStepMs", c.getInt(c.getColumnIndexOrThrow("coalesceStepMs")))
+                        addProperty("idleSlotsPerBucket", c.getInt(c.getColumnIndexOrThrow("idleSlotsPerBucket")))
+                        addProperty("remoteUrl", if (c.isNull(c.getColumnIndexOrThrow("remoteUrl"))) null else col("remoteUrl"))
+                        addProperty("isSelected", c.getInt(c.getColumnIndexOrThrow("isSelected")) != 0)
+                        addProperty("createdAt", c.getLong(c.getColumnIndexOrThrow("createdAt")))
+                    }
+                    rows.add(obj)
+                }
+            }
+            val snapshot = JsonObject().apply {
+                addProperty("schemaVersion", from)
+                add("profiles", gson.toJsonTree(rows))
+            }
+            val backupFile = File(
+                context.cacheDir,
+                "profiles_backup_v${from}_to_v${to}_${System.currentTimeMillis()}.json"
+            )
+            backupFile.writeText(gson.toJson(snapshot))
+        }
+    }
+
+    /**
+     * All registered migrations. Add new `SafetyExportMigration(...)`
+     * entries here as the schema evolves. Empty until v3→v4 is needed.
+     */
+    val ALL: Array<Migration> = arrayOf()
+}