Add Database versioning

Author: daplf

shared/src/main/kotlin/org/javacs/kt/database/DatabaseService.kt

@@ -1,23 +1,70 @@
 package org.javacs.kt.database
 
-import org.jetbrains.exposed.sql.Database
+import org.jetbrains.exposed.dao.IntEntity
+import org.jetbrains.exposed.dao.IntEntityClass
+import org.jetbrains.exposed.dao.id.EntityID
+import org.jetbrains.exposed.dao.id.IntIdTable
+import org.jetbrains.exposed.sql.*
+import org.jetbrains.exposed.sql.transactions.transaction
 import java.nio.file.Files
 import java.nio.file.Path
 
+private object DatabaseMetadata : IntIdTable() {
+    var version = integer("version")
+}
+
+class DatabaseMetadataEntity(id: EntityID<Int>) : IntEntity(id) {
+    companion object : IntEntityClass<DatabaseMetadataEntity>(DatabaseMetadata)
+
+    var version by DatabaseMetadata.version
+}
+
 class DatabaseService {
 
+    companion object {
+        const val CURRENT_VERSION = 1
+        const val DB_FILENAME = "kls_database.db"
+    }
+
     var db: Database? = null
         private set
 
     fun setup(storagePath: Path?) {
-        val dbName = "kls_database"
+        db = getDbFromFile(storagePath)
+
+        val currentVersion = transaction(db) {
+            SchemaUtils.createMissingTablesAndColumns(DatabaseMetadata)
+
+            DatabaseMetadataEntity.all().firstOrNull()?.version
+        }
 
-        db = storagePath?.let {
+        if ((currentVersion ?: 0) < CURRENT_VERSION) {
+            deleteDb(storagePath)
+
+            db = getDbFromFile(storagePath)
+
+            transaction(db) {
+                SchemaUtils.createMissingTablesAndColumns(DatabaseMetadata)
+
+                DatabaseMetadata.deleteAll()
+                DatabaseMetadata.insert { it[version] = CURRENT_VERSION }
+            }
+        }
+    }
+
+    private fun getDbFromFile(storagePath: Path?): Database? {
+        return storagePath?.let {
             if (Files.isDirectory(it)) {
-                Database.connect("jdbc:sqlite:${Path.of(storagePath.toString(), dbName)}.db")
+                Database.connect("jdbc:sqlite:${getDbFilePath(it)}")
             } else {
                 null
             }
         }
     }
+
+    private fun deleteDb(storagePath: Path?) {
+        storagePath?.let { Files.deleteIfExists(getDbFilePath(it)) }
+    }
+
+    private fun getDbFilePath(storagePath: Path) = Path.of(storagePath.toString(), DB_FILENAME)
 }