EtebaseLocalCache: add a class that implements a local cache for etebase.

app/src/main/java/com/etesync/syncadapter/EtebaseLocalCache.kt

@@ -0,0 +1,90 @@
+package com.etesync.syncadapter
+
+import android.content.Context
+import com.etebase.client.*
+import com.etebase.client.Collection
+import java.io.File
+
+/*
+File structure:
+cache_dir/
+    user1/ <--- the name of the user
+        cols/
+            UID1/ - The uid of the first col
+                ...
+            UID2/ - The uid of the second col
+                col <-- the col itself
+                items/
+                    item_uid1 <-- the item with uid 1
+                    item_uid2
+                    ...
+ */
+class EtebaseLocalCache private constructor(context: Context, username: String) {
+    private val filesDir: File
+    private val colsDir: File
+
+    init {
+        filesDir = File(context.filesDir, username)
+        colsDir = File(filesDir, "cols")
+        colsDir.mkdirs()
+    }
+
+    private fun getCollectionItemsDir(colUid: String): File {
+        val colsDir = File(filesDir, "cols")
+        val colDir = File(colsDir, colUid)
+        return File(colDir, "items")
+    }
+
+    fun clearUserCache() {
+        filesDir.deleteRecursively()
+    }
+
+    fun collectionList(colMgr: CollectionManager): List<Collection> {
+        return colsDir.list().map {
+            val colFile = File(it, "col")
+            val content = colFile.readBytes()
+            colMgr.cacheLoad(content)
+        }
+    }
+
+    fun collectionSet(colMgr: CollectionManager, collection: Collection) {
+        val colDir = File(colsDir, collection.uid)
+        colDir.mkdir()
+        val colFile = File(colDir, "col")
+        colFile.writeBytes(colMgr.cacheSave(collection))
+        val itemsDir = getCollectionItemsDir(collection.uid)
+        itemsDir.mkdir()
+    }
+
+    fun collectionUnset(colMgr: CollectionManager, colUid: String) {
+        val colDir = File(colsDir, colUid)
+        colDir.deleteRecursively()
+    }
+
+    fun itemList(itemMgr: ItemManager, colUid: String): List<Item> {
+        val itemsDir = getCollectionItemsDir(colUid)
+        return itemsDir.list().map {
+            val itemFile = File(it)
+            val content = itemFile.readBytes()
+            itemMgr.cacheLoad(content)
+        }
+    }
+
+    fun itemSet(itemMgr: ItemManager, colUid: String, item: Item) {
+        val itemsDir = getCollectionItemsDir(colUid)
+        val itemFile = File(itemsDir, item.uid)
+        itemFile.writeBytes(itemMgr.cacheSave(item))
+    }
+
+    fun itemUnset(itemMgr: ItemManager, colUid: String, itemUid: String) {
+        val itemsDir = getCollectionItemsDir(colUid)
+        val itemFile = File(itemsDir, itemUid)
+        itemFile.delete()
+    }
+
+    companion object {
+        fun getInstance(context: Context, username: String): EtebaseLocalCache {
+            return EtebaseLocalCache(context, username)
+        }
+    }
+}