Clear cache based on tile source

app/src/main/java/com/geeksville/mesh/util/SqlTileWriterExt.kt

@@ -0,0 +1,81 @@
+package com.geeksville.mesh.util
+
+import android.database.Cursor
+import org.osmdroid.tileprovider.modules.DatabaseFileArchive
+import org.osmdroid.tileprovider.modules.SqlTileWriter
+
+
+/**
+ * Extended the sqlite tile writer to have some additional query functions. A this point
+ * it's unclear if there is a need to put these with the osmdroid-android library, thus they were
+ * put here as more of an example.
+ *
+ *
+ * created on 12/21/2016.
+ *
+ * @author Alex O'Ree
+ * @since 5.6.2
+ */
+class SqlTileWriterExt() : SqlTileWriter() {
+    fun select(rows: Int, offset: Int): Cursor? {
+        return this.db?.rawQuery(
+            "select " + DatabaseFileArchive.COLUMN_KEY + "," + COLUMN_EXPIRES + "," + DatabaseFileArchive.COLUMN_PROVIDER + " from " + DatabaseFileArchive.TABLE + " limit ? offset ?",
+            arrayOf(rows.toString() + "", offset.toString() + "")
+        )
+    }
+
+    /**
+     * gets all the tiles sources that we have tiles for in the cache database and their counts
+     *
+     * @return
+     */
+    val sources: List<SourceCount>
+        get() {
+            val db = db
+            val ret: MutableList<SourceCount> = ArrayList()
+            if (db == null) {
+                return ret
+            }
+            var cur: Cursor? = null
+            try {
+                cur = db.rawQuery(
+                    "select "
+                            + DatabaseFileArchive.COLUMN_PROVIDER
+                            + ",count(*) "
+                            + ",min(length(" + DatabaseFileArchive.COLUMN_TILE + ")) "
+                            + ",max(length(" + DatabaseFileArchive.COLUMN_TILE + ")) "
+                            + ",sum(length(" + DatabaseFileArchive.COLUMN_TILE + ")) "
+                            + "from " + DatabaseFileArchive.TABLE + " "
+                            + "group by " + DatabaseFileArchive.COLUMN_PROVIDER, null
+                )
+                while (cur.moveToNext()) {
+                    val c = SourceCount()
+                    c.source = cur.getString(0)
+                    c.rowCount = cur.getLong(1)
+                    c.sizeMin = cur.getLong(2)
+                    c.sizeMax = cur.getLong(3)
+                    c.sizeTotal = cur.getLong(4)
+                    c.sizeAvg = c.sizeTotal / c.rowCount
+                    ret.add(c)
+                }
+            } catch (e: Exception) {
+                catchException(e)
+            } finally {
+                cur?.close()
+            }
+            return ret
+        }
+    val rowCountExpired: Long
+        get() = getRowCount(
+            "$COLUMN_EXPIRES<?", arrayOf(System.currentTimeMillis().toString())
+        )
+
+    class SourceCount() {
+        var rowCount: Long = 0
+        var source: String? = null
+        var sizeTotal: Long = 0
+        var sizeMin: Long = 0
+        var sizeMax: Long = 0
+        var sizeAvg: Long = 0
+    }
+}