Add label history

Save and display recently printed labels and allow easily selecting
one to print again.

Author: heston

LabelMaker/app/src/main/java/com/hestonliebowitz/labelmaker/HistoryService.kt

@@ -0,0 +1,59 @@
+package com.hestonliebowitz.labelmaker
+
+import android.content.Context
+
+const val HISTORY_DELIMITER = "~"
+const val MAX_HISTORY_ITEMS = 10
+
+class HistoryService(private val ctx: Context) {
+    private val _items : MutableList<String> = emptyList<String>().toMutableList()
+
+    fun getAll(): List<String> {
+        _items.clear()
+        val prefs = ctx.getSharedPreferences(DEFAULT, Context.MODE_PRIVATE)
+        val history = prefs.getString(
+            ctx.getString(R.string.pref_history),
+            ""
+        )
+        if (!history.isNullOrEmpty()) {
+            _items.addAll(history.split(HISTORY_DELIMITER))
+        }
+        return _items.toList()
+    }
+
+    fun save(value: String) {
+        // If item already exists, remove it
+        val idx = _items.indexOf(value)
+        if (idx > -1) {
+            _items.removeAt(idx)
+        }
+
+        // Add item to front of list
+        _items.add(0, value)
+
+        // Ensure list of favorites never exceeds MAX_HISTORY_ITEMS in length
+        if (_items.size > MAX_HISTORY_ITEMS) {
+            _items.subList(MAX_HISTORY_ITEMS, _items.size).clear()
+        }
+
+        // Serialize list into a string and save it
+        val newItems = _items.joinToString(HISTORY_DELIMITER)
+        val prefs = ctx.getSharedPreferences(DEFAULT, Context.MODE_PRIVATE)
+        val editor = prefs.edit()
+        editor.putString(
+            ctx.getString(R.string.pref_history),
+            newItems
+        )
+        editor.apply()
+    }
+
+    fun deleteAll() {
+        val prefs = ctx.getSharedPreferences(DEFAULT, Context.MODE_PRIVATE)
+        val editor = prefs.edit()
+        editor.putString(
+            ctx.getString(R.string.pref_history),
+            ""
+        )
+        editor.apply()
+    }
+}