add edit modes

src/model.rs

@@ -14,8 +14,23 @@ pub struct Taggart {
     pub column:  usize,
     pub columns: Columns<Entry, fn(&Entry)->Option<Arc<str>>, fn(&mut [Entry], usize, &str)>,
     pub display: Measure<TuiOut>,
-    pub editing: Option<(usize, String)>,
     pub tasks:   Vec<Task>,
+    pub mode:    Option<Mode>,
+}
+
+#[derive(Debug)]
+pub enum Mode {
+    Help,
+    Edit {
+        value: String,
+        index: usize,
+    },
+    Apply {
+        value: bool,
+    },
+    Unsaved {
+        value: u8
+    },
 }
 
 impl Taggart {
@@ -26,7 +41,7 @@ impl Taggart {
             offset:  0,
             column:  2,
             display: Measure::new(),
-            editing: None,
+            mode:    None,
             columns: Columns::default(),
             tasks:   vec![],
             entries,