Add milestone creation and editing

crates/app/src/presentation.rs

@@ -139,6 +139,13 @@ pub struct MilestoneListPage {
     pub has_more: bool,
 }
 
+#[derive(Clone, uniffi::Record)]
+pub struct MilestoneEditorPage {
+    pub title: String,
+    pub description: String,
+    pub due_date: Option<i64>,
+}
+
 #[derive(Clone, uniffi::Record)]
 pub struct PullFilterOptions {
     pub milestones: Vec<String>,
@@ -364,6 +371,23 @@ pub fn milestone_page(details: MilestoneDetails) -> MilestonePage {
     }
 }
 
+pub fn milestone_editor_page(milestone: Option<models::Milestone>) -> MilestoneEditorPage {
+    MilestoneEditorPage {
+        title: milestone
+            .as_ref()
+            .and_then(|milestone| milestone.title.clone())
+            .unwrap_or_default(),
+        description: milestone
+            .as_ref()
+            .and_then(|milestone| milestone.description.clone())
+            .unwrap_or_default(),
+        due_date: milestone
+            .as_ref()
+            .and_then(|milestone| milestone.due_on.as_deref())
+            .and_then(parse_api_date),
+    }
+}
+
 pub fn pull_filter_options(milestones: &[String], filter: &PullFilter) -> PullFilterOptions {
     let mut milestones = milestones.to_vec();
     if !filter.milestone.is_empty() {
@@ -1425,6 +1449,21 @@ mod tests {
         assert_eq!(page.pulls[0].number, 7);
     }
 
+    #[test]
+    fn milestone_editor_preserves_description_and_optional_due_date() {
+        let page = milestone_editor_page(Some(models::Milestone {
+            title: Some("Version 1".into()),
+            description: Some("Ship it".into()),
+            due_on: Some("2024-02-29T12:34:56Z".into()),
+            ..Default::default()
+        }));
+        assert_eq!(page.title, "Version 1");
+        assert_eq!(page.description, "Ship it");
+        assert_eq!(page.due_date, Some(1_709_164_800));
+
+        assert_eq!(milestone_editor_page(None).due_date, None);
+    }
+
     #[test]
     fn classifies_repository_files_in_rust() {
         let markdown = repository_file_page("docs/README.md", b"# Hello".to_vec());