Add comment collapsing (#40)

7 files changed, 207 insertions, 49 deletions

diff --git a/README.md b/README.md
index 0d2c906..2c0c119 100644
--- a/README.md
+++ b/README.md
@@ -181,7 +181,9 @@ In each `View`, press `?` to see a list of supported keyboard shortcuts and thei
 - `p`: Focus the previous top level comment
 - `l`: Focus the next comment with smaller or equal level
 - `h`: Focus the previous comment with smaller or equal level
+- `u`: Focus the parent comment (if exists)
 - `r`: Reload the comment view.
+- `tab`: Toggle collapsing the focused comment
 - `up`: Scroll up
 - `down`: Scroll down
 - `page_up`: Scroll up half a page
@@ -197,7 +199,7 @@ In each `View`, press `?` to see a list of supported keyboard shortcuts and thei
 
 In `SearchView`, there are two modes: `Navigation` and `Search`. The default mode is `Search`.
 
-`Search` mode is similar to Vim's Insert mode, in which users can input the query string.
+`Search` mode is similar to Vim's insert mode, in which users can input the query string.
 
 `Navigation` mode allows the `SearchView` to behave like a `StoryView` with all `StoryView` shortcuts enabled.
 
@@ -272,7 +274,7 @@ to view the application's log in `log.txt` file.
 
 - [x] make all commands customizable
 - [x] add a `View` to read the linked story in reader mode on the terminal. A list of possible suggestion can be found [here](https://news.ycombinator.com/item?id=26930466)
-- [ ] add commands to navigate parent comments and collapse a comment
+- [x] add commands to navigate parent comments and collapse a comment
 - [x] make all the configuration options optional
 - integrate [HackerNews Official APIs](https://github.com/HackerNews/API) for real-time updating, lazy-loading comments, and sorting stories
   - [x] lazy-loading comments
diff --git a/hackernews_tui/src/hn-tui-default.toml b/hackernews_tui/src/hn-tui-default.toml
index 097c156..7e1831a 100644
--- a/hackernews_tui/src/hn-tui-default.toml
+++ b/hackernews_tui/src/hn-tui-default.toml
@@ -130,6 +130,7 @@
 # prev_top_level_comment = "p"
 # next_leq_level_comment = "l"
 # prev_leq_level_comment = "h"
+# parent_comment = "u"
 # down = "down"
 # up = "up"
 # page_down = "page_down"
@@ -138,6 +139,7 @@
 # open_link_in_browser = "f"
 # open_link_in_article_view = "F"
 # reload_comment_view = "r"
+# toggle_collapse_comment = "tab"
 
 #[keymap.article_view_keymap]
 # down = "j"
diff --git a/hackernews_tui/src/keybindings.rs b/hackernews_tui/src/keybindings.rs
index 2ca2ed5..8b7ce9d 100644
--- a/hackernews_tui/src/keybindings.rs
+++ b/hackernews_tui/src/keybindings.rs
@@ -152,6 +152,7 @@ pub struct CommentViewKeyMap {
     pub prev_top_level_comment: Key,
     pub next_leq_level_comment: Key,
     pub prev_leq_level_comment: Key,
+    pub parent_comment: Key,
 
     // link opening keymaps
     pub open_comment_in_browser: Key,
@@ -164,6 +165,7 @@ pub struct CommentViewKeyMap {
     pub page_down: Key,
     pub page_up: Key,
 
+    pub toggle_collapse_comment: Key,
     pub reload_comment_view: Key,
 }
 
@@ -176,6 +178,7 @@ impl Default for CommentViewKeyMap {
             prev_top_level_comment: Key::new('p'),
             next_leq_level_comment: Key::new('l'),
             prev_leq_level_comment: Key::new('h'),
+            parent_comment: Key::new('u'),
 
             open_comment_in_browser: Key::new('c'),
             open_link_in_browser: Key::new('f'),
@@ -186,6 +189,7 @@ impl Default for CommentViewKeyMap {
             page_up: Key::new(event::Key::PageUp),
             page_down: Key::new(event::Key::PageDown),
 
+            toggle_collapse_comment: Key::new(event::Key::Tab),
             reload_comment_view: Key::new('r'),
         }
     }
diff --git a/hackernews_tui/src/view/comment_view.rs b/hackernews_tui/src/view/comment_view.rs
index 7bf5c6f..3818aa2 100644
--- a/hackernews_tui/src/view/comment_view.rs
+++ b/hackernews_tui/src/view/comment_view.rs
@@ -7,11 +7,31 @@ use super::text_view;
 
 use crate::prelude::*;
 
+type CommentComponent = HideableView<PaddedView<text_view::TextView>>;
+
+#[derive(Debug, Clone)]
+/// CommentState represents the state of a single comment component
+enum CommentState {
+    Collapsed,
+    PartiallyCollapsed,
+    Normal,
+}
+
+impl CommentState {
+    fn visible(&self) -> bool {
+        !matches!(self, Self::Collapsed)
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Comment {
+    state: CommentState,
     top_comment_id: u32,
     id: u32,
+
     text: StyledString,
+    minimized_text: StyledString,
+
     height: usize,
     links: Vec<String>,
 }
@@ -21,13 +41,16 @@ impl Comment {
         top_comment_id: u32,
         id: u32,
         text: StyledString,
+        minimized_text: StyledString,
         height: usize,
         links: Vec<String>,
     ) -> Self {
         Comment {
+            state: CommentState::Normal,
             top_comment_id,
             id,
             text,
+            minimized_text,
             height,
             links,
         }
@@ -36,8 +59,9 @@ impl Comment {
 
 /// CommentView is a View displaying a list of comments in a HN story
 pub struct CommentView {
-    story: hn_client::Story,
     view: ScrollListView,
+
+    story: hn_client::Story,
     comments: Vec<Comment>,
     lazy_loading_comments: hn_client::LazyLoadingComments,
 
@@ -49,7 +73,7 @@ impl ViewWrapper for CommentView {
 
     fn wrap_layout(&mut self, size: Vec2) {
         // to support focus the last focused comment on reloading,
-        // scroll the the focus element on view initialization
+        // scroll to the focus element during the view initialization
         let is_init = self.get_inner().get_scroller().last_available_size() == Vec2::zero();
 
         self.with_view_mut(|v| v.layout(size));
@@ -99,13 +123,13 @@ impl CommentView {
         );
 
         comments.iter().for_each(|comment| {
-            self.add_item(PaddedView::lrtb(
+            self.add_item(HideableView::new(PaddedView::lrtb(
                 comment.height * 2,
                 0,
                 0,
                 1,
                 text_view::TextView::new(comment.text.clone()),
-            ));
+            )));
         });
         self.comments.append(&mut comments);
 
@@ -219,18 +243,123 @@ impl CommentView {
                 );
                 comment_string.append(comment_content);
 
+                // minimized_comment is used to display collapsed comment
+                let minimized_comment_string = StyledString::styled(
+                    format!(
+                        "{} {} ago ({} more)",
+                        comment.author,
+                        get_elapsed_time_as_text(comment.time),
+                        subcomments.len() + 1,
+                    ),
+                    PaletteColor::Secondary,
+                );
+
                 subcomments.insert(
                     0,
-                    Comment::new(top_comment_id, comment.id, comment_string, height, links),
+                    Comment::new(
+                        top_comment_id,
+                        comment.id,
+                        comment_string,
+                        minimized_comment_string,
+                        height,
+                        links,
+                    ),
                 );
                 subcomments
             })
             .collect()
     }
 
-    /// Get the height of each comment in the comment tree
-    pub fn get_heights(&self) -> Vec<usize> {
-        self.comments.iter().map(|comment| comment.height).collect()
+    /// Return the `id` of the first (`direction` dependent and starting but not including `start_id`)
+    /// comment which has the `height` less than or equal the `max_height`
+    pub fn find_comment_id_by_max_height(
+        &self,
+        start_id: usize,
+        max_height: usize,
+        direction: bool,
+    ) -> usize {
+        if direction {
+            // ->
+            (start_id + 1..self.len())
+                .find(|&id| self.comments[id].height <= max_height)
+                .unwrap_or_else(|| self.len())
+        } else {
+            // <-
+            (0..start_id)
+                .rfind(|&id| self.comments[id].height <= max_height)
+                .unwrap_or(start_id)
+        }
+    }
+
+    /// Return the id of the next visible comment (`direction` dependent and starting but not including `start_id`)
+    pub fn find_next_visible_comment(&self, start_id: usize, direction: bool) -> usize {
+        if direction {
+            // ->
+            (start_id + 1..self.len())
+                .find(|&id| self.comments[id].state.visible())
+                .unwrap_or_else(|| self.len())
+        } else {
+            // <-
+            (0..start_id)
+                .rfind(|&id| self.comments[id].state.visible())
+                .unwrap_or(start_id)
+        }
+    }
+
+    fn get_comment_component_mut(&mut self, id: usize) -> &mut CommentComponent {
+        self.get_item_mut(id)
+            .unwrap()
+            .downcast_mut::<CommentComponent>()
+            .unwrap()
+    }
+
+    /// Toggle the collapsing state of children of `parent_comment_id` comment.
+    /// **Note**: partially collapsed comment's state is unchanged.
+    fn toggle_collapse_child_comments(&mut self, parent_comment_id: usize) {
+        let parent_height = self.comments[parent_comment_id].height;
+        let end = self.find_comment_id_by_max_height(parent_comment_id, parent_height, true);
+        (parent_comment_id + 1..end).for_each(|i| {
+            match self.comments[i].state {
+                CommentState::Collapsed => {
+                    self.comments[i].state = CommentState::Normal;
+                    self.get_comment_component_mut(i).unhide();
+                }
+                CommentState::Normal => {
+                    self.comments[i].state = CommentState::Collapsed;
+                    self.get_comment_component_mut(i).hide();
+                }
+                CommentState::PartiallyCollapsed => {} // for partially collapsed comment, keep the state unchanged
+            }
+        });
+    }
+
+    /// Toggle the collapsing state of currently focused comment and its children
+    pub fn toggle_collapse_focused_comment(&mut self) {
+        let id = self.get_focus_index();
+        let comment = self.comments[id].clone();
+        match comment.state {
+            CommentState::Collapsed => {
+                panic!(
+                    "invalid comment state `Collapsed` when calling `toggle_collapse_focused_comment`"
+                );
+            }
+            CommentState::PartiallyCollapsed => {
+                self.get_comment_component_mut(id)
+                    .get_inner_mut()
+                    .get_inner_mut()
+                    .set_content(comment.text);
+                self.toggle_collapse_child_comments(id);
+                self.comments[id].state = CommentState::Normal;
+            }
+            CommentState::Normal => {
+                self.get_comment_component_mut(id)
+                    .get_inner_mut()
+                    .get_inner_mut()
+                    .set_content(comment.minimized_text);
+                self.toggle_collapse_child_comments(id);
+                self.comments[id].state = CommentState::PartiallyCollapsed;
+            }
+        };
     }
 
     inner_getters!(self.view: ScrollListView);
@@ -287,62 +416,50 @@ fn get_comment_main_view(
         })
         // comment navigation shortcuts
         .on_pre_event_inner(comment_view_keymap.prev_comment, |s, _| {
-            let id = s.get_focus_index();
-            if id == 0 {
-                None
-            } else {
-                s.set_focus_index(id - 1)
-            }
+            s.set_focus_index(s.find_next_visible_comment(s.get_focus_index(), false))
         })
         .on_pre_event_inner(comment_view_keymap.next_comment, |s, _| {
-            let id = s.get_focus_index();
-            if id + 1 == s.len() {
+            let next_id = s.find_next_visible_comment(s.get_focus_index(), true);
+            if next_id == s.len() {
                 s.load_comments();
             }
-            s.set_focus_index(id + 1)
+            s.set_focus_index(next_id)
         })
         .on_pre_event_inner(comment_view_keymap.next_leq_level_comment, move |s, _| {
-            let heights = s.get_heights();
             let id = s.get_focus_index();
-            let (_, right) = heights.split_at(id + 1);
-            let offset = right.iter().position(|&h| h <= heights[id]);
-            let next_id = match offset {
-                None => s.len(),
-                Some(offset) => id + offset + 1,
-            };
+            let next_id = s.find_comment_id_by_max_height(id, s.comments[id].height, true);
             if next_id == s.len() {
                 s.load_comments();
             }
             s.set_focus_index(next_id)
         })
         .on_pre_event_inner(comment_view_keymap.prev_leq_level_comment, move |s, _| {
-            let heights = s.get_heights();
             let id = s.get_focus_index();
-            let (left, _) = heights.split_at(id);
-            let next_id = left.iter().rposition(|&h| h <= heights[id]).unwrap_or(id);
+            let next_id = s.find_comment_id_by_max_height(id, s.comments[id].height, false);
             s.set_focus_index(next_id)
         })
         .on_pre_event_inner(comment_view_keymap.next_top_level_comment, move |s, _| {
-            let heights = s.get_heights();
             let id = s.get_focus_index();
-            let (_, right) = heights.split_at(id + 1);
-            let offset = right.iter().position(|&h| h == 0);
-            let next_id = match offset {
-                None => s.len(),
-                Some(offset) => id + offset + 1,
-            };
+            let next_id = s.find_comment_id_by_max_height(id, 0, true);
             if next_id == s.len() {
                 s.load_comments();
             }
             s.set_focus_index(next_id)
         })
         .on_pre_event_inner(comment_view_keymap.prev_top_level_comment, move |s, _| {
-            let heights = s.get_heights();
             let id = s.get_focus_index();
-            let (left, _) = heights.split_at(id);
-            let next_id = left.iter().rposition(|&h| h == 0).unwrap_or(id);
+            let next_id = s.find_comment_id_by_max_height(id, 0, false);
             s.set_focus_index(next_id)
         })
+        .on_pre_event_inner(comment_view_keymap.parent_comment, move |s, _| {
+            let id = s.get_focus_index();
+            if s.comments[id].height > 0 {
+                let next_id = s.find_comment_id_by_max_height(id, s.comments[id].height - 1, false);
+                s.set_focus_index(next_id)
+            } else {
+                Some(EventResult::Consumed(None))
+            }
+        })
         // open external link shortcuts
         .on_pre_event_inner(comment_view_keymap.open_link_in_browser, |s, _| {
             match s.raw_command.parse::<usize>() {
@@ -377,6 +494,17 @@ fn get_comment_main_view(
                 Err(_) => None,
             },
         )
+        .on_pre_event_inner(comment_view_keymap.open_comment_in_browser, move |s, _| {
+            let id = s.comments[s.get_focus_index()].id;
+            let url = format!("{}/item?id={}", hn_client::HN_HOST_URL, id);
+            open_url_in_browser(&url);
+            Some(EventResult::Consumed(None))
+        })
+        // other commands
+        .on_pre_event_inner(comment_view_keymap.toggle_collapse_comment, move |s, _| {
+            s.toggle_collapse_focused_comment();
+            Some(EventResult::Consumed(None))
+        })
         .on_pre_event_inner(comment_view_keymap.reload_comment_view, move |s, _| {
             let comment = &s.comments[s.get_focus_index()];
             let focus_id = (comment.top_comment_id, comment.id);
@@ -385,12 +513,6 @@ fn get_comment_main_view(
                 move |s| add_comment_view_layer(s, client, &story, focus_id, true)
             }))
         })
-        .on_pre_event_inner(comment_view_keymap.open_comment_in_browser, move |s, _| {
-            let id = s.comments[s.get_focus_index()].id;
-            let url = format!("{}/item?id={}", hn_client::HN_HOST_URL, id);
-            open_url_in_browser(&url);
-            Some(EventResult::Consumed(None))
-        })
         .full_height()
 }
 
diff --git a/hackernews_tui/src/view/help_view.rs b/hackernews_tui/src/view/help_view.rs
index 4f280c6..8987e69 100644
--- a/hackernews_tui/src/view/help_view.rs
+++ b/hackernews_tui/src/view/help_view.rs
@@ -288,6 +288,10 @@ impl HasHelpView for CommentView {
                         comment_view_keymap.prev_leq_level_comment.to_string(),
                         "Focus the previous comment at smaller or equal level",
                     ),
+                    (
+                        comment_view_keymap.parent_comment.to_string(),
+                        "Focus the parent comment (if exists)",
+                    ),
                 ],
             ),
             (
@@ -338,10 +342,16 @@ impl HasHelpView for CommentView {
                 ],
             ),
             view_navigation_key_shortcuts!(),
-            other_key_shortcuts!((
-                comment_view_keymap.reload_comment_view.to_string(),
-                "Reload the comment view"
-            )),
+            other_key_shortcuts!(
+                (
+                    comment_view_keymap.reload_comment_view.to_string(),
+                    "Reload the comment view"
+                ),
+                (
+                    comment_view_keymap.toggle_collapse_comment.to_string(),
+                    "Toggle collapsing the focused comment"
+                )
+            ),
         ])
     }
 }
diff --git a/hackernews_tui/src/view/list_view.rs b/hackernews_tui/src/view/list_view.rs
index a55b173..056bd1a 100644
--- a/hackernews_tui/src/view/list_view.rs
+++ b/hackernews_tui/src/view/list_view.rs
@@ -9,6 +9,8 @@ pub trait ScrollableList {
     fn get_focus_index(&self) -> usize;
     fn set_focus_index(&mut self, id: usize) -> Option<EventResult>;
     fn add_item<V: IntoBoxedView + 'static>(&mut self, view: V);
+    fn get_item(&self, id: usize) -> Option<&(dyn View + 'static)>;
+    fn get_item_mut(&mut self, id: usize) -> Option<&mut (dyn View + 'static)>;
     fn get_scroller(&self) -> &scroll::Core;
     fn get_scroller_mut(&mut self) -> &mut scroll::Core;
     // Move the scroller to the focused area and adjust the scroller
@@ -97,6 +99,14 @@ macro_rules! impl_scrollable_list {
         fn get_scroller(&self) -> &scroll::Core {
             self.get_inner().get_scroller()
         }
+
+        fn get_item(&self, id: usize) -> Option<&(dyn View + 'static)> {
+            self.get_inner().get_inner().get_child(id)
+        }
+
+        fn get_item_mut(&mut self, id: usize) -> Option<&mut (dyn View + 'static)> {
+            self.get_inner_mut().get_inner_mut().get_child_mut(id)
+        }
     };
 }
 
diff --git a/hackernews_tui/src/view/text_view.rs b/hackernews_tui/src/view/text_view.rs
index 9591edf..7fa19c2 100644
--- a/hackernews_tui/src/view/text_view.rs
+++ b/hackernews_tui/src/view/text_view.rs
@@ -23,6 +23,14 @@ impl TextView {
         }
     }
 
+    pub fn set_content<S>(&mut self, content: S)
+    where
+        S: Into<utils::markup::StyledString>,
+    {
+        self.content = content.into();
+        self.size_cache = None;
+    }
+
     fn is_size_cache_valid(&self, size: Vec2) -> bool {
         match self.size_cache {
             None => false,