Implement common cursor movement logic

src/ui/chat2.rs

@@ -1,2 +1,3 @@
 mod blocks;
+mod cursor;
 mod renderer;

src/ui/chat2/cursor.rs

@@ -0,0 +1,528 @@
+//! Common cursor movement logic.
+
+use std::collections::HashSet;
+use std::hash::Hash;
+
+use crate::store::{Msg, MsgStore, Tree};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Cursor<Id> {
+    Bottom,
+    Msg(Id),
+    Editor {
+        coming_from: Option<Id>,
+        parent: Option<Id>,
+    },
+    Pseudo {
+        coming_from: Option<Id>,
+        parent: Option<Id>,
+    },
+}
+
+impl<Id: Clone + Eq + Hash> Cursor<Id> {
+    fn find_parent<M>(tree: &Tree<M>, id: &mut Id) -> bool
+    where
+        M: Msg<Id = Id>,
+    {
+        if let Some(parent) = tree.parent(id) {
+            *id = parent;
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Move to the previous sibling, or don't move if this is not possible.
+    ///
+    /// Always stays at the same level of indentation.
+    async fn find_prev_sibling<M, S>(
+        store: &S,
+        tree: &mut Tree<M>,
+        id: &mut Id,
+    ) -> Result<bool, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        let moved = if let Some(prev_sibling) = tree.prev_sibling(id) {
+            *id = prev_sibling;
+            true
+        } else if tree.parent(id).is_none() {
+            // We're at the root of our tree, so we need to move to the root of
+            // the previous tree.
+            if let Some(prev_root_id) = store.prev_root_id(tree.root()).await? {
+                *tree = store.tree(&prev_root_id).await?;
+                *id = prev_root_id;
+                true
+            } else {
+                false
+            }
+        } else {
+            false
+        };
+        Ok(moved)
+    }
+
+    /// Move to the next sibling, or don't move if this is not possible.
+    ///
+    /// Always stays at the same level of indentation.
+    async fn find_next_sibling<M, S>(
+        store: &S,
+        tree: &mut Tree<M>,
+        id: &mut Id,
+    ) -> Result<bool, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        let moved = if let Some(next_sibling) = tree.next_sibling(id) {
+            *id = next_sibling;
+            true
+        } else if tree.parent(id).is_none() {
+            // We're at the root of our tree, so we need to move to the root of
+            // the next tree.
+            if let Some(next_root_id) = store.next_root_id(tree.root()).await? {
+                *tree = store.tree(&next_root_id).await?;
+                *id = next_root_id;
+                true
+            } else {
+                false
+            }
+        } else {
+            false
+        };
+        Ok(moved)
+    }
+
+    fn find_first_child_in_tree<M>(folded: &HashSet<Id>, tree: &Tree<M>, id: &mut Id) -> bool
+    where
+        M: Msg<Id = Id>,
+    {
+        if folded.contains(id) {
+            return false;
+        }
+
+        if let Some(child) = tree.children(id).and_then(|c| c.first()) {
+            *id = child.clone();
+            true
+        } else {
+            false
+        }
+    }
+
+    fn find_last_child_in_tree<M>(folded: &HashSet<Id>, tree: &Tree<M>, id: &mut Id) -> bool
+    where
+        M: Msg<Id = Id>,
+    {
+        if folded.contains(id) {
+            return false;
+        }
+
+        if let Some(child) = tree.children(id).and_then(|c| c.last()) {
+            *id = child.clone();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Move to the message above, or don't move if this is not possible.
+    async fn find_above_msg_in_tree<M, S>(
+        store: &S,
+        folded: &HashSet<Id>,
+        tree: &mut Tree<M>,
+        id: &mut Id,
+    ) -> Result<bool, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        // Move to previous sibling, then to its last child
+        // If not possible, move to parent
+        let moved = if Self::find_prev_sibling(store, tree, id).await? {
+            while Self::find_last_child_in_tree(folded, tree, id) {}
+            true
+        } else {
+            Self::find_parent(tree, id)
+        };
+        Ok(moved)
+    }
+
+    /// Move to the next message, or don't move if this is not possible.
+    async fn find_below_msg_in_tree<M, S>(
+        store: &S,
+        folded: &HashSet<Id>,
+        tree: &mut Tree<M>,
+        id: &mut Id,
+    ) -> Result<bool, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        if Self::find_first_child_in_tree(folded, tree, id) {
+            return Ok(true);
+        }
+
+        if Self::find_next_sibling(store, tree, id).await? {
+            return Ok(true);
+        }
+
+        // Temporary id to avoid modifying the original one if no parent-sibling
+        // can be found.
+        let mut tmp_id = id.clone();
+        while Self::find_parent(tree, &mut tmp_id) {
+            if Self::find_next_sibling(store, tree, &mut tmp_id).await? {
+                *id = tmp_id;
+                return Ok(true);
+            }
+        }
+
+        Ok(false)
+    }
+
+    pub async fn move_to_top<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        if let Some(first_root_id) = store.first_root_id().await? {
+            *self = Self::Msg(first_root_id);
+        }
+        Ok(())
+    }
+
+    pub fn move_to_bottom(&mut self) {
+        *self = Self::Bottom;
+    }
+
+    pub async fn move_to_older_msg<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(id) => {
+                if let Some(prev_id) = store.older_msg_id(id).await? {
+                    *id = prev_id;
+                }
+            }
+            Self::Bottom | Self::Pseudo { .. } => {
+                if let Some(id) = store.newest_msg_id().await? {
+                    *self = Self::Msg(id);
+                }
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_newer_msg<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(id) => {
+                if let Some(prev_id) = store.newer_msg_id(id).await? {
+                    *id = prev_id;
+                } else {
+                    *self = Self::Bottom;
+                }
+            }
+            Self::Pseudo { .. } => {
+                *self = Self::Bottom;
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_older_unseen_msg<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(id) => {
+                if let Some(prev_id) = store.older_unseen_msg_id(id).await? {
+                    *id = prev_id;
+                }
+            }
+            Self::Bottom | Self::Pseudo { .. } => {
+                if let Some(id) = store.newest_unseen_msg_id().await? {
+                    *self = Self::Msg(id);
+                }
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_newer_unseen_msg<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(id) => {
+                if let Some(prev_id) = store.newer_unseen_msg_id(id).await? {
+                    *id = prev_id;
+                } else {
+                    *self = Self::Bottom;
+                }
+            }
+            Self::Pseudo { .. } => {
+                *self = Self::Bottom;
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_parent<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Editor { parent, .. } | Self::Pseudo { parent, .. } => {
+                if let Some(parent_id) = parent {
+                    *self = Self::Msg(parent_id.clone())
+                }
+            }
+
+            Self::Msg(id) => {
+                let path = store.path(id).await?;
+                if let Some(parent_id) = path.parent_segments().last() {
+                    *id = parent_id.clone();
+                }
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_root<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Pseudo {
+                parent: Some(parent),
+                ..
+            } => {
+                let path = store.path(parent).await?;
+                *self = Self::Msg(path.first().clone());
+            }
+            Self::Msg(id) => {
+                let path = store.path(id).await?;
+                *id = path.first().clone();
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_prev_sibling<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Bottom | Self::Pseudo { parent: None, .. } => {
+                if let Some(last_root_id) = store.last_root_id().await? {
+                    *self = Self::Msg(last_root_id);
+                }
+            }
+            Self::Msg(msg) => {
+                let path = store.path(msg).await?;
+                let mut tree = store.tree(path.first()).await?;
+                Self::find_prev_sibling(store, &mut tree, msg).await?;
+            }
+            Self::Editor { .. } => {}
+            Self::Pseudo {
+                parent: Some(parent),
+                ..
+            } => {
+                let path = store.path(parent).await?;
+                let tree = store.tree(path.first()).await?;
+                if let Some(children) = tree.children(parent) {
+                    if let Some(last_child) = children.last() {
+                        *self = Self::Msg(last_child.clone());
+                    }
+                }
+            }
+        }
+        Ok(())
+    }
+
+    pub async fn move_to_next_sibling<M, S>(&mut self, store: &S) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(msg) => {
+                let path = store.path(msg).await?;
+                let mut tree = store.tree(path.first()).await?;
+                if !Self::find_next_sibling(store, &mut tree, msg).await?
+                    && tree.parent(msg).is_none()
+                {
+                    *self = Self::Bottom;
+                }
+            }
+            Self::Pseudo { parent: None, .. } => {
+                *self = Self::Bottom;
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    pub async fn move_up_in_tree<M, S>(
+        &mut self,
+        store: &S,
+        folded: &HashSet<Id>,
+    ) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Bottom | Self::Pseudo { parent: None, .. } => {
+                if let Some(last_root_id) = store.last_root_id().await? {
+                    let tree = store.tree(&last_root_id).await?;
+                    let mut id = last_root_id;
+                    while Self::find_last_child_in_tree(folded, &tree, &mut id) {}
+                    *self = Self::Msg(id);
+                }
+            }
+            Self::Msg(msg) => {
+                let path = store.path(msg).await?;
+                let mut tree = store.tree(path.first()).await?;
+                Self::find_above_msg_in_tree(store, folded, &mut tree, msg).await?;
+            }
+            Self::Editor { .. } => {}
+            Self::Pseudo {
+                parent: Some(parent),
+                ..
+            } => {
+                let tree = store.tree(parent).await?;
+                let mut id = parent.clone();
+                while Self::find_last_child_in_tree(folded, &tree, &mut id) {}
+                *self = Self::Msg(id);
+            }
+        }
+        Ok(())
+    }
+
+    pub async fn move_down_in_tree<M, S>(
+        &mut self,
+        store: &S,
+        folded: &HashSet<Id>,
+    ) -> Result<(), S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        match self {
+            Self::Msg(msg) => {
+                let path = store.path(msg).await?;
+                let mut tree = store.tree(path.first()).await?;
+                if !Self::find_below_msg_in_tree(store, folded, &mut tree, msg).await? {
+                    *self = Self::Bottom;
+                }
+            }
+            Self::Pseudo { parent: None, .. } => {
+                *self = Self::Bottom;
+            }
+            Self::Pseudo {
+                parent: Some(parent),
+                ..
+            } => {
+                let mut tree = store.tree(parent).await?;
+                let mut id = parent.clone();
+                while Self::find_last_child_in_tree(folded, &tree, &mut id) {}
+                // Now we're at the previous message
+                if Self::find_below_msg_in_tree(store, folded, &mut tree, &mut id).await? {
+                    *self = Self::Msg(id);
+                } else {
+                    *self = Self::Bottom;
+                }
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
+    /// The outer `Option` shows whether a parent exists or not. The inner
+    /// `Option` shows if that parent has an id.
+    pub async fn parent_for_normal_tree_reply<M, S>(
+        &self,
+        store: &S,
+    ) -> Result<Option<Option<M::Id>>, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        Ok(match self {
+            Self::Bottom => Some(None),
+            Self::Msg(id) => {
+                let path = store.path(id).await?;
+                let tree = store.tree(path.first()).await?;
+
+                Some(Some(if tree.next_sibling(id).is_some() {
+                    // A reply to a message that has further siblings should be
+                    // a direct reply. An indirect reply might end up a lot
+                    // further down in the current conversation.
+                    id.clone()
+                } else if let Some(parent) = tree.parent(id) {
+                    // A reply to a message without younger siblings should be
+                    // an indirect reply so as not to create unnecessarily deep
+                    // threads. In the case that our message has children, this
+                    // might get a bit confusing. I'm not sure yet how well this
+                    // "smart" reply actually works in practice.
+                    parent
+                } else {
+                    // When replying to a top-level message, it makes sense to
+                    // avoid creating unnecessary new threads.
+                    id.clone()
+                }))
+            }
+            _ => None,
+        })
+    }
+
+    /// The outer `Option` shows whether a parent exists or not. The inner
+    /// `Option` shows if that parent has an id.
+    pub async fn parent_for_alternate_tree_reply<M, S>(
+        &self,
+        store: &S,
+    ) -> Result<Option<Option<M::Id>>, S::Error>
+    where
+        M: Msg<Id = Id>,
+        S: MsgStore<M>,
+    {
+        Ok(match self {
+            Self::Bottom => Some(None),
+            Self::Msg(id) => {
+                let path = store.path(id).await?;
+                let tree = store.tree(path.first()).await?;
+
+                Some(Some(if tree.next_sibling(id).is_none() {
+                    // The opposite of replying normally
+                    id.clone()
+                } else if let Some(parent) = tree.parent(id) {
+                    // The opposite of replying normally
+                    parent
+                } else {
+                    // The same as replying normally, still to avoid creating
+                    // unnecessary new threads
+                    id.clone()
+                }))
+            }
+            _ => None,
+        })
+    }
+}