Merge pull request #5 from helix-editor/lsp

LSP: mk1

7 files changed, 574 insertions, 269 deletions

diff --git a/helix-view/src/commands.rs b/helix-view/src/commands.rs
index 1d7737f0..c135a3da 100644
--- a/helix-view/src/commands.rs
+++ b/helix-view/src/commands.rs
@@ -3,52 +3,65 @@ use helix_core::{
     indent::TAB_WIDTH,
     regex::Regex,
     register, selection,
-    state::{Direction, Granularity, Mode, State},
+    state::{Direction, Granularity, State},
     ChangeSet, Range, Selection, Tendril, Transaction,
 };
 use once_cell::sync::Lazy;
 
 use crate::{
+    document::Mode,
     prompt::Prompt,
     view::{View, PADDING},
 };
 
+pub struct Context<'a, 'b> {
+    pub count: usize,
+    pub view: &'a mut View,
+    pub executor: &'a smol::Executor<'b>,
+}
+
 /// A command is a function that takes the current state and a count, and does a side-effect on the
 /// state (usually by creating and applying a transaction).
-pub type Command = fn(view: &mut View, count: usize);
+pub type Command = fn(cx: &mut Context);
 
-pub fn move_char_left(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    let selection = view
-        .state
-        .move_selection(Direction::Backward, Granularity::Character, count);
-    view.state.selection = selection;
+pub fn move_char_left(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .move_selection(Direction::Backward, Granularity::Character, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_char_right(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection =
-        view.state
-            .move_selection(Direction::Forward, Granularity::Character, count);
+pub fn move_char_right(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .move_selection(Direction::Forward, Granularity::Character, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_line_up(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection = view
-        .state
-        .move_selection(Direction::Backward, Granularity::Line, count);
+pub fn move_line_up(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .move_selection(Direction::Backward, Granularity::Line, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_line_down(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection = view
-        .state
-        .move_selection(Direction::Forward, Granularity::Line, count);
+pub fn move_line_down(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .move_selection(Direction::Forward, Granularity::Line, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_line_end(view: &mut View, _count: usize) {
-    // TODO: use a transaction
-    let lines = selection_lines(&view.state);
+pub fn move_line_end(cx: &mut Context) {
+    let lines = selection_lines(&cx.view.doc.state);
 
     let positions = lines
         .into_iter()
@@ -57,89 +70,80 @@ pub fn move_line_end(view: &mut View, _count: usize) {
 
             // Line end is pos at the start of next line - 1
             // subtract another 1 because the line ends with \n
-            view.state.doc.line_to_char(index + 1).saturating_sub(2)
+            cx.view.doc.text().line_to_char(index + 1).saturating_sub(2)
         })
         .map(|pos| Range::new(pos, pos));
 
     let selection = Selection::new(positions.collect(), 0);
 
-    let transaction = Transaction::new(&mut view.state).with_selection(selection);
-
-    transaction.apply(&mut view.state);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_line_start(view: &mut View, _count: usize) {
-    let lines = selection_lines(&view.state);
+pub fn move_line_start(cx: &mut Context) {
+    let lines = selection_lines(&cx.view.doc.state);
 
     let positions = lines
         .into_iter()
         .map(|index| {
             // adjust all positions to the start of the line.
-            view.state.doc.line_to_char(index)
+            cx.view.doc.text().line_to_char(index)
         })
         .map(|pos| Range::new(pos, pos));
 
     let selection = Selection::new(positions.collect(), 0);
 
-    let transaction = Transaction::new(&mut view.state).with_selection(selection);
-
-    transaction.apply(&mut view.state);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn move_next_word_start(view: &mut View, count: usize) {
-    let pos = view.state.move_pos(
-        view.state.selection.cursor(),
+pub fn move_next_word_start(cx: &mut Context) {
+    let pos = cx.view.doc.state.move_pos(
+        cx.view.doc.selection().cursor(),
         Direction::Forward,
         Granularity::Word,
-        count,
+        cx.count,
     );
 
-    // TODO: use a transaction
-    view.state.selection = Selection::single(pos, pos);
+    cx.view.doc.set_selection(Selection::point(pos));
 }
 
-pub fn move_prev_word_start(view: &mut View, count: usize) {
-    let pos = view.state.move_pos(
-        view.state.selection.cursor(),
+pub fn move_prev_word_start(cx: &mut Context) {
+    let pos = cx.view.doc.state.move_pos(
+        cx.view.doc.selection().cursor(),
         Direction::Backward,
         Granularity::Word,
-        count,
+        cx.count,
     );
 
-    // TODO: use a transaction
-    view.state.selection = Selection::single(pos, pos);
+    cx.view.doc.set_selection(Selection::point(pos));
 }
 
-pub fn move_next_word_end(view: &mut View, count: usize) {
+pub fn move_next_word_end(cx: &mut Context) {
     let pos = State::move_next_word_end(
-        &view.state.doc().slice(..),
-        view.state.selection.cursor(),
-        count,
+        &cx.view.doc.text().slice(..),
+        cx.view.doc.selection().cursor(),
+        cx.count,
     );
 
-    // TODO: use a transaction
-    view.state.selection = Selection::single(pos, pos);
+    cx.view.doc.set_selection(Selection::point(pos));
 }
 
-pub fn move_file_start(view: &mut View, _count: usize) {
-    // TODO: use a transaction
-    view.state.selection = Selection::single(0, 0);
+pub fn move_file_start(cx: &mut Context) {
+    cx.view.doc.set_selection(Selection::point(0));
 
-    view.state.mode = Mode::Normal;
+    cx.view.doc.mode = Mode::Normal;
 }
 
-pub fn move_file_end(view: &mut View, _count: usize) {
-    // TODO: use a transaction
-    let text = &view.state.doc;
+pub fn move_file_end(cx: &mut Context) {
+    let text = &cx.view.doc.text();
     let last_line = text.line_to_char(text.len_lines().saturating_sub(2));
-    view.state.selection = Selection::single(last_line, last_line);
+    cx.view.doc.set_selection(Selection::point(last_line));
 
-    view.state.mode = Mode::Normal;
+    cx.view.doc.mode = Mode::Normal;
 }
 
-pub fn check_cursor_in_view(view: &mut View) -> bool {
-    let cursor = view.state.selection().cursor();
-    let line = view.state.doc().char_to_line(cursor);
+pub fn check_cursor_in_view(view: &View) -> bool {
+    let cursor = view.doc.selection().cursor();
+    let line = view.doc.text().char_to_line(cursor);
     let document_end = view.first_line + view.size.1.saturating_sub(1) as usize;
 
     if (line > document_end.saturating_sub(PADDING)) | (line < view.first_line + PADDING) {
@@ -148,168 +152,186 @@ pub fn check_cursor_in_view(view: &mut View) -> bool {
     true
 }
 
-pub fn page_up(view: &mut View, _count: usize) {
-    if view.first_line < PADDING {
+pub fn page_up(cx: &mut Context) {
+    if cx.view.first_line < PADDING {
         return;
     }
 
-    view.first_line = view.first_line.saturating_sub(view.size.1 as usize);
+    cx.view.first_line = cx.view.first_line.saturating_sub(cx.view.size.1 as usize);
 
-    if !check_cursor_in_view(view) {
-        let text = view.state.doc();
-        let pos = text.line_to_char(view.last_line().saturating_sub(PADDING));
-        view.state.selection = Selection::single(pos, pos);
+    if !check_cursor_in_view(cx.view) {
+        let text = cx.view.doc.text();
+        let pos = text.line_to_char(cx.view.last_line().saturating_sub(PADDING));
+        cx.view.doc.set_selection(Selection::point(pos));
     }
 }
 
-pub fn page_down(view: &mut View, _count: usize) {
-    view.first_line += view.size.1 as usize + PADDING;
+pub fn page_down(cx: &mut Context) {
+    cx.view.first_line += cx.view.size.1 as usize + PADDING;
 
-    if view.first_line < view.state.doc().len_lines() {
-        let text = view.state.doc();
-        let pos = text.line_to_char(view.first_line as usize);
-        view.state.selection = Selection::single(pos, pos);
+    if cx.view.first_line < cx.view.doc.text().len_lines() {
+        let text = cx.view.doc.text();
+        let pos = text.line_to_char(cx.view.first_line as usize);
+        cx.view.doc.set_selection(Selection::point(pos));
     }
 }
 
-pub fn half_page_up(view: &mut View, _count: usize) {
-    if view.first_line < PADDING {
+pub fn half_page_up(cx: &mut Context) {
+    if cx.view.first_line < PADDING {
         return;
     }
 
-    view.first_line = view.first_line.saturating_sub(view.size.1 as usize / 2);
+    cx.view.first_line = cx
+        .view
+        .first_line
+        .saturating_sub(cx.view.size.1 as usize / 2);
 
-    if !check_cursor_in_view(view) {
-        let text = &view.state.doc;
-        let pos = text.line_to_char(view.last_line() - PADDING);
-        view.state.selection = Selection::single(pos, pos);
+    if !check_cursor_in_view(cx.view) {
+        let text = &cx.view.doc.text();
+        let pos = text.line_to_char(cx.view.last_line() - PADDING);
+        cx.view.doc.set_selection(Selection::point(pos));
     }
 }
 
-pub fn half_page_down(view: &mut View, _count: usize) {
-    let lines = view.state.doc().len_lines();
-    if view.first_line < lines.saturating_sub(view.size.1 as usize) {
-        view.first_line += view.size.1 as usize / 2;
+pub fn half_page_down(cx: &mut Context) {
+    let lines = cx.view.doc.text().len_lines();
+    if cx.view.first_line < lines.saturating_sub(cx.view.size.1 as usize) {
+        cx.view.first_line += cx.view.size.1 as usize / 2;
     }
-    if !check_cursor_in_view(view) {
-        let text = view.state.doc();
-        let pos = text.line_to_char(view.first_line as usize);
-        view.state.selection = Selection::single(pos, pos);
+    if !check_cursor_in_view(cx.view) {
+        let text = cx.view.doc.text();
+        let pos = text.line_to_char(cx.view.first_line as usize);
+        cx.view.doc.set_selection(Selection::point(pos));
     }
 }
 // avoid select by default by having a visual mode switch that makes movements into selects
 
-pub fn extend_char_left(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    let selection = view
-        .state
-        .extend_selection(Direction::Backward, Granularity::Character, count);
-    view.state.selection = selection;
+pub fn extend_char_left(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .extend_selection(Direction::Backward, Granularity::Character, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn extend_char_right(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection =
-        view.state
-            .extend_selection(Direction::Forward, Granularity::Character, count);
+pub fn extend_char_right(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .extend_selection(Direction::Forward, Granularity::Character, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn extend_line_up(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection =
-        view.state
-            .extend_selection(Direction::Backward, Granularity::Line, count);
+pub fn extend_line_up(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .extend_selection(Direction::Backward, Granularity::Line, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn extend_line_down(view: &mut View, count: usize) {
-    // TODO: use a transaction
-    view.state.selection =
-        view.state
-            .extend_selection(Direction::Forward, Granularity::Line, count);
+pub fn extend_line_down(cx: &mut Context) {
+    let selection =
+        cx.view
+            .doc
+            .state
+            .extend_selection(Direction::Forward, Granularity::Line, cx.count);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn split_selection_on_newline(view: &mut View, _count: usize) {
-    let text = &view.state.doc.slice(..);
+pub fn split_selection_on_newline(cx: &mut Context) {
+    let text = &cx.view.doc.text().slice(..);
     // only compile the regex once
     #[allow(clippy::trivial_regex)]
     static REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"\n").unwrap());
-    // TODO: use a transaction
-    view.state.selection = selection::split_on_matches(text, view.state.selection(), &REGEX)
+    let selection = selection::split_on_matches(text, cx.view.doc.selection(), &REGEX);
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn select_line(view: &mut View, _count: usize) {
+pub fn select_line(cx: &mut Context) {
     // TODO: count
-    let pos = view.state.selection().primary();
-    let text = view.state.doc();
+    let pos = cx.view.doc.selection().primary();
+    let text = cx.view.doc.text();
     let line = text.char_to_line(pos.head);
     let start = text.line_to_char(line);
     let end = text.line_to_char(line + 1).saturating_sub(1);
 
-    // TODO: use a transaction
-    view.state.selection = Selection::single(start, end);
+    cx.view.doc.set_selection(Selection::single(start, end));
 }
 
-pub fn delete_selection(view: &mut View, _count: usize) {
-    let transaction =
-        Transaction::change_by_selection(&view.state, |range| (range.from(), range.to() + 1, None));
-    transaction.apply(&mut view.state);
+pub fn delete_selection(cx: &mut Context) {
+    let transaction = Transaction::change_by_selection(&cx.view.doc.state, |range| {
+        (range.from(), range.to() + 1, None)
+    });
+    cx.view.doc.apply(&transaction);
 
-    append_changes_to_history(view);
+    append_changes_to_history(cx);
 }
 
-pub fn change_selection(view: &mut View, count: usize) {
-    delete_selection(view, count);
-    insert_mode(view, count);
+pub fn change_selection(cx: &mut Context) {
+    delete_selection(cx);
+    insert_mode(cx);
 }
 
-pub fn collapse_selection(view: &mut View, _count: usize) {
-    view.state.selection = view
-        .state
-        .selection
-        .transform(|range| Range::new(range.head, range.head))
+pub fn collapse_selection(cx: &mut Context) {
+    let selection = cx
+        .view
+        .doc
+        .selection()
+        .transform(|range| Range::new(range.head, range.head));
+
+    cx.view.doc.set_selection(selection);
 }
 
-pub fn flip_selections(view: &mut View, _count: usize) {
-    view.state.selection = view
-        .state
-        .selection
-        .transform(|range| Range::new(range.head, range.anchor))
+pub fn flip_selections(cx: &mut Context) {
+    let selection = cx
+        .view
+        .doc
+        .selection()
+        .transform(|range| Range::new(range.head, range.anchor));
+
+    cx.view.doc.set_selection(selection);
 }
 
-fn enter_insert_mode(view: &mut View) {
-    view.state.mode = Mode::Insert;
+fn enter_insert_mode(cx: &mut Context) {
+    cx.view.doc.mode = Mode::Insert;
 
-    append_changes_to_history(view);
+    append_changes_to_history(cx);
 }
 // inserts at the start of each selection
-pub fn insert_mode(view: &mut View, _count: usize) {
-    enter_insert_mode(view);
+pub fn insert_mode(cx: &mut Context) {
+    enter_insert_mode(cx);
 
-    view.state.selection = view
-        .state
-        .selection
-        .transform(|range| Range::new(range.to(), range.from()))
+    let selection = cx
+        .view
+        .doc
+        .selection()
+        .transform(|range| Range::new(range.to(), range.from()));
+    cx.view.doc.set_selection(selection);
 }
 
 // inserts at the end of each selection
-pub fn append_mode(view: &mut View, _count: usize) {
-    enter_insert_mode(view);
-    view.state.restore_cursor = true;
+pub fn append_mode(cx: &mut Context) {
+    enter_insert_mode(cx);
+    cx.view.doc.restore_cursor = true;
 
     // TODO: as transaction
-    let text = &view.state.doc.slice(..);
-    view.state.selection = view.state.selection.transform(|range| {
+    let text = &cx.view.doc.text().slice(..);
+    let selection = cx.view.doc.selection().transform(|range| {
         // TODO: to() + next char
         Range::new(
             range.from(),
             graphemes::next_grapheme_boundary(text, range.to()),
         )
-    })
+    });
+    cx.view.doc.set_selection(selection);
 }
 
 // TODO: I, A, o and O can share a lot of the primitives.
-
-pub fn command_mode(_view: &mut View, _count: usize) {
+pub fn command_mode(_cx: &mut Context) {
     unimplemented!()
 }
 
@@ -329,30 +351,30 @@ fn selection_lines(state: &State) -> Vec<usize> {
 }
 
 // I inserts at the start of each line with a selection
-pub fn prepend_to_line(view: &mut View, count: usize) {
-    enter_insert_mode(view);
+pub fn prepend_to_line(cx: &mut Context) {
+    enter_insert_mode(cx);
 
-    move_line_start(view, count);
+    move_line_start(cx);
 }
 
 // A inserts at the end of each line with a selection
-pub fn append_to_line(view: &mut View, count: usize) {
-    enter_insert_mode(view);
+pub fn append_to_line(cx: &mut Context) {
+    enter_insert_mode(cx);
 
-    move_line_end(view, count);
+    move_line_end(cx);
 }
 
 // o inserts a new line after each line with a selection
-pub fn open_below(view: &mut View, _count: usize) {
-    enter_insert_mode(view);
+pub fn open_below(cx: &mut Context) {
+    enter_insert_mode(cx);
 
-    let lines = selection_lines(&view.state);
+    let lines = selection_lines(&cx.view.doc.state);
 
     let positions: Vec<_> = lines
         .into_iter()
         .map(|index| {
             // adjust all positions to the end of the line/start of the next one.
-            view.state.doc.line_to_char(index + 1)
+            cx.view.doc.text().line_to_char(index + 1)
         })
         .collect();
 
@@ -373,111 +395,119 @@ pub fn open_below(view: &mut View, _count: usize) {
         0,
     );
 
-    let transaction = Transaction::change(&view.state, changes).with_selection(selection);
+    let transaction = Transaction::change(&cx.view.doc.state, changes).with_selection(selection);
 
-    transaction.apply(&mut view.state);
+    cx.view.doc.apply(&transaction);
 }
 
 // O inserts a new line before each line with a selection
 
-fn append_changes_to_history(view: &mut View) {
-    if view.state.changes.is_empty() {
+fn append_changes_to_history(cx: &mut Context) {
+    if cx.view.doc.changes.is_empty() {
         return;
     }
 
-    let new_changeset = ChangeSet::new(view.state.doc());
-    let changes = std::mem::replace(&mut view.state.changes, new_changeset);
+    let new_changeset = ChangeSet::new(cx.view.doc.text());
+    let changes = std::mem::replace(&mut cx.view.doc.changes, new_changeset);
     // Instead of doing this messy merge we could always commit, and based on transaction
     // annotations either add a new layer or compose into the previous one.
-    let transaction = Transaction::from(changes).with_selection(view.state.selection().clone());
+    let transaction = Transaction::from(changes).with_selection(cx.view.doc.selection().clone());
 
-    // HAXX: we need to reconstruct the state as it was before the changes..
-    let (doc, selection) = view.state.old_state.take().unwrap();
-    let mut old_state = State::new(doc);
-    old_state.selection = selection;
+    // increment document version
+    // TODO: needs to happen on undo/redo too
+    cx.view.doc.version += 1;
 
+    // TODO: trigger lsp/documentDidChange with changes
+
+    // HAXX: we need to reconstruct the state as it was before the changes..
+    let old_state = std::mem::replace(&mut cx.view.doc.old_state, cx.view.doc.state.clone());
     // TODO: take transaction by value?
-    view.history.commit_revision(&transaction, &old_state);
+    cx.view
+        .doc
+        .history
+        .commit_revision(&transaction, &old_state);
 
-    // TODO: need to start the state with these vals
-    // HAXX
-    view.state.old_state = Some((view.state.doc().clone(), view.state.selection.clone()));
+    // TODO: notify LSP of changes
 }
 
-pub fn normal_mode(view: &mut View, _count: usize) {
-    view.state.mode = Mode::Normal;
+pub fn normal_mode(cx: &mut Context) {
+    cx.view.doc.mode = Mode::Normal;
 
-    append_changes_to_history(view);
+    append_changes_to_history(cx);
 
     // if leaving append mode, move cursor back by 1
-    if view.state.restore_cursor {
-        let text = &view.state.doc.slice(..);
-        view.state.selection = view.state.selection.transform(|range| {
+    if cx.view.doc.restore_cursor {
+        let text = &cx.view.doc.text().slice(..);
+        let selection = cx.view.doc.selection().transform(|range| {
             Range::new(
                 range.from(),
                 graphemes::prev_grapheme_boundary(text, range.to()),
             )
         });
+        cx.view.doc.set_selection(selection);
 
-        view.state.restore_cursor = false;
+        cx.view.doc.restore_cursor = false;
     }
 }
 
-pub fn goto_mode(view: &mut View, _count: usize) {
-    view.state.mode = Mode::Goto;
+pub fn goto_mode(cx: &mut Context) {
+    cx.view.doc.mode = Mode::Goto;
 }
 
 // NOTE: Transactions in this module get appended to history when we switch back to normal mode.
 pub mod insert {
     use super::*;
     // TODO: insert means add text just before cursor, on exit we should be on the last letter.
-    pub fn insert_char(view: &mut View, c: char) {
+    pub fn insert_char(cx: &mut Context, c: char) {
         let c = Tendril::from_char(c);
-        let transaction = Transaction::insert(&view.state, c);
+        let transaction = Transaction::insert(&cx.view.doc.state, c);
 
-        transaction.apply(&mut view.state);
+        cx.view.doc.apply(&transaction);
     }
 
-    pub fn insert_tab(view: &mut View, _count: usize) {
-        insert_char(view, '\t');
+    pub fn insert_tab(cx: &mut Context) {
+        insert_char(cx, '\t');
     }
 
-    pub fn insert_newline(view: &mut View, _count: usize) {
-        let transaction = Transaction::change_by_selection(&view.state, |range| {
-            let indent_level =
-                helix_core::indent::suggested_indent_for_pos(&view.state, range.head);
+    pub fn insert_newline(cx: &mut Context) {
+        let transaction = Transaction::change_by_selection(&cx.view.doc.state, |range| {
+            let indent_level = helix_core::indent::suggested_indent_for_pos(
+                cx.view.doc.syntax.as_ref(),
+                &cx.view.doc.state,
+                range.head,
+            );
             let indent = " ".repeat(TAB_WIDTH).repeat(indent_level);
             let mut text = String::with_capacity(1 + indent.len());
             text.push('\n');
             text.push_str(&indent);
             (range.head, range.head, Some(text.into()))
         });
-        transaction.apply(&mut view.state);
+        cx.view.doc.apply(&transaction);
     }
 
     // TODO: handle indent-aware delete
-    pub fn delete_char_backward(view: &mut View, count: usize) {
-        let text = &view.state.doc.slice(..);
-        let transaction = Transaction::change_by_selection(&view.state, |range| {
+    pub fn delete_char_backward(cx: &mut Context) {
+        let text = &cx.view.doc.text().slice(..);
+        let transaction = Transaction::change_by_selection(&cx.view.doc.state, |range| {
             (
-                graphemes::nth_prev_grapheme_boundary(text, range.head, count),
+                graphemes::nth_prev_grapheme_boundary(text, range.head, cx.count),
                 range.head,
                 None,
             )
         });
-        transaction.apply(&mut view.state);
+        cx.view.doc.apply(&transaction);
     }
 
-    pub fn delete_char_forward(view: &mut View, count: usize) {
-        let text = &view.state.doc.slice(..);
-        let transaction = Transaction::change_by_selection(&view.state, |range| {
+    pub fn delete_char_forward(cx: &mut Context) {
+        let text = &cx.view.doc.text().slice(..);
+        let transaction = Transaction::change_by_selection(&cx.view.doc.state, |range| {
             (
                 range.head,
-                graphemes::nth_next_grapheme_boundary(text, range.head, count),
+                graphemes::nth_next_grapheme_boundary(text, range.head, cx.count),
                 None,
             )
         });
-        transaction.apply(&mut view.state);
+        cx.view.doc.apply(&transaction);
     }
 }
 
@@ -487,24 +517,32 @@ pub fn insert_char_prompt(prompt: &mut Prompt, c: char) {
 
 // Undo / Redo
 
-pub fn undo(view: &mut View, _count: usize) {
-    view.history.undo(&mut view.state);
+pub fn undo(cx: &mut Context) {
+    if let Some(revert) = cx.view.doc.history.undo() {
+        cx.view.doc.version += 1;
+        cx.view.doc.apply(&revert);
+    }
 
     // TODO: each command could simply return a Option<transaction>, then the higher level handles storing it?
 }
 
-pub fn redo(view: &mut View, _count: usize) {
-    view.history.redo(&mut view.state);
+pub fn redo(cx: &mut Context) {
+    if let Some(transaction) = cx.view.doc.history.redo() {
+        cx.view.doc.version += 1;
+        cx.view.doc.apply(&transaction);
+    }
 }
 
 // Yank / Paste
 
-pub fn yank(view: &mut View, _count: usize) {
+pub fn yank(cx: &mut Context) {
     // TODO: should selections be made end inclusive?
-    let values = view
+    let values = cx
+        .view
+        .doc
         .state
         .selection()
-        .fragments(&view.state.doc().slice(..))
+        .fragments(&cx.view.doc.text().slice(..))
         .map(|cow| cow.into_owned())
         .collect();
 
@@ -513,7 +551,7 @@ pub fn yank(view: &mut View, _count: usize) {
     register::set(reg, values);
 }
 
-pub fn paste(view: &mut View, _count: usize) {
+pub fn paste(cx: &mut Context) {
     // TODO: allow specifying reg
     let reg = '"';
     if let Some(values) = register::get(reg) {
@@ -545,19 +583,19 @@ pub fn paste(view: &mut View, _count: usize) {
         let transaction = if linewise {
             // paste on the next line
             // TODO: can simply take a range + modifier and compute the right pos without ifs
-            let text = view.state.doc();
-            Transaction::change_by_selection(&view.state, |range| {
+            let text = cx.view.doc.text();
+            Transaction::change_by_selection(&cx.view.doc.state, |range| {
                 let line_end = text.line_to_char(text.char_to_line(range.head) + 1);
                 (line_end, line_end, Some(values.next().unwrap()))
             })
         } else {
-            Transaction::change_by_selection(&view.state, |range| {
+            Transaction::change_by_selection(&cx.view.doc.state, |range| {
                 (range.head + 1, range.head + 1, Some(values.next().unwrap()))
             })
         };
 
-        transaction.apply(&mut view.state);
-        append_changes_to_history(view);
+        cx.view.doc.apply(&transaction);
+        append_changes_to_history(cx);
     }
 }
 
@@ -565,9 +603,9 @@ fn get_lines(view: &View) -> Vec<usize> {
     let mut lines = Vec::new();
 
     // Get all line numbers
-    for range in view.state.selection.ranges() {
-        let start = view.state.doc.char_to_line(range.from());
-        let end = view.state.doc.char_to_line(range.to());
+    for range in view.doc.selection().ranges() {
+        let start = view.doc.text().char_to_line(range.from());
+        let end = view.doc.text().char_to_line(range.to());
 
         for line in start..=end {
             lines.push(line)
@@ -578,29 +616,29 @@ fn get_lines(view: &View) -> Vec<usize> {
     lines
 }
 
-pub fn indent(view: &mut View, _count: usize) {
-    let lines = get_lines(view);
+pub fn indent(cx: &mut Context) {
+    let lines = get_lines(cx.view);
 
     // Indent by one level
     let indent = Tendril::from(" ".repeat(TAB_WIDTH));
 
     let transaction = Transaction::change(
-        &view.state,
+        &cx.view.doc.state,
         lines.into_iter().map(|line| {
-            let pos = view.state.doc.line_to_char(line);
+            let pos = cx.view.doc.text().line_to_char(line);
             (pos, pos, Some(indent.clone()))
         }),
     );
-    transaction.apply(&mut view.state);
-    append_changes_to_history(view);
+    cx.view.doc.apply(&transaction);
+    append_changes_to_history(cx);
 }
 
-pub fn unindent(view: &mut View, _count: usize) {
-    let lines = get_lines(view);
+pub fn unindent(cx: &mut Context) {
+    let lines = get_lines(cx.view);
     let mut changes = Vec::with_capacity(lines.len());
 
     for line_idx in lines {
-        let line = view.state.doc.line(line_idx);
+        let line = cx.view.doc.text().line(line_idx);
         let mut width = 0;
 
         for ch in line.chars() {
@@ -616,18 +654,27 @@ pub fn unindent(view: &mut View, _count: usize) {
         }
 
         if width > 0 {
-            let start = view.state.doc.line_to_char(line_idx);
+            let start = cx.view.doc.text().line_to_char(line_idx);
             changes.push((start, start + width, None))
         }
     }
 
-    let transaction = Transaction::change(&view.state, changes.into_iter());
+    let transaction = Transaction::change(&cx.view.doc.state, changes.into_iter());
 
-    transaction.apply(&mut view.state);
-    append_changes_to_history(view);
+    cx.view.doc.apply(&transaction);
+    append_changes_to_history(cx);
 }
 
-pub fn indent_selection(_view: &mut View, _count: usize) {
+pub fn indent_selection(_cx: &mut Context) {
     // loop over each line and recompute proper indentation
     unimplemented!()
 }
+
+//
+
+pub fn save(cx: &mut Context) {
+    // Spawns an async task to actually do the saving. This way we prevent blocking.
+
+    // TODO: handle save errors somehow?
+    cx.executor.spawn(cx.view.doc.save()).detach();
+}
diff --git a/helix-view/src/document.rs b/helix-view/src/document.rs
new file mode 100644
index 00000000..7c4596ad
--- /dev/null
+++ b/helix-view/src/document.rs
@@ -0,0 +1,209 @@
+use anyhow::Error;
+use std::future::Future;
+use std::path::PathBuf;
+
+use helix_core::{
+    syntax::LOADER, ChangeSet, Diagnostic, History, Position, Range, Rope, RopeSlice, Selection,
+    State, Syntax, Transaction,
+};
+
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
+pub enum Mode {
+    Normal,
+    Insert,
+    Goto,
+}
+
+pub struct Document {
+    pub state: State, // rope + selection
+    /// File path on disk.
+    pub path: Option<PathBuf>,
+
+    /// Current editing mode.
+    pub mode: Mode,
+    pub restore_cursor: bool,
+
+    /// Tree-sitter AST tree
+    pub syntax: Option<Syntax>,
+    /// Corresponding language scope name. Usually `source.<lang>`.
+    pub language: Option<String>,
+
+    /// Pending changes since last history commit.
+    pub changes: ChangeSet,
+    pub old_state: State,
+    pub history: History,
+    pub version: i32, // should be usize?
+
+    pub diagnostics: Vec<Diagnostic>,
+}
+
+/// Like std::mem::replace() except it allows the replacement value to be mapped from the
+/// original value.
+fn take_with<T, F>(mut_ref: &mut T, closure: F)
+where
+    F: FnOnce(T) -> T,
+{
+    use std::{panic, ptr};
+
+    unsafe {
+        let old_t = ptr::read(mut_ref);
+        let new_t = panic::catch_unwind(panic::AssertUnwindSafe(|| closure(old_t)))
+            .unwrap_or_else(|_| ::std::process::abort());
+        ptr::write(mut_ref, new_t);
+    }
+}
+
+use url::Url;
+
+impl Document {
+    fn new(state: State) -> Self {
+        let changes = ChangeSet::new(&state.doc);
+        let old_state = state.clone();
+
+        Self {
+            path: None,
+            state,
+            mode: Mode::Normal,
+            restore_cursor: false,
+            syntax: None,
+            language: None,
+            changes,
+            old_state,
+            diagnostics: Vec::new(),
+            version: 0,
+            history: History::default(),
+        }
+    }
+
+    // TODO: passing scopes here is awkward
+    // TODO: async fn?
+    pub fn load(path: PathBuf, scopes: &[String]) -> Result<Self, Error> {
+        use std::{env, fs::File, io::BufReader};
+        let _current_dir = env::current_dir()?;
+
+        let doc = Rope::from_reader(BufReader::new(File::open(path.clone())?))?;
+
+        // TODO: create if not found
+
+        let mut doc = Self::new(State::new(doc));
+
+        if let Some(language_config) = LOADER.language_config_for_file_name(path.as_path()) {
+            let highlight_config = language_config.highlight_config(scopes).unwrap().unwrap();
+            // TODO: config.configure(scopes) is now delayed, is that ok?
+
+            let syntax = Syntax::new(&doc.state.doc, highlight_config.clone());
+
+            doc.syntax = Some(syntax);
+            // TODO: maybe just keep an Arc<> pointer to the language_config?
+            doc.language = Some(language_config.scope().to_string());
+
+            // TODO: this ties lsp support to tree-sitter enabled languages for now. Language
+            // config should use Option<HighlightConfig> to let us have non-tree-sitter configs.
+
+            // TODO: circular dep: view <-> lsp
+            // helix_lsp::REGISTRY;
+            // view should probably depend on lsp
+        };
+
+        // canonicalize path to absolute value
+        doc.path = Some(std::fs::canonicalize(path)?);
+
+        Ok(doc)
+    }
+
+    // TODO: do we need some way of ensuring two save operations on the same doc can't run at once?
+    // or is that handled by the OS/async layer
+    pub fn save(&self) -> impl Future<Output = Result<(), anyhow::Error>> {
+        // we clone and move text + path into the future so that we asynchronously save the current
+        // state without blocking any further edits.
+
+        let text = self.text().clone();
+        let path = self.path.clone().expect("Can't save with no path set!"); // TODO: handle no path
+
+        // TODO: mark changes up to now as saved
+        // TODO: mark dirty false
+
+        async move {
+            use smol::{fs::File, prelude::*};
+            let mut file = File::create(path).await?;
+
+            // write all the rope chunks to file
+            for chunk in text.chunks() {
+                file.write_all(chunk.as_bytes()).await?;
+            }
+            // TODO: flush?
+
+            Ok(())
+        } // and_then(// lsp.send_text_saved_notification())
+    }
+
+    pub fn set_language(&mut self, scope: &str, scopes: &[String]) {
+        if let Some(language_config) = LOADER.language_config_for_scope(scope) {
+            let highlight_config = language_config.highlight_config(scopes).unwrap().unwrap();
+            // TODO: config.configure(scopes) is now delayed, is that ok?
+
+            let syntax = Syntax::new(&self.state.doc, highlight_config.clone());
+
+            self.syntax = Some(syntax);
+        };
+    }
+
+    pub fn set_selection(&mut self, selection: Selection) {
+        // TODO: use a transaction?
+        self.state.selection = selection;
+    }
+
+    pub fn apply(&mut self, transaction: &Transaction) -> bool {
+        let old_doc = self.text().clone();
+
+        let success = transaction.apply(&mut self.state);
+
+        if !transaction.changes().is_empty() {
+            // Compose this transaction with the previous one
+            take_with(&mut self.changes, |changes| {
+                changes.compose(transaction.changes().clone()).unwrap()
+            });
+
+            // TODO: when composing, replace transaction.selection too
+
+            // update tree-sitter syntax tree
+            if let Some(syntax) = &mut self.syntax {
+                // TODO: no unwrap
+                syntax
+                    .update(&old_doc, &self.state.doc, transaction.changes())
+                    .unwrap();
+            }
+
+            // TODO: map state.diagnostics over changes::map_pos too
+        }
+        success
+    }
+
+    #[inline]
+    pub fn mode(&self) -> Mode {
+        self.mode
+    }
+
+    #[inline]
+    pub fn path(&self) -> Option<&PathBuf> {
+        self.path.as_ref()
+    }
+
+    pub fn url(&self) -> Option<Url> {
+        self.path().map(|path| Url::from_file_path(path).unwrap())
+    }
+
+    pub fn text(&self) -> &Rope {
+        &self.state.doc
+    }
+
+    pub fn selection(&self) -> &Selection {
+        &self.state.selection
+    }
+
+    // pub fn slice<R>(&self, range: R) -> RopeSlice where R: RangeBounds {
+    //     self.state.doc.slice
+    // }
+
+    // TODO: transact(Fn) ?
+}
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index c292caed..9fb2ae36 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -1,24 +1,48 @@
-use crate::View;
+use crate::theme::Theme;
+use crate::{Document, View};
 
 use std::path::PathBuf;
 
 use anyhow::Error;
 
 pub struct Editor {
-    pub view: Option<View>,
+    pub views: Vec<View>,
+    pub focus: usize,
     pub should_close: bool,
+    pub theme: Theme, // TODO: share one instance
+}
+
+impl Default for Editor {
+    fn default() -> Self {
+        Self::new()
+    }
 }
 
 impl Editor {
     pub fn new() -> Self {
+        let theme = Theme::default();
+
         Self {
-            view: None,
+            views: Vec::new(),
+            focus: 0,
             should_close: false,
+            theme,
         }
     }
 
     pub fn open(&mut self, path: PathBuf, size: (u16, u16)) -> Result<(), Error> {
-        self.view = Some(View::open(path, size)?);
+        let pos = self.views.len();
+        let doc = Document::load(path, self.theme.scopes())?;
+        self.views.push(View::new(doc, size)?);
+        self.focus = pos;
         Ok(())
     }
+
+    pub fn view(&self) -> Option<&View> {
+        self.views.get(self.focus)
+    }
+
+    pub fn view_mut(&mut self) -> Option<&mut View> {
+        self.views.get_mut(self.focus)
+    }
 }
diff --git a/helix-view/src/keymap.rs b/helix-view/src/keymap.rs
index 69e6cabb..c815911e 100644
--- a/helix-view/src/keymap.rs
+++ b/helix-view/src/keymap.rs
@@ -1,5 +1,6 @@
 use crate::commands::{self, Command};
-use helix_core::{hashmap, state};
+use crate::document::Mode;
+use helix_core::hashmap;
 use std::collections::HashMap;
 
 // Kakoune-inspired:
@@ -81,14 +82,17 @@ use std::collections::HashMap;
 //          = = align?
 //          + =
 //      }
+//
+//      gd = goto definition
+//      gr = goto reference
 // }
 
 #[cfg(feature = "term")]
 pub use crossterm::event::{KeyCode, KeyEvent as Key, KeyModifiers as Modifiers};
 
 // TODO: could be trie based
-type Keymap = HashMap<Vec<Key>, Command>;
-type Keymaps = HashMap<state::Mode, Keymap>;
+pub type Keymap = HashMap<Vec<Key>, Command>;
+pub type Keymaps = HashMap<Mode, Keymap>;
 
 macro_rules! key {
     ($ch:expr) => {
@@ -128,7 +132,7 @@ macro_rules! ctrl {
 
 pub fn default() -> Keymaps {
     hashmap!(
-        state::Mode::Normal =>
+        Mode::Normal =>
             // as long as you cast the first item, rust is able to infer the other cases
             hashmap!(
                 vec![key!('h')] => commands::move_char_left as Command,
@@ -179,7 +183,7 @@ pub fn default() -> Keymaps {
                 vec![ctrl!('u')] => commands::half_page_up,
                 vec![ctrl!('d')] => commands::half_page_down,
             ),
-            state::Mode::Insert => hashmap!(
+            Mode::Insert => hashmap!(
                 vec![Key {
                     code: KeyCode::Esc,
                     modifiers: Modifiers::NONE
@@ -201,7 +205,7 @@ pub fn default() -> Keymaps {
                     modifiers: Modifiers::NONE
                 }] => commands::insert::insert_tab,
             ),
-            state::Mode::Goto => hashmap!(
+            Mode::Goto => hashmap!(
                 vec![Key {
                     code: KeyCode::Esc,
                     modifiers: Modifiers::NONE
diff --git a/helix-view/src/lib.rs b/helix-view/src/lib.rs
index 8ea634af..3b923744 100644
--- a/helix-view/src/lib.rs
+++ b/helix-view/src/lib.rs
@@ -1,9 +1,12 @@
 pub mod commands;
+pub mod document;
 pub mod editor;
 pub mod keymap;
 pub mod prompt;
 pub mod theme;
 pub mod view;
 
+pub use document::Document;
 pub use editor::Editor;
+pub use theme::Theme;
 pub use view::View;
diff --git a/helix-view/src/theme.rs b/helix-view/src/theme.rs
index 4cc399ed..809ec05d 100644
--- a/helix-view/src/theme.rs
+++ b/helix-view/src/theme.rs
@@ -157,6 +157,8 @@ impl Default for Theme {
             "ui.background" => Style::default().bg(Color::Rgb(59, 34, 76)), // midnight
             "ui.linenr" => Style::default().fg(Color::Rgb(90, 89, 119)), // comet
             "ui.statusline" => Style::default().bg(Color::Rgb(40, 23, 51)), // revolver
+
+            "warning" => Style::default().fg(Color::Rgb(255, 205, 28)),
         };
 
         let scopes = mapping.keys().map(ToString::to_string).collect();
diff --git a/helix-view/src/view.rs b/helix-view/src/view.rs
index 2b68dbc3..df41e3ae 100644
--- a/helix-view/src/view.rs
+++ b/helix-view/src/view.rs
@@ -1,44 +1,39 @@
 use anyhow::Error;
 
-use std::{borrow::Cow, path::PathBuf};
+use std::borrow::Cow;
 
-use crate::theme::Theme;
+use crate::Document;
 use helix_core::{
     graphemes::{grapheme_width, RopeGraphemes},
     indent::TAB_WIDTH,
-    History, Position, RopeSlice, State,
+    Position, RopeSlice,
 };
 use tui::layout::Rect;
 
 pub const PADDING: usize = 5;
 
+// TODO: view should be View { doc: Document(state, history,..) }
+// since we can have multiple views into the same file
 pub struct View {
-    pub state: State,
-    pub history: History,
+    pub doc: Document,
     pub first_line: usize,
     pub size: (u16, u16),
-    pub theme: Theme, // TODO: share one instance
 }
 
 impl View {
-    pub fn open(path: PathBuf, size: (u16, u16)) -> Result<Self, Error> {
-        let theme = Theme::default();
-        let state = State::load(path, theme.scopes())?;
-
+    pub fn new(doc: Document, size: (u16, u16)) -> Result<Self, Error> {
         let view = Self {
-            state,
+            doc,
             first_line: 0,
             size,
-            theme,
-            history: History::default(),
         };
 
         Ok(view)
     }
 
     pub fn ensure_cursor_in_view(&mut self) {
-        let cursor = self.state.selection().cursor();
-        let line = self.state.doc().char_to_line(cursor);
+        let cursor = self.doc.state.selection().cursor();
+        let line = self.doc.text().char_to_line(cursor);
         let document_end = self.first_line + (self.size.1 as usize).saturating_sub(2);
 
         // TODO: side scroll
@@ -58,7 +53,7 @@ impl View {
         let viewport = Rect::new(6, 0, self.size.0, self.size.1 - 2); // - 2 for statusline and prompt
         std::cmp::min(
             self.first_line + (viewport.height as usize),
-            self.state.doc().len_lines() - 1,
+            self.doc.text().len_lines() - 1,
         )
     }
 
@@ -90,4 +85,25 @@ impl View {
 
         Some(Position::new(row, col))
     }
+
+    // pub fn traverse<F>(&self, text: &RopeSlice, start: usize, end: usize, fun: F)
+    // where
+    //     F: Fn(usize, usize),
+    // {
+    //     let start = self.screen_coords_at_pos(text, start);
+    //     let end = self.screen_coords_at_pos(text, end);
+
+    //     match (start, end) {
+    //         // fully on screen
+    //         (Some(start), Some(end)) => {
+    //             // we want to calculate ends of lines for each char..
+    //         }
+    //         // from start to end of screen
+    //         (Some(start), None) => {}
+    //         // from start of screen to end
+    //         (None, Some(end)) => {}
+    //         // not on screen
+    //         (None, None) => return,
+    //     }
+    // }
 }