move commands and keymap back to terminal.

Command needs to be able to deal with UI. We'll separate it again later
on.

7 files changed, 1052 insertions, 30 deletions

diff --git a/helix-term/Cargo.toml b/helix-term/Cargo.toml
index c1560ee7..b8eea7c2 100644
--- a/helix-term/Cargo.toml
+++ b/helix-term/Cargo.toml
@@ -17,6 +17,7 @@ helix-view = { path = "../helix-view", features = ["term"]}
 helix-lsp = { path = "../helix-lsp"}
 
 anyhow = "1"
+once_cell = "1.4"
 
 smol = "1"
 num_cpus = "1"
diff --git a/helix-term/src/application.rs b/helix-term/src/application.rs
index 506735e8..8c454b5d 100644
--- a/helix-term/src/application.rs
+++ b/helix-term/src/application.rs
@@ -1,14 +1,14 @@
-use clap::ArgMatches as Args;
-use helix_core::{indent::TAB_WIDTH, syntax::HighlightEvent, Position, Range, State};
-use helix_view::{
+use crate::{
     commands,
-    document::Mode,
     keymap::{self, Keymaps},
-    prompt::Prompt,
-    Document, Editor, Theme, View,
 };
+use clap::ArgMatches as Args;
+use helix_core::{indent::TAB_WIDTH, syntax::HighlightEvent, Position, Range, State};
+
+use helix_view::{document::Mode, Document, Editor, Theme, View};
 
 use crate::compositor::{Component, Compositor, EventResult};
+use crate::prompt::Prompt;
 
 use log::{debug, info};
 
@@ -395,23 +395,16 @@ impl Component for EditorView {
                 EventResult::Consumed(None)
             }
             Event::Key(event) => {
-                // if there's a prompt, it takes priority
-                if let Some(prompt) = &mut self.prompt {
-                    self.prompt
-                        .as_mut()
-                        .unwrap()
-                        .handle_input(event, &mut self.editor);
-                    EventResult::Consumed(None)
-                } else if let Some(view) = self.editor.view_mut() {
+                if let Some(view) = self.editor.view_mut() {
                     let keys = vec![event];
                     // TODO: sequences (`gg`)
                     // TODO: handle count other than 1
                     match view.doc.mode() {
                         Mode::Insert => {
                             if let Some(command) = self.keymap[&Mode::Insert].get(&keys) {
-                                let mut cx = helix_view::commands::Context {
+                                let mut cx = commands::Context {
                                     view,
-                                    executor: executor,
+                                    executor,
                                     count: 1,
                                 };
 
@@ -421,9 +414,9 @@ impl Component for EditorView {
                                 ..
                             } = event
                             {
-                                let mut cx = helix_view::commands::Context {
+                                let mut cx = commands::Context {
                                     view,
-                                    executor: executor,
+                                    executor,
                                     count: 1,
                                 };
                                 commands::insert::insert_char(&mut cx, c);
@@ -488,9 +481,9 @@ impl Component for EditorView {
 
                             // HAXX: special casing for command mode
                             } else if let Some(command) = self.keymap[&Mode::Normal].get(&keys) {
-                                let mut cx = helix_view::commands::Context {
+                                let mut cx = commands::Context {
                                     view,
-                                    executor: executor,
+                                    executor,
                                     count: 1,
                                 };
                                 command(&mut cx);
@@ -501,9 +494,9 @@ impl Component for EditorView {
                         }
                         mode => {
                             if let Some(command) = self.keymap[&mode].get(&keys) {
-                                let mut cx = helix_view::commands::Context {
+                                let mut cx = commands::Context {
                                     view,
-                                    executor: executor,
+                                    executor,
                                     count: 1,
                                 };
                                 command(&mut cx);
@@ -530,13 +523,6 @@ impl Component for EditorView {
         let theme_ref = unsafe { &*(&self.editor.theme as *const Theme) };
         if let Some(view) = self.editor.view_mut() {
             renderer.render_view(view, viewport, theme_ref);
-            if let Some(prompt) = &self.prompt {
-                if prompt.should_close {
-                    self.prompt = None;
-                } else {
-                    renderer.render_prompt(view, prompt, theme_ref);
-                }
-            }
         }
 
         // TODO: drop unwrap
@@ -562,7 +548,6 @@ impl<'a> Application<'a> {
             renderer,
             // TODO; move to state
             compositor,
-            prompt: None,
 
             executor,
             language_server,
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
new file mode 100644
index 00000000..a791f243
--- /dev/null
+++ b/helix-term/src/commands.rs
@@ -0,0 +1,682 @@
+use helix_core::{
+    graphemes,
+    indent::TAB_WIDTH,
+    regex::Regex,
+    register, selection,
+    state::{Direction, Granularity, State},
+    ChangeSet, Range, Selection, Tendril, Transaction,
+};
+
+use once_cell::sync::Lazy;
+
+use crate::prompt::Prompt;
+
+use helix_view::{
+    document::Mode,
+    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(cx: &mut Context);
+
+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(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(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(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(cx: &mut Context) {
+    let lines = selection_lines(&cx.view.doc.state);
+
+    let positions = lines
+        .into_iter()
+        .map(|index| {
+            // adjust all positions to the end of the line.
+
+            // Line end is pos at the start of next line - 1
+            // subtract another 1 because the line ends with \n
+            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);
+
+    cx.view.doc.set_selection(selection);
+}
+
+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.
+            cx.view.doc.text().line_to_char(index)
+        })
+        .map(|pos| Range::new(pos, pos));
+
+    let selection = Selection::new(positions.collect(), 0);
+
+    cx.view.doc.set_selection(selection);
+}
+
+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,
+        cx.count,
+    );
+
+    cx.view.doc.set_selection(Selection::point(pos));
+}
+
+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,
+        cx.count,
+    );
+
+    cx.view.doc.set_selection(Selection::point(pos));
+}
+
+pub fn move_next_word_end(cx: &mut Context) {
+    let pos = State::move_next_word_end(
+        &cx.view.doc.text().slice(..),
+        cx.view.doc.selection().cursor(),
+        cx.count,
+    );
+
+    cx.view.doc.set_selection(Selection::point(pos));
+}
+
+pub fn move_file_start(cx: &mut Context) {
+    cx.view.doc.set_selection(Selection::point(0));
+
+    cx.view.doc.mode = Mode::Normal;
+}
+
+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));
+    cx.view.doc.set_selection(Selection::point(last_line));
+
+    cx.view.doc.mode = Mode::Normal;
+}
+
+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) {
+        return false;
+    }
+    true
+}
+
+pub fn page_up(cx: &mut Context) {
+    if cx.view.first_line < PADDING {
+        return;
+    }
+
+    cx.view.first_line = cx.view.first_line.saturating_sub(cx.view.size.1 as usize);
+
+    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(cx: &mut Context) {
+    cx.view.first_line += cx.view.size.1 as usize + PADDING;
+
+    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(cx: &mut Context) {
+    if cx.view.first_line < PADDING {
+        return;
+    }
+
+    cx.view.first_line = cx
+        .view
+        .first_line
+        .saturating_sub(cx.view.size.1 as usize / 2);
+
+    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(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(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(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(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(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(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(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());
+    let selection = selection::split_on_matches(text, cx.view.doc.selection(), &REGEX);
+    cx.view.doc.set_selection(selection);
+}
+
+pub fn select_line(cx: &mut Context) {
+    // TODO: count
+    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);
+
+    cx.view.doc.set_selection(Selection::single(start, end));
+}
+
+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(cx);
+}
+
+pub fn change_selection(cx: &mut Context) {
+    delete_selection(cx);
+    insert_mode(cx);
+}
+
+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(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(cx: &mut Context) {
+    cx.view.doc.mode = Mode::Insert;
+
+    append_changes_to_history(cx);
+}
+// inserts at the start of each selection
+pub fn insert_mode(cx: &mut Context) {
+    enter_insert_mode(cx);
+
+    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(cx: &mut Context) {
+    enter_insert_mode(cx);
+    cx.view.doc.restore_cursor = true;
+
+    // TODO: as transaction
+    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(_cx: &mut Context) {
+    unimplemented!()
+}
+
+// calculate line numbers for each selection range
+fn selection_lines(state: &State) -> Vec<usize> {
+    let mut lines = state
+        .selection
+        .ranges()
+        .iter()
+        .map(|range| state.doc.char_to_line(range.head))
+        .collect::<Vec<_>>();
+
+    lines.sort_unstable(); // sorting by usize so _unstable is preferred
+    lines.dedup();
+
+    lines
+}
+
+// I inserts at the start of each line with a selection
+pub fn prepend_to_line(cx: &mut Context) {
+    enter_insert_mode(cx);
+
+    move_line_start(cx);
+}
+
+// A inserts at the end of each line with a selection
+pub fn append_to_line(cx: &mut Context) {
+    enter_insert_mode(cx);
+
+    move_line_end(cx);
+}
+
+// o inserts a new line after each line with a selection
+pub fn open_below(cx: &mut Context) {
+    enter_insert_mode(cx);
+
+    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.
+            cx.view.doc.text().line_to_char(index + 1)
+        })
+        .collect();
+
+    // TODO: use same logic as insert_newline for indentation
+    let changes = positions.iter().copied().map(|index|
+        // generate changes
+        (index, index, Some(Tendril::from_char('\n'))));
+
+    // TODO: count actually inserts "n" new lines and starts editing on all of them.
+    // TODO: append "count" newlines and modify cursors to those lines
+
+    let selection = Selection::new(
+        positions
+            .iter()
+            .copied()
+            .map(|pos| Range::new(pos, pos))
+            .collect(),
+        0,
+    );
+
+    let transaction = Transaction::change(&cx.view.doc.state, changes).with_selection(selection);
+
+    cx.view.doc.apply(&transaction);
+}
+
+// O inserts a new line before each line with a selection
+
+fn append_changes_to_history(cx: &mut Context) {
+    if cx.view.doc.changes.is_empty() {
+        return;
+    }
+
+    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(cx.view.doc.selection().clone());
+
+    // 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?
+    cx.view
+        .doc
+        .history
+        .commit_revision(&transaction, &old_state);
+
+    // TODO: notify LSP of changes
+}
+
+pub fn normal_mode(cx: &mut Context) {
+    cx.view.doc.mode = Mode::Normal;
+
+    append_changes_to_history(cx);
+
+    // if leaving append mode, move cursor back by 1
+    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);
+
+        cx.view.doc.restore_cursor = false;
+    }
+}
+
+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(cx: &mut Context, c: char) {
+        let c = Tendril::from_char(c);
+        let transaction = Transaction::insert(&cx.view.doc.state, c);
+
+        cx.view.doc.apply(&transaction);
+    }
+
+    pub fn insert_tab(cx: &mut Context) {
+        insert_char(cx, '\t');
+    }
+
+    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()))
+        });
+        cx.view.doc.apply(&transaction);
+    }
+
+    // TODO: handle indent-aware delete
+    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, cx.count),
+                range.head,
+                None,
+            )
+        });
+        cx.view.doc.apply(&transaction);
+    }
+
+    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, cx.count),
+                None,
+            )
+        });
+        cx.view.doc.apply(&transaction);
+    }
+}
+
+pub fn insert_char_prompt(prompt: &mut Prompt, c: char) {
+    prompt.insert_char(c);
+}
+
+// Undo / Redo
+
+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(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(cx: &mut Context) {
+    // TODO: should selections be made end inclusive?
+    let values = cx
+        .view
+        .doc
+        .state
+        .selection()
+        .fragments(&cx.view.doc.text().slice(..))
+        .map(|cow| cow.into_owned())
+        .collect();
+
+    // TODO: allow specifying reg
+    let reg = '"';
+    register::set(reg, values);
+}
+
+pub fn paste(cx: &mut Context) {
+    // TODO: allow specifying reg
+    let reg = '"';
+    if let Some(values) = register::get(reg) {
+        let repeat = std::iter::repeat(
+            values
+                .last()
+                .map(|value| Tendril::from_slice(value))
+                .unwrap(),
+        );
+
+        // TODO: if any of values ends \n it's linewise paste
+        //
+        // p => paste after
+        // P => paste before
+        // alt-p => paste every yanked selection after selected text
+        // alt-P => paste every yanked selection before selected text
+        // R => replace selected text with yanked text
+        // alt-R => replace selected text with every yanked text
+        //
+        // append => insert at next line
+        // insert => insert at start of line
+        // replace => replace
+        // default insert
+
+        let linewise = values.iter().any(|value| value.ends_with('\n'));
+
+        let mut values = values.into_iter().map(Tendril::from).chain(repeat);
+
+        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 = 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(&cx.view.doc.state, |range| {
+                (range.head + 1, range.head + 1, Some(values.next().unwrap()))
+            })
+        };
+
+        cx.view.doc.apply(&transaction);
+        append_changes_to_history(cx);
+    }
+}
+
+fn get_lines(view: &View) -> Vec<usize> {
+    let mut lines = Vec::new();
+
+    // Get all line numbers
+    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)
+        }
+    }
+    lines.sort_unstable(); // sorting by usize so _unstable is preferred
+    lines.dedup();
+    lines
+}
+
+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(
+        &cx.view.doc.state,
+        lines.into_iter().map(|line| {
+            let pos = cx.view.doc.text().line_to_char(line);
+            (pos, pos, Some(indent.clone()))
+        }),
+    );
+    cx.view.doc.apply(&transaction);
+    append_changes_to_history(cx);
+}
+
+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 = cx.view.doc.text().line(line_idx);
+        let mut width = 0;
+
+        for ch in line.chars() {
+            match ch {
+                ' ' => width += 1,
+                '\t' => width = (width / TAB_WIDTH + 1) * TAB_WIDTH,
+                _ => break,
+            }
+
+            if width >= TAB_WIDTH {
+                break;
+            }
+        }
+
+        if width > 0 {
+            let start = cx.view.doc.text().line_to_char(line_idx);
+            changes.push((start, start + width, None))
+        }
+    }
+
+    let transaction = Transaction::change(&cx.view.doc.state, changes.into_iter());
+
+    cx.view.doc.apply(&transaction);
+    append_changes_to_history(cx);
+}
+
+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-term/src/compositor.rs b/helix-term/src/compositor.rs
index f859f947..158a8b28 100644
--- a/helix-term/src/compositor.rs
+++ b/helix-term/src/compositor.rs
@@ -20,6 +20,14 @@ use tui::buffer::Buffer as Surface;
 
 pub(crate) type Callback = Box<dyn Fn(&mut Compositor)>;
 
+// --> EventResult should have a callback that takes a context with methods like .popup(),
+// .prompt() etc. That way we can abstract it from the renderer.
+// Q: How does this interact with popups where we need to be able to specify the rendering of the
+// popup?
+// A: It could just take a textarea.
+//
+// If Compositor was specified in the callback that's then problematic because of
+
 // Cursive-inspired
 pub(crate) enum EventResult {
     Ignored,
diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
new file mode 100644
index 00000000..af46f7a4
--- /dev/null
+++ b/helix-term/src/keymap.rs
@@ -0,0 +1,217 @@
+use crate::commands::{self, Command};
+use helix_core::hashmap;
+use helix_view::document::Mode;
+use std::collections::HashMap;
+
+// Kakoune-inspired:
+// mode = {
+//      normal = {
+//          q = record_macro
+//          w = (next) word
+//          W = next WORD
+//          e = end of word
+//          E = end of WORD
+//          r =
+//          t = 'till char
+//          y = yank
+//          u = undo
+//          U = redo
+//          i = insert
+//          I = INSERT (start of line)
+//          o = open below (insert on new line below)
+//          O = open above (insert on new line above)
+//          p = paste (before cursor)
+//          P = PASTE (after cursor)
+//          ` =
+//          [ = select to text object start (alt = select whole object)
+//          ] = select to text object end
+//          { = extend to inner object start
+//          } = extend to inner object end
+//          a = append
+//          A = APPEND (end of line)
+//          s = split
+//          S = select
+//          d = delete()
+//          f = find_char()
+//          g = goto (gg, G, gc, gd, etc)
+//
+//          h = move_char_left(n)
+//          j = move_line_down(n)
+//          k = move_line_up(n)
+//          l = move_char_right(n)
+//          : = command line
+//          ; = collapse selection to cursor
+//          " = use register
+//          ` = convert case? (to lower) (alt = swap case)
+//          ~ = convert to upper case
+//          . = repeat last command
+//          \ = disable hook?
+//          / = search
+//          > = indent
+//          < = deindent
+//          % = select whole buffer (in vim = jump to matching bracket)
+//          * = search pattern in selection
+//          ( = rotate main selection backward
+//          ) = rotate main selection forward
+//          - = trim selections? (alt = merge contiguous sel together)
+//          @ = convert tabs to spaces
+//          & = align cursor
+//          ? = extend to next given regex match (alt = to prev)
+//
+//          in kakoune these are alt-h alt-l / gh gl
+//                              select from curs to begin end / move curs to begin end
+//          0 = start of line
+//          ^ = start of line (first non blank char)
+//          $ = end of line
+//
+//          z = save selections
+//          Z = restore selections
+//          x = select line
+//          X = extend line
+//          c = change selected text
+//          C = copy selection?
+//          v = view menu (viewport manipulation)
+//          b = select to previous word start
+//          B = select to previous WORD start
+//
+//
+//
+//
+//
+//
+//          = = 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
+pub type Keymap = HashMap<Vec<Key>, Command>;
+pub type Keymaps = HashMap<Mode, Keymap>;
+
+macro_rules! key {
+    ($ch:expr) => {
+        Key {
+            code: KeyCode::Char($ch),
+            modifiers: Modifiers::NONE,
+        }
+    };
+}
+
+macro_rules! shift {
+    ($ch:expr) => {
+        Key {
+            code: KeyCode::Char($ch),
+            modifiers: Modifiers::SHIFT,
+        }
+    };
+}
+
+macro_rules! ctrl {
+    ($ch:expr) => {
+        Key {
+            code: KeyCode::Char($ch),
+            modifiers: Modifiers::CONTROL,
+        }
+    };
+}
+
+// macro_rules! alt {
+//     ($ch:expr) => {
+//         Key {
+//             code: KeyCode::Char($ch),
+//             modifiers: Modifiers::ALT,
+//         }
+//     };
+// }
+
+pub fn default() -> Keymaps {
+    hashmap!(
+        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,
+                vec![key!('j')] => commands::move_line_down,
+                vec![key!('k')] => commands::move_line_up,
+                vec![key!('0')] => commands::move_line_start,
+                vec![key!('$')] => commands::move_line_end,
+                vec![key!('l')] => commands::move_char_right,
+                vec![shift!('H')] => commands::extend_char_left,
+                vec![shift!('J')] => commands::extend_line_down,
+                vec![shift!('K')] => commands::extend_line_up,
+                vec![shift!('L')] => commands::extend_char_right,
+                vec![key!('w')] => commands::move_next_word_start,
+                vec![key!('b')] => commands::move_prev_word_start,
+                vec![key!('e')] => commands::move_next_word_end,
+                vec![key!('g')] => commands::goto_mode,
+                vec![key!('i')] => commands::insert_mode,
+                vec![shift!('I')] => commands::prepend_to_line,
+                vec![key!('a')] => commands::append_mode,
+                vec![shift!('A')] => commands::append_to_line,
+                vec![key!('o')] => commands::open_below,
+                vec![key!('d')] => commands::delete_selection,
+                vec![key!('c')] => commands::change_selection,
+                vec![key!('s')] => commands::split_selection_on_newline,
+                vec![key!(';')] => commands::collapse_selection,
+                // TODO should be alt(;)
+                vec![key!('%')] => commands::flip_selections,
+                vec![key!('x')] => commands::select_line,
+                vec![key!('u')] => commands::undo,
+                vec![shift!('U')] => commands::redo,
+                vec![key!('y')] => commands::yank,
+                vec![key!('p')] => commands::paste,
+                vec![key!('>')] => commands::indent,
+                vec![key!('<')] => commands::unindent,
+                vec![key!(':')] => commands::command_mode,
+                vec![Key {
+                    code: KeyCode::Esc,
+                    modifiers: Modifiers::NONE
+                }] => commands::normal_mode,
+                vec![Key {
+                    code: KeyCode::PageUp,
+                    modifiers: Modifiers::NONE
+                }] => commands::page_up,
+                vec![Key {
+                    code: KeyCode::PageDown,
+                    modifiers: Modifiers::NONE
+                }] => commands::page_down,
+                vec![ctrl!('u')] => commands::half_page_up,
+                vec![ctrl!('d')] => commands::half_page_down,
+            ),
+            Mode::Insert => hashmap!(
+                vec![Key {
+                    code: KeyCode::Esc,
+                    modifiers: Modifiers::NONE
+                }] => commands::normal_mode as Command,
+                vec![Key {
+                    code: KeyCode::Backspace,
+                    modifiers: Modifiers::NONE
+                }] => commands::insert::delete_char_backward,
+                vec![Key {
+                    code: KeyCode::Delete,
+                    modifiers: Modifiers::NONE
+                }] => commands::insert::delete_char_forward,
+                vec![Key {
+                    code: KeyCode::Enter,
+                    modifiers: Modifiers::NONE
+                }] => commands::insert::insert_newline,
+                vec![Key {
+                    code: KeyCode::Tab,
+                    modifiers: Modifiers::NONE
+                }] => commands::insert::insert_tab,
+            ),
+            Mode::Goto => hashmap!(
+                vec![Key {
+                    code: KeyCode::Esc,
+                    modifiers: Modifiers::NONE
+                }] => commands::normal_mode as Command,
+                vec![key!('g')] => commands::move_file_start as Command,
+                vec![key!('e')] => commands::move_file_end as Command,
+            ),
+    )
+}
diff --git a/helix-term/src/main.rs b/helix-term/src/main.rs
index a43aebd8..92ab10c2 100644
--- a/helix-term/src/main.rs
+++ b/helix-term/src/main.rs
@@ -1,7 +1,10 @@
 #![allow(unused)]
 
 mod application;
+mod commands;
 mod compositor;
+mod keymap;
+mod prompt;
 
 use application::Application;
 
diff --git a/helix-term/src/prompt.rs b/helix-term/src/prompt.rs
new file mode 100644
index 00000000..4a39f2ec
--- /dev/null
+++ b/helix-term/src/prompt.rs
@@ -0,0 +1,126 @@
+use crate::Editor;
+use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+use std::string::String;
+
+pub struct Prompt {
+    pub prompt: String,
+    pub line: String,
+    pub cursor: usize,
+    pub completion: Vec<String>,
+    pub should_close: bool,
+    pub completion_selection_index: Option<usize>,
+    completion_fn: Box<dyn FnMut(&str) -> Vec<String>>,
+    callback_fn: Box<dyn FnMut(&mut Editor, &str)>,
+}
+
+impl Prompt {
+    pub fn new(
+        prompt: String,
+        mut completion_fn: impl FnMut(&str) -> Vec<String> + 'static,
+        callback_fn: impl FnMut(&mut Editor, &str) + 'static,
+    ) -> Prompt {
+        Prompt {
+            prompt,
+            line: String::new(),
+            cursor: 0,
+            completion: completion_fn(""),
+            should_close: false,
+            completion_selection_index: None,
+            completion_fn: Box::new(completion_fn),
+            callback_fn: Box::new(callback_fn),
+        }
+    }
+
+    pub fn insert_char(&mut self, c: char) {
+        self.line.insert(self.cursor, c);
+        self.cursor += 1;
+        self.completion = (self.completion_fn)(&self.line);
+        self.exit_selection();
+    }
+
+    pub fn move_char_left(&mut self) {
+        if self.cursor > 0 {
+            self.cursor -= 1;
+        }
+    }
+
+    pub fn move_char_right(&mut self) {
+        if self.cursor < self.line.len() {
+            self.cursor += 1;
+        }
+    }
+
+    pub fn move_start(&mut self) {
+        self.cursor = 0;
+    }
+
+    pub fn move_end(&mut self) {
+        self.cursor = self.line.len();
+    }
+
+    pub fn delete_char_backwards(&mut self) {
+        if self.cursor > 0 {
+            self.line.remove(self.cursor - 1);
+            self.cursor -= 1;
+            self.completion = (self.completion_fn)(&self.line);
+        }
+        self.exit_selection();
+    }
+
+    pub fn change_completion_selection(&mut self) {
+        if self.completion.is_empty() {
+            return;
+        }
+        let index =
+            self.completion_selection_index.map(|i| i + 1).unwrap_or(0) % self.completion.len();
+        self.completion_selection_index = Some(index);
+        self.line = self.completion[index].clone();
+    }
+    pub fn exit_selection(&mut self) {
+        self.completion_selection_index = None;
+    }
+
+    pub fn handle_event(&mut self, key_event: KeyEvent, editor: &mut Editor) {
+        match key_event {
+            KeyEvent {
+                code: KeyCode::Char(c),
+                modifiers: KeyModifiers::NONE,
+            } => self.insert_char(c),
+            KeyEvent {
+                code: KeyCode::Esc, ..
+            } => self.should_close = true,
+            KeyEvent {
+                code: KeyCode::Right,
+                ..
+            } => self.move_char_right(),
+            KeyEvent {
+                code: KeyCode::Left,
+                ..
+            } => self.move_char_left(),
+            KeyEvent {
+                code: KeyCode::Char('e'),
+                modifiers: KeyModifiers::CONTROL,
+            } => self.move_end(),
+            KeyEvent {
+                code: KeyCode::Char('a'),
+                modifiers: KeyModifiers::CONTROL,
+            } => self.move_start(),
+            KeyEvent {
+                code: KeyCode::Backspace,
+                modifiers: KeyModifiers::NONE,
+            } => self.delete_char_backwards(),
+            KeyEvent {
+                code: KeyCode::Enter,
+                ..
+            } => (self.callback_fn)(editor, &self.line),
+            KeyEvent {
+                code: KeyCode::Tab, ..
+            } => self.change_completion_selection(),
+            KeyEvent {
+                code: KeyCode::Char('q'),
+                modifiers: KeyModifiers::CONTROL,
+            } => self.exit_selection(),
+            _ => (),
+        }
+    }
+}