Readline style insert mode (#1039)

* readline style insert mode

* update keymap.md

* don't save change history in insert mode

* Revert "don't save change history in insert mode"

This reverts commit cb47f946d7fb62ceda68e7d1692a3914d0be7762.

* don't affect register and history in insert mode

* add insert_register

* don't call exit_select_mode in insert mode

* avoid set_selection

* avoid duplicated current!

4 files changed, 114 insertions, 9 deletions

diff --git a/book/src/keymap.md b/book/src/keymap.md
index 88610a77..7a896035 100644
--- a/book/src/keymap.md
+++ b/book/src/keymap.md
@@ -243,11 +243,26 @@ Mappings in the style of [vim-unimpaired](https://github.com/tpope/vim-unimpaire
 
 ## Insert Mode
 
-| Key      | Description           | Command                |
-| -----    | -----------           | -------                |
-| `Escape` | Switch to normal mode | `normal_mode`          |
-| `Ctrl-x` | Autocomplete          | `completion`           |
-| `Ctrl-w` | Delete previous word  | `delete_word_backward` |
+| Key                     | Description                 | Command                 |
+| -----                   | -----------                 | -------                 |
+| `Escape`                | Switch to normal mode       | `normal_mode`           |
+| `Ctrl-x`                | Autocomplete                | `completion`            |
+| `Ctrl-r`                | Insert a register content   | `insert_register`       |
+| `Ctrl-w`                | Delete previous word        | `delete_word_backward`  |
+| `Alt-d`                 | Delete next word            | `delete_word_forward`   |
+| `Alt-b`, `Alt-Left`     | Backward a word             | `move_prev_word_end`    |
+| `Ctrl-b`, `Left`        | Backward a char             | `move_char_left`        |
+| `Alt-f`, `Alt-Right`    | Forward a word              | `move_next_word_start`  |
+| `Ctrl-f`, `Right`       | Forward a char              | `move_char_right`       |
+| `Ctrl-e`, `End`         | move to line end            | `goto_line_end_newline` |
+| `Ctrl-a`, `Home`        | move to line start          | `goto_line_start`       |
+| `Ctrl-w`                | delete previous word        | `delete_word_backwar`   |
+| `Ctrl-u`                | delete to start of line     | `kill_to_line_start`    |
+| `Ctrl-k`                | delete to end of line       | `kill_to_line_end`      |
+| `backspace`, `Ctrl-h`   | delete previous char        | `delete_char_backward`  |
+| `delete`, `Ctrl-d`      | delete previous char        | `delete_char_forward`   |
+| `Ctrl-p`, `Up`          | move to previous line       | `move_line_up`          |
+| `Ctrl-n`, `Down`        | move to next line           | `move_line_down`        |
 
 ## Select / extend mode
 
@@ -285,6 +300,7 @@ Keys to use within prompt, Remapping currently not supported.
 | `Ctrl-e`, `End`         | Move prompt end                                                         |
 | `Ctrl-a`, `Home`        | Move prompt start                                                       |
 | `Ctrl-w`                | Delete previous word                                                    |
+| `Alt-d`                 | Delete next word                                                        |
 | `Ctrl-u`                | Delete to start of line                                                 |
 | `Ctrl-k`                | Delete to end of line                                                   |
 | `backspace`, `Ctrl-h`   | Delete previous char                                                    |
@@ -292,7 +308,7 @@ Keys to use within prompt, Remapping currently not supported.
 | `Ctrl-s`                | Insert a word under doc cursor, may be changed to Ctrl-r Ctrl-w later   |
 | `Ctrl-p`, `Up`          | Select previous history                                                 |
 | `Ctrl-n`, `Down`        | Select next history                                                     |
-| `Tab`                   | Select next completion item                                              |
-| `BackTab`               | Select previous completion item                                          |
+| `Tab`                   | Select next completion item                                             |
+| `BackTab`               | Select previous completion item                                         |
 | `Enter`                 | Open selected                                                           |
 
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index c7aab726..74bc52fd 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -187,6 +187,7 @@ impl Command {
         copy_selection_on_prev_line, "Copy selection on previous line",
         move_next_word_start, "Move to beginning of next word",
         move_prev_word_start, "Move to beginning of previous word",
+        move_prev_word_end, "Move to end of previous word",
         move_next_word_end, "Move to end of next word",
         move_next_long_word_start, "Move to beginning of next long word",
         move_prev_long_word_start, "Move to beginning of previous long word",
@@ -284,6 +285,9 @@ impl Command {
         delete_char_backward, "Delete previous char",
         delete_char_forward, "Delete next char",
         delete_word_backward, "Delete previous word",
+        delete_word_forward, "Delete next word",
+        kill_to_line_start, "Delete content till the start of the line",
+        kill_to_line_end, "Delete content till the end of the line",
         undo, "Undo change",
         redo, "Redo change",
         earlier, "Move backward in history",
@@ -330,6 +334,7 @@ impl Command {
         wclose, "Close window",
         wonly, "Current window only",
         select_register, "Select register",
+        insert_register, "Insert register",
         align_view_middle, "Align view middle",
         align_view_top, "Align view top",
         align_view_center, "Align view center",
@@ -572,6 +577,29 @@ fn extend_to_line_start(cx: &mut Context) {
     goto_line_start_impl(view, doc, Movement::Extend)
 }
 
+fn kill_to_line_start(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let text = doc.text().slice(..);
+
+    let selection = doc.selection(view.id).clone().transform(|range| {
+        let line = range.cursor_line(text);
+        range.put_cursor(text, text.line_to_char(line), true)
+    });
+    delete_selection_insert_mode(doc, view, &selection);
+}
+
+fn kill_to_line_end(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let text = doc.text().slice(..);
+
+    let selection = doc.selection(view.id).clone().transform(|range| {
+        let line = range.cursor_line(text);
+        let pos = line_end_char_index(&text, line);
+        range.put_cursor(text, pos, true)
+    });
+    delete_selection_insert_mode(doc, view, &selection);
+}
+
 fn goto_first_nonwhitespace(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
     let text = doc.text().slice(..);
@@ -684,6 +712,10 @@ fn move_prev_word_start(cx: &mut Context) {
     move_word_impl(cx, movement::move_prev_word_start)
 }
 
+fn move_prev_word_end(cx: &mut Context) {
+    move_word_impl(cx, movement::move_prev_word_end)
+}
+
 fn move_next_word_end(cx: &mut Context) {
     move_word_impl(cx, movement::move_next_word_end)
 }
@@ -1586,6 +1618,17 @@ fn delete_selection_impl(reg: &mut Register, doc: &mut Document, view_id: ViewId
     doc.apply(&transaction, view_id);
 }
 
+#[inline]
+fn delete_selection_insert_mode(doc: &mut Document, view: &View, selection: &Selection) {
+    let view_id = view.id;
+
+    // then delete
+    let transaction = Transaction::change_by_selection(doc.text(), selection, |range| {
+        (range.from(), range.to(), None)
+    });
+    doc.apply(&transaction, view_id);
+}
+
 fn delete_selection(cx: &mut Context) {
     let reg_name = cx.register.unwrap_or('"');
     let (view, doc) = current!(cx.editor);
@@ -4010,8 +4053,19 @@ pub mod insert {
             .selection(view.id)
             .clone()
             .transform(|range| movement::move_prev_word_start(text, range, count));
-        doc.set_selection(view.id, selection);
-        delete_selection(cx)
+        delete_selection_insert_mode(doc, view, &selection);
+    }
+
+    pub fn delete_word_forward(cx: &mut Context) {
+        let count = cx.count();
+        let (view, doc) = current!(cx.editor);
+        let text = doc.text().slice(..);
+
+        let selection = doc
+            .selection(view.id)
+            .clone()
+            .transform(|range| movement::move_next_word_start(text, range, count));
+        delete_selection_insert_mode(doc, view, &selection);
     }
 }
 
@@ -4973,6 +5027,15 @@ fn select_register(cx: &mut Context) {
     })
 }
 
+fn insert_register(cx: &mut Context) {
+    cx.on_next_key(move |cx, event| {
+        if let Some(ch) = event.char() {
+            cx.editor.selected_register = Some(ch);
+            paste_before(cx);
+        }
+    })
+}
+
 fn align_view_top(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
     align_view(doc, view, Align::Top);
diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
index 010714dc..fdf43d87 100644
--- a/helix-term/src/keymap.rs
+++ b/helix-term/src/keymap.rs
@@ -731,21 +731,38 @@ impl Default for Keymaps {
             "esc" => normal_mode,
 
             "backspace" => delete_char_backward,
+            "C-h" => delete_char_backward,
             "del" => delete_char_forward,
+            "C-d" => delete_char_forward,
             "ret" => insert_newline,
             "tab" => insert_tab,
             "C-w" => delete_word_backward,
+            "A-d" => delete_word_forward,
 
             "left" => move_char_left,
+            "C-b" => move_char_left,
             "down" => move_line_down,
+            "C-n" => move_line_down,
             "up" => move_line_up,
+            "C-p" => move_line_up,
             "right" => move_char_right,
+            "C-f" => move_char_right,
+            "A-b" => move_prev_word_end,
+            "A-left" => move_prev_word_end,
+            "A-f" => move_next_word_start,
+            "A-right" => move_next_word_start,
             "pageup" => page_up,
             "pagedown" => page_down,
             "home" => goto_line_start,
+            "C-a" => goto_line_start,
             "end" => goto_line_end_newline,
+            "C-e" => goto_line_end_newline,
+
+            "C-k" => kill_to_line_end,
+            "C-u" => kill_to_line_start,
 
             "C-x" => completion,
+            "C-r" => insert_register,
         });
         Keymaps(hashmap!(
             Mode::Normal => Keymap::new(normal),
diff --git a/helix-term/src/ui/prompt.rs b/helix-term/src/ui/prompt.rs
index deed1609..e90b0772 100644
--- a/helix-term/src/ui/prompt.rs
+++ b/helix-term/src/ui/prompt.rs
@@ -231,6 +231,14 @@ impl Prompt {
         self.completion = (self.completion_fn)(&self.line);
     }
 
+    pub fn delete_word_forwards(&mut self) {
+        let pos = self.eval_movement(Movement::ForwardWord(1));
+        self.line.replace_range(self.cursor..pos, "");
+
+        self.exit_selection();
+        self.completion = (self.completion_fn)(&self.line);
+    }
+
     pub fn kill_to_start_of_line(&mut self) {
         let pos = self.eval_movement(Movement::StartOfLine);
         self.line.replace_range(pos..self.cursor, "");
@@ -435,6 +443,7 @@ impl Component for Prompt {
             ctrl!('e') | key!(End) => self.move_end(),
             ctrl!('a') | key!(Home) => self.move_start(),
             ctrl!('w') => self.delete_word_backwards(),
+            alt!('d') => self.delete_word_forwards(),
             ctrl!('k') => self.kill_to_end_of_line(),
             ctrl!('u') => self.kill_to_start_of_line(),
             ctrl!('h') | key!(Backspace) => {