Add command to inc/dec number under cursor (#1027)

* Add command to inc/dec number under cursor

With the cursor over a number in normal mode, Ctrl + A will increment the
number and Ctrl + X will decrement the number. It works with binary, octal,
decimal, and hexidecimal numbers. Here are some examples.

0b01110100
0o1734
-24234
0x1F245

If the number isn't over a number it will try to find a number after the
cursor on the same line.

* Move several functions to helix-core

* Change to work based on word under selection

* It no longer finds the next number if the cursor isn't already over
  a number.
* It only matches numbers that are part of words with other characters
  like "foo123bar".
* It now works with multiple selections.

* Add some unit tests

* Fix for clippy

* Simplify some things

* Keep previous selection after incrementing

* Use short word instead of long word

This change requires us to manually handle minus sign.

* Don't pad decimal numbers if no leading zeros

* Handle numbers with `_` separators

* Refactor and add tests

* Move most of the code into core
* Add tests for the incremented output

* Use correct range

* Formatting

* Rename increment functions

* Make docs more specific

* This is easier to read

* This is clearer

* Type can be inferred

2 files changed, 41 insertions, 0 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 74bc52fd..7ef8f56c 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -6,6 +6,7 @@ use helix_core::{
     line_ending::{get_line_ending_of_str, line_end_char_index, str_is_line_ending},
     match_brackets,
     movement::{self, Direction},
+    numbers::NumberIncrementor,
     object, pos_at_coords,
     regex::{self, Regex, RegexBuilder},
     register::Register,
@@ -354,6 +355,8 @@ impl Command {
         shell_keep_pipe, "Filter selections with shell predicate",
         suspend, "Suspend",
         rename_symbol, "Rename symbol",
+        increment, "Increment",
+        decrement, "Decrement",
     );
 }
 
@@ -5459,3 +5462,38 @@ fn rename_symbol(cx: &mut Context) {
     );
     cx.push_layer(Box::new(prompt));
 }
+
+/// Increment object under cursor by count.
+fn increment(cx: &mut Context) {
+    increment_impl(cx, cx.count() as i64);
+}
+
+/// Decrement object under cursor by count.
+fn decrement(cx: &mut Context) {
+    increment_impl(cx, -(cx.count() as i64));
+}
+
+/// Decrement object under cursor by `amount`.
+fn increment_impl(cx: &mut Context, amount: i64) {
+    let (view, doc) = current!(cx.editor);
+    let selection = doc.selection(view.id);
+    let text = doc.text();
+
+    let changes = selection.ranges().iter().filter_map(|range| {
+        let incrementor = NumberIncrementor::from_range(text.slice(..), *range)?;
+        let new_text = incrementor.incremented_text(amount);
+        Some((
+            incrementor.range.from(),
+            incrementor.range.to(),
+            Some(new_text),
+        ))
+    });
+
+    if changes.clone().count() > 0 {
+        let transaction = Transaction::change(doc.text(), changes);
+        let transaction = transaction.with_selection(selection.clone());
+
+        doc.apply(&transaction, view.id);
+        doc.append_changes_to_history(view.id);
+    }
+}
diff --git a/helix-term/src/keymap.rs b/helix-term/src/keymap.rs
index fdf43d87..bf3b594e 100644
--- a/helix-term/src/keymap.rs
+++ b/helix-term/src/keymap.rs
@@ -698,6 +698,9 @@ impl Default for Keymaps {
             "A-!" => shell_append_output,
             "$" => shell_keep_pipe,
             "C-z" => suspend,
+
+            "C-a" => increment,
+            "C-x" => decrement,
         });
         let mut select = normal.clone();
         select.merge_nodes(keymap!({ "Select mode"