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

5 files changed, 543 insertions, 0 deletions

diff --git a/book/src/keymap.md b/book/src/keymap.md
index 7a896035..335e393b 100644
--- a/book/src/keymap.md
+++ b/book/src/keymap.md
@@ -72,6 +72,8 @@
 | `=`         | Format selection (**LSP**)                      | `format_selections`   |
 | `d`         | Delete selection                                | `delete_selection`    |
 | `c`         | Change selection (delete and enter insert mode) | `change_selection`    |
+| `Ctrl-a`    | Increment object (number) under cursor          | `increment`           |
+| `Ctrl-x`    | Decrement object (number) under cursor          | `decrement`           |
 
 #### Shell
 
diff --git a/helix-core/src/lib.rs b/helix-core/src/lib.rs
index d1720df0..de7e95c1 100644
--- a/helix-core/src/lib.rs
+++ b/helix-core/src/lib.rs
@@ -10,6 +10,7 @@ pub mod line_ending;
 pub mod macros;
 pub mod match_brackets;
 pub mod movement;
+pub mod numbers;
 pub mod object;
 pub mod path;
 mod position;
diff --git a/helix-core/src/numbers.rs b/helix-core/src/numbers.rs
new file mode 100644
index 00000000..e9f3c898
--- /dev/null
+++ b/helix-core/src/numbers.rs
@@ -0,0 +1,499 @@
+use std::borrow::Cow;
+
+use ropey::RopeSlice;
+
+use crate::{
+    textobject::{textobject_word, TextObject},
+    Range, Tendril,
+};
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct NumberIncrementor<'a> {
+    pub range: Range,
+    pub value: i64,
+    pub radix: u32,
+
+    text: RopeSlice<'a>,
+}
+
+impl<'a> NumberIncrementor<'a> {
+    /// Return information about number under rang if there is one.
+    pub fn from_range(text: RopeSlice, range: Range) -> Option<NumberIncrementor> {
+        // If the cursor is on the minus sign of a number we want to get the word textobject to the
+        // right of it.
+        let range = if range.to() < text.len_chars()
+            && range.to() - range.from() <= 1
+            && text.char(range.from()) == '-'
+        {
+            Range::new(range.from() + 1, range.to() + 1)
+        } else {
+            range
+        };
+
+        let range = textobject_word(text, range, TextObject::Inside, 1, false);
+
+        // If there is a minus sign to the left of the word object, we want to include it in the range.
+        let range = if range.from() > 0 && text.char(range.from() - 1) == '-' {
+            range.extend(range.from() - 1, range.from())
+        } else {
+            range
+        };
+
+        let word: String = text
+            .slice(range.from()..range.to())
+            .chars()
+            .filter(|&c| c != '_')
+            .collect();
+        let (radix, prefixed) = if word.starts_with("0x") {
+            (16, true)
+        } else if word.starts_with("0o") {
+            (8, true)
+        } else if word.starts_with("0b") {
+            (2, true)
+        } else {
+            (10, false)
+        };
+
+        let number = if prefixed { &word[2..] } else { &word };
+
+        let value = i128::from_str_radix(number, radix).ok()?;
+        if (value.is_positive() && value.leading_zeros() < 64)
+            || (value.is_negative() && value.leading_ones() < 64)
+        {
+            return None;
+        }
+
+        let value = value as i64;
+        Some(NumberIncrementor {
+            range,
+            value,
+            radix,
+            text,
+        })
+    }
+
+    /// Add `amount` to the number and return the formatted text.
+    pub fn incremented_text(&self, amount: i64) -> Tendril {
+        let old_text: Cow<str> = self.text.slice(self.range.from()..self.range.to()).into();
+        let old_length = old_text.len();
+        let new_value = self.value.wrapping_add(amount);
+
+        // Get separator indexes from right to left.
+        let separator_rtl_indexes: Vec<usize> = old_text
+            .chars()
+            .rev()
+            .enumerate()
+            .filter_map(|(i, c)| if c == '_' { Some(i) } else { None })
+            .collect();
+
+        let format_length = if self.radix == 10 {
+            match (self.value.is_negative(), new_value.is_negative()) {
+                (true, false) => old_length - 1,
+                (false, true) => old_length + 1,
+                _ => old_text.len(),
+            }
+        } else {
+            old_text.len() - 2
+        } - separator_rtl_indexes.len();
+
+        let mut new_text = match self.radix {
+            2 => format!("0b{:01$b}", new_value, format_length),
+            8 => format!("0o{:01$o}", new_value, format_length),
+            10 if old_text.starts_with('0') || old_text.starts_with("-0") => {
+                format!("{:01$}", new_value, format_length)
+            }
+            10 => format!("{}", new_value),
+            16 => {
+                let (lower_count, upper_count): (usize, usize) =
+                    old_text.chars().skip(2).fold((0, 0), |(lower, upper), c| {
+                        (
+                            lower + c.is_ascii_lowercase().then(|| 1).unwrap_or(0),
+                            upper + c.is_ascii_uppercase().then(|| 1).unwrap_or(0),
+                        )
+                    });
+                if upper_count > lower_count {
+                    format!("0x{:01$X}", new_value, format_length)
+                } else {
+                    format!("0x{:01$x}", new_value, format_length)
+                }
+            }
+            _ => unimplemented!("radix not supported: {}", self.radix),
+        };
+
+        // Add separators from original number.
+        for &rtl_index in &separator_rtl_indexes {
+            if rtl_index < new_text.len() {
+                let new_index = new_text.len() - rtl_index;
+                new_text.insert(new_index, '_');
+            }
+        }
+
+        // Add in additional separators if necessary.
+        if new_text.len() > old_length && !separator_rtl_indexes.is_empty() {
+            let spacing = match separator_rtl_indexes.as_slice() {
+                [.., b, a] => a - b - 1,
+                _ => separator_rtl_indexes[0],
+            };
+
+            let prefix_length = if self.radix == 10 { 0 } else { 2 };
+            if let Some(mut index) = new_text.find('_') {
+                while index - prefix_length > spacing {
+                    index -= spacing;
+                    new_text.insert(index, '_');
+                }
+            }
+        }
+
+        new_text.into()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::Rope;
+
+    #[test]
+    fn test_decimal_at_point() {
+        let rope = Rope::from_str("Test text 12345 more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 15),
+                value: 12345,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_uppercase_hexadecimal_at_point() {
+        let rope = Rope::from_str("Test text 0x123ABCDEF more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 21),
+                value: 0x123ABCDEF,
+                radix: 16,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_lowercase_hexadecimal_at_point() {
+        let rope = Rope::from_str("Test text 0xfa3b4e more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 18),
+                value: 0xfa3b4e,
+                radix: 16,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_octal_at_point() {
+        let rope = Rope::from_str("Test text 0o1074312 more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 19),
+                value: 0o1074312,
+                radix: 8,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_binary_at_point() {
+        let rope = Rope::from_str("Test text 0b10111010010101 more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 26),
+                value: 0b10111010010101,
+                radix: 2,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_negative_decimal_at_point() {
+        let rope = Rope::from_str("Test text -54321 more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 16),
+                value: -54321,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_decimal_with_leading_zeroes_at_point() {
+        let rope = Rope::from_str("Test text 000045326 more text.");
+        let range = Range::point(12);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 19),
+                value: 45326,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_negative_decimal_cursor_on_minus_sign() {
+        let rope = Rope::from_str("Test text -54321 more text.");
+        let range = Range::point(10);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(10, 16),
+                value: -54321,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_number_under_range_start_of_rope() {
+        let rope = Rope::from_str("100");
+        let range = Range::point(0);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(0, 3),
+                value: 100,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_number_under_range_end_of_rope() {
+        let rope = Rope::from_str("100");
+        let range = Range::point(2);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(0, 3),
+                value: 100,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_number_surrounded_by_punctuation() {
+        let rope = Rope::from_str(",100;");
+        let range = Range::point(1);
+        assert_eq!(
+            NumberIncrementor::from_range(rope.slice(..), range),
+            Some(NumberIncrementor {
+                range: Range::new(1, 4),
+                value: 100,
+                radix: 10,
+                text: rope.slice(..),
+            })
+        );
+    }
+
+    #[test]
+    fn test_not_a_number_point() {
+        let rope = Rope::from_str("Test text 45326 more text.");
+        let range = Range::point(6);
+        assert_eq!(NumberIncrementor::from_range(rope.slice(..), range), None);
+    }
+
+    #[test]
+    fn test_number_too_large_at_point() {
+        let rope = Rope::from_str("Test text 0xFFFFFFFFFFFFFFFFF more text.");
+        let range = Range::point(12);
+        assert_eq!(NumberIncrementor::from_range(rope.slice(..), range), None);
+    }
+
+    #[test]
+    fn test_number_cursor_one_right_of_number() {
+        let rope = Rope::from_str("100 ");
+        let range = Range::point(3);
+        assert_eq!(NumberIncrementor::from_range(rope.slice(..), range), None);
+    }
+
+    #[test]
+    fn test_number_cursor_one_left_of_number() {
+        let rope = Rope::from_str(" 100");
+        let range = Range::point(0);
+        assert_eq!(NumberIncrementor::from_range(rope.slice(..), range), None);
+    }
+
+    #[test]
+    fn test_increment_basic_decimal_numbers() {
+        let tests = [
+            ("100", 1, "101"),
+            ("100", -1, "99"),
+            ("99", 1, "100"),
+            ("100", 1000, "1100"),
+            ("100", -1000, "-900"),
+            ("-1", 1, "0"),
+            ("-1", 2, "1"),
+            ("1", -1, "0"),
+            ("1", -2, "-1"),
+        ];
+
+        for (original, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::point(0);
+            assert_eq!(
+                NumberIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .incremented_text(amount),
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_increment_basic_hexadedimal_numbers() {
+        let tests = [
+            ("0x0100", 1, "0x0101"),
+            ("0x0100", -1, "0x00ff"),
+            ("0x0001", -1, "0x0000"),
+            ("0x0000", -1, "0xffffffffffffffff"),
+            ("0xffffffffffffffff", 1, "0x0000000000000000"),
+            ("0xffffffffffffffff", 2, "0x0000000000000001"),
+            ("0xffffffffffffffff", -1, "0xfffffffffffffffe"),
+            ("0xABCDEF1234567890", 1, "0xABCDEF1234567891"),
+            ("0xabcdef1234567890", 1, "0xabcdef1234567891"),
+        ];
+
+        for (original, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::point(0);
+            assert_eq!(
+                NumberIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .incremented_text(amount),
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_increment_basic_octal_numbers() {
+        let tests = [
+            ("0o0107", 1, "0o0110"),
+            ("0o0110", -1, "0o0107"),
+            ("0o0001", -1, "0o0000"),
+            ("0o7777", 1, "0o10000"),
+            ("0o1000", -1, "0o0777"),
+            ("0o0107", 10, "0o0121"),
+            ("0o0000", -1, "0o1777777777777777777777"),
+            ("0o1777777777777777777777", 1, "0o0000000000000000000000"),
+            ("0o1777777777777777777777", 2, "0o0000000000000000000001"),
+            ("0o1777777777777777777777", -1, "0o1777777777777777777776"),
+        ];
+
+        for (original, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::point(0);
+            assert_eq!(
+                NumberIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .incremented_text(amount),
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_increment_basic_binary_numbers() {
+        let tests = [
+            ("0b00000100", 1, "0b00000101"),
+            ("0b00000100", -1, "0b00000011"),
+            ("0b00000100", 2, "0b00000110"),
+            ("0b00000100", -2, "0b00000010"),
+            ("0b00000001", -1, "0b00000000"),
+            ("0b00111111", 10, "0b01001001"),
+            ("0b11111111", 1, "0b100000000"),
+            ("0b10000000", -1, "0b01111111"),
+            (
+                "0b0000",
+                -1,
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+            ),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                1,
+                "0b0000000000000000000000000000000000000000000000000000000000000000",
+            ),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                2,
+                "0b0000000000000000000000000000000000000000000000000000000000000001",
+            ),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                -1,
+                "0b1111111111111111111111111111111111111111111111111111111111111110",
+            ),
+        ];
+
+        for (original, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::point(0);
+            assert_eq!(
+                NumberIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .incremented_text(amount),
+                expected.into()
+            );
+        }
+    }
+
+    #[test]
+    fn test_increment_with_separators() {
+        let tests = [
+            ("999_999", 1, "1_000_000"),
+            ("1_000_000", -1, "999_999"),
+            ("-999_999", -1, "-1_000_000"),
+            ("0x0000_0000_0001", 0x1_ffff_0000, "0x0001_ffff_0001"),
+            ("0x0000_0000_0001", 0x1_ffff_0000, "0x0001_ffff_0001"),
+            ("0x0000_0000_0001", 0x1_ffff_0000, "0x0001_ffff_0001"),
+            ("0x0000_0000", -1, "0xffff_ffff_ffff_ffff"),
+            ("0x0000_0000_0000", -1, "0xffff_ffff_ffff_ffff"),
+            ("0b01111111_11111111", 1, "0b10000000_00000000"),
+            ("0b11111111_11111111", 1, "0b1_00000000_00000000"),
+        ];
+
+        for (original, amount, expected) in tests {
+            let rope = Rope::from_str(original);
+            let range = Range::point(0);
+            assert_eq!(
+                NumberIncrementor::from_range(rope.slice(..), range)
+                    .unwrap()
+                    .incremented_text(amount),
+                expected.into()
+            );
+        }
+    }
+}
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"