Separate jump behavior from increment/decrement (#4123)

increment/decrement (C-a/C-x) had some buggy behavior where selections
could be offset incorrectly or the editor could panic with some edits
that changed the number of characters in a number or date. These stemmed
from the automatic jumping behavior which attempted to find the next
date or integer to increment. The jumping behavior also complicated the
code quite a bit and made the behavior somewhat difficult to predict
when using many cursors.

This change removes the automatic jumping behavior and only increments
or decrements when the full text in a range of a selection is a number
or date. This simplifies the code and fixes the panics and buggy
behaviors from changing the number of characters.

1 files changed, 235 insertions, 0 deletions

diff --git a/helix-core/src/increment/integer.rs b/helix-core/src/increment/integer.rs
new file mode 100644
index 00000000..30803e17
--- /dev/null
+++ b/helix-core/src/increment/integer.rs
@@ -0,0 +1,235 @@
+const SEPARATOR: char = '_';
+
+/// Increment an integer.
+///
+/// Supported bases:
+///     2 with prefix 0b
+///     8 with prefix 0o
+///     10 with no prefix
+///     16 with prefix 0x
+///
+/// An integer can contain `_` as a separator but may not start or end with a separator.
+/// Base 10 integers can go negative, but bases 2, 8, and 16 cannot.
+/// All addition and subtraction is saturating.
+pub fn increment(selected_text: &str, amount: i64) -> Option<String> {
+    if selected_text.is_empty()
+        || selected_text.ends_with(SEPARATOR)
+        || selected_text.starts_with(SEPARATOR)
+    {
+        return None;
+    }
+
+    let radix = if selected_text.starts_with("0x") {
+        16
+    } else if selected_text.starts_with("0o") {
+        8
+    } else if selected_text.starts_with("0b") {
+        2
+    } else {
+        10
+    };
+
+    // Get separator indexes from right to left.
+    let separator_rtl_indexes: Vec<usize> = selected_text
+        .chars()
+        .rev()
+        .enumerate()
+        .filter_map(|(i, c)| if c == SEPARATOR { Some(i) } else { None })
+        .collect();
+
+    let word: String = selected_text.chars().filter(|&c| c != SEPARATOR).collect();
+
+    let mut new_text = if radix == 10 {
+        let number = &word;
+        let value = i128::from_str_radix(number, radix).ok()?;
+        let new_value = value.saturating_add(amount as i128);
+
+        let format_length = match (value.is_negative(), new_value.is_negative()) {
+            (true, false) => number.len() - 1,
+            (false, true) => number.len() + 1,
+            _ => number.len(),
+        } - separator_rtl_indexes.len();
+
+        if number.starts_with('0') || number.starts_with("-0") {
+            format!("{:01$}", new_value, format_length)
+        } else {
+            format!("{}", new_value)
+        }
+    } else {
+        let number = &word[2..];
+        let value = u128::from_str_radix(number, radix).ok()?;
+        let new_value = (value as i128).saturating_add(amount as i128);
+        let new_value = if new_value < 0 { 0 } else { new_value };
+        let format_length = selected_text.len() - 2 - separator_rtl_indexes.len();
+
+        match radix {
+            2 => format!("0b{:01$b}", new_value, format_length),
+            8 => format!("0o{:01$o}", new_value, format_length),
+            16 => {
+                let (lower_count, upper_count): (usize, usize) =
+                    number.chars().fold((0, 0), |(lower, upper), c| {
+                        (
+                            lower + c.is_ascii_lowercase().then(|| 1).unwrap_or(0),
+                            upper + c.is_ascii_uppercase().then(|| 1).unwrap_or(0),
+                        )
+                    });
+                if upper_count > lower_count {
+                    format!("0x{:01$X}", new_value, format_length)
+                } else {
+                    format!("0x{:01$x}", new_value, format_length)
+                }
+            }
+            _ => unimplemented!("radix not supported: {}", 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().saturating_sub(rtl_index);
+            if new_index > 0 {
+                new_text.insert(new_index, SEPARATOR);
+            }
+        }
+    }
+
+    // Add in additional separators if necessary.
+    if new_text.len() > selected_text.len() && !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 radix == 10 { 0 } else { 2 };
+        if let Some(mut index) = new_text.find(SEPARATOR) {
+            while index - prefix_length > spacing {
+                index -= spacing;
+                new_text.insert(index, SEPARATOR);
+            }
+        }
+    }
+
+    Some(new_text)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[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 {
+            assert_eq!(increment(original, amount).unwrap(), expected);
+        }
+    }
+
+    #[test]
+    fn test_increment_basic_hexadecimal_numbers() {
+        let tests = [
+            ("0x0100", 1, "0x0101"),
+            ("0x0100", -1, "0x00ff"),
+            ("0x0001", -1, "0x0000"),
+            ("0x0000", -1, "0x0000"),
+            ("0xffffffffffffffff", 1, "0x10000000000000000"),
+            ("0xffffffffffffffff", 2, "0x10000000000000001"),
+            ("0xffffffffffffffff", -1, "0xfffffffffffffffe"),
+            ("0xABCDEF1234567890", 1, "0xABCDEF1234567891"),
+            ("0xabcdef1234567890", 1, "0xabcdef1234567891"),
+        ];
+
+        for (original, amount, expected) in tests {
+            assert_eq!(increment(original, amount).unwrap(), expected);
+        }
+    }
+
+    #[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, "0o0000"),
+            ("0o1777777777777777777777", 1, "0o2000000000000000000000"),
+            ("0o1777777777777777777777", 2, "0o2000000000000000000001"),
+            ("0o1777777777777777777777", -1, "0o1777777777777777777776"),
+        ];
+
+        for (original, amount, expected) in tests {
+            assert_eq!(increment(original, amount).unwrap(), expected);
+        }
+    }
+
+    #[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, "0b0000"),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                1,
+                "0b10000000000000000000000000000000000000000000000000000000000000000",
+            ),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                2,
+                "0b10000000000000000000000000000000000000000000000000000000000000001",
+            ),
+            (
+                "0b1111111111111111111111111111111111111111111111111111111111111111",
+                -1,
+                "0b1111111111111111111111111111111111111111111111111111111111111110",
+            ),
+        ];
+
+        for (original, amount, expected) in tests {
+            assert_eq!(increment(original, amount).unwrap(), expected);
+        }
+    }
+
+    #[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", -1, "0x0000_0000"),
+            ("0x0000_0000_0000", -1, "0x0000_0000_0000"),
+            ("0b01111111_11111111", 1, "0b10000000_00000000"),
+            ("0b11111111_11111111", 1, "0b1_00000000_00000000"),
+        ];
+
+        for (original, amount, expected) in tests {
+            assert_eq!(increment(original, amount).unwrap(), expected);
+        }
+    }
+
+    #[test]
+    fn test_leading_and_trailing_separators_arent_a_match() {
+        assert_eq!(increment("9_", 1), None);
+        assert_eq!(increment("_9", 1), None);
+        assert_eq!(increment("_9_", 1), None);
+    }
+}