fix: chat input crashing when moving the cursor (#33)

Reviewed-on: https://git.reya.su/reya/coop/pulls/33

crates/ui/src/input/selection.rs

@@ -0,0 +1,140 @@
+use std::ops::Range;
+
+use gpui::{Context, Window};
+use ropey::Rope;
+use sum_tree::Bias;
+
+use crate::input::{InputState, RopeExt};
+
+impl InputState {
+    /// Select the word at the given offset on double-click.
+    ///
+    /// The offset is the UTF-8 offset.
+    pub(super) fn select_word(&mut self, offset: usize, _: &mut Window, cx: &mut Context<Self>) {
+        let Some(range) = TextSelector::word_range(&self.text, offset) else {
+            return;
+        };
+
+        self.selected_range = (range.start..range.end).into();
+        self.selected_word_range = Some(self.selected_range);
+        cx.notify()
+    }
+
+    /// Select the line at the given offset on triple-click.
+    ///
+    /// The offset is the UTF-8 offset.
+    pub(super) fn select_line(&mut self, offset: usize, _: &mut Window, cx: &mut Context<Self>) {
+        let range = TextSelector::line_range(&self.text, offset);
+        self.selected_range = (range.start..range.end).into();
+        self.selected_word_range = None;
+        cx.notify()
+    }
+}
+
+struct TextSelector;
+impl TextSelector {
+    /// Select a line in the given text at the specified offset.
+    ///
+    /// The offset is the UTF-8 offset.
+    ///
+    /// Returns the start and end offsets of the selected line.
+    pub fn line_range(text: &Rope, offset: usize) -> Range<usize> {
+        let offset = text.clip_offset(offset, Bias::Left);
+        let row = text.offset_to_point(offset).row;
+        let start = text.line_start_offset(row);
+        let end = text.line_end_offset(row);
+
+        start..end
+    }
+
+    /// Select a word in the given text at the specified offset.
+    ///
+    /// The offset is the UTF-8 offset.
+    ///
+    /// Returns the start and end offsets of the selected word.
+    pub fn word_range(text: &Rope, offset: usize) -> Option<Range<usize>> {
+        let offset = text.clip_offset(offset, Bias::Left);
+        let char = text.char_at(offset)?;
+        let end = offset + char.len_utf8();
+        let prev_chars = text.chars_at(offset).reversed().take(128);
+        let next_chars = text.chars_at(end).take(128);
+
+        Some(word_range_from_chars(offset, char, prev_chars, next_chars))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum CharType {
+    /// a-z, A-Z, 0-9, _
+    Word,
+    /// '\t', ' ', '\u{00A0}' etc.
+    Whitespace,
+    /// \n, \r
+    Newline,
+    /// . , ; : ( ) [ ] { } ... or CJK characters: `汉`, `🎉` etc.
+    Other,
+}
+
+impl From<char> for CharType {
+    fn from(c: char) -> Self {
+        match c {
+            c if is_word_char(c) => CharType::Word,
+            c if c == '\n' || c == '\r' => CharType::Newline,
+            c if c.is_whitespace() => CharType::Whitespace,
+            _ => CharType::Other,
+        }
+    }
+}
+
+impl CharType {
+    fn is_connectable(self, c: char) -> bool {
+        matches!(
+            (self, CharType::from(c)),
+            (CharType::Word, CharType::Word) | (CharType::Whitespace, CharType::Whitespace)
+        )
+    }
+}
+
+fn is_word_char(c: char) -> bool {
+    matches!(c, '_')
+        // ASCII alphanumeric characters, for English, numbers: `Hello123`, etc.
+        || c.is_ascii_alphanumeric()
+        // Latin script in Unicode for French, German, Spanish, etc.
+        || matches!(c, '\u{00C0}'..='\u{00FF}')
+        || matches!(c, '\u{0100}'..='\u{017F}')
+        || matches!(c, '\u{0180}'..='\u{024F}')
+        // Cyrillic for Russian, Ukrainian, etc.
+        || matches!(c, '\u{0400}'..='\u{04FF}')
+        // Vietnamese
+        || matches!(c, '\u{1E00}'..='\u{1EFF}')
+        || matches!(c, '\u{0300}'..='\u{036F}')
+}
+
+pub(crate) fn word_range_from_chars(
+    offset: usize,
+    c: char,
+    prev_chars: impl Iterator<Item = char>,
+    next_chars: impl Iterator<Item = char>,
+) -> Range<usize> {
+    let char_type = CharType::from(c);
+    let mut start = offset;
+    let mut end = offset + c.len_utf8();
+
+    for prev in prev_chars.take(128) {
+        if char_type.is_connectable(prev) {
+            start -= prev.len_utf8();
+        } else {
+            break;
+        }
+    }
+
+    for next in next_chars.take(128) {
+        if char_type.is_connectable(next) {
+            end += next.len_utf8();
+        } else {
+            break;
+        }
+    }
+
+    start..end
+}