1 files changed, 334 insertions, 0 deletions

diff --git a/crates/ra_ide_db/src/line_index_utils.rs b/crates/ra_ide_db/src/line_index_utils.rs
new file mode 100644
index 000000000..daf9d8ab9
--- /dev/null
+++ b/crates/ra_ide_db/src/line_index_utils.rs
@@ -0,0 +1,334 @@
+//! FIXME: write short doc here
+
+use ra_syntax::{TextRange, TextUnit};
+use ra_text_edit::{AtomTextEdit, TextEdit};
+
+use crate::line_index::{LineCol, LineIndex, Utf16Char};
+
+#[derive(Debug, Clone)]
+enum Step {
+    Newline(TextUnit),
+    Utf16Char(TextRange),
+}
+
+#[derive(Debug)]
+struct LineIndexStepIter<'a> {
+    line_index: &'a LineIndex,
+    next_newline_idx: usize,
+    utf16_chars: Option<(TextUnit, std::slice::Iter<'a, Utf16Char>)>,
+}
+
+impl<'a> LineIndexStepIter<'a> {
+    fn from(line_index: &LineIndex) -> LineIndexStepIter {
+        let mut x = LineIndexStepIter { line_index, next_newline_idx: 0, utf16_chars: None };
+        // skip first newline since it's not real
+        x.next();
+        x
+    }
+}
+
+impl<'a> Iterator for LineIndexStepIter<'a> {
+    type Item = Step;
+    fn next(&mut self) -> Option<Step> {
+        self.utf16_chars
+            .as_mut()
+            .and_then(|(newline, x)| {
+                let x = x.next()?;
+                Some(Step::Utf16Char(TextRange::from_to(*newline + x.start, *newline + x.end)))
+            })
+            .or_else(|| {
+                let next_newline = *self.line_index.newlines.get(self.next_newline_idx)?;
+                self.utf16_chars = self
+                    .line_index
+                    .utf16_lines
+                    .get(&(self.next_newline_idx as u32))
+                    .map(|x| (next_newline, x.iter()));
+                self.next_newline_idx += 1;
+                Some(Step::Newline(next_newline))
+            })
+    }
+}
+
+#[derive(Debug)]
+struct OffsetStepIter<'a> {
+    text: &'a str,
+    offset: TextUnit,
+}
+
+impl<'a> Iterator for OffsetStepIter<'a> {
+    type Item = Step;
+    fn next(&mut self) -> Option<Step> {
+        let (next, next_offset) = self
+            .text
+            .char_indices()
+            .filter_map(|(i, c)| {
+                if c == '\n' {
+                    let next_offset = self.offset + TextUnit::from_usize(i + 1);
+                    let next = Step::Newline(next_offset);
+                    Some((next, next_offset))
+                } else {
+                    let char_len = TextUnit::of_char(c);
+                    if char_len.to_usize() > 1 {
+                        let start = self.offset + TextUnit::from_usize(i);
+                        let end = start + char_len;
+                        let next = Step::Utf16Char(TextRange::from_to(start, end));
+                        let next_offset = end;
+                        Some((next, next_offset))
+                    } else {
+                        None
+                    }
+                }
+            })
+            .next()?;
+        let next_idx = (next_offset - self.offset).to_usize();
+        self.text = &self.text[next_idx..];
+        self.offset = next_offset;
+        Some(next)
+    }
+}
+
+#[derive(Debug)]
+enum NextSteps<'a> {
+    Use,
+    ReplaceMany(OffsetStepIter<'a>),
+    AddMany(OffsetStepIter<'a>),
+}
+
+#[derive(Debug)]
+struct TranslatedEdit<'a> {
+    delete: TextRange,
+    insert: &'a str,
+    diff: i64,
+}
+
+struct Edits<'a> {
+    edits: &'a [AtomTextEdit],
+    current: Option<TranslatedEdit<'a>>,
+    acc_diff: i64,
+}
+
+impl<'a> Edits<'a> {
+    fn from_text_edit(text_edit: &'a TextEdit) -> Edits<'a> {
+        let mut x = Edits { edits: text_edit.as_atoms(), current: None, acc_diff: 0 };
+        x.advance_edit();
+        x
+    }
+    fn advance_edit(&mut self) {
+        self.acc_diff += self.current.as_ref().map_or(0, |x| x.diff);
+        match self.edits.split_first() {
+            Some((next, rest)) => {
+                let delete = self.translate_range(next.delete);
+                let diff = next.insert.len() as i64 - next.delete.len().to_usize() as i64;
+                self.current = Some(TranslatedEdit { delete, insert: &next.insert, diff });
+                self.edits = rest;
+            }
+            None => {
+                self.current = None;
+            }
+        }
+    }
+
+    fn next_inserted_steps(&mut self) -> Option<OffsetStepIter<'a>> {
+        let cur = self.current.as_ref()?;
+        let res = Some(OffsetStepIter { offset: cur.delete.start(), text: &cur.insert });
+        self.advance_edit();
+        res
+    }
+
+    fn next_steps(&mut self, step: &Step) -> NextSteps {
+        let step_pos = match *step {
+            Step::Newline(n) => n,
+            Step::Utf16Char(r) => r.end(),
+        };
+        match &mut self.current {
+            Some(edit) => {
+                if step_pos <= edit.delete.start() {
+                    NextSteps::Use
+                } else if step_pos <= edit.delete.end() {
+                    let iter = OffsetStepIter { offset: edit.delete.start(), text: &edit.insert };
+                    // empty slice to avoid returning steps again
+                    edit.insert = &edit.insert[edit.insert.len()..];
+                    NextSteps::ReplaceMany(iter)
+                } else {
+                    let iter = OffsetStepIter { offset: edit.delete.start(), text: &edit.insert };
+                    // empty slice to avoid returning steps again
+                    edit.insert = &edit.insert[edit.insert.len()..];
+                    self.advance_edit();
+                    NextSteps::AddMany(iter)
+                }
+            }
+            None => NextSteps::Use,
+        }
+    }
+
+    fn translate_range(&self, range: TextRange) -> TextRange {
+        if self.acc_diff == 0 {
+            range
+        } else {
+            let start = self.translate(range.start());
+            let end = self.translate(range.end());
+            TextRange::from_to(start, end)
+        }
+    }
+
+    fn translate(&self, x: TextUnit) -> TextUnit {
+        if self.acc_diff == 0 {
+            x
+        } else {
+            TextUnit::from((x.to_usize() as i64 + self.acc_diff) as u32)
+        }
+    }
+
+    fn translate_step(&self, x: &Step) -> Step {
+        if self.acc_diff == 0 {
+            x.clone()
+        } else {
+            match *x {
+                Step::Newline(n) => Step::Newline(self.translate(n)),
+                Step::Utf16Char(r) => Step::Utf16Char(self.translate_range(r)),
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+struct RunningLineCol {
+    line: u32,
+    last_newline: TextUnit,
+    col_adjust: TextUnit,
+}
+
+impl RunningLineCol {
+    fn new() -> RunningLineCol {
+        RunningLineCol { line: 0, last_newline: TextUnit::from(0), col_adjust: TextUnit::from(0) }
+    }
+
+    fn to_line_col(&self, offset: TextUnit) -> LineCol {
+        LineCol {
+            line: self.line,
+            col_utf16: ((offset - self.last_newline) - self.col_adjust).into(),
+        }
+    }
+
+    fn add_line(&mut self, newline: TextUnit) {
+        self.line += 1;
+        self.last_newline = newline;
+        self.col_adjust = TextUnit::from(0);
+    }
+
+    fn adjust_col(&mut self, range: TextRange) {
+        self.col_adjust += range.len() - TextUnit::from(1);
+    }
+}
+
+pub fn translate_offset_with_edit(
+    line_index: &LineIndex,
+    offset: TextUnit,
+    text_edit: &TextEdit,
+) -> LineCol {
+    let mut state = Edits::from_text_edit(&text_edit);
+
+    let mut res = RunningLineCol::new();
+
+    macro_rules! test_step {
+        ($x:ident) => {
+            match &$x {
+                Step::Newline(n) => {
+                    if offset < *n {
+                        return res.to_line_col(offset);
+                    } else {
+                        res.add_line(*n);
+                    }
+                }
+                Step::Utf16Char(x) => {
+                    if offset < x.end() {
+                        // if the offset is inside a multibyte char it's invalid
+                        // clamp it to the start of the char
+                        let clamp = offset.min(x.start());
+                        return res.to_line_col(clamp);
+                    } else {
+                        res.adjust_col(*x);
+                    }
+                }
+            }
+        };
+    }
+
+    for orig_step in LineIndexStepIter::from(line_index) {
+        loop {
+            let translated_step = state.translate_step(&orig_step);
+            match state.next_steps(&translated_step) {
+                NextSteps::Use => {
+                    test_step!(translated_step);
+                    break;
+                }
+                NextSteps::ReplaceMany(ns) => {
+                    for n in ns {
+                        test_step!(n);
+                    }
+                    break;
+                }
+                NextSteps::AddMany(ns) => {
+                    for n in ns {
+                        test_step!(n);
+                    }
+                }
+            }
+        }
+    }
+
+    loop {
+        match state.next_inserted_steps() {
+            None => break,
+            Some(ns) => {
+                for n in ns {
+                    test_step!(n);
+                }
+            }
+        }
+    }
+
+    res.to_line_col(offset)
+}
+
+#[cfg(test)]
+mod test {
+    use proptest::{prelude::*, proptest};
+    use ra_text_edit::test_utils::{arb_offset, arb_text_with_edit};
+    use ra_text_edit::TextEdit;
+
+    use crate::line_index;
+
+    use super::*;
+
+    #[derive(Debug)]
+    struct ArbTextWithEditAndOffset {
+        text: String,
+        edit: TextEdit,
+        edited_text: String,
+        offset: TextUnit,
+    }
+
+    fn arb_text_with_edit_and_offset() -> BoxedStrategy<ArbTextWithEditAndOffset> {
+        arb_text_with_edit()
+            .prop_flat_map(|x| {
+                let edited_text = x.edit.apply(&x.text);
+                let arb_offset = arb_offset(&edited_text);
+                (Just(x), Just(edited_text), arb_offset).prop_map(|(x, edited_text, offset)| {
+                    ArbTextWithEditAndOffset { text: x.text, edit: x.edit, edited_text, offset }
+                })
+            })
+            .boxed()
+    }
+
+    proptest! {
+        #[test]
+        fn test_translate_offset_with_edit(x in arb_text_with_edit_and_offset()) {
+            let expected = line_index::to_line_col(&x.edited_text, x.offset);
+            let line_index = LineIndex::new(&x.text);
+            let actual = translate_offset_with_edit(&line_index, x.offset, &x.edit);
+
+            assert_eq!(actual, expected);
+        }
+    }
+}