Render every LSP snippets for every cursor

This refactors the snippet logic to be largely unaware of the rest of
the document. The completion application logic is moved into
generate_transaction_from_snippet which is extended to support
dynamically computing replacement text.

1 files changed, 79 insertions, 0 deletions

diff --git a/helix-lsp/src/lib.rs b/helix-lsp/src/lib.rs
index cce848ab..5b4f7ee4 100644
--- a/helix-lsp/src/lib.rs
+++ b/helix-lsp/src/lib.rs
@@ -60,6 +60,7 @@ pub mod util {
     use super::*;
     use helix_core::line_ending::{line_end_byte_index, line_end_char_index};
     use helix_core::{diagnostic::NumberOrString, Range, Rope, Selection, Tendril, Transaction};
+    use helix_core::{smallvec, SmallVec};
 
     /// Converts a diagnostic in the document to [`lsp::Diagnostic`].
     ///
@@ -282,6 +283,84 @@ pub mod util {
         })
     }
 
+    /// Creates a [Transaction] from the [snippet::Snippet] in a completion response.
+    /// The transaction applies the edit to all cursors.
+    pub fn generate_transaction_from_snippet(
+        doc: &Rope,
+        selection: &Selection,
+        edit_range: &lsp::Range,
+        snippet: snippet::Snippet,
+        line_ending: &str,
+        include_placeholder: bool,
+        offset_encoding: OffsetEncoding,
+    ) -> Transaction {
+        let text = doc.slice(..);
+        let primary_cursor = selection.primary().cursor(text);
+
+        let start_offset = match lsp_pos_to_pos(doc, edit_range.start, offset_encoding) {
+            Some(start) => start as i128 - primary_cursor as i128,
+            None => return Transaction::new(doc),
+        };
+        let end_offset = match lsp_pos_to_pos(doc, edit_range.end, offset_encoding) {
+            Some(end) => end as i128 - primary_cursor as i128,
+            None => return Transaction::new(doc),
+        };
+
+        // For each cursor store offsets for the first tabstop
+        let mut cursor_tabstop_offsets = Vec::<SmallVec<[(i128, i128); 1]>>::new();
+        let transaction = Transaction::change_by_selection(doc, selection, |range| {
+            let cursor = range.cursor(text);
+            let replacement_start = (cursor as i128 + start_offset) as usize;
+            let replacement_end = (cursor as i128 + end_offset) as usize;
+            let newline_with_offset = format!(
+                "{line_ending}{blank:width$}",
+                line_ending = line_ending,
+                width = replacement_start - doc.line_to_char(doc.char_to_line(replacement_start)),
+                blank = ""
+            );
+
+            let (replacement, tabstops) =
+                snippet::render(&snippet, newline_with_offset, include_placeholder);
+
+            let replacement_len = replacement.chars().count();
+            cursor_tabstop_offsets.push(
+                tabstops
+                    .first()
+                    .unwrap_or(&smallvec![(replacement_len, replacement_len)])
+                    .iter()
+                    .map(|(from, to)| -> (i128, i128) {
+                        (
+                            *from as i128 - replacement_len as i128,
+                            *to as i128 - replacement_len as i128,
+                        )
+                    })
+                    .collect(),
+            );
+
+            (replacement_start, replacement_end, Some(replacement.into()))
+        });
+
+        // Create new selection based on the cursor tabstop from above
+        let mut cursor_tabstop_offsets_iter = cursor_tabstop_offsets.iter();
+        let selection = selection
+            .clone()
+            .map(transaction.changes())
+            .transform_iter(|range| {
+                cursor_tabstop_offsets_iter
+                    .next()
+                    .unwrap()
+                    .iter()
+                    .map(move |(from, to)| {
+                        Range::new(
+                            (range.anchor as i128 + *from) as usize,
+                            (range.anchor as i128 + *to) as usize,
+                        )
+                    })
+            });
+
+        transaction.with_selection(selection)
+    }
+
     pub fn generate_transaction_from_edits(
         doc: &Rope,
         mut edits: Vec<lsp::TextEdit>,