Auto pairs selection (#1254)

* use auto pairs with selections

Previously, the auto pairs code was converting the user selection into
its cursor form, and setting the transaction's selection to that cursor.
This has the effect of destroying the user's selection if they type a
pair character that gets auto completed.

This fixes the code to work with the user's selection, inserting auto
pairs where appropriate, but either keeping or extending the user's
selection.

* use movement::Direction instead of bool

* assume 0-width cursor is forward

2 files changed, 275 insertions, 80 deletions

diff --git a/helix-core/src/auto_pairs.rs b/helix-core/src/auto_pairs.rs
index c037afef..1b3de6ea 100644
--- a/helix-core/src/auto_pairs.rs
+++ b/helix-core/src/auto_pairs.rs
@@ -1,7 +1,7 @@
 //! When typing the opening character of one of the possible pairs defined below,
 //! this module provides the functionality to insert the paired closing character.
 
-use crate::{Range, Rope, Selection, Tendril, Transaction};
+use crate::{movement::Direction, Range, Rope, Selection, Tendril, Transaction};
 use log::debug;
 use smallvec::SmallVec;
 
@@ -30,7 +30,6 @@ const CLOSE_BEFORE: &str = ")]}'\":;,> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{20
 
 // [TODO]
 // * delete implementation where it erases the whole bracket (|) -> |
-// * do not reduce to cursors; use whole selections, and surround with pair
 // * change to multi character pairs to handle cases like placing the cursor in the
 //   middle of triple quotes, and more exotic pairs like Jinja's {% %}
 
@@ -38,20 +37,18 @@ const CLOSE_BEFORE: &str = ")]}'\":;,> \n\r\u{000B}\u{000C}\u{0085}\u{2028}\u{20
 pub fn hook(doc: &Rope, selection: &Selection, ch: char) -> Option<Transaction> {
     debug!("autopairs hook selection: {:#?}", selection);
 
-    let cursors = selection.clone().cursors(doc.slice(..));
-
     for &(open, close) in PAIRS {
         if open == ch {
             if open == close {
-                return Some(handle_same(doc, &cursors, open, CLOSE_BEFORE, OPEN_BEFORE));
+                return Some(handle_same(doc, selection, open, CLOSE_BEFORE, OPEN_BEFORE));
             } else {
-                return Some(handle_open(doc, &cursors, open, close, CLOSE_BEFORE));
+                return Some(handle_open(doc, selection, open, close, CLOSE_BEFORE));
             }
         }
 
         if close == ch {
             // && char_at pos == close
-            return Some(handle_close(doc, &cursors, open, close));
+            return Some(handle_close(doc, selection, open, close));
         }
     }
 
@@ -66,6 +63,36 @@ fn prev_char(doc: &Rope, pos: usize) -> Option<char> {
     doc.get_char(pos - 1)
 }
 
+/// calculate what the resulting range should be for an auto pair insertion
+fn get_next_range(
+    start_range: &Range,
+    offset: usize,
+    typed_char: char,
+    len_inserted: usize,
+) -> Range {
+    let end_head = start_range.head + offset + typed_char.len_utf8();
+
+    let end_anchor = match (start_range.len(), start_range.direction()) {
+        // if we have a zero width cursor, it shifts to the same number
+        (0, _) => end_head,
+
+        // if we are inserting for a regular one-width cursor, the anchor
+        // moves with the head
+        (1, Direction::Forward) => end_head - 1,
+        (1, Direction::Backward) => end_head + 1,
+
+        // if we are appending, the anchor stays where it is; only offset
+        // for multiple range insertions
+        (_, Direction::Forward) => start_range.anchor + offset,
+
+        // when we are inserting in front of a selection, we need to move
+        // the anchor over by however many characters were inserted overall
+        (_, Direction::Backward) => start_range.anchor + offset + len_inserted,
+    };
+
+    Range::new(end_anchor, end_head)
+}
+
 fn handle_open(
     doc: &Rope,
     selection: &Selection,
@@ -74,36 +101,32 @@ fn handle_open(
     close_before: &str,
 ) -> Transaction {
     let mut end_ranges = SmallVec::with_capacity(selection.len());
-
     let mut offs = 0;
 
     let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
-        let start_head = start_range.head;
-
-        let next = doc.get_char(start_head);
-        let end_head = start_head + offs + open.len_utf8();
-
-        let end_anchor = if start_range.is_empty() {
-            end_head
-        } else {
-            start_range.anchor + offs
-        };
-
-        end_ranges.push(Range::new(end_anchor, end_head));
+        let cursor = start_range.cursor(doc.slice(..));
+        let next_char = doc.get_char(cursor);
+        let len_inserted;
 
-        match next {
+        let change = match next_char {
             Some(ch) if !close_before.contains(ch) => {
-                offs += open.len_utf8();
-                (start_head, start_head, Some(Tendril::from_char(open)))
+                len_inserted = open.len_utf8();
+                (cursor, cursor, Some(Tendril::from_char(open)))
             }
             // None | Some(ch) if close_before.contains(ch) => {}
             _ => {
                 // insert open & close
                 let pair = Tendril::from_iter([open, close]);
-                offs += open.len_utf8() + close.len_utf8();
-                (start_head, start_head, Some(pair))
+                len_inserted = open.len_utf8() + close.len_utf8();
+                (cursor, cursor, Some(pair))
             }
-        }
+        };
+
+        let next_range = get_next_range(start_range, offs, open, len_inserted);
+        end_ranges.push(next_range);
+        offs += len_inserted;
+
+        change
     });
 
     let t = transaction.with_selection(Selection::new(end_ranges, selection.primary_index()));
@@ -117,28 +140,28 @@ fn handle_close(doc: &Rope, selection: &Selection, _open: char, close: char) ->
     let mut offs = 0;
 
     let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
-        let start_head = start_range.head;
-        let next = doc.get_char(start_head);
-        let end_head = start_head + offs + close.len_utf8();
+        let cursor = start_range.cursor(doc.slice(..));
+        let next_char = doc.get_char(cursor);
+        let mut len_inserted = 0;
 
-        let end_anchor = if start_range.is_empty() {
-            end_head
+        let change = if next_char == Some(close) {
+            // return transaction that moves past close
+            (cursor, cursor, None) // no-op
         } else {
-            start_range.anchor + offs
+            len_inserted += close.len_utf8();
+            (cursor, cursor, Some(Tendril::from_char(close)))
         };
 
-        end_ranges.push(Range::new(end_anchor, end_head));
+        let next_range = get_next_range(start_range, offs, close, len_inserted);
+        end_ranges.push(next_range);
+        offs += len_inserted;
 
-        if next == Some(close) {
-            // return transaction that moves past close
-            (start_head, start_head, None) // no-op
-        } else {
-            offs += close.len_utf8();
-            (start_head, start_head, Some(Tendril::from_char(close)))
-        }
+        change
     });
 
-    transaction.with_selection(Selection::new(end_ranges, selection.primary_index()))
+    let t = transaction.with_selection(Selection::new(end_ranges, selection.primary_index()));
+    debug!("auto pair transaction: {:#?}", t);
+    t
 }
 
 /// handle cases where open and close is the same, or in triples ("""docstring""")
@@ -154,42 +177,41 @@ fn handle_same(
     let mut offs = 0;
 
     let transaction = Transaction::change_by_selection(doc, selection, |start_range| {
-        let start_head = start_range.head;
-        let end_head = start_head + offs + token.len_utf8();
+        let cursor = start_range.cursor(doc.slice(..));
+        let mut len_inserted = 0;
 
-        // if selection, retain anchor, if cursor, move over
-        let end_anchor = if start_range.is_empty() {
-            end_head
-        } else {
-            start_range.anchor + offs
-        };
+        let next_char = doc.get_char(cursor);
+        let prev_char = prev_char(doc, cursor);
 
-        end_ranges.push(Range::new(end_anchor, end_head));
-
-        let next = doc.get_char(start_head);
-        let prev = prev_char(doc, start_head);
-
-        if next == Some(token) {
+        let change = if next_char == Some(token) {
             //  return transaction that moves past close
-            (start_head, start_head, None) // no-op
+            (cursor, cursor, None) // no-op
         } else {
             let mut pair = Tendril::with_capacity(2 * token.len_utf8() as u32);
             pair.push_char(token);
 
             // for equal pairs, don't insert both open and close if either
             // side has a non-pair char
-            if (next.is_none() || close_before.contains(next.unwrap()))
-                && (prev.is_none() || open_before.contains(prev.unwrap()))
+            if (next_char.is_none() || close_before.contains(next_char.unwrap()))
+                && (prev_char.is_none() || open_before.contains(prev_char.unwrap()))
             {
                 pair.push_char(token);
             }
 
-            offs += pair.len();
-            (start_head, start_head, Some(pair))
-        }
+            len_inserted += pair.len();
+            (cursor, cursor, Some(pair))
+        };
+
+        let next_range = get_next_range(start_range, offs, token, len_inserted);
+        end_ranges.push(next_range);
+        offs += len_inserted;
+
+        change
     });
 
-    transaction.with_selection(Selection::new(end_ranges, selection.primary_index()))
+    let t = transaction.with_selection(Selection::new(end_ranges, selection.primary_index()));
+    debug!("auto pair transaction: {:#?}", t);
+    t
 }
 
 #[cfg(test)]
@@ -252,7 +274,20 @@ mod test {
             &Selection::single(1, 0),
             PAIRS,
             |open, close| format!("{}{}", open, close),
-            &Selection::single(1, 1),
+            &Selection::single(2, 1),
+        );
+    }
+
+    /// [] -> append ( -> ([])
+    #[test]
+    fn test_append_blank() {
+        test_hooks_with_pairs(
+            // this is what happens when you have a totally blank document and then append
+            &Rope::from("\n\n"),
+            &Selection::single(0, 2),
+            PAIRS,
+            |open, close| format!("\n{}{}\n", open, close),
+            &Selection::single(0, 3),
         );
     }
 
@@ -276,26 +311,50 @@ mod test {
                 )
             },
             &Selection::new(
-                smallvec!(Range::point(1), Range::point(4), Range::point(7),),
+                smallvec!(Range::new(2, 1), Range::new(5, 4), Range::new(8, 7),),
                 0,
             ),
         );
     }
 
-    // [TODO] broken until it works with selections
     /// fo[o] -> append ( -> fo[o(])
-    #[ignore]
     #[test]
     fn test_append() {
         test_hooks_with_pairs(
-            &Rope::from("foo"),
+            &Rope::from("foo\n"),
             &Selection::single(2, 4),
-            PAIRS,
-            |open, close| format!("foo{}{}", open, close),
+            differing_pairs(),
+            |open, close| format!("foo{}{}\n", open, close),
             &Selection::single(2, 5),
         );
     }
 
+    /// fo[o]                fo[o(])
+    /// fo[o] -> append ( -> fo[o(])
+    /// fo[o]                fo[o(])
+    #[test]
+    fn test_append_multi() {
+        test_hooks_with_pairs(
+            &Rope::from("foo\nfoo\nfoo\n"),
+            &Selection::new(
+                smallvec!(Range::new(2, 4), Range::new(6, 8), Range::new(10, 12)),
+                0,
+            ),
+            differing_pairs(),
+            |open, close| {
+                format!(
+                    "foo{open}{close}\nfoo{open}{close}\nfoo{open}{close}\n",
+                    open = open,
+                    close = close
+                )
+            },
+            &Selection::new(
+                smallvec!(Range::new(2, 5), Range::new(8, 11), Range::new(14, 17)),
+                0,
+            ),
+        );
+    }
+
     /// ([]) -> insert ) -> ()[]
     #[test]
     fn test_insert_close_inside_pair() {
@@ -307,7 +366,23 @@ mod test {
                 &Selection::single(2, 1),
                 *close,
                 &doc,
-                &Selection::point(2),
+                &Selection::single(3, 2),
+            );
+        }
+    }
+
+    /// [(]) -> append ) -> [()]
+    #[test]
+    fn test_append_close_inside_pair() {
+        for (open, close) in PAIRS {
+            let doc = Rope::from(format!("{}{}\n", open, close));
+
+            test_hooks(
+                &doc,
+                &Selection::single(0, 2),
+                *close,
+                &doc,
+                &Selection::single(0, 3),
             );
         }
     }
@@ -323,8 +398,33 @@ mod test {
         );
 
         let expected_sel = Selection::new(
-            // smallvec!(Range::new(3, 2), Range::new(6, 5), Range::new(9, 8),),
-            smallvec!(Range::point(2), Range::point(5), Range::point(8),),
+            smallvec!(Range::new(3, 2), Range::new(6, 5), Range::new(9, 8),),
+            0,
+        );
+
+        for (open, close) in PAIRS {
+            let doc = Rope::from(format!(
+                "{open}{close}\n{open}{close}\n{open}{close}\n",
+                open = open,
+                close = close
+            ));
+
+            test_hooks(&doc, &sel, *close, &doc, &expected_sel);
+        }
+    }
+
+    /// [(])                [()]
+    /// [(]) -> append ) -> [()]
+    /// [(])                [()]
+    #[test]
+    fn test_append_close_inside_pair_multi_cursor() {
+        let sel = Selection::new(
+            smallvec!(Range::new(0, 2), Range::new(3, 5), Range::new(6, 8),),
+            0,
+        );
+
+        let expected_sel = Selection::new(
+            smallvec!(Range::new(0, 3), Range::new(3, 6), Range::new(6, 9),),
             0,
         );
 
@@ -343,7 +443,7 @@ mod test {
     #[test]
     fn test_insert_open_inside_pair() {
         let sel = Selection::single(2, 1);
-        let expected_sel = Selection::point(2);
+        let expected_sel = Selection::single(3, 2);
 
         for (open, close) in differing_pairs() {
             let doc = Rope::from(format!("{}{}", open, close));
@@ -357,11 +457,49 @@ mod test {
         }
     }
 
+    /// [word(]) -> append ( -> [word((]))
+    #[test]
+    fn test_append_open_inside_pair() {
+        let sel = Selection::single(0, 6);
+        let expected_sel = Selection::single(0, 7);
+
+        for (open, close) in differing_pairs() {
+            let doc = Rope::from(format!("word{}{}", open, close));
+            let expected_doc = Rope::from(format!(
+                "word{open}{open}{close}{close}",
+                open = open,
+                close = close
+            ));
+
+            test_hooks(&doc, &sel, *open, &expected_doc, &expected_sel);
+        }
+    }
+
     /// ([]) -> insert " -> ("[]")
     #[test]
     fn test_insert_nested_open_inside_pair() {
         let sel = Selection::single(2, 1);
-        let expected_sel = Selection::point(2);
+        let expected_sel = Selection::single(3, 2);
+
+        for (outer_open, outer_close) in differing_pairs() {
+            let doc = Rope::from(format!("{}{}", outer_open, outer_close,));
+
+            for (inner_open, inner_close) in matching_pairs() {
+                let expected_doc = Rope::from(format!(
+                    "{}{}{}{}",
+                    outer_open, inner_open, inner_close, outer_close
+                ));
+
+                test_hooks(&doc, &sel, *inner_open, &expected_doc, &expected_sel);
+            }
+        }
+    }
+
+    /// [(]) -> append " -> [("]")
+    #[test]
+    fn test_append_nested_open_inside_pair() {
+        let sel = Selection::single(0, 2);
+        let expected_sel = Selection::single(0, 3);
 
         for (outer_open, outer_close) in differing_pairs() {
             let doc = Rope::from(format!("{}{}", outer_open, outer_close,));
@@ -385,21 +523,44 @@ mod test {
             &Selection::single(1, 0),
             PAIRS,
             |open, _| format!("{}word", open),
-            &Selection::point(1),
+            &Selection::single(2, 1),
         )
     }
 
-    // [TODO] broken until it works with selections
     /// [wor]d -> insert ( -> ([wor]d
     #[test]
-    #[ignore]
     fn test_insert_open_with_selection() {
         test_hooks_with_pairs(
             &Rope::from("word"),
-            &Selection::single(0, 4),
+            &Selection::single(3, 0),
             PAIRS,
             |open, _| format!("{}word", open),
-            &Selection::single(1, 5),
+            &Selection::single(4, 1),
+        )
+    }
+
+    /// [wor]d -> append ) -> [wor)]d
+    #[test]
+    fn test_append_close_inside_non_pair_with_selection() {
+        let sel = Selection::single(0, 4);
+        let expected_sel = Selection::single(0, 5);
+
+        for (_, close) in PAIRS {
+            let doc = Rope::from("word");
+            let expected_doc = Rope::from(format!("wor{}d", close));
+            test_hooks(&doc, &sel, *close, &expected_doc, &expected_sel);
+        }
+    }
+
+    /// foo[ wor]d -> insert ( -> foo([) wor]d
+    #[test]
+    fn test_insert_open_trailing_word_with_selection() {
+        test_hooks_with_pairs(
+            &Rope::from("foo word"),
+            &Selection::single(7, 3),
+            differing_pairs(),
+            |open, close| format!("foo{}{} word", open, close),
+            &Selection::single(9, 4),
         )
     }
 
@@ -413,7 +574,7 @@ mod test {
     fn test_insert_open_after_non_pair() {
         let doc = Rope::from("word");
         let sel = Selection::single(5, 4);
-        let expected_sel = Selection::point(5);
+        let expected_sel = Selection::single(6, 5);
 
         test_hooks_with_pairs(
             &doc,
@@ -431,4 +592,18 @@ mod test {
             &expected_sel,
         );
     }
+
+    /// appending with only a cursor should stay a cursor
+    ///
+    /// [] -> append to end "foo -> "foo[]"
+    #[test]
+    fn test_append_single_cursor() {
+        test_hooks_with_pairs(
+            &Rope::from("\n"),
+            &Selection::single(0, 1),
+            PAIRS,
+            |open, close| format!("{}{}\n", open, close),
+            &Selection::single(1, 2),
+        );
+    }
 }
diff --git a/helix-core/src/selection.rs b/helix-core/src/selection.rs
index 116a1c7c..884c98ac 100644
--- a/helix-core/src/selection.rs
+++ b/helix-core/src/selection.rs
@@ -7,6 +7,7 @@ use crate::{
         ensure_grapheme_boundary_next, ensure_grapheme_boundary_prev, next_grapheme_boundary,
         prev_grapheme_boundary,
     },
+    movement::Direction,
     Assoc, ChangeSet, RopeSlice,
 };
 use smallvec::{smallvec, SmallVec};
@@ -82,6 +83,13 @@ impl Range {
         std::cmp::max(self.anchor, self.head)
     }
 
+    /// Total length of the range.
+    #[inline]
+    #[must_use]
+    pub fn len(&self) -> usize {
+        self.to() - self.from()
+    }
+
     /// The (inclusive) range of lines that the range overlaps.
     #[inline]
     #[must_use]
@@ -102,6 +110,18 @@ impl Range {
         self.anchor == self.head
     }
 
+    /// `Direction::Backward` when head < anchor.
+    /// `Direction::Backward` otherwise.
+    #[inline]
+    #[must_use]
+    pub fn direction(&self) -> Direction {
+        if self.head < self.anchor {
+            Direction::Backward
+        } else {
+            Direction::Forward
+        }
+    }
+
     /// Check two ranges for overlap.
     #[must_use]
     pub fn overlaps(&self, other: &Self) -> bool {