Add paragraph textobject

Change parameter/argument key from p to a since paragraph only have p
but parameter are also called arguments sometimes and a is not used.

5 files changed, 162 insertions, 14 deletions

diff --git a/book/src/keymap.md b/book/src/keymap.md
index e588ac92..2fbc7b3f 100644
--- a/book/src/keymap.md
+++ b/book/src/keymap.md
@@ -277,6 +277,8 @@ Mappings in the style of [vim-unimpaired](https://github.com/tpope/vim-unimpaire
 | `[a`     | Go to previous argument/parameter (**TS**)   | `goto_prev_parameter` |
 | `]o`     | Go to next comment (**TS**)                  | `goto_next_comment`   |
 | `[o`     | Go to previous comment (**TS**)              | `goto_prev_comment`   |
+| `]p`     | Go to next paragraph                         | `goto_next_paragraph` |
+| `[p`     | Go to previous paragraph                     | `goto_prev_paragraph` |
 | `[space` | Add newline above                            | `add_newline_above`   |
 | `]space` | Add newline below                            | `add_newline_below`   |
 
diff --git a/helix-core/src/movement.rs b/helix-core/src/movement.rs
index dec6eeb9..970aff88 100644
--- a/helix-core/src/movement.rs
+++ b/helix-core/src/movement.rs
@@ -153,12 +153,12 @@ fn word_move(slice: RopeSlice, range: Range, count: usize, target: WordMotionTar
 pub fn move_prev_para(slice: RopeSlice, range: Range, count: usize, behavior: Movement) -> Range {
     let mut line = range.cursor_line(slice);
     let first_char = slice.line_to_char(line) == range.cursor(slice);
+    let prev_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
     let curr_line_empty = rope_is_line_ending(slice.line(line));
-    let last_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
-    let line_to_empty = last_line_empty && !curr_line_empty;
+    let prev_empty_to_line = prev_line_empty && !curr_line_empty;
 
-    // iterate current line if first character after paragraph boundary
-    if line_to_empty && !first_char {
+    // skip character before paragraph boundary
+    if prev_empty_to_line && !first_char {
         line += 1;
     }
     let mut lines = slice.lines_at(line);
@@ -176,7 +176,7 @@ pub fn move_prev_para(slice: RopeSlice, range: Range, count: usize, behavior: Mo
     let head = slice.line_to_char(line);
     let anchor = if behavior == Movement::Move {
         // exclude first character after paragraph boundary
-        if line_to_empty && first_char {
+        if prev_empty_to_line && first_char {
             range.cursor(slice)
         } else {
             range.head
@@ -193,13 +193,12 @@ pub fn move_next_para(slice: RopeSlice, range: Range, count: usize, behavior: Mo
         prev_grapheme_boundary(slice, slice.line_to_char(line + 1)) == range.cursor(slice);
     let curr_line_empty = rope_is_line_ending(slice.line(line));
     let next_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
-    let empty_to_line = curr_line_empty && !next_line_empty;
+    let curr_empty_to_line = curr_line_empty && !next_line_empty;
 
-    // iterate current line if first character after paragraph boundary
-    if empty_to_line && last_char {
+    // skip character after paragraph boundary
+    if curr_empty_to_line && last_char {
         line += 1;
     }
-
     let mut lines = slice.lines_at(line).map(rope_is_line_ending).peekable();
     for _ in 0..count {
         while lines.next_if(|&e| !e).is_some() {
@@ -211,7 +210,7 @@ pub fn move_next_para(slice: RopeSlice, range: Range, count: usize, behavior: Mo
     }
     let head = slice.line_to_char(line);
     let anchor = if behavior == Movement::Move {
-        if empty_to_line && last_char {
+        if curr_empty_to_line && last_char {
             range.head
         } else {
             range.cursor(slice)
@@ -1256,7 +1255,7 @@ mod test {
     #[test]
     fn test_behaviour_when_moving_to_prev_paragraph_single() {
         let tests = [
-            ("^@", "@^"),
+            ("^@", "^@"),
             ("^s@tart at\nfirst char\n", "@s^tart at\nfirst char\n"),
             ("start at\nlast char^\n@", "@start at\nlast char\n^"),
             ("goto\nfirst\n\n^p@aragraph", "@goto\nfirst\n\n^paragraph"),
@@ -1315,7 +1314,7 @@ mod test {
     #[test]
     fn test_behaviour_when_moving_to_next_paragraph_single() {
         let tests = [
-            ("^@", "@^"),
+            ("^@", "^@"),
             ("^s@tart at\nfirst char\n", "^start at\nfirst char\n@"),
             ("start at\nlast char^\n@", "start at\nlast char^\n@"),
             (
diff --git a/helix-core/src/test.rs b/helix-core/src/test.rs
index 983c9a57..da4f8fac 100644
--- a/helix-core/src/test.rs
+++ b/helix-core/src/test.rs
@@ -97,8 +97,9 @@ pub fn plain(s: &str, selection: Selection) -> String {
         .enumerate()
         .flat_map(|(i, range)| {
             [
-                (range.anchor, '^'),
+                // sort like this before reversed so anchor < head later
                 (range.head, if i == primary { '@' } else { '|' }),
+                (range.anchor, '^'),
             ]
         })
         .collect();
diff --git a/helix-core/src/textobject.rs b/helix-core/src/textobject.rs
index 5a55a6f1..fb6b7142 100644
--- a/helix-core/src/textobject.rs
+++ b/helix-core/src/textobject.rs
@@ -4,7 +4,8 @@ use ropey::RopeSlice;
 use tree_sitter::{Node, QueryCursor};
 
 use crate::chars::{categorize_char, char_is_whitespace, CharCategory};
-use crate::graphemes::next_grapheme_boundary;
+use crate::graphemes::{next_grapheme_boundary, prev_grapheme_boundary};
+use crate::line_ending::rope_is_line_ending;
 use crate::movement::Direction;
 use crate::surround;
 use crate::syntax::LanguageConfiguration;
@@ -111,6 +112,71 @@ pub fn textobject_word(
     }
 }
 
+pub fn textobject_para(
+    slice: RopeSlice,
+    range: Range,
+    textobject: TextObject,
+    count: usize,
+) -> Range {
+    let mut line = range.cursor_line(slice);
+    let prev_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
+    let curr_line_empty = rope_is_line_ending(slice.line(line));
+    let next_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
+    let last_char =
+        prev_grapheme_boundary(slice, slice.line_to_char(line + 1)) == range.cursor(slice);
+    let prev_empty_to_line = prev_line_empty && !curr_line_empty;
+    let curr_empty_to_line = curr_line_empty && !next_line_empty;
+
+    // skip character before paragraph boundary
+    let mut line_back = line; // line but backwards
+    if prev_empty_to_line || curr_empty_to_line {
+        line_back += 1;
+    }
+    let mut lines = slice.lines_at(line_back);
+    // do not include current paragraph on paragraph end (include next)
+    if !(curr_empty_to_line && last_char) {
+        lines.reverse();
+        let mut lines = lines.map(rope_is_line_ending).peekable();
+        while lines.next_if(|&e| e).is_some() {
+            line_back -= 1;
+        }
+        while lines.next_if(|&e| !e).is_some() {
+            line_back -= 1;
+        }
+    }
+
+    // skip character after paragraph boundary
+    if curr_empty_to_line && last_char {
+        line += 1;
+    }
+    let mut lines = slice.lines_at(line).map(rope_is_line_ending).peekable();
+    for _ in 0..count - 1 {
+        while lines.next_if(|&e| !e).is_some() {
+            line += 1;
+        }
+        while lines.next_if(|&e| e).is_some() {
+            line += 1;
+        }
+    }
+    while lines.next_if(|&e| !e).is_some() {
+        line += 1;
+    }
+    // handle last whitespaces part separately depending on textobject
+    match textobject {
+        TextObject::Around => {
+            while lines.next_if(|&e| e).is_some() {
+                line += 1;
+            }
+        }
+        TextObject::Inside => {}
+        TextObject::Movement => unreachable!(),
+    }
+
+    let anchor = slice.line_to_char(line_back);
+    let head = slice.line_to_char(line);
+    Range::new(anchor, head)
+}
+
 pub fn textobject_surround(
     slice: RopeSlice,
     range: Range,
@@ -289,6 +355,85 @@ mod test {
     }
 
     #[test]
+    fn test_textobject_paragraph_inside_single() {
+        let tests = [
+            ("^@", "^@"),
+            ("firs^t@\n\nparagraph\n\n", "^first\n@\nparagraph\n\n"),
+            ("second\n\npa^r@agraph\n\n", "second\n\n^paragraph\n@\n"),
+            ("^f@irst char\n\n", "^first char\n@\n"),
+            ("last char\n^\n@", "last char\n\n^@"),
+            (
+                "empty to line\n^\n@paragraph boundary\n\n",
+                "empty to line\n\n^paragraph boundary\n@\n",
+            ),
+            (
+                "line to empty\n\n^p@aragraph boundary\n\n",
+                "line to empty\n\n^paragraph boundary\n@\n",
+            ),
+        ];
+
+        for (before, expected) in tests {
+            let (s, selection) = crate::test::print(before);
+            let text = Rope::from(s.as_str());
+            let selection =
+                selection.transform(|r| textobject_para(text.slice(..), r, TextObject::Inside, 1));
+            let actual = crate::test::plain(&s, selection);
+            assert_eq!(actual, expected, "\nbefore: `{before:?}`");
+        }
+    }
+
+    #[test]
+    fn test_textobject_paragraph_inside_double() {
+        let tests = [
+            (
+                "last two\n\n^p@aragraph\n\nwithout whitespaces\n\n",
+                "last two\n\n^paragraph\n\nwithout whitespaces\n@\n",
+            ),
+            (
+                "last two\n^\n@paragraph\n\nwithout whitespaces\n\n",
+                "last two\n\n^paragraph\n\nwithout whitespaces\n@\n",
+            ),
+        ];
+
+        for (before, expected) in tests {
+            let (s, selection) = crate::test::print(before);
+            let text = Rope::from(s.as_str());
+            let selection =
+                selection.transform(|r| textobject_para(text.slice(..), r, TextObject::Inside, 2));
+            let actual = crate::test::plain(&s, selection);
+            assert_eq!(actual, expected, "\nbefore: `{before:?}`");
+        }
+    }
+
+    #[test]
+    fn test_textobject_paragraph_around_single() {
+        let tests = [
+            ("^@", "^@"),
+            ("firs^t@\n\nparagraph\n\n", "^first\n\n@paragraph\n\n"),
+            ("second\n\npa^r@agraph\n\n", "second\n\n^paragraph\n\n@"),
+            ("^f@irst char\n\n", "^first char\n\n@"),
+            ("last char\n^\n@", "last char\n\n^@"),
+            (
+                "empty to line\n^\n@paragraph boundary\n\n",
+                "empty to line\n\n^paragraph boundary\n\n@",
+            ),
+            (
+                "line to empty\n\n^p@aragraph boundary\n\n",
+                "line to empty\n\n^paragraph boundary\n\n@",
+            ),
+        ];
+
+        for (before, expected) in tests {
+            let (s, selection) = crate::test::print(before);
+            let text = Rope::from(s.as_str());
+            let selection =
+                selection.transform(|r| textobject_para(text.slice(..), r, TextObject::Around, 1));
+            let actual = crate::test::plain(&s, selection);
+            assert_eq!(actual, expected, "\nbefore: `{before:?}`");
+        }
+    }
+
+    #[test]
     fn test_textobject_surround() {
         // (text, [(cursor position, textobject, final range, surround char, count), ...])
         let tests = &[
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index beb564ad..ed3b45ae 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -3991,6 +3991,7 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
                         'f' => textobject_treesitter("function", range),
                         'a' => textobject_treesitter("parameter", range),
                         'o' => textobject_treesitter("comment", range),
+                        'p' => textobject::textobject_para(text, range, objtype, count),
                         'm' => {
                             let ch = text.char(range.cursor(text));
                             if !ch.is_ascii_alphanumeric() {