From e93c0fa155a47f66f88d86374baf980decf47b8a Mon Sep 17 00:00:00 2001
From: Pascal Kuthe <pascal.kuthe@semimod.de>
Date: Wed, 30 Nov 2022 19:17:00 +0100
Subject: [PATCH] add textobject for change

---
 book/src/usage.md          |  1 +
 helix-term/src/commands.rs | 22 ++++++++++++++++++++++
 helix-vcs/src/diff.rs      | 30 ++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/book/src/usage.md b/book/src/usage.md
index 646bf926d536..a6eb9ec1d4f1 100644
--- a/book/src/usage.md
+++ b/book/src/usage.md
@@ -143,6 +143,7 @@ though, we climb the syntax tree and then take the previous selection. So
 | `a`                    | Argument/parameter       |
 | `o`                    | Comment                  |
 | `t`                    | Test                     |
+| `g`                    | Change                   |
 
 > NOTE: `f`, `c`, etc need a tree-sitter grammar active for the current
 document and a special tree-sitter query file to work properly. [Only
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index a1bbad380ba3..fe043ae401a1 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -4608,6 +4608,27 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
                     )
                 };
 
+                if ch == 'g' && doc.diff_handle().is_none() {
+                    editor.set_status("Diff is not available in current buffer");
+                    return;
+                }
+
+                let textobject_change = |range: Range| -> Range {
+                    let diff_handle = doc.diff_handle().unwrap();
+                    let hunks = diff_handle.hunks();
+                    let line = range.cursor_line(text);
+                    let hunk_idx = if let Some(hunk_idx) = hunks.hunk_at(line as u32, false) {
+                        hunk_idx
+                    } else {
+                        return range;
+                    };
+                    let hunk = hunks.nth_hunk(hunk_idx).after;
+
+                    let start = text.line_to_char(hunk.start as usize);
+                    let end = text.line_to_char(hunk.end as usize);
+                    Range::new(start, end).with_direction(range.direction())
+                };
+
                 let selection = doc.selection(view.id).clone().transform(|range| {
                     match ch {
                         'w' => textobject::textobject_word(text, range, objtype, count, false),
@@ -4621,6 +4642,7 @@ fn select_textobject(cx: &mut Context, objtype: textobject::TextObject) {
                         'm' => textobject::textobject_pair_surround_closest(
                             text, range, objtype, count,
                         ),
+                        'g' => textobject_change(range),
                         // TODO: cancel new ranges if inconsistent surround matches across lines
                         ch if !ch.is_ascii_alphanumeric() => {
                             textobject::textobject_pair_surround(text, range, objtype, ch, count)
diff --git a/helix-vcs/src/diff.rs b/helix-vcs/src/diff.rs
index e70293fe7c28..ef42d9cff35d 100644
--- a/helix-vcs/src/diff.rs
+++ b/helix-vcs/src/diff.rs
@@ -246,4 +246,34 @@ impl FileHunks<'_> {
             Err(pos) | Ok(pos) => Some(pos as u32 - 1),
         }
     }
+
+    pub fn hunk_at(&self, line: u32, include_removal: bool) -> Option<u32> {
+        let hunk_range = if self.inverted {
+            |hunk: &Hunk| hunk.before.clone()
+        } else {
+            |hunk: &Hunk| hunk.after.clone()
+        };
+
+        let res = self
+            .hunks
+            .binary_search_by_key(&line, |hunk| hunk_range(hunk).start);
+
+        match res {
+            // Search found a hunk that starts exactly at this line, return it
+            Ok(pos) => Some(pos as u32),
+
+            // No hunk starts exactly at this line, so the search returns
+            // the position where a hunk starting at this line should be inserted.
+            // The previous hunk contains this hunk if it exists and doesn't end before this line
+            Err(0) => None,
+            Err(pos) => {
+                let hunk = hunk_range(&self.hunks[pos - 1]);
+                if hunk.end > line || include_removal && hunk.start == line && hunk.is_empty() {
+                    Some(pos as u32 - 1)
+                } else {
+                    None
+                }
+            }
+        }
+    }
 }