From d22f5ae32eba67e7ab4af9af1902bdbe0cdac819 Mon Sep 17 00:00:00 2001
From: Pascal Kuthe <pascal.kuthe@semimod.de>
Date: Sun, 6 Nov 2022 19:36:55 +0100
Subject: [PATCH] add command and keybding to jump to next/prev hunk

---
 helix-term/src/commands.rs       | 34 +++++++++++++++++++
 helix-term/src/keymap/default.rs |  2 ++
 helix-vcs/src/diff.rs            | 56 ++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index 4e3c321cb8fd0..46265368898cb 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -306,6 +306,8 @@ impl MappableCommand {
         goto_last_diag, "Goto last diagnostic",
         goto_next_diag, "Goto next diagnostic",
         goto_prev_diag, "Goto previous diagnostic",
+        goto_next_hunk, "Goto next hunk of changes",
+        goto_prev_hunk, "Goto previous hunk of changes",
         goto_line_start, "Goto line start",
         goto_line_end, "Goto line end",
         goto_next_buffer, "Goto next buffer",
@@ -2895,6 +2897,38 @@ fn goto_prev_diag(cx: &mut Context) {
     goto_pos(editor, pos);
 }
 
+fn goto_next_hunk(cx: &mut Context) {
+    goto_next_hunk_impl::<false>(cx)
+}
+
+fn goto_prev_hunk(cx: &mut Context) {
+    goto_next_hunk_impl::<true>(cx)
+}
+
+fn goto_next_hunk_impl<const REVERSE: bool>(cx: &mut Context) {
+    let editor = &mut cx.editor;
+    let (view, doc) = current!(editor);
+
+    let cursor_pos = doc
+        .selection(view.id)
+        .primary()
+        .cursor(doc.text().slice(..));
+
+    let cursor_line = doc.text().char_to_line(cursor_pos);
+
+    let next_changed_line = doc.diff_handle().and_then(|diff_handle| {
+        let hunks = diff_handle.hunks();
+        let hunk_idx = hunks.next_hunk::<REVERSE>(cursor_line as u32)?;
+        let line = hunks.nth_hunk(hunk_idx).after.start;
+        Some(line)
+    });
+
+    if let Some(next_change_line) = next_changed_line {
+        let pos = doc.text().line_to_char(next_change_line as usize);
+        goto_pos(cx.editor, pos)
+    }
+}
+
 pub mod insert {
     use super::*;
     pub type Hook = fn(&Rope, &Selection, char) -> Option<Transaction>;
diff --git a/helix-term/src/keymap/default.rs b/helix-term/src/keymap/default.rs
index 118764d975858..118e7591a4ef1 100644
--- a/helix-term/src/keymap/default.rs
+++ b/helix-term/src/keymap/default.rs
@@ -100,6 +100,7 @@ pub fn default() -> HashMap<Mode, Keymap> {
         "[" => { "Left bracket"
             "d" => goto_prev_diag,
             "D" => goto_first_diag,
+            "h" => goto_prev_hunk,
             "f" => goto_prev_function,
             "c" => goto_prev_class,
             "a" => goto_prev_parameter,
@@ -111,6 +112,7 @@ pub fn default() -> HashMap<Mode, Keymap> {
         "]" => { "Right bracket"
             "d" => goto_next_diag,
             "D" => goto_last_diag,
+            "h" => goto_next_hunk,
             "f" => goto_next_function,
             "c" => goto_next_class,
             "a" => goto_next_parameter,
diff --git a/helix-vcs/src/diff.rs b/helix-vcs/src/diff.rs
index 6a397ac886177..32ed7d62dd4ce 100644
--- a/helix-vcs/src/diff.rs
+++ b/helix-vcs/src/diff.rs
@@ -159,4 +159,60 @@ impl FileHunks<'_> {
             None => Hunk::NONE,
         }
     }
+
+    fn next_hunk_impl<const INVERT: bool, const REVERSE: bool>(&self, line: u32) -> Option<u32> {
+        let hunk_range = |hunk: &Hunk| {
+            if INVERT {
+                hunk.before.clone()
+            } else {
+                hunk.after.clone()
+            }
+        };
+        let res = self.hunks.binary_search_by_key(&line, |hunk| {
+            let range = hunk_range(hunk);
+            if REVERSE {
+                range.end
+            } else {
+                range.start
+            }
+        });
+
+        if REVERSE {
+            match res {
+                // Search found a hunk that ends exactly at this line (so it does not include the current line).
+                // We can usually just return that hunk, howver a specical special case for empty hunk is necessary
+                // which represents a pure removal.
+                // Removals are technically empty but are still shown as single line hunks
+                // and as such we must jump to the previus hunk (if it exists) if we are already inside the removal
+                Ok(pos) if !hunk_range(&self.hunks[pos]).is_empty() => Some(pos as u32),
+
+                // No hunk ends exactly at this line, so the search returns
+                // the position where a hunk ending at this line should be inserted.
+                // That position before this one is exactly the position of the previous hunk
+                Err(0) | Ok(0) => None,
+                Err(pos) | Ok(pos) => Some(pos as u32 - 1),
+            }
+        } else {
+            match res {
+                // Search found a hunk that starts exactly at this line, return the next hunk if it exists.
+                Ok(pos) if pos + 1 == self.hunks.len() => None,
+                Ok(pos) => Some(pos as u32 + 1),
+
+                // No hunk starts exactly at this line, so the search returns
+                // the position where a hunk starting at this line should be inserted.
+                // That position is exactly the position of the next hunk or the end
+                // of the list if no such hunk exists
+                Err(pos) if pos == self.hunks.len() => None,
+                Err(pos) => Some(pos as u32),
+            }
+        }
+    }
+
+    pub fn next_hunk<const REVERSE: bool>(&self, line: u32) -> Option<u32> {
+        if self.inverted {
+            self.next_hunk_impl::<true, REVERSE>(line)
+        } else {
+            self.next_hunk_impl::<false, REVERSE>(line)
+        }
+    }
 }